How oil gas wells are drilled. How are oil and gas wells drilled? Documents and equipment: basic requirements

General information about drilling oil and gas wells

1.1. BASIC TERMS AND DEFINITIONS

Rice. 1. Elements of the well structure

A well is a cylindrical mine working without human access and having a diameter that is many times smaller than its length (Fig. 1).

The main elements of the borehole:

Wellhead (1) - intersection of the well route with the day surface

Bottom hole (2) - the bottom of a borehole moving as a result of the impact of a rock cutting tool on the rock

Borehole walls (3) - lateral surfaces drilling wells

Borehole axis (6) - an imaginary line connecting the centers of the borehole cross-sections

* Wellbore (5) - the space in the bowels occupied by the borehole.

Casing strings (4) - strings of interconnected casing pipes. If the borehole walls are made of stable rocks, then the casing strings are not run into the borehole.

The wells are deepened, destroying the rock over the entire bottomhole area (solid bottom, Fig. 2 a) or along its peripheral part (annular bottom, Fig. 2 b). In the latter case, a rock column remains in the center of the well - a core, which is periodically raised to the surface for direct study.

The diameter of the wells, as a rule, decreases from the head to the bottom in steps at certain intervals. Initial diameter oil and gas wells usually do not exceed 900 mm, and the final is rarely less than 165 mm. Depths oil and gas wells vary within a few thousand meters.

By spatial location in the earth's crust, boreholes are subdivided (Fig. 3):

1. Vertical;

2. Inclined;

3. Straight-line curved;

4. Curved;

5. Rectilinearly curved (with a horizontal section);

Rice. 3. Spatial location of wells

Complicatedly curved.

Oil and gas wells are drilled onshore and offshore using drilling rigs. In the latter case, drilling rigs are mounted on racks, floating drilling platforms or ships (Fig. 4).

V oil and gas industries are drilling wells for the following purposes:

1. Operational- for oil production, gas and gas condensate.

2. Injection - for pumping into productive horizons of water (less often air, gas) in order to maintain reservoir pressure and extend the fountain period of field development, increase the flow rate operational wells equipped with pumps and air lifters.

3. Exploration - to identify productive horizons, delineate, test and assess their industrial value.

4. Special - reference, parametric, assessment, control - for studying the geological structure of a little-known area, determining changes in reservoir properties of productive formations, monitoring formation pressure and the front of movement of oil-water contact, the degree of development of individual sections of the formation, thermal effects on the formation, ensuring in-situ combustion , oil gasification, wastewater discharge into deep-seated absorbing strata, etc.

5. Structural search - to clarify the position of promising oil-gas bearing structures according to the upper marking (defining) horizons repeating their outlines, according to the data of drilling small, less expensive wells of small diameter.

Today oil and gas wells are expensive capital structures that have served for many decades. This is achieved by connecting the reservoir to the surface of the earth in a sealed, strong and durable channel. However, the drilled wellbore does not yet represent such a channel, due to the instability of rocks, the presence of layers saturated with various fluids (water, oil, gas and mixtures thereof), which are under different pressures. Therefore, during the construction of a well, it is necessary to anchor its wellbore and separate (isolate) formations containing various fluids.

The wellbore is cased by running special pipes called casing pipes. A series of casing pipes connected in series with each other make up the casing string. For well casing, steel casing pipes are used (Fig. 5).

The layers saturated with various fluids are separated by impermeable rocks - "covers". When drilling a well, these impermeable separating covers are disturbed and the possibility of interstratal crossflows, spontaneous outflow of formation fluids to the surface, watering of productive formations, pollution of water supply sources and the atmosphere, and corrosion of casing strings lowered into the well is created.

In the process of drilling a well in unstable rocks, intense cavities, talus, landslides, etc. are possible. In some cases, further deepening of the wellbore becomes impossible without prior fixing of its walls.

To exclude such phenomena, the annular channel (annular space) between the borehole wall and the casing string lowered into it is filled with plugging (insulating) material (Fig. 6). These are formulations that include an astringent, inert and active fillers, and chemical reagents. They are prepared in the form of solutions (usually water) and pumped into the well with pumps. Of the binders, the most widely used are oil-well Portland cements. Therefore, the process of separation of layers is called cementing.

Thus, as a result of borehole drilling, its subsequent fastening and separation of layers, a stable underground structure of a certain design is created.

Well design is understood as a set of data on the number and size (diameter and length) of casing strings, borehole diameters for each string, cementing intervals, as well as methods and intervals of connecting the well with the productive formation (Fig. 7).

Information about the diameters, wall thicknesses and steel grades of casing pipes by intervals, about the types of casing pipes, equipment the bottom of the casing is included in the concept of casing design.

Casing strings of a certain purpose are lowered into the well: direction, conductor, intermediate strings, operational Column.

The direction is lowered into the borehole to prevent erosion and collapse of rocks around the wellhead when drilling under a surface guide, as well as to connect the borehole to the drilling mud cleaning system. The annular space behind the direction is filled along the entire length with grouting mortar or concrete. The direction is lowered to a depth of several meters in stable rocks, up to tens of meters in swamps and silty soils.

The conductor usually covers the upper part of the geological section, where there are unstable rocks, reservoirs that absorb drilling solution or developing, supplying formation fluids to the surface, i. e. all those intervals that will complicate the process of further drilling and cause environmental pollution. The conductor must necessarily cover all layers saturated with fresh water.

Rice. 7. Well design diagram

The jig is also used to install a blowout preventer wellhead equipment and suspension of subsequent casing strings. The conductor is lowered to a depth of several hundred meters. For reliable separation of layers, giving sufficient strength and stability, the casing is cemented along its entire length.

Operational the string is run into the well to recover oil, gas or injection into the productive horizon of water or gas in order to maintain reservoir pressure. The height of the grouting slurry rise above the top of the productive horizons, as well as a stage cementing device or a junction of the upper sections of the casing strings in oil and gas wells should be at least 150-300 m and 500 m, respectively.

Intermediate (technical) columns must be lowered if it is impossible to drill to the design depth without first separating the zones of complications (manifestations, landslides). The decision to run them is made after analyzing the pressure ratio arising during drilling in the "well-reservoir" system.

If the pressure in the well Pc is less than the formation pressure Рпл (pressure of the fluids saturating the formation), then fluids from the formation will flow into the well, and a manifestation will occur. Depending on the intensity, manifestations are accompanied by self-pouring liquid ( gas) at the wellhead (overflows), blowouts, open (uncontrolled) flowing. These phenomena complicate the process of well construction, pose a threat of poisoning, fires, and explosions.

When the pressure in the well rises to a certain value, called the pressure of the onset of absorption Ploss, the fluid from the well enters the formation. This process is called absorption drilling solution. Pogl can be close to or equal to the reservoir pressure, and sometimes it approaches the value of the vertical rock pressure, determined by the weight of the rocks located above.

Sometimes losses are accompanied by fluid flows from one reservoir to another, which leads to pollution of water supply sources and productive horizons. A decrease in the liquid level in the well due to absorption in one of the reservoirs causes a decrease in pressure in the other reservoir and the possibility of manifestations from it.

The pressure at which natural closed fractures open or new ones are formed is called the pressure of hydraulic fracturing, Ргрп. This phenomenon is accompanied by a catastrophic absorption drilling solution.

It is characteristic that in many oil and gas regions, the reservoir pressure Рпл is close to the hydrostatic pressure of the fresh water column Рг (hereinafter simply the hydrostatic pressure) with a height Нж, equal to the depth Нп, on which the given formation lies. This is due to the fact that the pressure of fluids in the reservoir is often caused by the pressure of edge waters, the recharge area of ​​which is connected with the day surface at considerable distances from the field.

Since the absolute values ​​of pressures depend on the depth H, it is more convenient to analyze their ratios using the values ​​of relative pressures, which are the ratios of the absolute values ​​of the corresponding pressures to the hydrostatic pressure Pr, i.e.:

Rpl * = Rpl / Rg;

Ргр * = Ргр / Рг;

Рпогл * = Рпогл / Рг;

Ргрп * = Ргрп / Рг.

Here Рпл - reservoir pressure; Ргр - hydrostatic pressure of the drilling mud; Рпогл - pressure of the beginning of absorption; Ргрп - hydraulic fracturing pressure.

The relative reservoir pressure Ppl * is often called the abnormality coefficient Ka. When Рпл * is approximately equal to 1.0, the formation pressure is considered normal, with Рпл * greater than 1.0 - abnormally high (abnormally high pressure), and with Рпл * less than 1.0 - abnormally low (AIPP).

One of the conditions for a normal uncomplicated drilling process is the ratio

a) Rpl *< Ргр* < Рпогл*(Ргрп*)

The drilling process is complicated if, for some reason, the relative pressures are in the ratio:

b) Ppl *> Pgr *< Рпогл*

or

c) Rpl *< Ргр* >Рпогл * (Ргрп *)

If relation b) is true, then only manifestations are observed, if c), then manifestations and absorptions are also observed.

Intermediate columns can be solid (they are lowered from the mouth to the bottom) and not solid (not reaching the mouth). The latter are called shanks.

It is generally accepted that a well has a single-column structure if intermediate columns are not run into it, although both the direction and the conductor are lowered. With one intermediate string, the well has a two-string structure. When there are two or more technical strings, the well is considered multi-string.

The well design is set as follows: 426, 324, 219, 146 - casing diameters in mm; 40, 450, 1600, 2700 - casing running depths in m; 350, 1500 - the level of the grouting slurry behind the liner and operational column in m; 295, 190 - bit diameters in mm for drilling wells for 219 - and 146 - mm strings.

1.2. WELL DRILLING METHODS

Wells can be drilled by mechanical, thermal, electrical impulse and other methods (several dozen). However, only mechanical drilling methods - percussion and rotary drilling - find industrial application. The rest have not yet left the experimental development stage.

1.2.1. IMPACT DRILLING

Percussion drilling. Of all its varieties, percussion-rope drilling is the most widespread (Fig. 8).

The drill, which consists of a chisel 1, an impact rod 2, a sliding shear bar 3 and a rope lock 4, is lowered into the borehole on a rope 5, which, bending around block 6, pull-off roller 8 and a guide roller 10, is unwound from the drum 11 of the drilling rig ... The speed of lowering the drill string is controlled by the brake 12. Block 6 is installed at the top of the mast 18. To damp vibrations arising during drilling, shock absorbers 7 are used.

The crank 14 with the help of the connecting rod 15 vibrates the balance frame 9. When the frame is lowered, the take-off roller 8 pulls the rope and lifts the drill above the bottom. When the frame is raised, the rope is lowered, the projectile falls, and when the chisel hits the rock, the latter is destroyed.

As the borehole deepens, the rope is lengthened by winding it off the drum 11. The borehole cylindricality is ensured by turning the bit as a result of unwinding the rope under load (while lifting the drill string) and twisting it when removing the load (when the bit strikes the rock).

The efficiency of rock destruction during percussive drilling is directly proportional to the mass of the drill, the height of its fall, the acceleration of the fall, the number of blows of the bit against the bottomhole per unit of time and is inversely proportional to the square of the borehole diameter.

In the process of drilling fractured and viscous formations, bit jamming is possible. To free the bit in the drill string, a shear bar is used, made in the form of two elongated rings, connected to each other like chain links.

The drilling process will be the more efficient, the less resistance to the drill bit is provided by the cuttings accumulating at the bottom of the well, mixed with the formation fluid. In the absence or insufficient inflow of formation fluid into the well from the wellhead, water is periodically added. An even distribution of cuttings particles in the water is achieved by periodic striding (raising and lowering) drilling projectile. As the destruction of rock (cuttings) accumulates at the bottom hole, it becomes necessary to clean up the well. To do this, using the drum, the drill is lifted out of the borehole and the thief 13 is repeatedly lowered into it on the rope 17, which is unwound from the drum 16. There is a valve in the bottom of the thief. When the thief is immersed in the slurry liquid, the valve opens and the thief is filled with this mixture, when the thief is lifted, the valve closes. The sludge liquid raised to the surface is poured into a collection container. To completely clean the well, you have to run the bailer several times in a row.

After cleaning the bottom hole, a drill is lowered into the well, and the drilling process continues.

With shock drilling the well is usually not filled with liquid. Therefore, in order to avoid rock collapse from its walls, a casing string consisting of metal casing pipes connected to each other by means of threads or welding is lowered. As the well deepens, the casing is pushed to the bottom and periodically extended (built up) by one pipe.

The impact method has not been applied for more than 50 years. oil and gas industries of Russia. However, in the exploration drilling at placer deposits, during engineering and geological surveys, drilling water wells, etc. finds its application.

1.2.2. ROTARY DRILLING OF WELLS

In rotary drilling, rock breakdown occurs as a result of the simultaneous action of load and torque on the bit. Under the action of the load, the bit penetrates into the rock, and under the influence of the torque it cleaves it.

There are two types of rotary drilling - rotary and downhole drilling.

In rotary drilling (Fig. 9), the power from the motors 9 is transmitted through the winch 8 to the rotor 16 - a special rotary mechanism installed above the wellhead in the center of the rig. The rotor rotates drilling drill string and a bit screwed to it 1. The drill string consists of a leading pipe 15 and 6 drill pipes 5 screwed to it using a special sub.

Consequently, during rotary drilling, the deepening of the bit into the rock occurs when the rotating drill string moves along the axis of the borehole, and when drilling with downhole motor - non-rotating drilling columns. Rotary drilling is characterized by flushing

At drilling with a downhole motor, bit 1 is screwed to the shaft, and the drill string is screwed to the motor casing 2. When the motor is running, its shaft with the bit rotates, and the drill string receives the reactive torque of the motor casing, which is damped by a non-rotating rotor (a special plug is installed in the rotor).

Mud pump 20, driven by motor 21, pumps drilling fluid through a manifold (pipeline high pressure) 19 into the riser - pipe 17, vertically installed in the right corner of the tower, then into the flexible drilling hose (sleeve) 14, swivel 10 and into drilling column. Having reached the bit, the drilling fluid passes through the holes in it and rises to the surface along the annular space between the borehole wall and the drill string. Here in the system of tanks 18 and cleaning mechanisms (not shown in the figure) drilling the solution is cleaned of cuttings, then enters the receiving tanks 22 of drilling pumps and is again pumped into the well.

Currently, three types of downhole motors are used - a turbodrill, a screw engine and an electric drill (the latter is used extremely rarely).

When drilling with a turbodrill or screw motor, the hydraulic energy of the flow of drilling fluid moving down the drill string is converted into mechanical energy on the shaft of the downhole motor to which the bit is connected.

When drilling with an electric drill Electric Energy supplied by cable, the sections of which are mounted inside drilling string and is converted by an electric motor into mechanical energy on the shaft, which is directly transmitted to the bit.

As the well deepens boring a string, suspended from a chain hoist system, consisting of a crown block (not shown in the figure), traveling block 12, hook 13 and wire rope 11, is fed into the well. When the kelly 15 enters the full length of the rotor 16, the winch is turned on, the drill string is raised the length of the kelly and the drill string is suspended by wedges on the rotor table. Then, the leading pipe 15 is unscrewed together with the swivel 10 and lowered into a borehole (a casing pipe previously installed in a specially drilled inclined well) with a length equal to the length of the leading pipe. The borehole is drilled in advance in the right corner of the rig approximately in the middle of the distance from the center to its leg. After that, the drill string is lengthened (built up) by screwing to it a two-pipe or three-pipe plug (two or three drill pipes screwed together), remove it from the wedges, lowered into the well for the length of the plug, suspended with wedges on the rotor table, lifted from hole leading pipe with a swivel, screw it to the drill string, free the drill string from wedges, bring the bit to the bottom and continue drilling.

To replace a worn-out bit, the entire drill string is pulled out of the well and then lowered again. Lowering and lifting operations are also carried out using a chain hoist system. When the drum of the winch rotates, the wire rope is wound on the drum or unwound from it, which ensures the lifting or lowering of the traveling block and the hook. To the latter, a raised or lowered drill string is suspended with the help of links and an elevator.

When lifting, the BC is unscrewed onto the candles and installed inside the tower with the lower ends on the candlesticks, and the upper ends are wound by the special fingers on the balcony of the riding worker. BK is lowered into the well in reverse order.

Thus, the process of bit operation at the bottom of the well is interrupted by the extension of the drill string and trips to change the worn-out bit.

As a rule, the upper sections of the well section are easily washed out deposits. Therefore, before drilling a well, a shaft (hole) is built to stable rocks (3-30 m) and pipe 7 or several screwed pipes (with a cut-out window in the upper part) are lowered into it, 1-2 m longer than the depth of the hole. The annular space is cemented or concreted. As a result, the wellhead is reliably strengthened.

A short metal groove is welded to the window in the pipe, along which, during drilling, the drilling fluid is directed to the system of tanks 18 and then, passing through the cleaning mechanisms (not shown in the figure), enters the receiving tank 22 of drilling pumps.

The pipe (pipe string) 7 installed in the pit is called the direction. Setting the direction and a number of other work performed before the start drilling are preparatory. After their fulfillment, an act of entry into exploitation drilling rig and start drilling a well.

By drilling unstable, soft, fractured and cavernous rocks, complicating the process drilling(usually 400-800 m), cover these horizons with a conductor 4 and cement the annular space 3 to the mouth. With further deepening, horizons may also be encountered, which are also subject to isolation; such horizons are overlapped by intermediate (technical) casing strings.

Having drilled the well to the design depth, lowered and cemented operational column (EC).

After that, all casing strings at the wellhead are tied to each other using a special equipment... Then, several tens (hundreds) of holes are punched against the productive formation in the EC and cement stone, through which, in the process of testing, development and subsequent exploitation of oil (gas) will flow into the well.

The essence of well development is reduced to the fact that the pressure of the column of the drilling mud in the well becomes less than the formation pressure. As a result of the created pressure drop, oil ( gas) from the formation will begin to flow into the well. After the complex research works the well is handed over to exploitation.

For each well, a passport is entered, where its structure, location of the mouth, bottom hole and spatial position shaft according to the data of directional measurements of its deviations from the vertical (zenith angles) and azimuth (azimuthal angles). The latter data is especially important for cluster drilling of directional wells in order to avoid the wellbore being drilled into the wellbore of a previously drilled or already producing well. The actual deviation of the bottom from the design must not exceed the specified tolerances.

Drilling operations must be carried out in compliance with health and safety laws. Construction of a site for a drilling rig, routes for the movement of a drilling rig, access roads, power lines, communications, pipelines for water supply, collection oil and gas, earthen barns, purification devices, sludge disposal should be carried out only on a territory specially designated by the relevant organizations. After the completion of the construction of a well or a cluster of wells, all pits and trenches must be backfilled, the entire site for the drilling site must be restored (reclaimed) as much as possible for economic use.

1.3. BRIEF HISTORY OF DRILLING OIL AND GAS WELL

The first wells in the history of mankind were drilled by the percussion-rope method in 2000 BC for mining pickles in China.

Until the middle of the 19th century oil was mined in small quantities, mainly from shallow wells near its natural outlets to the surface. Since the second half of the 19th century, the demand for oil began to increase in connection with the widespread use of steam engines and the development on their basis of industry, which required large quantities of lubricants and more powerful than tallow candles, light sources.

Research recent years found that the first well on oil was drilled by hand rotary method on the Apsheron Peninsula (Russia) in 1847 at the initiative of V.N. Semenova. The first well in the USA oil(25m) was drilled in Pennsylvania by Edwin Drake in 1959. This year is considered the beginning of development oil producing industry in the United States. Birth of the Russian oil industry is usually counted from 1964, when in the Kuban in the valley of the Kudako river A.N. Novosiltsev began drilling the first well at oil(depth 55 m) with the use of mechanical percussion-rope drilling.

At the turn of the 19th and 20th centuries, diesel and gasoline internal combustion engines were invented. Their introduction into practice led to the rapid development of the world oil producing industry.

In 1901, rotary rotary drilling was first used in the USA with bottom hole washing with a circulating fluid flow. It should be noted that the removal of cuttings by a circulating stream of water was invented in 1848 by the French engineer Fauvelle and was the first to use this method when drilling an artesian well in the monastery of St. Dominica. In Russia, the first well was drilled by the rotary method in 1902 to a depth of 345 m in the Grozny region.

One of the most difficult problems encountered when drilling wells, especially with the rotary method, was the problem of sealing the annular space between the casing pipes and the wellbore walls. This problem was solved by the Russian engineer A.A. Bogushevsky, who developed and patented in 1906 a method for pumping cement slurry into the casing with its subsequent displacement through the bottom (shoe) of the casing into the annulus. This method of cementing quickly spread in domestic and foreign practice. drilling.

In 1923, a graduate of the Tomsk Technological Institute M.A. Kapelyushnikov in collaboration with S.M. Volokh and N.A. Korneev invented a downhole hydraulic motor - a turbodrill, which determined a fundamentally new way of development of technology and technology drilling oil and gas wells. In 1924, the world's first well was drilled in Azerbaijan using a single-stage turbodrill, which was named Kapelyushnikov's turbodrill.

Turbodrills have a special place in the history of development. drilling inclined wells. For the first time a deviated well was drilled by the turbine method in 1941 in Azerbaijan. The improvement of such drilling has made it possible to accelerate the development of fields located under the seabed or under highly rugged terrain (swamps of Western Siberia). In these cases, several inclined wells are drilled from one small site, the construction of which requires significantly less costs than the construction of sites for each drilling site. drilling vertical wells. This method of well construction is called cluster drilling.

In 1937-40. A.P. Ostrovsky, N.G. Grigoryan, N.V. Aleksandrov and others developed the design of a fundamentally new downhole motor - an electric drill.

In the USA, in 1964, a single-pass hydraulic screw downhole motor was developed, and in 1966 in Russia, a multi-pass screw motor was developed, which makes it possible to drill directional and horizontal wells for oil and gas.

In Western Siberia, the first well, which gave a powerful fountain of natural gas On September 23, 1953, it was drilled near the village. Berezovo in the north of the Tyumen region. Here, in the Berezovsky district, it was born in 1963. gas producing industry of Western Siberia. The first oil well in Western Siberia gushed out on June 21, 1960 in the Mulym'inskaya area in the Konda river basin.

For most people, having their own oil or gas well means deciding financial difficulties for the rest of your life and live without thinking about anything.
But is it so easy to drill a well? How does it work? Unfortunately, very few people ask this question.

Drilling well 39629G is located very close to Almetyevsk, in the village of Karabash. After the night rain, all around in the fog and in front of the car, rabbits were running every now and then.

And finally, the drilling rig itself appeared. There, a drilling foreman was already waiting for us - the main person on the site, he makes all operational decisions and is responsible for everything that happens during drilling, as well as the head of the drilling department.

Basically, drilling is called the destruction of rocks at the bottom (at the lowest point) and the extraction of destroyed rocks to the surface. A drilling rig is a complex of machinery such as an oil rig, mud pumps, mud cleaning systems, generators, living quarters, etc.

The drilling site, on which all the elements are located (we will talk about them below), is a zone cleared of a fertile layer of earth and covered with sand. After the completion of the work, this layer is restored and, thus, no significant harm to the environment is caused. A layer of sand is required, because clay in the first rains will turn into an impenetrable slurry. I myself saw how the multi-ton Urals got stuck in such a liquid.
But first things first.

At well 39629G, a rig (actually a tower) SBU-3000/170 (stationary drilling rig, maximum lifting capacity 170 tons) was installed. The machine is made in China and compares favorably with what I have seen before. Drilling rigs are also produced in Russia, but Chinese rigs are cheaper both in purchase and in maintenance.

Cluster drilling is underway at this site, which is typical for horizontal and directional wells. This type of drilling means that the wellheads are located at a close distance from each other.
Therefore, the drilling rig is equipped with a self-sliding rail system. The system works according to the "push-pull" principle and the machine moves as if by itself with the help of hydraulic cylinders. It takes a couple of hours to move from one point to another (the first tens of meters) with all the accompanying operations.

We rise to the drilling platform. This is where most of the drillers' work takes place. The photo shows the pipes of the drill string (left) and the hydraulic tong, with the help of which the string is extended with new pipes and continues drilling. Drilling takes place thanks to a bit at the end of the string and rotation, which is transmitted by a rotor.

I was especially delighted workplace driller. Once upon a time, in the Komi Republic, I saw a driller who controlled all processes with the help of three rusty levers and his own intuition. To move the lever from its place, he literally hung on it. As a result, the drill hook nearly hit him.
Here, the driller is like the captain of a spaceship. He sits in an isolated cockpit surrounded by monitors and controls everything with a joystick.

It goes without saying that the cabin is heated in winter and cooled in summer. In addition, the roof, also made of glass, has a protective mesh in case something falls from a height and a wiper to clean the glass. The latter causes genuine delight among the drillers :)

We climb up!

In addition to the rotor, the rig is equipped with a top drive system (made in the USA). This system combines a crane block and a rotor. Roughly speaking, this is a crane with an electric motor attached to it. The top drive system is more convenient, faster and more modern than the rotor.

Video of how the top drive system works:

The tower offers an excellent view of the site and the surroundings :)

In addition to beautiful views, at the top of the drilling site, you can find a riding pombur (assistant driller) workplace. His responsibilities include pipe installation work and general supervision.

Since the horseman is at the workplace for the entire 12-hour shift and in any weather and any time of the year, a heated room is equipped for him. This has never happened on the old towers!

In the event of an emergency, the horseman can be evacuated using a trolley:

When the well is drilled, the wellbore is flushed several times from the drilled rock (cuttings) and a casing string, which consists of many pipes twisted together, is lowered into it. One typical casing ID is 146 millimeters. The borehole length can reach 2-3 kilometers or more. Thus, the length of the well exceeds its diameter by tens of thousands of times. Approximately the same proportions have, for example, a piece of ordinary thread 2-3 meters long.

Pipes are fed through a special chute:

After running the casing, the well is flushed again and cementing of the annular space (the space between the wall of the well and the casing) begins. Cement is fed to the bottom and pushed into the annulus.

After the cement hardens, it is checked with a probe (a device lowered into the well) OCC - acoustic control of cementing, the well is pressurized (tightness is checked), if everything is OK, then drilling continues - a cement nozzle is drilled out at the bottom and the bit moves on.

The letter "g" in the well number 39629G means that the wellbore is horizontal. From the wellhead to a certain point, the well is drilled without deviation, but then with the help of a swivel diverter and / or a rotary diverter, it goes to the horizontal. The first is a swivel pipe and the second is a directional nozzle bit that is deflected by the mud pressure. Usually, in the pictures, the deflection of the trunk is depicted almost at an angle of 90 degrees, but in reality this angle is about 5-10 degrees per 100 meters.

Special people - "crooks" or telemetry engineers are watching to ensure that the wellbore goes where it is needed. According to the indications of the natural radioactivity of rocks, resistance and other parameters, they control and correct the course of drilling.

Schematically, it all looks like this:

Any manipulation with anything at the bottom (bottom hole) of the well turns into a very exciting experience. If you accidentally drop a tool, a pump or several pipes into a well, then it is quite possible that the dropped one will never be reached, after which you can put an end to a well worth tens or hundreds of millions of rubles. Digging into the cases and history of repairs, you can find real wells-pearls, on the bottom of which there is a pump, on top of which there is a fishing tool (for removing the pump), on top of which there is a tool for extracting fish
new tool. When I was in the well, they dropped, for example, a sledgehammer :)

In order for oil to flow into the well at all, holes must be made in the casing and the cement ring behind it, since they separate the reservoir from the well. These holes are made with shaped charges; they are essentially the same as, for example, anti-tank, only without a fairing, because they do not need to fly anywhere. The charges pierce not only the casing and cement, but also the rock layer itself a few tens of centimeters deep. The whole process is called perforation.

To reduce the friction of the tool, carry out the destroyed rock, prevent shattering of the borehole walls and compensate for the difference in reservoir pressure and pressure at the wellhead (at the bottom, the pressure is several times higher), the well is filled with drilling fluid. Its composition and density are selected depending on the nature of the cut.
The drilling fluid is pumped by a compressor station and must be constantly circulated in the well to avoid shattering of the borehole walls, sticking of the tool (situations when the string is blocked and it is impossible to rotate or pull it out - this is one of the most common accidents during drilling) and other things.

We get down from the tower, we go to watch the pumps.

During the drilling process, the drilling fluid carries cuttings (drilled rock) to the surface. Analyzing the cuttings, drillers and geologists can draw conclusions about the rocks that the well is currently passing through. Then the solution must be cleaned of sludge and sent back to the well to work. For this, a system of treatment plants and a "barn" are equipped, where the cleaned sludge is stored (the barn is visible in the previous photo on the right).

The solution of the vibrating sieve is taken first - they separate the largest fractions.

Then the solution passes the sludge (left) and sand separators (right):

Finally, the finest fraction is removed using a centrifuge:

Then the solution enters the tank blocks, if necessary, its properties are restored (density, composition, etc.) and from there it is pumped back into the well with the help of a pump.
Capacitive block:

Mud pump (produced in the Russian Federation!). The red thing on top is a hydraulic compensator, it smooths out the pulsation of the solution due to back pressure. Usually on drilling rigs there are two pumps: one is working, the second is backup in case of breakdown.

All this pumping facility is managed by one person. Due to the noise of the equipment, he has to wear earplugs or ear protectors for the entire shift.

"And what about the daily life of drillers?" - you ask. We also did not miss this moment!
On this site, drillers work in short shifts of 4 days, because drilling is carried out almost within the city, but the residential modules are practically no different from those that are used, for example, in the Arctic (perhaps for the better).

There are 15 trailers in total on the site.
Some of them are residential, drillers live in them for 4 people. The trailers are divided into a vestibule with a coat rack, washbasin and cabinets, and the living area itself.

In addition, a bathhouse and a kitchen-dining room are located in separate trailers (in the local slang - "beams" "). In the latter we had a great breakfast and discussed the details of the work. I will not retell, otherwise you will accuse me of very frank advertising, but I will that I immediately wanted to stay in Almetyevsk ... Pay attention to the prices!

We spent about 2.5 hours at the drilling rig and I was once again convinced that such a difficult and dangerous business how drilling and oil production in general can only be good people... They also explained to me that bad people don't stay here.

Friends, thanks for reading to the end. Hopefully you now have a slightly better idea of ​​the drilling process. If you still have questions, ask them in the comments. I myself or with the help of experts - I will definitely answer!

Today these are the main Natural resources, which are needed for the full life of mankind. Oil plays a special role in the fuel and energy balance; it is used to make motor fuels, solvents, plastics, detergents and much more. Gas is mainly used as a source of heating, cooking fuel, machine fuel and raw material for the manufacture of various organic substances. That is why their mining has become the main industry in the world. In order to extract these fossils, located deep underground, you need oil gas well.

1 - casing pipes;

2 - cement stone;

4 - perforation in the casing and cement stone;

I - direction;

II - conductor;

III - intermediate column;

IV - production casing.

What it is?

A well is a cylindrical hole in the ground with soil walls reinforced with a special solution, where a person has no access. The length ranges from several meters to several kilometers, depending on the depth of the mineral deposits.

Gas well construction is the process of creating a mine working in the ground. A high-quality process requires powerful drilling rigs. Today, half of the rigs are diesel powered. They are very convenient to use in the absence of electricity. Their power is constantly being improved by manufacturers. It must be remembered that the process of destruction of rocks is high-tech, which requires high-quality equipment and qualified specialists.

Well and its components

What is and how is it different from mines and wells? If necessary, people can descend into mines or wells, but they will not have access to the well. In addition, the length is larger than the diameter. From the above, we can conclude that a well is a cylindrical mine working without people accessing it.

Oil gas well consists of the mouth - this is the upper part of it, the trunk is the walls and the lower part is the bottom. The structure itself consists of several parts. These parts are guides, conductors and production strings. Drilling an oil and gas well must be carried out efficiently so that the soil layers are not eroded during further exploitation. Therefore, after the installation of the guide column, the space between the soil and the pipe wall is carefully cemented. This is especially important, because active, fresh waters pass through the upper layers of the soil. The next process is to build a conductor. This is the descent of the columns to an even greater depth and, again, the cementing of the space between them and the soil. Then all these operations are completed by running the production string to the bottom and again the entire space from the bottom to the wellhead is cemented. This will provide good protection against delamination of soil layers and groundwater.

Types of mine workings

Oil construction gas wells subdivided into:

• Horizontal
• Vertical
• Oblique
• Multi-barreled
• Multi-hole

Classification by purpose

Each has its own purpose, below we will consider what categories they are divided into:

• search engines
• exploratory
• operational

The most common are vertical. When they are installed, the angle of inclination from the vertical does not exceed 5 degrees. If it exceeds, then it is already called inclined. The horizontal one has an inclination angle of 80 to 90 degrees from the vertical, but since it makes no sense to drill at such an inclination, they pierce an ordinary well or an inclined one, and then the wellbore itself is launched along the required trajectory. Design implies the use of multi-barrel and multi-hole structures. The difference is that the multilateral one has several trunks, which branch out from a point above the productive soil layer. And the multilateral one has several faces, while the branch point is lower.

Gas well drilling

It will not do without exploration, because it allows you to clarify mineral reserves and collect data for drawing up a project for the development of a deposit.

The most important part of gas production work is the operational "pit", because it is with the help of it that this magical process of oil and gas production takes place. Operational, in turn, can be divided into several subtypes, such as:

• Mining main
• Discharge
• Reserve
• Estimated
• Control
• Special purpose
• Understudy

All of them play a huge role in this complex of gas production operations. The first ones are intended directly for gas production. Injection - to maintain the required pressure in productive formations. Reserve - used to support the main fund when the reservoir is heterogeneous. Evaluation and control are used to monitor changes in pressure in the formations, its saturation and clarify its boundaries. Special purposes are required for collecting industrial water and eliminating industrial water. And back-ups are needed in case of wear of the main production and injection ones.

Drilling methods

Experts identify several methods by which oil drilling is carried out.

• rotary - is one of the most commonly used drilling methods. A bit runs deep into the rock and rotates simultaneously with the drill pipes. Rotary drilling speed directly depends on the strength of the rocks and their resistance index. The popularity of this method is due to the fact that it is possible to adjust the value of the smoking moment depending on the strength and density of rocks and soils. In addition, rotary drilling is capable of withstanding rather heavy loads during a long-term working process;
• turbine - the main difference between this method and the rotary one is the use of a bit, which works in tandem with the turbine of a turbine drill. The process of rotation of the bit and drill is provided due to the pressure of the force of water, which moves in a certain direction between the stator and the rotor;
• screw - the working unit, with the help of which screw drilling for oil is carried out, consists of many mechanical screws that drive the drill bit. At the moment, the screw method is rarely used.

Its stages

The modern industry uses several types of drilling, but they all consist of these basic stages.

Well design for oil and gas developed and refined in accordance with the specific geological conditions of drilling in a given area. It must ensure the fulfillment of the assigned task, i.e. reaching the design depth, opening oil and gas deposits and carrying out the entire set of studies and work in the well, including its use in the field development system.

The design of the well depends on the complexity of the geological section, the method of drilling, the purpose of the well, the method of opening the productive horizon and other factors.

Initial data for well design design include the following information:

the purpose and depth of the well;

target horizon and reservoir rock characteristics;

geological section at the location of the well with identification of zones of possible complications and indication of reservoir pressures and hydraulic fracturing pressure by intervals;

the diameter of the production string or the final diameter of the well, if the running of the production string is not provided.

Design order well designs for oil and gas next.

Is selected bottomhole section of a well ... The design of the well in the interval of the productive formation should provide the best conditions for the flow of oil and gas into the well and the most efficient use of the formation energy of the oil and gas reservoir.

The required the number of casing strings and the depths of their running... For this purpose, a graph of changes in the coefficient of anomalous formation pressures k, and the index of absorption pressures kspl.

The choice is justified the diameter of the production string and the diameters of the casing strings and bits are agreed... The diameters are calculated from the bottom up.

Cementing intervals selected... From the casing shoe to the wellhead, the following are cemented: casing conductors in all wells; intermediate and production strings in exploration, prospecting, parametric, reference and gas wells; intermediate columns in oil wells depth over 3000 m; on a section with a length of at least 500 m from the shoe of an intermediate string in oil wells with a depth of up to 3004) m (provided that all permeable and unstable rocks are covered with a grouting slurry).

The interval for cementing production strings in oil wells can be limited by the section from the shoe to the section located at least 100 m above the lower end of the previous intermediate string.

All casing strings in offshore wells are cemented along their entire length.

Stages of designing a hydraulic program for flushing a well with drilling fluids.

The hydraulic program is understood as a set of adjustable parameters of the well flushing process. The nomenclature of the adjustable parameters is as follows: indicators of the properties of the drilling fluid, the flow of mud pumps, the diameter and the number of jet nozzles.

When drawing up a hydraulic program, it is assumed:

Eliminate formation fluids and lost circulation;

Prevent erosion of the borehole walls and mechanical dispersion of the transported cuttings in order to exclude the production of drilling mud;

Ensure the removal of drilled rock from the annular space of the well;

Create conditions for maximum use of the jetting effect;

Rationally use the hydraulic power of the pumping unit;

Exclude emergency situations when stopping, circulating and starting mud pumps.

The listed requirements for the hydraulic program are satisfied provided that the multifactor optimization problem is formalized and solved. Known design schemes for the flushing process of drilled wells are based on calculations of hydraulic resistances in the system for a given pump flow and indicators of the properties of drilling fluids.

Such hydraulic calculations are carried out according to the following scheme. First, based on empirical recommendations, the speed of movement of the drilling fluid in the annular space is set and the required flow of mud pumps is calculated. According to the passport characteristics of the mud pumps, the diameter of the bushings is selected, capable of providing the required flow. Then, according to the appropriate formulas, hydraulic losses in the system are determined without taking into account the pressure losses in the bit. The area of ​​the jetting bit nozzles is selected based on the difference between the maximum rated discharge pressure (corresponding to the selected bushings) and the calculated pressure losses due to hydraulic resistances.

The principles of choosing a drilling method: the main selection criteria, taking into account the depth of the well, temperature in the wellbore, the complexity of drilling, the design profile, and other factors.

The choice of a drilling method, the development of more effective methods for destroying rocks at the bottom of a well and solving many issues related to the construction of a well are impossible without studying the properties of the rocks themselves, the conditions of their occurrence and the effect of these conditions on the properties of rocks.

The choice of the drilling method depends on the structure of the formation, its reservoir properties, the composition of the liquids and / or gases contained in it, the number of productive layers and the coefficients of anomalous formation pressures.

The choice of the drilling method is based on a comparative assessment of its effectiveness, which is determined by many factors, each of which, depending on the geological and methodological requirements (GMT), purpose and drilling conditions, can be of decisive importance.

The choice of the method for drilling a well is also influenced by the purpose of drilling operations.

When choosing a drilling method, one should be guided by the purpose of the well, the hydrogeological characteristics of the aquifer and the depth of its occurrence, the volume of work on the development of the formation.

Combination of BHA parameters.

When choosing a drilling method, in addition to technical and economic factors, it should be borne in mind that, in comparison with the BHA, rotary BHA based on a downhole motor are much more technologically advanced and reliable in operation, more stable on the design trajectory.

Deflection force on the bit versus borehole curvature for stabilizing BHA with two centralizers.

When choosing a drilling method, in addition to technical and economic factors, it should be taken into account that, in comparison with a BHA based on a downhole motor, rotary BHAs are much more technologically advanced and more reliable in operation, more stable on the design trajectory.

To substantiate the choice of the method of drilling in post-salt deposits and confirm the above conclusion about the rational method of drilling, the technical indicators of turbine and rotary drilling of wells were analyzed.

In case of choosing the method of drilling with downhole hydraulic motors, after calculating the axial load on the bit, it is necessary to select the type of downhole motor. This choice is made taking into account the specific torque on the bit rotation, the axial load on the bit and the density of the drilling fluid. The technical characteristics of the selected downhole motor are taken into account when designing the bit RPM and the hydraulic flush program.

Question about choice of drilling method should be decided on the basis of a feasibility study. The main indicator for choosing a drilling method is profitability - the cost of 1 meter of penetration. [ 1 ]

Before proceeding to choice of drilling method for deepening the wellbore using gaseous agents, it should be borne in mind that their physical and mechanical properties introduce quite definite limitations, since some types of gaseous agents are not applicable for a number of drilling methods. In fig. 46 shows possible combinations different types gaseous agents with modern drilling methods. As can be seen from the diagram, the most universal from the point of view of the use of gaseous agents are the methods of drilling with a rotor and an electric drill, less universal is the turbine method, which is used only when using aerated liquids. [ 2 ]

The power-to-weight ratio of the PBU has less effect on choice of drilling methods and their varieties than the power-to-weight ratio of the onshore drilling rig, since, in addition to the drilling equipment itself, the PBU is equipped with auxiliary equipment necessary for its operation and holding at the drilling point. In practice, the drilling and auxiliary equipment works alternately. The minimum required power-to-weight ratio of the MODU is determined by the energy consumed by the auxiliary equipment, which is sometimes greater than that required for the drilling drive. [ 3 ]

Eighth, section technical project dedicated to choice of drilling method, sizes of downhole motors and drilling lengths, development of drilling modes. [ 4 ]

In other words, the choice of one or another well profile determines to a large extent choice of drilling method5 ]

The transportability of the PBU does not depend on the metal consumption and power-to-weight ratio of the equipment and does not affect choice of drilling method, since it is towed without dismantling the equipment. [ 6 ]

In other words, the choice of a particular type of well profile determines to a large extent choice of drilling method, bit type, hydraulic drilling program, drilling parameters and vice versa. [ 7 ]

The pitching parameters of a floating base should be determined by calculation already at the initial stages of hull design, since the operating range of sea waves depends on this, at which normal and safe operation is possible, as well as choice of drilling method, systems and devices to reduce the impact of rolling on the working process. Decrease in pitching can be achieved by rational selection of the size of the hulls, their mutual arrangement and the use of passive and active means to combat pitching. [ 8 ]

Drilling of wells and wells remains the most common method for exploration and exploitation of groundwater. Choosing a drilling method determine: the degree of hydrogeological study of the area, the purpose of the work, the required reliability of the obtained geological and hydrogeological information, the technical and economic indicators of the considered drilling method, the cost of 1 m3 of produced water, the life of the well. The choice of drilling technology is influenced by the temperature of groundwater, the degree of their mineralization and aggressiveness towards concrete (cement) and iron. [ 9 ]

When drilling ultra-deep wells, the prevention of borehole deviations is very important due to the negative consequences of the borehole curvature during its deepening. Therefore, at selection of methods for drilling ultra-deep wells, and especially their upper intervals, attention should be paid to maintaining the verticality and straightness of the wellbore. [ 10 ]

The choice of the drilling method should be decided on the basis of a feasibility study. The main indicator for choice of drilling method is profitability - the cost of 1 m of penetration. [ 11 ]

So, the speed of rotary drilling with mud washing exceeds the speed of percussion-rope drilling by 3 - 5 times. Therefore, the decisive factor for choice of drilling method it should be economic analysis. [12 ]

The technical and economic efficiency of a project for the construction of oil and gas wells largely depends on the validity of the deepening and flushing process. The design of the technology of these processes includes choice of drilling method, the type of rock-breaking tool and drilling modes, the design of the drill string and its bottom layout, the hydraulic deepening program and indicators of the properties of the drilling fluid, the types of drilling fluids and the required amounts of chemicals and materials to maintain their properties. The adoption of design decisions determines the choice of the type of drilling rig, which also depends on the design of the casing strings and the geographic conditions of drilling. [ 13 ]

Application of the results of solving the problem creates a wide opportunity for deep, extensive analysis of bit development in a large number of objects with a wide variety of drilling conditions. In this case, it is also possible to prepare recommendations for choice of drilling methods, downhole motors, mud pumps and flushing fluid. [ 14 ]

In the practice of constructing water wells, the following drilling methods have become widespread: rotary with direct flushing, rotary with back flushing, rotary with air blowing and percussion rope. Terms of use different ways drilling is determined by the actual technical and technological features of drilling rigs, as well as the quality of work on the construction of wells. It should be noted that for choosing a method for drilling wells on water, it is necessary to take into account not only the rate of penetration of wells and the manufacturability of the method, but also the provision of such parameters of the opening of the aquifer, in which the deformation of the rocks in the bottomhole zone is observed to a minimum and its permeability does not decrease in comparison with the reservoir. [ 1 ]

It is much more difficult to choose a drilling method for deepening a vertical wellbore. If, when drilling out the interval selected based on the practice of drilling with the use of drilling fluids, it is possible to expect the curvature of the vertical wellbore, then, as a rule, hammers with the appropriate type of bit are used. If no curvature is observed, then choice of drilling method is carried out as follows. For soft rocks (soft shale, gypsum, chalk, anhydrite, salt and soft limestone), it is advisable to use electric drilling with bit rotation rates up to 325 rpm. As the rock hardness increases, the drilling methods are arranged in the following sequence: positive displacement motor, rotary drilling and rotary percussion drilling. [ 2 ]

From the point of view of increasing the speed and reducing the cost of construction of wells with a PBU, the method of drilling with a hydrotransport of the core is interesting. This method, with the exclusion of the above-mentioned limitations of its application, can be used in the exploration of placers from the rig at the prospecting and prospecting and appraisal stages of geological exploration. The cost of drilling equipment, regardless of the drilling method, does not exceed 10% of the total cost of the rig. Therefore, the change in the cost of drilling equipment alone does not have a significant effect on the cost of manufacturing and maintenance of the PBU and on choice of drilling method... The increase in the cost of the MODU is justified only if it improves the working conditions, increases the safety and speed of drilling, reduces the number of downtime due to meteorological conditions, and extends the drilling season in time. [ 3 ]

Choosing the type of bit and drilling mode: selection criteria, methods of obtaining information and processing it to establish optimal modes, control the value of parameters .

The choice of a bit is made on the basis of knowledge of the rocks (g / p) that make up the given interval, i.e. by the category of hardness and by the category of abrasiveness g / p.

In the process of drilling an exploration well, and sometimes a production well, rocks are periodically sampled in the form of intact pillars (cores) for compiling a stratigraphic section, studying the lithological characteristics of rocks passed through, revealing the content of oil, gas in the pores of rocks, etc.

Core bits are used to extract the core to the surface (Fig. 2.7). Such a bit consists of a drill head 1 and a core set connected to the drill head body by means of a thread.

Rice. 2.7. Diagram of a core bit device: 1 - drill head; 2 - core; 3 - grouper; 4 - core set body; 5 - ball valve

Depending on the properties of the rock in which core drilling is carried out, roller cone, diamond and carbide drill heads are used.

Drilling mode is a combination of parameters that significantly affect the performance of the bit, which the driller can change from his console.

Pd [kN] - load on the bit, n [rpm] - rotational speed of the bit, Q [l / s] - flow rate (feed) of industrial. w, H [m] - drilling on the bit, Vm [m / h] - fur. penetration rate, Vav = H / tБ - average,

Vм (t) = dh / dtБ - instantaneous, Vр [m / h] - running speed of drilling, Vр = H / (tБ + tССО + tВ), C [rub / m] - operating costs per 1m of penetration, C = ( Cd + Cch (tB + tSPO + tB)) / H, Cd - bit cost; Cch - the cost of 1 hour of work of the drill. rev.

Stages of the search for the optimal mode - at the design stage - operational optimization of the drilling mode - adjusting the design mode taking into account information obtained during the drilling process.

In the design process, we use inf. obtained by drilling well. in this

region, analog. conv., data on golog. section of the well., the recommendations of the manufacturer of the drill. tools., working characteristics of downhole motors.

There are 2 ways to choose a bit at the bottom: graphic and analytical.

The cutters in the drill head are mounted in such a way that the rock in the center of the borehole bottom does not collapse during drilling. This creates conditions for the formation of core 2. There are four-, six- and further eight-cone drill heads designed for coring in various formations. The location of rock cutting elements in diamond and carbide drill heads also allows rock formation to be destroyed only along the periphery of the borehole bottom.

When the well is deepened, the formed rock column enters the core set, which consists of body 4 and a core barrel (ground pad) 3. The body of the core barrel is used to connect the drill head to the drill string, place the ground pad and protect it from mechanical damage, as well as for the passage of flushing fluid between him and the grunton. The ground tool is designed to receive core samples, preserve it during drilling and when lifting to the surface. To perform these functions, in the lower part of the soil sock, core lifters and core holders are installed, and at the top - a ball valve 5, which passes through itself the liquid displaced from the soil soak when it is filled with a core.

According to the method of installation of the soil drill in the body of the core set and in the drill head, there are core bits with a removable and non-removable soil drill.

Core bits with a removable dredger allow you to lift a dredger with a core without lifting the drill string. To do this, a catcher is lowered into the drill string on a rope, with the help of which a grounding tool is removed from the core set and lifted to the surface. Then, using the same catcher, an empty dredger is lowered and installed in the body of the core set, and drilling with coring continues.

Core bits with a removable ground support are used for turbine drilling, and with fixed ones - for rotary drilling.

Schematic diagram of testing a productive horizon using a pipe formation tester.

Formation testers are widely used in drilling and provide the greatest amount of information about the target being tested. A modern domestic formation tester consists of the following main units: a filter, a packer, a sampler itself with equalizing and main inlet valves, a shut-off valve and a circulation valve.

Schematic diagram of one-stage cementing. The change in pressure in the cementing pumps involved in this process.

The one-stage well cementing method is the most common. With this method, the cement slurry is supplied at a given interval at a time.

The final stage of drilling operations is accompanied by a process that involves cementing the wells. The viability of the entire structure depends on how well these works are carried out. The main goal pursued in the process of carrying out this procedure is to replace the drilling mud with cement, which has another name - cement slurry. Well cementing involves the introduction of a composition that must harden, turning into stone. Today there are several ways to carry out the process of cementing wells, the most commonly used of them is more than 100 years old. It is a single-stage casing cementing that was introduced to the world in 1905 and is used today with only a few modifications.

Cementing process

The technology for cementing wells involves 5 main types of work: the first is mixing the grouting solution, the second is the injection of the composition into the well, the third is the supply of the mixture by the selected method to the annulus, the fourth is the hardening of the grouting mixture, the fifth is checking the quality of the work performed.

Before starting work, a cementing scheme should be drawn up, which is based on the technical calculations of the process. It will be important to take into account mining and geological conditions; the length of the interval that needs strengthening; borehole design characteristics, as well as its condition. It should be used in the process of calculations and the experience of carrying out such work in a certain area.

Figure 1. Schematic of the single-stage cementing process.

In fig. 1 you can see the schematic diagram of the single-stage cementing process. "I" - start of the mixture supply to the barrel. "II" is the supply of the mixture injected into the well when the solution moves down the casing, "III" is the start of pushing the grouting compound into the annulus, "IV" is the final stage of pushing the mixture. Diagram 1 - a pressure gauge, which is responsible for monitoring the pressure level; 2 - cementing head; 3 - top stopper; 4 - bottom plug; 5 - casing; 6 - borehole walls; 7 - stop ring; 8 - liquid intended for forcing the cement slurry; 9 - drilling mud; 10 - cement mixture.

The schematic diagram of a two-stage cementing with a fracture in time. Advantages and disadvantages.

Step cementing with a break in time. The cementing interval is divided into two parts, and a special cementing sleeve is installed in the well near the interface. Outside the column, above and below the coupling, centering lights are placed. First, cement the lower part of the column. To do this, 1 portion of cr is pumped into the casing in the volume required to fill the cp from the casing shoe to the cementing sleeve, then the displacement fluid. For stage 1 cementing, the volume of displacement fluid must be equal to the internal volume of the column. After pumping the pz, the ball is dropped into the column. Under the force of gravity, the ball descends down the string and sits on the lower sleeve of the cementing sleeve. Then they start pumping the PS into the column again: the pressure in it above the plug increases, the sleeve moves down to the stop, and the PS goes out of the column through the open holes. Through these holes, the well is flushed until the cement slurry hardens (from several hours to a day). After that, 2 portions of cr are pumped in, freeing the upper plug and the solution is displaced with 2 portions of pzh. The plug, having reached the sleeve, is reinforced with pins in the body of the cementing sleeve and pushes it down; in this case, the sleeve closes the holes of the coupling and separates the cavity of the column from the checkpoint. After hardening, the plug is drilled out. The place of installation of the coupling is chosen depending on the reasons that prompted the use of cementing steps. In gas wells, the cementing sleeve is installed 200-250m above the top of the productive horizon. If there is a risk of loss during well cementing, the location of the collar is calculated so that the sum of the hydrodynamic pressures and the static pressure of the mud column in the annulus is less than the fracture pressure of the weak formation. Always place the cement sleeve against stable impermeable rock and center it with lanterns. They are used: a) if the absorption of the solution is inevitable during single-stage cementing; b) if a reservoir with AED is opened and during the setting of the solution after one-stage cementing, overflows and gas showings may occur; c) if single-stage cementing requires simultaneous participation in the operation of a large number of cement pumps and mixing machines. Disadvantages: large gap in time between the end of the cementing of the lower section and the beginning of the cementing of the upper section. This disadvantage can be mainly eliminated by installing an external packer at approx, below the cement sleeve. If, at the end of the lower stage cementing, the annular space of the well is sealed with a packer, then you can immediately start cementing the upper section.

Principles of calculating the axial tensile strength of the casing for vertical wells. The specifics of calculating columns for deviated and deviated wells.

Casing calculation start by determining the excess external pressures. [ 1 ]

Calculation of casing strings carried out during design in order to select the wall thicknesses and strength groups of the casing pipe material, as well as to verify the compliance of the standard safety factors laid down in the design with the expected ones, taking into account the prevailing geological, technological, market conditions of production. [ 2 ]

Calculation of casing strings with a trapezoidal thread in tension is carried out based on the permissible load. When running casing in sections, the length of the section is taken as the length of the casing. [ 3 ]

Casing calculation includes the identification of factors affecting casing damage and the selection of the most appropriate steel grades for each specific operation in terms of reliability and economy. The casing string design must meet the string requirements for completing and operating a well. [ 4 ]

Calculation of casing strings for deviated wells differs from that adopted for vertical wells by the choice of the tensile strength depending on the intensity of the borehole deviation, as well as by determining the external and internal pressures, in which the position of the points characteristic of a deviated well is determined by its vertical projection.

Calculation of casing strings produced according to the maximum values ​​of excess external and internal pressures, as well as axial loads (during drilling, testing, operation, well workover), while taking into account their separate and joint action.

The main difference casing calculation for directional wells from the calculation for vertical wells, it consists in determining the tensile strength, which is made depending on the intensity of the borehole curvature, as well as calculating the external and internal pressures taking into account the elongation of the wellbore

Casing selection and casing calculation strength tests are carried out taking into account the maximum expected excess external and internal pressures with complete replacement of the solution by the formation fluid, as well as axial loads on pipes and the aggressiveness of the fluid at the stages of well construction and operation based on existing structures.

The main loads when calculating the strength of the string are axial tensile loads from dead weight, as well as external and internal overpressure during cementing and well operation. In addition, other loads act on the column:

· Axial dynamic loads during unsteady column motion;

· Axial loads from the forces of friction of the string against the walls of the well during its running;

· Compressive loads from a part of its own weight when unloading the casing to the bottom;

· Bending loads arising in deviated wells.

Calculation of production casing for an oil well

Symbols used in formulas:

Distance from the wellhead to the casing shoe, m L

Distance from the wellhead to the cement slurry, m h

Distance from the wellhead to the liquid level in the string, m N

Density of the pressure fluid, g / cm 3 r coolant

Drilling fluid density behind the casing, g / cm 3 r BR

Density of liquid in the column r B

Density of grouting cement slurry behind the casing r CR

Internal overpressure at a depth z, MPa P VIz

Excessive external pressure at a depth z P NIz

Excessive critical external pressure, at which the voltage

The pressure in the pipe body reaches the yield point Р КР

Reservoir pressure at depth z R PL

Crimping pressure

Total column weight of selected sections, N (MN) Q

Unloading factor of the cement ring k

Safety factor when calculating for external overpressure n КР

Safety factor for tensile design n STR

Figure 69. Well cementing scheme

At h> H Determine the excess external pressure (at the stage of the end of operation) for the following characteristic points.

1: z = 0; P n and z = 0.01ρ b.p * z; (86)

2: z = H; R n and z = 0.01ρ b. p * H, (MPa); (87)

3: z = h; R n and z = (0.01 [ρ b.p h - ρ in (h - H)]), (MPa); (88)

4: z = L; R n and z = (0.01 [(ρ center - ρ in) L - (ρ center - ρ b. R) h + ρ in H)] (1 - k), (MPa). (89)

We build a diagram ABCD(Figure 70). To do this, in the horizontal direction on the accepted scale, we postpone the values ρ n and z in points 1 -4 (see diagram) and we connect these points in series with each other by straight line segments

Figure 70. Diagrams of external and internal

excess pressures

We determine the excess internal pressures from the condition of testing the casing for tightness in one step without a packer.

Wellhead pressure: R y = R pl - 0.01 ρ v L (MPa). (90)

The main factors affecting the quality of well cementing and the nature of their influence.

The quality of separation of permeable formations by cementing depends on the following groups of factors: a) the composition of the plugging mixture; b) the composition and properties of the cement slurry; c) cementing method; d) completeness of replacement of the displacement fluid with cement slurry in the annulus of the well; e) the strength and tightness of the adhesion of the plugging stone with the casing and the borehole walls; f) the use of additional means to prevent the occurrence of filtration and the formation of suffusion channels in the cement slurry during the period of thickening and setting; g) well dormancy during the period of thickening and setting of the cement slurry.

Principles of calculating the required quantities of grouting materials, mixing machines and cementing units for the preparation and injection of grouting slurry into the casing. Scheme of piping of cementing equipment.

It is necessary to calculate the cementing for the following conditions:

- the reserve factor at the height of the cement slurry, introduced to compensate for factors that cannot be taken into account (determined statistically from the cementing data of previous wells); and - respectively, the average well diameter and the outer diameter of the production casing, m; - the length of the cementing section, m; - the average inner diameter of the production casing, m; - the height (length) of the cement nozzle left in the casing, m; - the safety factor of the displacement fluid , taking into account its compressibility, - = 1.03; - - coefficient taking into account the loss of cement during loading and unloading operations and preparation of the solution; - - - cement slurry density, kg / m3; - drilling fluid density, kg / m3; n - relative water content; - water density, kg / m3; - bulk density of cement, kg / m3;

The volume of cement slurry required for cementing a given interval of the well (m3): Vc.p. = 0.785 * kp * [(2-dn2) * lc + d02 * hc]

Displacement fluid volume: Vpr = 0.785 * - * d2 * (Lc-);

Buffer fluid volume: Vb = 0.785 * (2-dн2) * lb;

Mass of backfill Portland cement: Мts = - ** Vtsr / (1 + n);

The volume of water for the preparation of grouting solution, m3: Vw = Mts * n / (kts * pw);

Before cementing, dry grouting material is loaded into the bins of mixing machines, the required number of which is: nc = MC / Vcm, where Vcm is the volume of the mixer bunker.

Methods of equipping the lower section of the well in the zone of the productive formation. Conditions under which it is possible to use each of these methods.

1. A productive deposit is drilled without preliminarily overlapping the overlying rocks with a special casing string, then the casing string is lowered to the bottom and cemented. To communicate the inner cavity of the casing string with the productive reservoir, it is perforated, i.e. a large number of holes are shot through the column. The method has the following advantages: easy to implement; allows you to selectively communicate the well with any interlayer of a productive reservoir; the cost of the actual drilling work may be less than with other methods of entry.

2. Previously, the casing string is lowered and cemented to the top of the productive reservoir, isolating the overlying rocks. The reservoir is then drilled with smaller bits and the wellbore is left open below the casing shoe. The method is applicable only if the productive deposit is composed of stable rocks and is saturated with only one fluid; it does not allow for the selective exploitation of any interlayer.

3. It differs from the previous one in that the wellbore in the productive reservoir is blocked with a filter, which is suspended in the casing; the space between the screen and the string is often isolated with a packer. The method has the same advantages and limitations as the previous one. Unlike the previous one, it can be adopted in cases where a productive deposit is composed of rocks that are not sufficiently stable during exploitation.

4. The well is cased with a string of pipes to the top of the productive deposit, then the latter is drilled out and covered with a liner. The liner is cemented along its full length and then perforated against a predetermined interval. With this method, significant contamination of the reservoir can be avoided by choosing a flushing fluid only taking into account the situation in the reservoir itself. It allows selective exploitation of various interlayers and allows you to quickly and cost-effectively develop a well.

5. It differs from the first method only in that the casing string is lowered into the well after drilling the productive reservoir, the lower section of which is pre-made of pipes with slotted holes, and in that it is cemented only above the top of the productive reservoir. The perforated section of the column is placed against the pay reservoir. With this method, it is impossible to ensure selective exploitation of one or another interlayer.

Factors taken into account when choosing a grouting material for cementing a specific interval of a well.

The choice of grouting materials for cementing casing strings is determined by the lithofacies characteristics of the section, and the main factors that determine the composition of the grouting slurry are temperature, reservoir pressure, fracturing pressure, the presence of salt deposits, the type of fluid, etc. In general, grouting slurry consists of grouting cement, medium mixing, reagents - accelerators and retarders of the setting time, reagents - reducers of the filtration rate and special additives. Oil well cement is selected as follows: according to the temperature interval, according to the interval of measuring the density of the cement slurry, according to the types of fluid and deposits in the cementing interval, the brand of cements is specified. The mixing medium is selected depending on the presence of salt deposits in the section of the well or the degree of salinity of formation waters. To prevent premature thickening of the cement slurry and watering of productive horizons, it is necessary to reduce the filtration rate of the cement slurry. NTF, hypane, CMC, PVS-TR are used as reducers of this indicator. To increase the thermal stability of chemical additives, structure dispersion systems and remove side effects when using some reagents, clay, caustic soda, calcium chloride and chromates are used.

Selecting a core set for obtaining high-quality core.

Core-receiving tool - a tool that provides reception, separation from the massif of l / c and preservation of the core during the drilling process and during transportation through the well. up to retrieving it for repetition for research. Varieties: - P1 - for rotary drilling with a removable (retrievable by BT) core receiver, - P2 - non-removable core receiver, - T1 - for turbine drilling with a removable core receiver, - T2 - with a non-removable core receiver. Types: - for taking coring from a massif of dense g / p (double core barrel with a core receiver, insulated from the pan ducts and rotating together with the body of the projectile), - for sampling coring in g / c fractured, crumpled, or alternating in density and hardness (non-rotating core receiver, suspended on one or several bearings and reliable core removers and core holders), - for taking coring in bulk l / c, easily resolved. and erosion. PZh (must ensure complete sealing of the core and overlap of the core hole at the end of drilling)

Design features and areas of application of drill pipes.

Leading drill pipes are used to transfer rotation from the rotor to the drill string. Drill pipes are usually square or hexagonal. They are made in two versions: prefabricated and one-piece. Drill pipes with upset ends are upset outwards and inwards. Drill pipes with welded connecting ends are made of two types: TBPV - with welded connecting ends along the outwardly upsetting part and TBP - with welded connecting ends along the non-upsetting part. at the ends of the pipe, cylindrical thread with a pitch of 4 mm, persistent connection of the pipe with the lock, tight mating with the lock. Drill pipes with stabilizing collars differ from standard pipes by the presence of smooth pipe sections directly behind the screwed on nipple and lock sleeve and stabilizing sealing collars on the locks, tapered (1:32) trapezoidal thread with a pitch of 5.08 mm with an inner diameter mating ……….

The principles of calculating the drill string when drilling with a downhole motor .

Calculation of the BK when drilling the SP of a straight-inclined section of an inclined well

Qprod = Qcosα; Qnorm = Qsinα; Ftr = μQn = μQsinα; (μ ~ 0.3);

Pprod = Qprod + Ftr = Q (sinα + μsinα)

LI> = Lsd + Lubt + Lnk + lI1 +… + l1n If not, then lIny = LI- (Lsd + Lubt + Lnk + lI1 +… + l1 (n-1))

Calculation of the drilling hole when drilling the SD of a curved section of an inclined well.

II

Pi = FIItr + QIIprojects QIIprojects = | goR (sinαк-sinαн) |

Pi = μ | ± 2goR2 (sinαк-sinαн) -goR2sinαкΔα ± PнΔα | + | goR2 (sinαк-sinαн) |

Δα = - If>, then cos “+”

"-Pн" - when dialing curvature "+ Pн" - when resetting curvature

it is believed that the BC section consists of one section = πα / 180 = 0.1745α

The principles of calculating the drill string for rotary drilling.

Static calculation, when alternating cyclic stresses are not taken into account, but constant bending and torsion stresses are taken into account

For sufficient strength or endurance

Static calculation for vertical wells:

;

Kz = 1.4 - at norm. conv. Kz = 1.45 - with complications. conv.

for sloping areas

;

;

Drilling mode. Optimization technique

Drilling mode is a combination of parameters that significantly affect the performance of the bit and which the driller can change from his control panel.

Pd [kN] - load on the bit, n [rpm] - rotational speed of the bit, Q [l / s] - flow rate (feed) of industrial. w, H [m] - drilling on the bit, Vm [m / h] - fur. penetration rate, Vsr = H / tБ - average, Vm (t) = dh / dtБ - instantaneous, Vр [m / h] - trip speed of drilling, Vр = H / (tБ + tСПП + tВ), C [rub / m ] - operating costs per 1m of penetration, C = (Cd + Cch (tB + tSPO + tB)) / H, Cd - cost price of the bit; Cch - the cost of 1 hour of work of the drill. rev. Drilling mode optimization: maxVp - exploration. well, minC - explo. well ..

(Pd, n, Q) opt = minC, maxVp

C = f1 (Pd, n, Q); Vp = f2 (Pd, n, Q)

Stages of the search for the optimal mode - at the design stage - operational optimization of the drilling mode - adjusting the design mode taking into account the information obtained during the drilling process

In the design process, we use inf. obtained by drilling well. in this region, in an analogue. conv., data on golog. section of the well., the recommendations of the manufacturer of the drill. tools., working characteristics of downhole motors.

2 ways to select the top of the bit downhole:

- graphic tgα = dh / dt = Vm (t) = h (t) / (topt + tsp + tv) - analytical

Classification of methods of stimulation of inflow during well development.

Development means a set of works to induce fluid flow from a productive formation, clean up the near-wellbore zone from contamination and provide conditions for obtaining the highest possible well productivity.

To get an inflow from the productive horizon, it is necessary to reduce the pressure in the well significantly below the reservoir pressure. Exists different ways pressure reductions based either on replacing a heavy drilling fluid with a lighter one, or on a smooth or sharp decrease in the fluid level in the production casing. To induce an inflow from a formation composed of weakly stable rocks, methods of smooth pressure reduction or with a small amplitude of pressure fluctuations are used in order to prevent the destruction of the reservoir. If the reservoir is composed of a very solid rock, then often the greatest effect is obtained with a sharp creation of large depressions. When choosing the method of inflow stimulation, the magnitude and nature of the depression, it is necessary to take into account the stability and structure of the reservoir rock, the composition and properties of the liquids saturating it, the degree of contamination during opening, the presence of permeable horizons located close to the top and bottom, the strength of the casing and the state of the well support. With a very sharp creation of a large depression, a violation of the strength and tightness of the lining is possible, and with a short but strong increase in pressure in the well, fluid absorption into the productive formation is possible.

Replacing a heavy liquid with a lighter one. The tubing string is run almost to the bottom if the reservoir is composed of well-stable rock, or approximately to the top perforations if the rock is not stable enough. The fluid is usually replaced by the reverse circulation method: a mobile piston pump is pumped into the annular space, the density of which is less than the density of the drilling fluid in the production string. As the lighter fluid fills the annulus and displaces the heavier fluid in the tubing, the pressure in the pump increases. It reaches its maximum the moment the light fluid approaches the tubing shoe. p umt = (p pr -r standby) qz nkt + p nkt + p mt, where p pr and p standby is the density of heavy and lightweight liquids, kg / m; z tubing - the depth of running the tubing string, m; p nkt and p mt are hydraulic losses in the tubing string and in the annular space, Pa. This pressure should not exceed the pressure of the production casing pressure p umt< p оп.

If the rock is weakly resistant, the value of the density decrease in one circulation cycle is reduced even more, sometimes to p -p = 150-200 kg / m3. When planning work to call the inflow, you should take this into account and prepare in advance containers with a stock of liquids of appropriate densities, as well as equipment for regulating density.

When pumping a lighter fluid, the well is monitored according to the readings of manometers and the ratio of the flow rates of the fluids pumped into the annular space and flowing out of the tubing. If the flow rate of the outgoing fluid increases, this is a sign of the beginning of inflow from the formation. In the case of a rapid increase in flow rate at the outlet of the tubing and a drop in pressure in the annular space, the outflow flow is directed through a line with a choke.

If the replacement of the heavy drilling fluid with clean water or degassed oil is not enough to obtain a stable flow from the formation, other methods of increasing the drawdown or stimulating effect are resorted to.

When the reservoir is composed of poorly stable rock, further pressure reduction is possible by replacing water or oil with a gas-liquid mixture. To do this, a piston pump and a mobile compressor are connected to the annulus of the well. After flushing the well to clean water, the pump flow is adjusted so that the pressure in it is significantly lower than the allowable pressure for the compressor, and the downward flow rate is about 0.8-1 m / s, and the compressor is turned on. The air flow supplied by the compressor is mixed in the aerator with the water flow supplied by the pump, and the gas-liquid mixture enters the annular space; At the same time, the pressure in the compressor and pump will begin to increase and reach a maximum at the moment when the mixture approaches the tubing shoe. As the gas-liquid mixture moves along the tubing string and the still water is displaced, the pressure in the compressor and pump will decrease. The degree of aeration and reduction of static pressure in the well is increased in small steps after completion of one or two circulation cycles so that the pressure in the annular space at the wellhead does not exceed the allowable compressor.

A significant drawback of this method is the need to maintain a sufficiently high flow rate of air and water. It is possible to significantly reduce the consumption of air and water and ensure an effective pressure reduction in the well by using two-phase foam instead of the water-air mixture. Such foams are prepared on the basis of saline water, air and a suitable foaming surfactant.

Reducing the pressure in the well using a compressor. To induce inflow from strata composed of strong, stable rocks, the compressor method is widely used to reduce the liquid level in the well. The essence of one of the varieties of this method is as follows. A mobile compressor injects air into the annular space in such a way as to push the liquid level in it as deeply as possible, aerate the liquid in the tubing and create a depression necessary to obtain an inflow from the productive formation. If the static fluid level in the well before the start of the operation is at the wellhead, the depth to which the level in the annular space can be pushed back when air is injected.

If z cn> z tubing, then the air pumped by the compressor will break into the tubing and begin to aerate the liquid in them as soon as the level in the annular space drops to the tubing shoe.

If z cn> z tubing, then preliminarily when running the tubing into the wells, special starting valves are installed in them. The upper starting valve is installed at a depth of z "start = z" cn - 20m. When air is injected by the compressor, the starting valve will open at the moment when the pressures in the tubing and in the annular space at the depth of its installation are equal; in this case, air will begin to escape through the valve into the tubing and aerate the liquid, and the pressure in the annulus and in the tubing will decrease. If, after reducing the pressure in the well, inflow from the formation does not begin and almost all of the liquid from the tubing above the valve is displaced by air, the valve will close, the pressure in the annular space will again increase, and the fluid level will drop to the next valve. The depth z "" of the installation of the next valve can be found from the equation if we put in it z = z "" + 20 and z st = z "ch.

If, before the start of the operation, the static fluid level in the well is located significantly below the wellhead, then when air is injected into the annular space and the fluid level is pushed back to the depth z cf, the pressure on the reservoir increases, which can cause the absorption of part of the fluid into it. It is possible to prevent absorption of fluid into the formation if a packer is installed at the lower end of the tubing string, and a special valve is installed inside the tubing, and with the help of these devices, the zone of the productive formation is separated from the rest of the well. In this case, when air is injected into the annular space, the pressure on the formation will remain unchanged until the pressure in the tubing string above the valve drops below the formation pressure. As soon as the drawdown is sufficient for the formation fluid inflow, the valve will rise and the formation fluid will begin to rise along the tubing.

After receiving an inflow of oil or gas, the well must work for some time with the highest possible flow rate, so that the drilling fluid and its filtrate, as well as other silty particles that have penetrated there, can be removed from the near-wellbore zone; in this case, the flow rate is regulated so that the destruction of the reservoir does not begin. Samples of the fluid flowing out of the well are periodically taken in order to study its composition and properties and control the content of solid particles in it. The decrease in the content of solid particles is used to judge the progress of cleaning the near-wellbore zone from pollution.

If, despite the creation of a large drawdown, the well flow rate is low, then they usually resort to various methods of stimulating the formation.

Classification of stimulation methods during well development.

Based on the analysis of controlled factors, it is possible to construct a classification of methods of artificial stimulation both on the formation as a whole and on the bottom-hole zone of each specific well. According to the principle of action, all methods of artificial influence are divided into the following groups:

1. Hydro-gas-dynamic.

2. Physicochemical.

3. Thermal.

4. Combined.

Among the methods of artificial stimulation of the reservoir, the most widespread are hydro-gas-dynamic methods associated with controlling the magnitude of reservoir pressure by injecting various fluids into the reservoir. Today, more than 90% of oil produced in Russia is associated with reservoir pressure control methods by injecting water into the reservoir, called reservoir pressure maintenance (RPM) methods of waterflooding. In a number of fields, reservoir pressure maintenance is carried out by gas injection.

Field development analysis shows that if the reservoir pressure is not high, the supply circuit is far enough from the wells, or the drainage mode is not active, the rate of oil recovery may be quite low; the oil recovery factor is also low. In all these cases, the use of one or another RPM system is necessary.

Thus, the main problems of managing the process of developing reserves by artificially stimulating the reservoir are associated with the study of waterflooding.

Methods of artificial influence on the bottomhole zones of the well have a significantly wider range of possibilities. The impact on the near wellbore zone is carried out already at the stage of the initial opening of the productive horizon in the process of well construction, which, as a rule, leads to a deterioration in the properties of the bottomhole zone. The most widely used methods of influencing the bottomhole zone during the operation of wells, which, in turn, are divided into methods of stimulation of inflow or injectivity and methods of limiting or isolating water inflow (repair and isolation works - RIR).

The classification of methods for stimulating the near wellbore zone in order to stimulate the inflow or injectivity is presented in tab. 1, and to restrict or isolate water inflows - in tab. 2... It is quite obvious that the above tables, being quite complete, contain only the most tested in practice methods of artificial influence on the CCD. They do not exclude, but on the contrary, suggest the need for additions both in terms of the methods of exposure and the materials used.

Before proceeding to consider the methods of managing the process of developing reserves, we note that the object of study is a complex system consisting of a reservoir (oil-saturated zone and a recharge area) with its own reservoir properties and saturating fluids and a certain number of wells systematically located on the reservoir. This system is unified in a hydrodynamic respect, from which it follows that any change in any of its elements automatically leads to a corresponding change in the operation of the entire system, i.e. this system is auto-adjustable.

Describe the technical means for obtaining operational information while drilling.

Information support for the process of drilling oil and gas wells is the most important link in the process of well construction, especially when introducing and developing new oil and gas fields.

The requirements for information support for the construction of oil and gas wells in this situation are to transfer information technologies to the category of information and information technologies, in which information support, along with obtaining the required amount of information, would give an additional economic, technological, or other effect. These technologies include the following complex works:

control of surface technological parameters and selection of the most optimal drilling modes (for example, selection of optimal loads on the bit, ensuring high speed penetrations);

downhole measurements and logging while drilling (MWD and LWD systems);

measurements and information collection, accompanied by simultaneous control of the drilling technological process (control of the trajectory of a horizontal well using controlled downhole orientators according to the data of downhole telemetry systems).

In the information support of the well construction process, a particularly important role is played by geological and technological research (GTI)... The main task of the GTI service is to study the geological structure of the well section, identify and evaluate productive formations and improve the quality of well construction based on the geological, geochemical, geophysical and technological information obtained during drilling. The operational information received by the GTI service is of great importance when drilling exploratory wells in poorly studied regions with difficult mining and geological conditions, as well as when drilling directional and horizontal wells.

However, due to the new requirements for the information support of the drilling process, the tasks solved by the GTI service can be significantly expanded. The highly qualified operator staff of the GTI batch working on the drilling rig is able to solve practically a full range of tasks for information support of the drilling process:

geological, geochemical and technological research;

maintenance and work with telemetry systems (MWD and LWD systems);

maintenance of stand-alone measurement and logging systems lowered on pipes;

control of drilling mud parameters;

well casing quality control;

formation fluid studies during testing and well testing;

wireline logging;

supervising services, etc.

In a number of cases, the combination of these works in GTI batches is economically more profitable and allows you to save on non-productive costs for the maintenance of specialized, narrowly focused geophysical crews, to minimize transportation costs.

However, there are currently no technical and software-methodological means to combine the listed works into a single technological chain at the GTI station.

Therefore, it became necessary to develop a more advanced GTI station of a new generation, which will expand the functionality of the GTI station. Consider the main areas of work in this case.

Basic requirements for modern GTI station is reliability, versatility, modularity and information content.

Station structure is shown in Fig. 1. It is built on the principle of distributed remote acquisition systems that are interconnected using a standard serial interface. The main downstream gathering systems are concentrators designed to decouple the serial interface and connect through them separate components of the station: a gas logging module, a geological instrument module, digital or analog sensors, information displays. Through the same concentrators, other autonomous modules and systems are connected to the acquisition system (to the operator's recording computer) - a well casing quality control module (manifold block), surface modules of downhole telemetry systems, geophysical data recording systems such as "Hector" or "Volcano" and etc.

Rice. 1. Simplified structural scheme GTI stations

Hubs must simultaneously provide galvanic isolation of communication and power supply circuits. Depending on the tasks assigned to the GTI station, the number of concentrators can be different - from several units to several dozen units. Software GTI station provides full compatibility and well-coordinated work in a single software environment of all technical means.

Process parameters sensors

Technological parameters sensors used in GTI stations are one of the most important components of the station. The accuracy of the readings and the reliability of the sensors' operation largely determines the efficiency of the mud logging service in solving problems of monitoring and operational management of the drilling process. However, due to the harsh operating conditions (wide temperature range from –50 to +50 ºС, aggressive environment, strong vibrations, etc.), the sensors remain the weakest and most unreliable link in the technical means of GTI.

Most of the sensors used in production batches of GTI were developed in the early 90s using domestic hardware components and primary measuring elements of domestic production. Moreover, due to the lack of choice, publicly available primary converters were used, which did not always meet the stringent requirements of work in a drilling rig. This explains the insufficiently high reliability of the sensors used.

The principles of measuring sensors and their design solutions are selected in relation to domestic drilling rigs of the old model, and therefore their installation on modern drilling rigs, and even more so on foreign-made drilling rigs, is difficult.

It follows from the above that the development of a new generation of sensors is extremely relevant and timely.

When developing GTI sensors, one of the requirements is their adaptation to all drilling rigs existing on the Russian market.

The availability of a wide selection of high-precision primary converters and highly integrated small-sized microprocessors makes it possible to develop high-precision, programmable sensors with great functionality. The sensors have a unipolar supply voltage and simultaneously digital and analog outputs. The sensors are calibrated and configured using software from a computer from the station; the possibility of software compensation of temperature error and linearization of sensor characteristics is provided. The digital part of the electronic board for all types of sensors is the same type and differs only in the setting of the internal program, which makes it unified and interchangeable during repair work. Appearance sensors are shown in Fig. 2.

Rice. 2. Sensors of technological parameters

Hook Load Cell has a number of features (Fig. 3). The principle of operation of the sensor is based on measuring the tension force of the wire rope at the "dead" end using a strain gauge force sensor. The sensor has a built-in processor and non-volatile memory. All information is recorded and stored in this memory. The memory capacity allows you to save the monthly amount of information. The sensor can be equipped with an autonomous power source, which ensures the operation of the sensor when the external power source is disconnected.

Rice. 3. Weight sensor on the hook

Driller Information Board designed to display and visualize information received from sensors. The appearance of the scoreboard is shown in Fig. 4.

On the front panel of the driller's console, there are six linear scales with additional digital indication for displaying parameters: torque on the rotor, inlet pressure, inlet density of the inlet, water level in the tank, inlet flow rate, and outlet flow rate. The parameters of the weight on the hook, the load on the bit, by analogy with the GIV, are displayed on two dials with additional duplication in digital form. In the lower part of the display there is one linear scale for displaying the drilling speed, three digital indicators for displaying parameters - bottom hole depth, position above the bottom hole, gas content. The alphanumeric indicator is intended for displaying text messages and warnings.

Rice. 4. Appearance of the information board

Geochemical module

The geochemical module of the station includes a gas chromatograph, an analyzer of the total gas content, an air-gas line and a drilling mud degasser.

The most important part of the geochemical module is a gas chromatograph. For an error-free, clear identification of productive intervals in the process of opening them, a very reliable, accurate, highly sensitive device is needed, which makes it possible to determine the concentration and composition of saturated hydrocarbon gases in the range from 110 -5 to 100%. For this purpose, to complete the GTI station, a gas chromatograph "Rubin"(Fig. 5) (see article in this issue of NTV).

Rice. 5. Field chromatograph "Rubin"

The sensitivity of the geochemical module of the GTI station can also be increased by increasing the coefficient of degassing of the drilling mud.

To isolate bottomhole gas dissolved in drilling mud, are used degassers of two types(fig. 6):

float degassers of passive action;

active degassers with forced flow splitting.

Float degassers simple and reliable in operation, however, they provide a degassing coefficient of no more than 1-2%. Degassers with forced flow splitting can provide a degassing ratio of up to 80-90%, but are less reliable and require constant monitoring.

Rice. 6. Drilling mud degassers

a) a passive float degasser; b) active degasser

Continuous analysis of the total gas content is carried out using remote total gas sensor... The advantage of this sensor over traditional total gas analyzers located in the station lies in the efficiency of the information received, since the sensor is located directly on the rig and the delay time for gas transportation from the rig to the station is eliminated. In addition, for the complete set of stations, gas sensors for measuring the concentrations of non-hydrocarbon components of the analyzed gas mixture: hydrogen H 2, carbon monoxide CO, hydrogen sulfide H 2 S (Fig. 7).

Rice. 7. Sensors for measuring gas content

Geological module

The geological module of the station provides for the study of drill cuttings, cores and formation fluid in the process of drilling a well, registration and processing of the obtained data.

The studies carried out by the operators of the GTI station make it possible to solve the following main geological tasks:

lithological dissection of the section;

allocation of collectors;

assessment of the nature of reservoir saturation.

For the prompt and high-quality solution of these problems, the most optimal list of instruments and equipment was determined and, on the basis of this, a complex of geological instruments was developed (Fig. 8).

Rice. 8. Equipment and instruments of the geological module of the station

Microprocessor-based carbonate meter KM-1A is designed to determine the mineral composition of rocks in carbonate sections using cuttings and cores. This device allows you to determine the percentage of calcite, dolomite and insoluble residue in the studied rock sample. The device has a built-in microprocessor that calculates the percentage of calcite and dolomite, the values ​​of which are displayed on a digital display or on a monitor screen. A modification of the carbonatomer has been developed, which makes it possible to determine the content of the mineral siderite in the rock (density 3.94 g / cm 3), which affects the density of carbonate rocks and cement of terrigenous rocks, which can significantly reduce the values ​​of porosity.

Sludge density meter PSh-1 designed for express density measurement and assessment of the total porosity of rocks by cuttings and core. The measuring principle of the device is hydrometric, based on weighing the investigated sample of sludge in air and water. The PSh-1 density meter can be used to measure the density of rocks with a density of 1.1-3 g / cm³ .

Installation PP-3 is designed to identify reservoir rocks and study the reservoir properties of rocks. This device allows you to determine the volumetric, mineralogical density and total porosity. The measuring principle of the device is thermogravimetric, based on high-precision measurement of the weight of the investigated rock sample, previously saturated with water, and continuous monitoring of the weight change this sample as moisture evaporates when heated. By the time of evaporation of moisture, one can judge the value of the permeability of the studied rock.

Liquid distillation unit UDZh-2 intended for assessing the nature of saturation of rock reservoirs by cuttings and cores, filtration-density properties, and also allows to determine the residual oil water saturation from cores and drill cuttings directly at the drilling rig due to the use of a new approach in the distillate cooling system. The unit uses a condensate cooling system based on a Peltier thermoelectric element instead of the water heat exchangers used in such devices. This reduces condensate losses by providing controlled cooling. The principle of operation of the installation is based on the displacement of reservoir fluids from the pores of rock samples due to excess pressure arising during thermostatically controlled heating from 90 to 200 ºС ( 3 ºС), condensation of vapors in a heat exchanger and separation of condensate formed during distillation by density into oil and water.

Thermal desorption and pyrolysis unit allows to determine the presence of free and sorbed hydrocarbons based on small samples of rocks (cuttings, pieces of core), as well as to assess the presence and degree of transformation of organic matter, and, based on the interpretation of the data obtained, to distinguish in the sections of wells the intervals of reservoirs, covers of producing sediments, and also to assess the nature of saturation of collectors.

IR spectrometer created for determination of the presence and quantitative assessment of the hydrocarbon present in the studied rock (gas condensate, light oil, heavy oil, bitumen, etc.) in order to assess the nature of reservoir saturation.

Luminoscope LU-1M with a remote UV illuminator and a device for photographing, it is intended for examining drill cuttings and core samples under ultraviolet illumination in order to determine the presence of bituminous substances in the rock, as well as for their quantitative assessment. The measuring principle of the device is based on the property of bitumoids, when irradiated with ultraviolet rays, to emit a "cold" glow, the intensity and color of which make it possible to visually determine the presence, qualitative and quantitative composition of bitumen in the studied rock in order to assess the nature of reservoir saturation. A device for photographing hoods is designed to document the results of luminescence analysis and helps to eliminate the subjective factor in evaluating the analysis results. The remote illuminator allows for preliminary examination of a large-sized core at the drilling site in order to detect the presence of bitumoids.

Sludge dryer OSH-1 designed for rapid drying of sludge samples under the influence of a heat flow. The dehumidifier has a built-in adjustable timer and several modes for adjusting the intensity and temperature of the air flow.

The technical and informational capabilities of the described GTI station meet modern requirements and make it possible to implement new technologies for information support for the construction of oil and gas wells.

Mining and geological characteristics of the section, affecting the occurrence, prevention and elimination of complications.

Complications in the process of drilling arise for the following reasons: difficult mining and geological conditions; poor awareness of them; low drilling speed, for example, due to long downtime, poor technological solutions incorporated in the technical design for the construction of a well.

With complicated drilling, accidents occur more often.

Mining and geological characteristics must be known in order to correctly draw up a project for the construction of a well, to prevent and deal with complications during the implementation of the project.

Reservoir pressure (Ppl) - fluid pressure in rocks with open porosity. This is the name of the rocks in which the voids communicate with each other. In this case, the formation fluid can flow according to the laws of hydromechanics. Such rocks include plugging rocks, sandstones, reservoirs of productive horizons.

Pore ​​pressure (Ppor) is the pressure in closed voids, that is, the pressure of the fluid in the pore space, in which the pores do not communicate with each other. Such properties are possessed by clays, salt rocks, reservoir covers.

Rock pressure (Pr) is the hydrostatic (geostatic) pressure at the considered depth from the upstream HF strata.

The static level of the formation fluid in the well, determined by the equality of the pressure of this column with the formation pressure. The level can be below the surface of the earth (the well will absorb), coincide with the surface (there is equilibrium) or be above the surface (the well is gushing) Рпл = rgz.

Dynamic fluid level in the well - set above the static level when adding to the well and below it when withdrawing fluid, for example, when pumping out with a submersible pump.

Depression P = Pbw-Rpl<0 – давление в скважине меньше пластового. Наличие депрессии – необходимое условие для притока пластового флюида.

Repression Р = Рskv-Рpl> 0 - well pressure is not more than reservoir pressure. Absorption takes place.

The coefficient of anomalous formation pressure Ka = Ppl / rvgzpl (1), where zpl is the depth of the top of the reservoir under consideration, rw is the water density, g is the acceleration of gravity. Ka<1=>ANPD; Ka> 1 => AHPD.

Loss or fracturing pressure Pp - pressure at which all phases of the drilling or backfill fluid are absorbed. The value of Pp is determined empirically from observation data during drilling, or with the help of special studies in the well. The data obtained is used for drilling other similar wells.

Compound pressure graph for complication. Selection of the first variant of the well design.

Combined pressure graph. Selection of the first variant of the well design.

To correctly draw up a technical design for the construction of wells, it is necessary to know exactly the distribution of reservoir (pore) pressures and absorption (hydraulic fracturing) pressures over depth, or, which is the same, the distribution of Ka and Kp (in dimensionless form). The distribution of Ka and Kp is presented on the combined pressure graph.

Distribution of Ka and Kp along the depth z.

· Well design (1st option), which is later specified.

It can be seen from this graph that we have three depth intervals with compatible drilling conditions, that is, those in which a fluid with the same density can be used.

It is especially difficult to drill when Ka = Kp. Drilling becomes super difficult when Ka = Kp<1. В этих случаях обычно бурят на поглощение или применяют промывку аэрированной жидкостью.

After opening the absorbing interval, isolation works are performed, due to which Kp increases (artificially), making it possible, for example, to cement the casing.

Well circulation system diagram

Scheme of the circulation system of wells and the pressure distribution diagram in it.

Scheme: 1. Chisel, 2. Downhole motor, 3. Drill hole, 4. BT, 5. Tool joint, 6. Square, 7. Swivel, 8. Drilling sleeve, 9. Riser, 10. Pressure pipeline (manifold), 11 Pump, 12. Suction nozzle, 13. Chute system, 14. Vibrating screen.

1. Line of hydrostatic pressure distribution.

2. Line of hydraulic pressure distribution in the gearbox.

3. Line of hydraulic pressure distribution in BT.

The pressure of the drilling fluid on the formation should always be inside the shaded area between Ppl and Pp.

Through each threaded connection of the BK, the liquid tries to flow from the pipe into the annulus (during circulation). This trend is caused by the pressure drop in the pipes and the BC. Leakage destroys the threaded connection. All other things being equal, the organic disadvantage of drilling with a hydraulic downhole motor is an increased pressure drop at each threaded connection, since in the downhole motor

The circulating system is used to supply drilling fluid from the wellhead to receiving tanks, to remove cuttings and degassing.

The figure shows a simplified diagram of the TsS100E circulation system: 1 - topping-up pipeline; 2 - mortar pipeline; 3 - cleaning unit; 4 - receiving block; 5 - electrical equipment control cabinet.

The simplified design of the circulation system is a gutter system that consists of a gutter for the movement of mortar, a flooring near the gutter for walking and cleaning gutters, railings and a base.

The gutters can be made of 40 mm wooden planks and 3-4 mm metal sheets. Width - 700-800 mm, height - 400-500 mm. Rectangular and semicircular gutters are used. In order to reduce the flow rate of the solution and the slab falling out of it, partitions and drops with a height of 15-18 cm are installed in the gutters. At the bottom of the gutter, in these places, hatches with valves are installed through which the settled rock is removed. The total length of the gutter system depends on the parameters of the fluids used, the conditions and technology of drilling, as well as on the mechanisms used for cleaning and degassing the fluids. The length, as a rule, can be in the range of 20-50 m.

When using sets of mechanisms for cleaning and degassing solution (vibrating screens, sand separators, sludge separators, degassers, centrifuges), the gutter system is used only for supplying solution from the well to the mechanism and receiving tanks. In this case, the length of the gutter system depends only on the location of the mechanisms and containers in relation to the well.

In most cases, the gutter system is mounted on metal bases in sections with a length of 8-10 m and a height of up to 1 m. Such sections are installed on steel telescopic racks that regulate the installation height of the gutters, this makes it easier to dismantle the gutter system in winter. So, when the cuttings accumulate and freeze under the grooves, the grooves together with the bases can be removed from the racks. A gutter system is mounted with a slope in the direction of the solution movement; the gutter system is connected to the wellhead with a pipe or gutter of a smaller section and with a greater slope to increase the speed of the solution and reduce the slurry fallout in this place.

In modern well drilling technology, special requirements are imposed on drilling fluids, according to which the equipment for cleaning the solution must ensure high-quality cleaning of the solution from the solid phase, mix and cool it, and also remove the mud from the solution that entered it from gas-saturated formations during drilling. In connection with these requirements, modern drilling rigs are equipped with circulation systems with a certain set of unified mechanisms - tanks, devices for cleaning and preparing drilling fluids.

The circulating system mechanisms provide a three-stage cleaning of the drilling fluid. From the well, the solution enters the vibrating sieve in the first stage of coarse cleaning and is collected in the sump of the tank, where coarse sand is deposited. From the settling tank, the solution passes into the section of the circulation system and is fed by a centrifugal slurry pump to the degasser if it is necessary to degass the solution, and then to the sand separator, where the second stage of cleaning from rocks up to 0.074-0.08 mm in size passes. After that, the solution is fed to the sludge separator - the third stage of cleaning, where rock particles up to 0.03 mm are removed. Sand and sludge are discharged into a container, from where they are fed to a centrifuge for additional separation of the solution from the rock. The purified solution from the third stage enters the receiving tanks - to the receiving block of mud pumps for supplying it to the well.

The equipment of circulation systems is completed by the plant in the following units:

solution purification unit;

intermediate block (one or two);

receiving block.

The basis for assembling the blocks is rectangular containers installed on the sled base.

Hydraulic pressure of clay and cement slurries after stopping circulation.

Absorption. The reasons for their occurrence.

BySwallowing of drilling or grouting fluids is a type of complication, which is manifested by the escape of fluid from the well into the formation of rocks. Unlike filtration, absorptions are characterized by the fact that all phases of the liquid enter the HP. And when filtering, only a few. In practice, losses are also defined as the daily withdrawal of drilling fluid into the formation in a volume exceeding the natural loss due to filtration and with cuttings. Each region has its own norm. Usually several m3 per day are allowed. Absorption is the most common type of complications, especially in the Ural-Volga regions of eastern and southeastern Siberia. Absorptions occur in sections, which usually have fractured MS, the greatest deformations of rocks are located and their erosion is caused by tectonic processes. For example, in Tatarstan, 14% of the calendar time is spent annually on the fight against acquisitions, which exceeds the time spent on fur. drilling. As a result of losses, well drilling conditions worsen:

1. The sticking hazard of the tool increases, because the velocity of the upward flow of the drilling fluid is sharply reduced above the absorption zone, if at the same time large particles of cuttings do not go into the formation, then it accumulates in the wellbore, causing tightening and sticking of the tool. The likelihood of sticking of the tool in the settling sludge increases especially after the pump stops (circulation).

2. Sloughs and landslides are increasing in unstable rocks. HNVP may arise from the fluid-bearing horizons available in the section. The reason is a decrease in the pressure of the liquid column. In the presence of two or more simultaneously opened layers with different coefficients. Ka and Kp between them, crossflows may occur, complicating the isolation work and subsequent cementing of the well.

A lot of time and material resources (inert fillers, plugging materials) are wasted for insulation, downtime and accidents that cause absorption.

Reasons for acquisitions

The qualitative role of the factor that determines the magnitude of the drift of the solution into the absorption zone can be traced by considering the flow of a viscous fluid in a circular porous formation or a circular slot. The formula for calculating the flow rate of absorbed fluid in a porous circular formation will be obtained by solving the system of equations:

1. Equation of motion (Darcy form)

V = K / M * (dP / dr): (1) where V, P, r, M are the flow velocity, current pressure, formation radius, viscosity, respectively.

2. Equation of conservation of mass (continuity)

V = Q / F (2) where Q, F = 2πrh, h -, respectively, the absorption rate of the liquid, the area variable along the radius, and the thickness of the absorption zone.

3. Equation of state

ρ = const (3) solving this system of equations: 2 and 3 in 1 we get:

Q = (K / M) * 2π rH (dP / dr)

Q = (2π HK (Pwith-Ppl)) / Mln (rk / rc) (4)formula Dupies

A similar formula (4) Bussensco can be obtained for m circular cracks (slots) equally open and equally spaced from each other.

Q = [(πδ3 (Pс-Ppl)) / 6Mln (rk / rc)] * m (5)

δ - opening (height) of the slot;

m is the number of cracks (slots);

M is the effective viscosity.

It is clear that in order to reduce the flow rate of the absorbed liquid according to the formulas (4) and (5), it is necessary to increase the parameters in the denominators and decrease them in the numerator.

According to (4) and (5)

Q = £ (H (or m), Ppl, rk, Pc, rc, M, K, (or δ)) (6)

The parameters included in function (6) by origin at the moment of opening the absorption zone can be conditionally divided into 3 groups.

1.group - geological parameters;

2.group - technological parameters;

3rd group - mixed.

This division is conditional, since during operation, i.e. technological impact (fluid withdrawal, waterflooding, etc.) on the reservoir also changes Ppl, rk

Loss in rocks with closed fractures. Feature of indicator curves. Hydraulic fracturing and its prevention.

Feature of indicator curves.

Further we will consider line 2.

An approximate indicator curve for rocks with artificially opened closed fractures can be described by the following formula: Pc = Pb + Ppl + 1 / A * Q + BQ2 (1)

For rocks with naturally open fractures, the indicator curve is a special case of the formula (1)

Рс-Рпл = ΔР = 1 / А * Q = А * ΔР

Thus, in rocks with open fractures, loss will begin at any values ​​of repression, and in rocks with closed fractures - only after the creation of a pressure equal to the hydraulic fracturing pressure Pc * in the well. The main measure to combat lost circulation in rocks with closed fractures (clay, salt) is to avoid hydraulic fracturing.

Evaluation of the effectiveness of work to eliminate absorption.

The effectiveness of insulation work is characterized by the injectivity (A) of the absorption zone, which can be achieved during insulation work. If, in this case, the obtained injectivity A turns out to be lower than a certain technologically permissible value of the injectivity Aq, which is characteristic for each region, then the insulation work can be considered successful. Thus, the isolation conditions can be written as A≤Aq (1) A = Q / Pc- P * (2) For rocks with artificially opened cracks P * = Pb + Ppl + Pp (3) where Pb is the lateral pressure of the rock, Rr - tensile strength g.p. In particular cases Рb and Рр = 0 for rocks with natural open fractures А = Q / Pc - Рпл (4), if the slightest absorption is not allowed, then Q = 0 and А → 0,

then Ps<Р* (5) Для зоны с открытыми трещинами формула (5) заменяется Рс=Рпл= Рпогл (6). Если давление в скважине определяется гидростатикой Рс = ρqL то (5 и 6) в привычных обозначениях примет вид: ρо≤Кп (7) и ρо= Ка=Кп (8). На практике трудно определить давление поглощения Р* , поэтому в ряде районов, например в Татарии оценка эффективности изоляционных работ проводят не по индексу давления поглощения Кп а по дополнительной приемистости Аq. В Татарии допустимые приемистости по тех. воде принято Аq≤ 4 м3/ч*МПа. Значение Аq свое для каждого района и различных поглощаемых жидкостей. Для воды оно принимается обычно более, а при растворе с наполнителем Аq берется меньше. Согласно 2 и 4 А=f (Q; Рс) (9). Т.е все способы борьбы с поглощениями основаны на воздействии на две управляемые величины (2 и 4) , т.е. на Q и Рс.

Methods of dealing with absorption in the process of opening the absorption zone.

Traditional methods of prevention of losses are based on a decrease in pressure drops on the absorbing formation or a change in a / t) of the filtering fluid. If, instead of reducing the pressure drop across the formation, the viscosity is increased by adding plugging materials, bentonite or other substances, the absorption rate will change inversely with the increase in viscosity, as follows from formula (2.86). In practice, if you adjust the parameters of the solution, the viscosity can only be changed within relatively narrow limits. Prevention of losses by switching to flushing with a solution with increased viscosity is possible only if scientifically substantiated requirements for these fluids are developed, taking into account the peculiarities of their flow in the formation. Improvement of the methods of prevention of losses, based on the reduction of pressure drops on the absorbing formations, is inextricably linked with the deep study and development of methods for drilling wells in equilibrium in the well-formation system. The drilling mud, penetrating into the absorbing formation to a certain depth and thickening in the absorption channels, creates an additional obstacle to the movement of the drilling mud from the wellbore into the formation. The property of the solution to create resistance to the movement of fluid within the formation is used when carrying out preventive measures in order to prevent losses. The strength of such resistance depends on the structural and mechanical properties of the solution, the size and shape of the channels, as well as the depth of penetration of the solution into the formation.

To formulate the requirements for the rheological properties of drilling fluids when passing through absorbing formations, we will consider the curves (Fig. 2.16) reflecting the dependence of the shear stress and the deformation rate de / df for some models of non-Newtonian fluid. Straight line 1 corresponds to the model of a viscoplastic medium, which is characterized by the limiting shear stress τ0. Curve 2 characterizes the behavior of pseudoplastic fluids, in which the stress growth rate slows down with an increase in the shear rate, and the curves flatten. Line 3 reflects the rheological properties of a viscous fluid (Newtonian). Curve 4 characterizes the behavior of viscoelastic and dilatant fluids, in which the shear stress increases sharply with increasing strain rate. Viscoelastic fluids, in particular, include weak solutions of some polymers (polyethylene oxide, guar gum, polyacrylamide, etc.) in water, which exhibit the property of drastically reducing (2-3 times) hydrodynamic resistance during the flow of fluids with high Reynolds numbers (Toms effect). At the same time, the viscosity of these fluids as they move through the absorbing channels will be high due to the high shear rates in the channels. Drilling with flushing with aerated drilling fluids is one of the radical measures in a set of measures and methods designed to prevent and eliminate lost circulation when drilling deep wells. Aeration of the drilling fluid reduces the hydrostatic pressure, thereby facilitating its return in sufficient quantity to the surface and, accordingly, normal cleaning of the wellbore, as well as the selection of representative samples of rock and formation fluids. The technical and economic indicators when drilling wells with bottomhole flushing with aerated solution are higher than those when water or other flushing fluids are used as drilling fluid. The quality of penetration of productive formations is also significantly improved, especially in fields where these formations have abnormally low pressures.

An effective measure to prevent lost circulation is the introduction of fillers into the circulating drilling fluid. The purpose of their use is to create tampons in the absorption channels. These swabs serve as the basis for the deposition of a filter cake (clay) and isolation of absorbing formations. V.F. Rogers believes that the bridging agent can be almost any material that is composed of particles of small enough size and, when introduced into the drilling fluid, it can be pumped by mud pumps. In the United States, more than a hundred types of fillers and their combinations are used to plug absorption channels. As clogging agents, wood chips or bast, fish scales, hay, rubber waste, gutta-percha leaves, cotton, cotton bolls, sugarcane fibers, nutshells, granular plastics, perlite, expanded clay, textile fibers, bitumen, mica, asbestos, cut paper, moss, shredded hemp, cellulose flakes, leather, wheat bran, beans, peas, rice, chicken feathers, clumps of clay, sponge, coke, stone, etc. These materials can be used alone and in combinations made by industry or formulated prior to use ... Determining the suitability of each plugging material in the laboratory is difficult due to the lack of knowledge of the size of the holes to be plugged.

In foreign practice, special attention is paid to ensuring "tight" packing of fillers. The opinion of Fernas is adhered to, according to which the densest packing of particles meets the condition of their size distribution according to the law of geometric progression; when eliminating lost circulation, the greatest effect can be obtained with a maximally compacted plug, especially in the case of instant mud withdrawal.

Fillers are subdivided according to their quality characteristics into fibrous, lamellar and granular. Fibrous materials are of plant, animal, and mineral origin. This also includes synthetic materials. Fiber type and size significantly affect the quality of work. The stability of the fibers during their circulation in the drilling fluid is important. The materials give good results when plugging sandy and gravel formations with grains up to 25 mm in diameter, as well as when plugging cracks in coarse-grained (up to 3 mm) and fine-grained (up to 0.5 mm) rocks.

Lamellar materials are suitable for plugging coarse gravel formations and cracks up to 2.5 mm in size. These include: cellophane, mica, husks, cotton seeds, etc.

Granular materials: perlite, crushed rubber, pieces of plastic, nutshells, etc. Most of them effectively plug gravel beds with grains up to 25 mm in diameter. Perlite gives good results in gravel formations with grain diameters up to 9-12 mm. A nut shell with a size of 2.5 mm or less clogs cracks up to 3 mm in size, while larger (up to 5 mm) and crushed rubber clogs cracks up to 6 mm in size, i.e. they can plug cracks in 2 times more than when using fibrous or lamellar materials.

In the absence of data on the size of the grains and cracks of the absorbing horizon, mixtures of fibrous with lamellar or granular materials, cellophane with mica, fibrous with flaky and granular materials are used, as well as when mixing granular materials: perlite with rubber or nutshells. The best mixture for eliminating absorption at low pressures is a highly colloidal mud with addition of fibrous materials and mica leaves. Fibrous materials, deposited on the borehole wall, form a mesh. Mica leaves strengthen this mesh and plug the larger channels in the rock, and a thin, dense mud cake forms on top of it all.

Gas-water-oil showings. Their reasons. Signs of formation fluids entry. Classification and recognition of the types of manifestations.

During absorption, fluid (flushing or grouting) flows from the well into the formation, and when it manifests, vice versa, from the formation into the well. Reasons for admission: 1) entry into the well in place from the cuttings of fluid-containing formations. In this case, the pressure in the well is not necessarily higher and lower than the reservoir pressure; 2) if the pressure in the well is lower than the reservoir pressure, i.e. there is pressure on the reservoir, the main reasons for the occurrence of pressure in the well, that is, the decrease in pressure on the reservoir in the well are as follows: 1) not topping up the well with drilling fluid when lifting the tool. A device for autofilling into the well is required; 2) a decrease in the density of the flushing liquid due to its foaming (gassing) when the liquid comes into contact with air on the surface in the gutter system, as well as due to the treatment of p.zh with a surfactant. Degassing is required (mechanical, chemical); 3) drilling a well in incompatible conditions. There are two layers in the diagram. The first layer is characterized by Ka1 and Kp1; for the second Ka2 and Kn2. first layer should be drilled with a mud ρ0.1 (between Ka1 and Kp1), the second layer ρ0.2 (Fig.)

It is impossible to open the second layer on a solution with a density for the first layer, since there will be absorption in the second layer; 4) sharp fluctuations in hydrodynamic pressure when the pump is stopped, tripping and other work, aggravated by an increase in static shear stress and the presence of oil seals on the column;

5) underestimated density of p.w. adopted in the technical design due to poor knowledge of the actual distribution of reservoir pressure (Ka), i.e. the geology of the area. These reasons are more related to exploration wells; 6) a low level of operational clarification of reservoir pressures by predicting them in the course of deepening the well. Not using methods for predicting the d-exponent, σ (sigma) -exponent, etc. 7) dropping out of the weighting agent from the drilling fluid and decreasing the hydraulic pressure. Signs of the formation fluid inflow are: 1) an increase in the level of the circulating fluid in the pump receiving tank. A level gauge is needed; 2) gas is released from the solution coming out of the well at the wellhead, boiling of the solution is observed; 3) after the circulation is stopped, the solution continues to flow out of the well (the well overflows); 4) the pressure rises sharply at an unexpected opening of the formation with abnormally high pressure. When oil enters from the reservoirs, its film remains on the walls of the troughs or flows over the solution in the troughs. When formation water arrives, the properties of the p.zh change. Its density usually decreases, the viscosity may decrease, and may increase (after the influx of salt water). Fluid loss usually increases, pH changes, and electrical resistance usually decreases.

Classification of fluid intake. It is carried out according to the complexity of the measures necessary for their liquidation. They are subdivided into three groups: 1) manifestation - non-hazardous inflow of formation fluids that do not disturb the drilling process and the accepted work technology; 2) outburst - the flow of fluids that can be eliminated only by a special purposeful change in the drilling technology with the means and equipment available on the drilling rig; 3) a fountain - the entry of a fluid, the elimination of which requires the use of additional means and equipment (except for those available at the drilling unit) and which is associated with the occurrence of pressures in the well-reservoir system that threaten the integrity of the o.c. , wellhead equipment and formations in the unsecured part of the well.

Installation of cement bridges. Features of the choice of the recipe and the preparation of the grouting solution for the installation of bridges.

One of the serious varieties of the cementing process technology is the installation of cement bridges for various purposes. Improving the quality and efficiency of cement bridges is an integral part of improving the drilling, completion and operation of wells. The quality of bridges and their durability also determine the reliability of environmental protection. At the same time, field data indicate that there are often cases of installation of low-strength and leaky bridges, premature setting of cement slurry, stuck pipes, etc. These complications are caused not only and not so much by the properties of the used grouting materials, but by the specifics of the works themselves during the installation of bridges.

In deep high-temperature wells during these operations, accidents often occur associated with intensive thickening and setting of a mixture of clay and cement solutions. In some cases, bridges are leaking or not strong enough. The successful installation of bridges depends on many natural and technical factors that determine the peculiarities of the formation of cement stone, as well as its contact and "adhesion" with rocks and pipe metal. Therefore, the assessment of the bearing capacity of the bridge as an engineering structure and the study of the conditions existing in the well are mandatory when carrying out these works.

The purpose of installing the bridges is to obtain a stable water-gas and oil-tight nozzle of cement stone of a certain strength for transition to the overlying horizon, drilling a new borehole, strengthening the unstable and cavernous part of the wellbore, testing the horizon with the help of a reservoir tester, workover and conservation or abandonment of wells.

By the nature of the acting loads, two categories of bridges can be distinguished:

1) under pressure of liquid or gas and 2) under load from the weight of the tool during drilling a second borehole, using a formation tester or in other cases (bridges of this category, in addition to being gas-tight, must have a very high mechanical strength).

Analysis of field data shows that bridges can be subjected to pressures up to 85 MPa, axial loads up to 2100 kN, and shear stresses occur per 1 m of the bridge length up to 30 MPa. Such significant loads arise during well testing with the help of reservoir testers and in other types of work.

The bearing capacity of cement bridges largely depends on their height, the presence (or absence) and condition of the mud cake or mud residues on the string. When removing the loose part of the mud cake, the shear stress is 0.15-0.2 MPa. In this case, even with the occurrence of maximum loads, a bridge height of 18-25 m is sufficient. The presence of a layer of drilling (clay) mud with a thickness of 1-2 mm on the walls of the column leads to a decrease in the shear stress and to an increase in the required height to 180-250 m. the height of the bridge should be calculated using the formula Nm ≥ But - Qm / pDc [τm] (1) where H0 is the installation depth of the lower part of the bridge; QM is the axial load on the bridge due to the pressure drop and unloading of the pipe string or formation tester; Dс - borehole diameter; [τm] is the specific bearing capacity of the bridge, the values ​​of which are determined both by the adhesive properties of the plugging material and by the method of installing the bridge. The tightness of the bridge also depends on its height and the state of the contact surface, since the pressure at which water breakthrough occurs is directly proportional to the length and inversely proportional to the thickness of the crust. If there is a clay cake between the casing and the cement stone with a shear stress of 6.8-4.6 MPa, a thickness of 3-12 mm, the water breakthrough pressure gradient is 1.8 and 0.6 MPa per 1 m, respectively. In the absence of a crust, water breakthrough occurs at a pressure gradient of more than 7.0 MPa per 1 m.

Consequently, the tightness of the bridge also largely depends on the conditions and method of its installation. In this regard, the height of the cement bridge should also be determined from the expression

Nm ≥ But - Рм / [∆р] (2) where Рм is the maximum value of the pressure drop acting on the bridge during its operation; [∆р] - permissible pressure gradient of fluid breakthrough along the zone of contact between the bridge and the borehole wall; this value is also determined mainly depending on the method of installing the bridge, on the grouting materials used. From the values ​​of the height of the cement bridges, determined by formulas (1) and (2), choose a larger one.

The installation of a bridge has much in common with the process of cementing columns and has features that boil down to the following:

1) a small amount of plugging materials is used;

2) the lower part of the filling pipes is not equipped with anything, the stop ring is not installed;

3) rubber dividing plugs are not used;

4) in many cases, wells are backflushed to "cut" the bridge roof;

5) the bridge is not limited by anything from below and can spread out under the influence of the density difference between cement and drilling mud.

The installation of the bridge is a simple operation in concept and method, which in deep wells is significantly complicated by such factors as temperature, pressure, gas-water and oil showings, etc. The length, diameter and configuration of filling pipes, rheological properties of cement and drilling mud are also of great importance. wellbore cleanliness and downdraft and upflow modes. The borehole cavernousness has a significant effect on the installation of the bridge in the uncased part of the well.

Cement bridges must be strong enough. Practice shows that if, during strength testing, the bridge does not collapse when a specific axial load of 3.0-6.0 MPa is created on it and simultaneous flushing, then its strength properties satisfy the conditions for both drilling a new shaft and loading from the weight of the pipe string or a formation tester.

When installing bridges for drilling a new shaft, an additional height requirement is imposed on them. This is due to the fact that the strength of the upper part (H1) of the bridge should ensure the possibility of drilling a new borehole with a permissible curvature intensity, and the lower part (H0) - reliable isolation of the old borehole. Nm = Н1 + Ho = (2Dc * Rc) 0.5+ Ho (3)

where Rc is the radius of curvature of the trunk.

Analysis of the available data shows that obtaining reliable bridges in deep wells depends on a set of simultaneously acting factors, which can be divided into three groups.

The first group is natural factors: temperature, pressure and geological conditions (cavernousness, fracturing, the action of aggressive waters, water and gas production and absorption).

The second group - technological factors: the speed of the flow of cement and drilling fluids in pipes and annular space, the rheological properties of the solutions, the chemical and mineralogical composition of the binder, the physical and mechanical properties of the cement slurry and stone, the contraction effect of the oil well cement, the compressibility of the drilling fluid, the heterogeneity of the densities , coagulation of drilling mud when mixing it with cement (the formation of highly viscous pastes), the size of the annular gap and the eccentricity of the pipes in the well, the contact time of the buffer fluid and cement slurry with the mud cake.

The third group - subjective factors: the use of plugging materials unacceptable for the given conditions; incorrect selection of the solution formulation in the laboratory; inadequate preparation of the wellbore and the use of drilling mud with high values ​​of viscosity, SST and fluid loss; errors in determining the amount of squeezing fluid, the location of the filling tool, the dosage of reagents for mixing cement slurry in the well; the use of an insufficient number of cementing units; the use of an insufficient amount of cement; low degree of organization of the process of installing the bridge.

An increase in temperature and pressure contributes to an intensive acceleration of all chemical reactions, causing a rapid thickening (loss of pumpability) and setting of cement slurries, which, after short-term interruptions in circulation, sometimes cannot be forced through.

Until now, the main method for installing cement bridges has been to inject cement slurry into the well into the design depth interval along the pipe string, lowered to the level of the lower mark of the bridge, followed by lifting this string above the cementing zone. As a rule, work is carried out without dividing plugs and means of monitoring their movement. The process is controlled by the volume of the displacement fluid, calculated from the condition of equality of the levels of the cement slurry in the pipe string and the annular space, and the volume of the cement slurry is taken equal to the volume of the well in the interval of the bridge installation. The efficiency of the method is low.

First of all, it should be noted that the cementitious materials used for cementing casing strings are suitable for the installation of strong and tight bridges. Poor-quality installation of bridges or their absence at all, premature setting of a solution of binders and other factors to a certain extent are caused by the incorrect selection of the formulation of solutions of binders in terms of thickening (setting) time or deviations from the formulation selected in the laboratory, made during the preparation of a solution of binders.

It was found that in order to reduce the likelihood of complications, the setting time, and at high temperatures and pressures, the thickening time should exceed the duration of work on the installation of bridges by at least 25%. In a number of cases, when selecting formulations of binders solutions, the specifics of work on the installation of bridges are not taken into account, which consists in stopping circulation to lift the string of filling pipes and seal the wellhead.

At high temperatures and pressures, the resistance to shear of the cement slurry, even after short-term stops (10-20 min) of circulation, can sharply increase. Therefore, it is not possible to restore the circulation and in most cases the filling pipe string is stuck. As a result, when selecting a cement slurry formulation, it is necessary to study the dynamics of its thickening on a consistometer (CC) using a program that simulates the process of installing a bridge. The thickening time of the cement slurry Tzag correspond to the condition

Tzag> T1 + T2 + T3 + 1.5 (T4 + T5 + T6) + 1.2T7 where T1, T2, T3 are the time spent, respectively, for preparing, pumping and pushing the cement slurry into the well; Т4, Т5, Т6 - the time spent on lifting the string of filling pipes to the point where the bridge was cut off, on sealing the mouth and carrying out preparatory work for cutting off the bridge; Тт - time spent on cutting the bridge.

According to a similar program, it is necessary to study the mixture of cement slurry with drilling in the ratio of 3: 1.1: 1 and 1: 3 when installing cement bridges in wells with high temperature and pressure. The success of the installation of a cement bridge largely depends on the exact observance of the recipe selected in the laboratory when preparing the cement slurry. Here, the main conditions are maintaining the selected content of chemical reagents and mixing liquid and water-cement ratio. To obtain the most homogeneous grouting slurry, it should be prepared using an average tank.

Complications and accidents when drilling oil and gas wells in permafrost conditions and measures to prevent them .

When drilling in the intervals of permafrost propagation, as a result of joint physicochemical impact and erosion on the borehole walls, ice-consolidated sandy-argillaceous deposits are destroyed and easily washed out by the flow of drilling mud. This leads to intense cavities and associated rock falls and talus.

The most intensively destroyed rocks with a low ice content and weakly compacted rocks. The heat capacity of such rocks is low, and therefore their destruction occurs much faster than rocks with high ice content.

Among the frozen rocks, there are interlayered thawed rocks, many of which are prone to losses of drilling mud at pressures slightly exceeding the hydrostatic pressure of the water column in the well. Absorption into such layers can be very intense and require special measures to prevent or eliminate them.

In the permafrost sections, rocks of the Quaternary age are usually most unstable in the interval 0-200 m. With traditional drilling technology, the actual borehole volume in them can exceed the nominal volume by 3-4 times. As a result of strong cavities. which is accompanied by the appearance of benches, sliding cuttings and rock falls, the conductors in many wells were not run to the design depth.

As a result of the destruction of the permafrost, in a number of cases, subsidence of the conductor and the direction was observed, and sometimes whole craters formed around the wellhead, which did not allow drilling.

In the interval of permafrost propagation, it is difficult to provide cementing and borehole fastening due to the creation of stagnant zones of drilling mud in large caverns, from where it cannot be displaced with grouting fluid. Cementing is often one-sided and the cement ring is not continuous. This creates favorable conditions for inter-layer flows and the formation of griffins, for collapse of columns in the case of reverse freezing of rocks in the case of long "interlayers" of the well.

The processes of destruction of IMF are rather complex and poorly studied. 1 The drilling fluid circulating in the well interacts thermally and hydrodynamically with both rock and ice, and this interaction can be significantly enhanced by physicochemical processes (for example, dissolution, "which do not stop even at negative temperatures.

At present, the presence of osmotic processes in the system rock (ice) - cake on the borehole wall - drilling fluid in the wellbore can be considered proven. These processes are spontaneous and directed in the direction opposite to the potential gradient (temperature, pressure, concentration), i.e. strive to equalize concentrations, temperatures, pressures. The role of a semi-permeable baffle can be played by both the filter cake and the near-well raceway layer of the rock itself. And in the composition of the frozen rock, in addition to ice as its cementing substance, there may be non-freezing pore water with varying degrees of mineralization. The amount of non-freezing water in MMG1 depends on temperature, material composition, salinity and can be estimated using the empirical formula

w = aT ~ b .

1pa = 0.2618 + 0.55191nS;

1p (- B)= 0.3711 + 0.264S:

S is the specific surface of the rock. m a / p G - rock temperature, "C.

Due to the presence of drilling mud in the open borehole, and in the permafrost - pore fluid with a certain degree of mineralization, the process of spontaneous equalization of iodine concentrations occurs under the action of osmotic pressure. As a result, the destruction of frozen rock can occur. If the drilling fluid has an increased concentration of some dissolved salt in comparison with pore water, then phase transformations will begin at the ice-liquid interface associated with a decrease in the melting point of ice, i.e. the process of its destruction will begin. And since the stability of the borehole wall depends mainly on ice, as a substance cementing the rock, then under these conditions the stability of permafrost, c, patching the borehole wall will be lost, which can cause sloughs, collapses, the formation of caverns and sludge plugs, landings and puffs during tripping operations, stoppages of casing strings being lowered into the well, absorption of drilling flushing and grouting fluids.

If the degrees of mineralization of the drilling mud and the pore water of the permafrost are the same, then the well-rock system will be in isotonic equilibrium, and the destruction of permafrost under physicochemical impact is unlikely.

With an increase in the degree of salinity of the flushing agent, conditions arise under which pore water with a lower salinity will move from the rock to the well. Due to the loss of immobilized water, the mechanical strength of the ice will decrease, the ice may break, which will lead to the formation of a cavity in the wellbore being drilled. This process is intensified by the erosive action of the circulating flushing agent.

The destruction of ice by saline flushing fluid has been noted in the works of many researchers. Experiments carried out at the Leningrad Mining Institute have shown that with an increase in the concentration of salt in the liquid washing the ice, the destruction of ice intensifies. So. with a content of 23 and 100 kg / m ‘NaCl in the circulating water, the intensity of ice destruction at a temperature of minus 1 ″ C was 0.0163 and 0.0882 kg / h, respectively.

The process of ice destruction is also influenced by the duration of the effect of the saline flushing liquid. Thus, when the ice is exposed to a 3% NaCl solution, the weight loss of an ice sample with a temperature of minus 1 'C will be: after 0.5 h 0.62 p through 1.0 h 0.96 g: after 1.5 h 1.96 g.

As the near-wellbore zone of the permafrost melts, part of its burrow space is released, where the drilling fluid or its dispersion medium can also be filtered. This process may turn out to be another physic / imic factor contributing to the destruction of permafrost. It can be accompanied by osmotic fluid flow from wells into the formation if the concentration of any soluble salt in the permafrost fluid is higher than in the fluid. filling the wellbore.

Consequently, in order to minimize the negative effect of physicochemical processes on the state of the wellbore being drilled in the permafrost, it is necessary, first of all, to ensure the equilibrium concentration of the components of the drilling mud and interstitial fluid in the permafrost on the borehole wall.

Unfortunately, this requirement is not always feasible in practice. Therefore, they often resort to protecting the cementing permafrost ice from the physicochemical effects of drilling fluid with films of viscous fluids that cover not only the ice surfaces exposed by the borehole, but also the pore space partially adjacent to the borehole. thereby breaking the direct contact of the mineralized liquid with ice.

As AV Maramzin and AA Ryazanov point out, during the transition from flushing the wells with salt water to flushing with a more viscous clay solution, the intensity of ice destruction decreased by 3.5 - 4 times with the same concentration of NaCl in them. It decreased even more when the drilling fluid was treated with protective colloids (CMC, SSB |. The positive role of additives to the drilling fluid of highly colloidal bentonite glnopowder and hypane was also confirmed.

Thus, to prevent cavities, destruction of the wellhead zone, talus and rock falls when drilling wells in the permafrost. The drilling mud must meet the following basic requirements:

have a low filtration rate:

have the ability to create a dense, impenetrable film on the ice surface in permafrost:

have a low erosion ability; have a low specific heat;

to form a filtrate that does not create true solutions with the rock fluid;

be hydrophobic to the ice surface.

Zavgorodny Ivan Alexandrovich

2nd year student, mechanical department, specializing in "Drilling of oil and gas wells" Astrakhan State Polytechnic College, Astrakhan

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Marina Kuznetsova

teacher of special disciplines at the Astrakhan State Polytechnic College, Astrakhan

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Introduction. Since ancient times, mankind has been producing oil, at first primitive methods were used: using wells, collecting oil from the surface of reservoirs, processing limestone or sandstone soaked in oil. In 1859, in the US state of Pennsylvania, mechanical drilling of wells for oil appears, at about the same time drilling of wells began in Russia. In 1864 and 1866, the first wells were drilled in the Kuban with a flow rate of 190 tons / day.

Initially, oil wells were drilled by hand rotary rod method, soon they switched to hand rod percussion drilling. The shock-rod method has become widespread in the oil fields of Azerbaijan. The transition from the manual method to mechanical drilling of wells led to the need for mechanization of drilling operations, a major contribution to the development of which was made by the Russian mining engineers G.D. Romanovsky and S.G. Voislav. In 1901, for the first time in the United States, rotary drilling with bottom hole washing with a circulating fluid flow (using drilling mud) was used, and the raising of cuttings by a circulating water stream was invented by the French engineer Fauvelle back in 1848. From that moment on, a period of development and improvement of the rotary drilling method began. In 1902, the first well 345 m deep was drilled in Russia using the rotary method in the Grozny region.

Today, the United States occupies a leading position in the oil industry, 2 million wells are drilled annually, a quarter of them are productive, while Russia is only second so far. In Russia and abroad, the following are used: manual drilling (water extraction); mechanical; guided spindle drilling (safe drilling system developed in England); explosive drilling technologies; thermal; physicochemical, electrospark and other methods. In addition, many new well drilling technologies are being developed, for example, in the USA, the Colorado Mining Institute has developed a laser drilling technology based on rock burning.

Drilling technology. The mechanical drilling method is the most common; it is carried out by percussion, rotary and percussion-rotary drilling methods. With the percussion method of drilling, the destruction of rocks occurs due to the blows of the rock cutting tool on the bottom of the well. The destruction of rocks due to the rotation of a rock cutting tool (chisel, bit) pressed against the bottom is called a rotary drilling method.

When drilling oil and gas wells in Russia, an exclusively rotary drilling method is used. When using the rotary drilling method, the well is drilled with a rotating bit, while the drilled rock particles during the drilling process are carried to the surface by a continuously circulating stream of drilling fluid or air or gas injected into the well. Depending on the location of the motor, rotary drilling is divided into rotary drilling and turbodrill drilling. In rotary drilling - the rotator (rotor) is located on the surface, driving the bit at the bottomhole with the help of a string of drill pipes, the rotation speed is 20-200 rpm. When drilling with a downhole motor (turbodrill, screw auger or electric drill) - the torque is transmitted from the downhole motor installed above the bit.

The drilling process consists of the following main operations: lowering drill pipes with a bit into the borehole to the bottom and lifting the drill pipes with a spent bit out of the well and working the bit at the bottom, that is, destruction of the drilling rock. These operations are periodically interrupted to run the casing into the well to prevent the walls from collapsing and to separate the oil (gas) and water horizons. At the same time, in the process of drilling wells, a number of auxiliary works are performed: coring, preparation of flushing fluid (drilling mud), logging, measuring the curvature, well development in order to induce the flow of oil (gas) into the well, etc.

Figure 1 shows the flow diagram of the drilling rig.

Figure 1. Scheme of a drilling rig for rotary drilling: 1 - wireline; 2 - traveling block; 3 - tower; 4 - hook; 5 - drill hose; 6 - leading pipe; 7 - gutters; 8 - mud pump; 9 - pump motor; 10 - pump piping; 11 - receiving tank (capacity); 12 - drill joint; 13 - drill pipe; 14 - downhole hydraulic motor; 15 - chisel; 16 - rotor; 17 - winch; 18 - winch and rotor motor; 19 - swivel

A drilling rig is a complex of machines and mechanisms designed for drilling and casing wells. The drilling process is accompanied by lowering and lifting of the drill string, as well as keeping it suspended. To reduce the load on the rope and reduce the power of the engines, lifting equipment is used, consisting of a tower, a drawworks and a traveling system. The tackle system consists of a fixed part of the crown block, installed at the top of the tower canopy and a movable part of the traveling block, a wire rope, a hook and links. The hoist system is designed to convert the rotary motion of the winch drum into translational movement of the hook. The drilling tower is designed for lifting and lowering the drill string and casing pipes into the well, as well as for holding the drill string on the weight during drilling and for its uniform feeding and placement of the traveling system, drill pipes and part of the equipment in it. Hoisting operations are carried out using a drill winch. Drawworks consists of a base on which the winch shafts are fixed and connected to each other by gears, all shafts are connected to a gearbox, and the gearbox, in turn, is connected to the engine.

The surface drilling equipment includes a receiving bridge designed for laying drill pipes and moving equipment, tools, materials and spare parts along it. A system of devices for cleaning drilling mud from cuttings. And a number of auxiliary structures.

The drill string connects the drill bit (rock cutting tool) to the surface equipment, i.e. the drilling rig. The top pipe in the drill string is square, it can be hex or grooved. The lead tube passes through the opening of the rotor table. The rotor is positioned in the center of the derrick. The upper end of the leading pipe is connected to a swivel designed to rotate the drill string suspended on the hook and supply drilling fluid through it. The lower part of the swivel is connected to the kelly and can rotate with the drill string. The upper part of the swivel is always motionless.

Let's consider the technology of the drilling process (Figure 1). A flexible hose 5 is connected to the opening of the fixed part of the swivel 19, through which the drilling fluid is pumped into the well using mud pumps 8. The flushing fluid passes along the entire length of the drill string 13 and enters the hydraulic downhole motor 14, which drives the motor shaft into rotation, and then the fluid enters the bit 15. Coming out of the bit holes, the fluid washes the bottom hole, picks up the drilled rock particles and together with them rises upward through the annular space between the borehole walls and the drill pipes and goes to the pump intake. On the surface, the drilling fluid is cleaned from the drilled rock using special equipment, after which it is again fed into the well.

The drilling technological process depends a lot on the drilling mud, which, depending on the geological characteristics of the field, is prepared on a water basis, on an oil basis, using a gaseous agent or air.

Output. From the above, it can be seen that the technologies for the behavior of drilling processes are different, but suitable for the given conditions (depth of the well, its constituent rock, pressures, etc.) should be selected based on geological and climatic conditions. Since, the operational characteristics of the well, namely its flow rate and productivity, depend on the quality of the drilling of the productive horizon in the field.

Bibliography:

1.Vadetsky Yu.V. Drilling oil and gas wells: a textbook for the beginning. prof. education. M .: Publishing Center "Academy", 2003. - 352 p. ISB # 5-7695-1119-2.

2.Vadetsky Yu.V. Driller's Handbook: textbook. manual for the beginning. prof. education. M .: Publishing Center "Academy", 2008. - 416 p. ISB # 978-5-7695-2836-1.