Geological conditions for drilling oil and gas wells. The process of drilling oil wells. Methods for drilling production wells

Initially, drilling was used in our country for the construction of salt wells. Information about drilling wells for oil exploration dates back to the 30s of the 19th century in Taman. At the suggestion of mining engineer N.I. Voskoboynikov in 1848, a well was drilled on Bibi-Heybat with the help of a drill, from which oil was obtained. It was the first oil well in the world to be built by drilling using a continuous fluid flushing process to clean the well of drilled rock.

Wells are drilled vertical, inclined, horizontal. The method of directional cluster drilling is widely used, when 15 or more wells are drilled in an inclined way from one site. This method is successfully used in wetlands, when drilling wells from offshore drilling platforms, to preserve fertile arable land, etc.

The concept of a well

A well is a mine working (vertical or inclined) of a circular cross section, with a depth of several meters to several kilometers, of various diameters, constructed in the thickness of the earth's crust. The top of the well is called the mouth, the bottom of the well is called the bottom, and the side surface is called the wellbore. The distance from the wellhead to the bottom along the axis of the wellbore is called the length of the well. The projection of the length on the vertical axis is called the depth of the well.

Wells are oil, gas, gas condensate, injection, observation, appraisal, etc. Well design must meet the following requirements:

• 1. Ensure mechanical stability of the wellbore walls and reliable isolation of all (oil, gas, water) formations from each other, free access to the bottom of the wells for lowering equipment, and prevention of rock collapse in the wellbore.
• 2. Efficient and reliable connection of the bottom hole with a productive (oil or gas) reservoir.
• 3. The possibility of sealing the wellhead and ensuring the direction of the extracted products to the system for collecting, treating and transporting oil and gas or injecting an impact agent into the formation.
• 4. The possibility of carrying out research work in wells, as well as various geological and technical and repair and preventive work.

The stability of the walls of the wellbore and the isolation of the layers from each other is achieved by drilling and lowering into the well several pipes, called casing. First, the well is drilled to a depth of 50-100 meters, a steel pipe is lowered into it (1 = 500 mm or more - direction. The space between the outer wall of the pipe and the wall of the well (rock) is filled with a special grouting cement mortar under pressure in order to prevent the collapse of the upper rocks and crossflows between the upper layers.Then the well is drilled with a smaller diameter bit to a depth of 500-600 m, a pipe with a diameter of 249-273 mm is lowered into it and cemented, as well as a direction, to the mouth.This pipe string is called a conductor and is designed to prevent erosion of the upper layers, and also to create a channel for drilling mud.After that, the well is drilled to the design bottomhole.A production string (steel pipe with a diameter of 146-168 mm) is lowered into it, and the space between the pipe and the rock is filled under pressure with cement mortar to the mouth. its injection pressure is determined by calculation.After hardening of the cement slurry (usually 48 hours) in the annular space between the outer wall of the pipe and the rock, a cement stone is formed, which separates the layers from each other.

Depending on the characteristics of the deposit, its reservoir pressure, geological section, etc., the design of wells can be single-string or multi-string (two or three). The last column is called the production column.

After completion of drilling, descent of the production casing, its cementation in the well in the interval of the oil or gas reservoir, through holes are made through the steel pipe and cement stone using special perforators.

After that, the well is developed and put into operation. The well can be closed or open hole. An open hole is used when the productive formation is composed of dense rocks - carbonate, calcareous or dense sandstones. With an open hole, the well is drilled to the top of the productive formation, the production string is lowered and cemented. Then, with a bit of a smaller diameter, a productive formation is opened (drilled out) through the production string. This does not require perforation, because. the productive formation is not blocked by a metal pipe.

If the productive formation consists of unstable and weakly cemented sandstones or limestones, then the bottom hole is equipped with a closed one. At the same time, the well is drilled to the design depth (the so-called “sumf” is created a little lower by 15-20 m of the productive formation), a production string is lowered into it, which is cemented, and then the productive sections of the formation are perforated to connect the formation with the bottom of the well. If the formation is represented by weakly cemented sandstones or siltstones, then the productive formation can be opened at an open hole, followed by a liner filter. The filter is represented as holes in the production string in the reservoir interval.

Methods for drilling oil and gas wells.

There are several ways of drilling, but mechanical drilling has found industrial application. Mechanical drilling is divided into percussion and rotary. In percussion drilling, the drilling tool consists of a bit 1, a shock rod 2, a rope lock 3. A mast 12 is installed on the drilled well, which has a block 5 in the upper part, a draw roller of the balancer 6, an auxiliary roller 8 and a drum of the drilling machine 11. The rope is wound around drum 11 of the drilling machine. The drilling tool is suspended on a rope 4, which is thrown over the block 5 of the mast 12. When the gears 10 rotate, the connecting rod 9, reciprocating, raises and lowers the balancing frame 6. When the frame is lowered, the draw roller 7 pulls the rope and raises the drilling tool above the bottom of the well . When the frame is raised, the rope is lowered, the bit falls on the face and destroys the rock. To clean the bottom from the destroyed rock (sludge), a drilling tool is lifted from the well and a bailer (an elongated bucket-type cylinder with a valve in the bottom) is lowered into it. To increase the efficiency of percussion drilling, it is necessary to promptly clean the bottom of the well from drill cuttings.

Rotary drilling.

Oil and gas wells are currently drilled using the rotary drilling method. In rotary drilling, the destruction of the rock occurs due to the rotating bit. Under the weight of the tool, the bit enters the rock and, under the influence of torque, destroys the rock. Torque is transmitted to the bit by means of a rotor installed at the wellhead through the drill string. This drilling method is called rotary drilling. If the torque is transmitted to the bit from a downhole motor (turbodrill, electric drill), then this method is called turbine drilling.

A turbodrill is a hydraulic turbine driven by a drilling fluid pumped into the well by pumps.

The electric drill is an electric motor in a sealed design, electric current is supplied to it via a cable from the surface.

A drilling rig is a metal structure above a well for lowering and retrieving a drilling tool with a bit, downhole motors, casing pipes, placing drill stands after they are pulled out of the well, etc.

Towers are produced in several modifications. The main characteristics of the derricks are the carrying capacity, height, capacity of the "magazines" (a place for the candlesticks of drill pipes), the dimensions of the lower and upper bases, weight (mass of the derrick).

The lifting capacity of the derrick is the maximum, maximum permissible load on the derrick in the process of drilling a well. The height of the tower determines the length of the candle that can be removed from the well, the size of which determines the duration of tripping operations.

To drill wells to a depth of 400-600 m, a derrick 16-18 m high is used, to a depth of 2000-3000 m - a height of 42 m, and to a depth of 4000 to 6500 m - 53 m. The capacity of the "store" shows what the total length of the drilling pipes with a diameter of 114-168 mm can be placed in them. The dimensions of the upper and lower bases characterize the conditions of the drilling crew, taking into account the placement of drilling equipment, drilling tools and means of mechanization of tripping operations. The dimensions of the upper base of the towers are 2x2 or 2.6x2.6 m, and the lower ones are 8x8 or 10x10 m.

The total mass of drilling rigs is tens of tons.

Well construction cycle.

Before starting drilling at the well drilling site, the site is freed from foreign objects, if there is a forest, it is cut down and uprooted. If drilling will be carried out in a wetland, then the road to the drilling site is first filled, and the site is filled, eliminating the wetlands, under the drilling rig. They make the layout of the site, bring the power line, communications and water conduit.

Drilling rigs, if the terrain and distance allow, are transported without disassembly on special caterpillar carts or on sledges with skids, and the method of pneumatic movement is also possible. After transportation and installation at the site of the drilling rig, the installation of the rest of the equipment begins, i.e. installation of piston pumps with diesel drive or pumps with electric drive; drilling fluid cleaning system, switchboard, wellhead equipment (rotor, preventer, hydraulic weight indicator), drilling shelter for near-well structures, etc. If drilling starts in a new area, remote from the drilling site, in this case, all equipment, including the drilling rig, pumping unit, treatment facilities, etc., are delivered disassembled to the drilling site and the drilling rig is assembled here and all other equipment.

After the installation of the drilling rig and all equipment, preparatory work for drilling the well begins.

Preparatory work includes:

• 1. Equipment of the traveling block and crown block with a steel rope and suspension of the lifting hook.
• 2. Installation and testing of small-scale mechanization.
• 3. Assembly and suspension to the square swivel hook (lead pipe), connecting a flexible high-pressure hose to the riser pipe and to the swivel.
• 4. Tower alignment.
• 5. Installation of the rotor.
• 6. Drilling the direction of the well.

Wells are drilled vertical, directional and horizontal. For a long time, the main type of well drilling was vertical drilling. In recent years, the method of directional drilling has been increasingly used, i.e. when, according to drilling projects, the well is drilled along a trajectory with a deviation from the vertical. Usually, it is advisable to drill inclined wells under the bottom of the sea, rivers, lakes, as well as under mountains, ravines; in swampy areas, protected forests, for large industrial facilities, cities and villages. Inclined wells are also used in the liquidation of open oil and gas fountains, as well as in order to preserve fertile lands, in order to reduce the cost of drilling wells by reducing preparatory work and communications (communications, electricity, water lines, etc.). To deviate the well profile from the vertical, special devices are used. These include: a crooked sub, a crooked drill pipe, various types of deflectors, etc. More and more in our country in recent years, horizontal drilling of wells and drilling of lateral horizontal wellbores is used in depleted and unprofitable wells, where there are undeveloped interlayers with oil.

Well perforation. After the casing pipes are lowered into the well and cemented, holes are made against the productive part of the formation using perforators in the production string and cement stone to connect the productive part of the formation with the bottom of the well. This operation is called perforation. Various methods of well perforation are used: bullet, torpedo, cumulative and hydrosandblasting.

Bullet perforator (PP) is a pipe 1 m long and 100 mm in diameter, which is loaded with compressed gunpowder and 10 steel bullets. On a logging cable, a bullet perforator is lowered into a well filled with a clay solution, set against a given interval of a productive formation, and shots are fired. The depth of the holes in the rock does not exceed 5-7 cm. Many bullets get stuck in the production string, in the cement stone, and only a small number of them penetrate the column and cement stone. Practically at present it does not find application.

Torpedo puncher (TP). Torpedo perforation is carried out by cable-launched vehicles that fire explosive projectiles with a diameter of 22 mm. The apparatus consists of sections, each of which has two horizontal shafts. The projectile is equipped with a pin-type detonator. When the projectile stops, an internal charge explodes and cracks the surrounding rock. The depth of the channels, according to tests, is 100-160 mm, the diameter of the channel is 22 mm. No more than four holes are made per 1 m of the productive part of the formation, since torpedo perforation often results in the destruction of the casing string. Just like bullet perforation, torpedo perforation is used very limitedly.

Currently, cumulative perforation (PC) is mainly used. Cumulative perforators have charges with a cone notch, which allow you to focus explosive gas flows and direct them at high speed perpendicular to the walls of the well.

A piece of compressed powdered explosive is inserted into the cumulative perforator, which has a conical recess lined with a metal plate.

Cumulative perforation is carried out by firing perforators that do not have bullets or projectiles. The piercing of the column, cement stone and rock is achieved by a focused explosion. Such focusing is due to the conical shape of the surface of the explosive charge (BB), lined with a thin metal coating (copper sheet 0.6 mm thick). The energy of the explosion in the form of a thin beam of gases - lining products - breaks through the channel. The cumulative jet has a speed in the head of up to 6-8 km/s and creates a pressure of 3-5 thousand MPa.

When fired with a shaped charge in the column and cement stone, a narrow perforation channel is formed up to 350 mm deep and 8-14 mm in diameter in the middle part.

In the oil fields, a hydrosandblast perforator (GPP) is also used.

The hydrosandblasting perforator consists of a thick-walled body, into which up to ten nozzles made of abrasive-resistant material (ceramics, hard alloys) with hole diameters of 3-6 mm are screwed.

A hydro-sandblaster is lowered into the well on tubing pipes. Before perforation of the well, a ball is thrown from the surface into the tubing, which blocks the through hole of the perforator. After that, using pumping units AN-500 or AN-700, liquid with sand is pumped into the well through the tubing. The injected fluid with sand exits only through the nozzles. When exiting the nozzles, huge speeds of the abrasive jet develop. As a result, holes are punched in casing pipes, cement stone and rock in a short time, the wellbore is connected to the productive formation. Depending on the diameter of the nozzles, their number and the speed of pumping the liquid, the depth of the perforations reaches 40-60 cm. At the same time, the tightness of the cement stone behind the column is maintained. During hydro-sand-jet perforation, a pressure of up to 40 MPa is created at the wellhead. The rate of pumping liquid with sand is 3-4 l / s per nozzle. At the same time, the volumetric velocity of the jet in the nozzle reaches 200-300 m3/day, and the pressure drop is 18-22 MPa. Duration of perforation of one interval - 15-20 minutes. At the end of the perforation of a given interval, the perforator is raised and set to the next interval, and the operation is repeated.

call inflow into the well.

In field practice, the following methods are used to cause the influx of fluid from the reservoir to the bottom of the well: bouncing, pistoning, replacing the fluid in the well with a lighter one, the compressor method, pumping a gas-liquid mixture, pumping out with downhole pumps. Before the development of the well, reinforcement is installed at the wellhead. In any case, a high-pressure valve should be installed on the casing flange to shut off the wellbore in emergency situations.

pistoning. During pistoning (swabbing), the piston, or swab, descends into the tubing on a steel cable. The piston (swab) is a pipe with a diameter of 25-37.5 mm with a valve in the lower part that opens upwards. Rubber cuffs (3-4 pieces) reinforced with wire mesh are installed on the outer surface of the pipe (at the joints). When the swab is lowered below the level, the liquid in the well flows through the valve into the space above the piston. When the swab is lifted, the valve closes, and the cuffs, bursting under the pressure of the liquid column above them, are pressed against the tubing walls and sealed. For one rise, the piston takes out a liquid column equal to the depth of its immersion under the liquid level. The immersion depth is limited by the strength of the tether rope and is usually 100-150 m.

Tartaning is the extraction of fluid from a well with a bailer lowered on a steel (16 mm) rope using a winch on a tractor (car). A bailer is made from a pipe 7.5-8 m long, which has a valve in the lower part with a stem that opens when it rests on the stem. In the upper part of the bailer there is a bracket for fastening the rope. The bailer diameter should not exceed 0.7 of the casing string diameter. For one descent of the bailer, the liquid from the well is carried out with a volume of not more than 0.06 m3.

Tartaning is a laborious and inefficient way. At the same time, bailing makes it possible to extract mud from the bottomhole and control the level of fluid in the well. Repeated descent and raising of the piston lead to a gradual decrease in the liquid level in the well. The big disadvantage of this method is that you have to work with an open mouth, which is associated with the danger of liquid ejection and open flowing. Therefore, pistoning is mainly used in the development of injection wells.

Fluid replacement in the well. A well completed by drilling is usually filled with mud. If we replace the clay solution in the well with water or degassed oil, then we will reduce the bottomhole pressure. In this way, wells with high reservoir pressure and good reservoir properties are developed.

Compressor way of development. The compressor method has a wider application in the development of wells. Tubing pipes are lowered into the well before development, and the wellhead is equipped with a Christmas tree. A mobile compressor or a high-pressure gas line from a gas compressor station is connected to the annular space through the discharge pipeline. When gas is injected into the well, the liquid in the annular space is pushed back to the tubing shoe or to the starting hole (3-4 mm) in the tubing, made in advance at a depth of 700-800 m from the wellhead, and breaks into the tubing. Gas entering the tubing aerates the liquid in them. As a result, downhole pressure is significantly reduced. By adjusting the gas flow, the density of the gas-liquid mixture in the pipes is changed, and, accordingly, the pressure at the bottom of the well. When the bottomhole pressure is below the formation pressure, the inflow of liquid and gas into the well begins. After receiving a stable inflow, the well is transferred to a stationary mode of operation. This method makes it possible to relatively quickly obtain significant drawdown pressures, which is especially important for efficient cleaning of the bottomhole zone of the well. Under the conditions of hard rocks (sandstones, limestones), this leads to intensive cleaning of the pore space from the calming (plugging) material, and in the conditions of loose rocks, to the destruction of the bottomhole formation zone. To ensure a smoother start-up of the well, aerated oil is pumped through the annular space using a compressor, a flushing unit and a mixer. After the gas-liquid mixture is ejected through the flow line into the receiving tank, the supply of aerated oil is gradually reduced until it stops completely.

The development of wells with compressed air is mainly carried out using mobile compressors UKP-80 or KS-100. The UKP-80 compressor develops a pressure of 8 MPa with an air supply of 8 m3/min, and the KS-100 develops a pressure of 10 MPa with an air supply of 16 m3/min. It should be noted that explosions are possible during the development of wells with compressed air, since an explosive mixture is formed when the content of hydrocarbon gas in a mixture with air is from 6 to 15%.

Development of wells by injection of carbonated liquid.

The development of wells with carbonated liquid is that instead of gas or air, a mixture of gas and liquid (water or oil) is pumped into the annulus. The density of such a gas-liquid mixture depends on the ratio of the flow rates of the injected gas and liquid, which makes it possible to control the parameters of the development process. Taking into account the fact that the density of the gas-liquid mixture is greater than the density of pure gas, this method makes it possible to develop deep wells with compressors that create less pressure.

Development of injection wells. Injection wells must have high injectivity throughout the thickness of the productive formation. This can be achieved by good cleaning of the bottomhole zone of the productive formation from dirt and other calmatizing materials. The bottomhole formation zone is cleaned before starting the injection well for injection by the same methods as in the development of oil wells, but the drainage of the bottomhole formation zones is carried out much longer in time. The duration of flushing reaches one day or more and depends on the amount of mechanical impurities contained in the water leaving the well. The content of mechanical impurities at the end of washing should not exceed 10-20 mg/l.

The maximum cleaning of the pore space of the bottomhole formation zone occurs using such drainage methods that allow you to create very high pressure drawdowns on the formation, providing high fluid filtration rates to the well bottoms in unsteady conditions. Most often, reservoir drainage is carried out by the methods of self-discharge, fluid aeration, pumping using high-performance submersible centrifugal pumps, etc.

In the development of injection wells, the method of variable pressures (MPD) has been widely used. When using this method, a high discharge pressure is periodically created into the bottomhole formation zone through the tubing using pumping units for a short time, which is then abruptly released through the annular space (they “discharge” are carried out). When fluid is injected with high pressure in the bottomhole formation zone, existing cracks are opened and new ones are formed, and when the pressure is released, fluid flows to the bottomhole at a high speed. Good results are obtained when using the method of periodic drainage of bottomhole zones by creating multiple instantaneous high drawdowns at the bottomhole.

Sometimes poor injectivity of injection wells occurs either due to the low natural permeability of the reservoir rocks, or a large number of clay interlayers, which cannot be developed by draining bottomhole zones. In such cases, to increase the injectivity of injection wells, other methods of influence are used, which allow increasing the diameters of filtration channels or creating a system of cracks in the reservoir rocks. Such methods include various acid treatments, thermal methods, hydraulic fracturing, slot unloading, treatment of the formation with an oxidate, etc.

Vladimir Khomutko

Reading time: 3 minutes

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Methods for drilling oil and gas wells

The well is a vertical or inclined mine working of a circular cross section, the construction of which takes place without access to the interior of the working of a person. The length of such a working is several times greater than its diameter.

How oil wells are drilled

The main elements of any well are:

• mouth (uppermost part);
• trunk (intermediate part);
• bottomhole (the lowest part located in the reservoir).

The distance between the mouth and the bottom along the axis of the working shaft is called the length of the well, and the same distance, but taken along the vertical projection of the axis, is called its depth.

Derrick

In other words, the length and depth of a vertical well are the same, but an inclined one is not.

Drilling oil and gas wells, as a rule. occurs with a gradual decrease in the diameter of the trunk after a certain section has been drilled. The initial diameter of such a working, as a rule, is not more than 900 millimeters, and the diameter in the face area is from 75 millimeters or more.

The process of deepening such a mine working is the destruction of rocks either over the entire area of ​​the face (the so-called continuous drilling) or along its periphery (core drilling). In the second case, a piece of cylindrical rock, called a core, remains in the mine shaft. Cores are periodically retrieved from the well to study the composition of the passed rocks. The specialty of a person who is engaged in drilling is called a driller.

Many of you are interested in the question: “How are wells drilled?”

Methods of deepening mine workings according to the criterion of the nature of the impact on passable rocks are divided into:

• mechanical;
• thermal;
• physical and chemical;
• electrical and so on.

In the industrial development of deposits, only mechanical methods are used. All other listed techniques are at the stage of experimental verification of effectiveness.

Mechanical methods are rotational and impact.

The impact method involves the mechanical destruction of the rock with the help of a special tool suspended on a rope, which is called a chisel. In addition, the composition of such a drilling device includes a rope lock and a shock rod. The device is suspended on a rope thrown over a block, which is placed on a mast, and a special drilling machine gives this tool a reciprocating motion.

As the depth of the trunk increases, the rope is gradually lengthened. The cylindrical shape of the barrel is formed by turning the bit during operation.

To clean the bottomhole from the drilled rock, the tool must be periodically raised to the surface. Instead, a special device called a bailer is lowered. It looks like a long bucket, equipped with a valve at the bottom.

The bailer is immersed in the liquid (either reservoir or surface supplied) and the valve opens. A mixture of liquid and pieces of destroyed rock enters the “bucket”, after which all this is removed to the surface (as soon as the bailer is lifted, the valve immediately closes). After the end of the bottomhole cleaning, the drilling tool is lowered into the shaft again, and the process is repeated again and again.

To prevent the walls from collapsing, a special pipe, called a casing, is lowered into it. From such pipes, as the mine working deepens, a whole pipe string is formed.

Well drilling bit

In Russia, at the moment, the shock method is not used in practice.

The rotational method involves the deepening of the tool into the rock mass due to the simultaneous impact on the bit of torque and vertical load. The vertical load drives the bit into the rock being drilled, and the torque allows the tool to shear, abrade and crush the rock.

Depending on where the unit's engine is located, rotary drilling is divided into rotary drilling (the engine is located on the surface and rotates the bit through a tubular string made up of special drill pipes) and downhole drilling (the engine is located in the bottom hole and is placed directly above the bit).

In the rotary method, the motor rotates the rotor, which, in turn, rotates the drill string, at the end of which the bit is attached. In the downhole method, the motor rotates the bit itself, while the drill string and the body of the motor itself remain stationary.

For the rotary drilling method, a characteristic feature is the use of constant flushing of the borehole with either water or specially prepared drilling fluids. For this purpose, special mud pumps are used, the operation of which is provided by engines of various types. It is these pumping units that pump the flushing fluid through the riser pipeline, which is mounted, as a rule, in the right corner of the drilling rig. Further, by means of a flexible drill hose and a swivel, the fluid is fed directly into the drill string itself.

Reaching the level of the bit, this flushing fluid enters the rock through the holes that are in this tool, and then through the annular free space that remains between the wall of the wellbore and the drill string. rises up, washing out pieces of drilled rock. Further, with the help of a system of gutters and special cleaning devices, this liquid is cleaned of cuttings, after which it enters a tank located on the mud pump. After that, it can be reused.

Drilling is the construction of a mining directional working of small diameter and great depth. The mouth of the well is located on the surface of the earth, and the bottom is located at the bottom. Today, drilling of oil and gas wells for the extraction of the corresponding minerals is widespread.

Tasks and goals of drilling for oil and gas

Today, oil and gas are extracted from wells. Despite the large number of different ways to make a well, they are still developing, new methods are being developed to speed up the work and reduce the cost of their cost.

The modern drilling process consists of the following steps:

• shaft sinking
• Separation of layers
• Well development and operation

The drilling of wells is divided into two stages, which should take place in parallel to each other: the deepening of the bottom and its cleaning from destructible rocks. Separation of rocks is also carried out in two stages: installation of casing pipes, their joining and sealing with each other.

Despite the fact that at home no one will drill an industrial well for oil and gas, it is interesting to know how much an oil well costs and which methods are most widely used.

Oil drilling process - video

Basic drilling methods

Today, various methods of drilling oil wells are practiced, but the most common among them are:

• Rotary drilling with a caisson for a well
• Turbine drilling
• Screw drilling

Rotary drilling of oil wells is one of the popular methods. The chisel, passing into the depths of the soil rocks, rotates together with the drill pipes. The torque of such a system, first of all, depends on the resistance of the rocks that come across on the way.

Rotary well drilling owes its popularity to such advantages as the ability to withstand large WOB fluctuations, independence of settings from extraneous factors, and a large passage in one run.

Turbine drilling of wells for oil is carried out by means of an installation in which the bit interacts with the turbodrill turbine. The unit is driven into rotation by a fluid flow that circulates under high pressure through a system of stators and rotors. Due to this, including the lifting and pumping of well water.

Torque is independent of well depth, rock properties, rotational speed and axial load. At the same time, the transmission coefficient in turbine drilling is an order of magnitude higher than in rotary drilling, but the cost of work is higher due to the need for a large amount of energy, it is impossible to quickly reconfigure the installation parameters.

Screw drilling of oil and gas wells lies in the fact that the main working mechanism consists of a large number of screw mechanisms, due to which the optimal bit rotation frequency is achieved. Despite all the prospects, this method has not yet received proper distribution, but it has a huge potential for this.

Issue price

Having found out for yourself how oil wells are drilled, the question of how much you have to spend to drill the next meter of the funnel certainly becomes interesting.

Today, the cost of drilling an oil well is very huge and depends on a large number of factors:

• Well depth
• The need to purchase casing plastic pipes for wells
• Ambient conditions
• Deadlines

If we talk about exact figures, then the price of a well with a depth of 2000-3000 meters will be from 30 to 60 million rubles. Exploratory drilling will cost about 40-50% of the cost of drilling.

It is important to note that the drilling of oil and gas wells can only be carried out with the strictest observance of all rules and requirements. And this is not at all surprising, because you have to work with a rather dangerous and sensitive material, the extraction of which in any case requires a competent approach. And in order to understand all aspects of working with such, it is necessary first of all to consider all the basics of this case and its components.

So, a well is called a mine working, which is created without the need for access inside a person and has a cylindrical shape - its length is many times greater than the diameter. The beginning of the well is called the mouth, the surface of the cylindrical column is called the trunk or wall, and the bottom of the object is called the bottom.

The length of the object is measured from the mouth to the bottom, while the depth is measured by the projection of the axis onto the vertical. The initial diameter of such an object at the maximum does not exceed 900 mm, while the final diameter in rare cases is less than 165 mm - this is the specificity of the process called drilling of oil and gas wells and its features.

Features of drilling oil and gas wells

The creation of wells as a separate process consists mostly of drilling, and it, in turn, is based on the following operations:

• The process of deepening when destroying rocks with a drilling tool,


• Removal of crushed rock from the well,


• Strengthening the shaft with casing strings as the mine deepens,


• Performance of geological and geophysical works to search for productive horizons,


• Production string cementing.

Classification of oil and gas wells

It is known that the necessary materials that are planned to be mined can occur at different depths. And therefore, drilling can also be performed at different depths, and at the same time, if we are talking about a depth of up to 1500 meters, drilling is considered shallow, up to 4500 - medium, up to 6000 - deep.

To date, drilling of oil and gas wells is carried out at ultra-deep horizons, deeper than 6000 meters - in this regard, the Kola well is very indicative, the depth of which is 12650 meters.

If we consider drilling methods, focusing on the method of destruction of rocks, then here we can cite as an example mechanical methods, for example, rotational, which are implemented using an electric drill and screw-type downhole motors.

There are also percussion methods. And they also use non-mechanical methods, among which are electropulse, explosive, electrical, hydraulic and others. All of them are not widely used.

Works while drilling for oil or gas

In the classic case of drilling for oil or gas, drill bits are used to break the rock, and flushing fluid flows constantly clean the bottomhole. In rare cases, a gaseous type working reagent is used for purge.

In any case, drilling is carried out vertically, inclined drilling is used only when necessary, and cluster, directional, double-lateral or multilateral drilling is also used.

Deepening of wells is carried out with or without core sampling, the first option is used when working along the periphery, and the second - over the entire area. If the core is taken, it is examined for the passed rock layers, periodically lifting it to the surface.

Drilling for oil and gas is carried out today both onshore and offshore, and such work is carried out using special drilling rigs that provide rotary drilling using specialized drill pipes that are connected by socket-and-lock threaded connections.

Also, sometimes continuous flexible pipes are used, which are wound on drums and can have a length of about 5 thousand meters or more.

Thus, such works cannot be called simple by any means - they are very specific and complex, and special emphasis here should be placed on new technologies, the study of which can be a difficult task even for professionals in this industry.

New technologies for drilling oil and gas wells at the exhibition

Sharing information and learning about innovations can ensure optimal progress, and therefore such a need simply cannot be left aside.

If you decide to join modern achievements and plunge into the professional environment, professional events are held for this purpose, and you should definitely take part in one of them. We are talking about exhibitions that are held annually at the Expocentre Fairgrounds and gather hundreds and thousands of specialists in this area during the opening days.

At the annual oil and gas exhibition you can easily access new developments, study advanced technologies (for example, oil and gas drilling technologies), see modern equipment and at the same time acquire useful contacts in the required volume, find customers and partners.

Opportunities like these are not to be missed, because they don't come around very often and can make a big difference if done right!

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Drilling oil or gas wells is a complex and, in some cases, dangerous process. The drilling of oil or gas wells can only be successfully carried out with the obligatory observance of a number of rules and regulations. Well drilling is used for various purposes, including: studying the structure of the earth's crust, prospecting and exploration of oil, gas, water and solid minerals, as well as in the construction of roads for studying the soil, etc. At the same time, when searching for oil and gas, deep drilling is carried out, which is a complex process and is usually time-consuming for the people carrying out the drilling. It requires large material and technical means, including special tools, materials, equipment and installations.

In a number of places in our country, drilling for oil and gas is carried out in difficult geological and climatic conditions with the achievement of productive horizons at a depth of less than 3 km, and often 4-5 km.

As mentioned earlier, drilling at great depths, including under saline strata, as well as hard-to-reach areas of the tundra with permafrost and taiga, of course, requires drillers in modern conditions to carry out all types of work related to drilling deep wells for oil and gas, with special responsibility and high qualifications. Otherwise, various complications are possible during well drilling, which can adversely affect people and the environment. Therefore, a thorough and responsible approach to their duties for each member of the drilling crew is the main principle of trouble-free work of drillers in the process of drilling deep wells for oil and gas.

A number of drilling crews in recent years, when the development of uninhabited and hard-to-reach areas began, including Western Siberia, use a rotational method, i.e. with. crews of drillers go to the drilling site for a short time, living in field conditions. And then they return to their stationary drilling organizations.

Drilling of deep wells is carried out by mechanical destruction of rocks using special engines. There are two types of mechanical drilling: percussion and rotary. Percussion drilling, also called shock-rope, is as follows. We hang a chisel on a rope, which periodically falls on the faces and destroys the rock. The rope is located on the drum of the drilling rig and can be lowered and raised with the help of various devices.

Destroyed rock at the bottom, called cuttings, is periodically removed. To do this, the drilling tool is raised, the bailer is lowered down (a bucket with a valve in the bottom). When the bailer is submerged, the valve opens and it is filled with a mixture of formation or topped-up fluid and drilled rock. When the bailer is raised, the valve closes. As a result of repeated lowering and raising of the bailer, the bottom of the well is cleared, and drilling of the well continues again.

When percussion drilling, as a rule, no drilling fluid is used. But in order to preserve the drilled wellbore, I case the well, i.e., they lower the casing string, which consists of metal pipes connected through a thread or by welding. As the well deepens, the casing string is advanced to the bottom and lengthened by adding one more pipe. If it is impossible to move the casing down, a second casing string of smaller diameter is lowered inside. To do this, the well is deepened with a chisel, and the column is built up. It is possible to run subsequent columns of smaller diameter until the design depth is reached.

The effectiveness of the percussion drilling method depends on the choice of bit for drilling a certain rock, on the mass of the drilling tool, the number of hits of the bit on the bottom and other reasons.

The impact drilling method uses machines with a small mass (up to 20 tons), which makes it easy to transport them for drilling shallow wells far from populated areas.

But when drilling oil and gas wells, the impact method is not used. Drilling for oil and gas is carried out by the rotary drilling method.

Rotary drilling is performed as a result of the simultaneous impact on the bit of the load and torque. This method of drilling is carried out using a rotor or downhole motors: a turbodrill or an electric drill.

During rotary drilling, the power from the engine will be transferred to the rotor - a rotary mechanism installed above the wellhead in the center of the tower. The rotor rotates the drill string of pipes with a bit.

When drilling with a downhole motor, the bit is screwed to the shaft, and the drill string is screwed to the motor housing. When the engine is running, its shaft and bit rotate, but the drill string does not rotate. Consequently, in rotary drilling, the bit is deepened into the rock when the drill string is moving along the axis of the well and the drill string is rotating, and when drilling with a downhole motor, the drill string is not rotating.

With the rotary drilling method, the well is flushed with water or clay solution during the entire time the bit is at the bottomhole. The flushing fluid is injected into the well and brings the cuttings to the surface, into special containers (chutes), then it is cleaned and cleaned by cleaning mechanisms and again enters the receiving tanks of the mud pumps and is pumped into the well.

Drill pipes are lifted to change worn bits, they are unscrewed into sections called candles. Candles are installed and the lantern of the tower on the candlestick. Then the drill string is lowered into the well in reverse order.

Downhole motors include: turbodrill and electric drill. The rotation of the turbodrill shaft occurs due to the conversion of the hydraulic energy of the flushing fluid flow through the drill string entering the turbodrill into the mechanical energy of the turbodrill, with which the bit is rigidly connected.

When drilling with an electric drill, energy is supplied to its engine through a cable, the sections of which are fixed concentrically inside the drill string.

Various rotary drilling methods have specific features of the drilling mode. The drilling mode is characterized by a complex of drilling buyers, including: penetration rate, bottom hole load, bit rotation frequency, flushing fluid consumption, etc.

The optimal drilling regime is understood as a combination of such drilling parameters at which the greatest effect is achieved, i.e., high drilling speeds are obtained at relatively low costs of material and money, and the actual wellbore is close to the design one.

For each rock, it is possible to choose the optimal drilling parameters: weight on bit, bit speed and drilling fluid flow rate.

In the case of drilling with the help of a rotor, there is no relationship between the parameters of the drilling mode, so I select the optimal mode! for each parameter separately. At the same time, depending on the geology of the section, taking into account the hardness of the rocks, the load on the bit and the frequency of its rotation are selected, and the flow rate of the drilling fluid is set depending on the degree of cleaning of the bottom hole.

In contrast to rotary drilling, when drilling with a turbodrill, there is a relationship between the parameters of the drilling mode. For example, with an increase in the flow rate of the flushing fluid at the same load on the bottom, the rotational speed of the turbodrill also increases. And depending on the rock hardness, the load changes, and accordingly the bit rotation frequency changes, which leads to optimal well drilling performance. When drilling with an electric drill, in contrast to turbine drilling, no relationship is established between the parameters of the drilling mode, however, the speed of the bit is high, which ensures the optimal drilling mode.

In most cases, the project drills vertical wells, the borehole of which is close to vertical. Vertical wells include wells in which the angle between the axis of the well and the vertical (zenith angle) along the entire wellbore has a deviation of no more than 2°. If the deviation is more than 2°, the wells are considered deviated.

The reasons for the curvature of wells can be different and depend both on the natural geological conditions of well drilling, and on the result of the activities of drillers and other services associated with drilling wells for oil and gas. The geological reasons for the curvature of wells include: inclined occurrence of layers, tectonic disturbances, the presence of capernes, interbedding of rocks of different hardness, as well as solid inclusions such as boulders, etc. Technical reasons include: curvature of drill pipes, skew in threaded connections, etc. Technological reasons include: incorrect choice of well design, incorrect ratio of drill pipes and well diameters, use of unfavorable drilling conditions, etc.

A significant deviation from the design wellbore leads to major drilling complications, including accidents.

As a result of involuntary well curvature, the following difficulties may occur: complication of tripping, more intensive wear of drill pipes and couplings, rock falls, abrasion of casing pipes, difficulty in lowering them into the well, an increase in the risk of pipe collapse, complications during cementing, etc.

Lateral deviated wells are unreliable during operation and quickly fail due to premature wear of downhole pumping equipment, pumping rods and production string.

However, in a number of cases, specially inclined and horizontal drilling of wells is carried out, including under the seabed, under ravines, mountains, in areas occupied by nature reserves, under industrial facilities and residential villages, when extinguishing burning fountains and eliminating open emissions of oil and gas, etc. .

In this case, special deflectors are used, which are installed between the turbodrill and the drill string.

To drill wells for oil and gas, bits are used, which are drilling tools for the mechanical destruction of rocks. Usually, for drilling medium-hard, hard, strong and very hard rocks, bits of crushing-shearing action, the so-called cone bits, are used.

In some cases, cutting-abrasive bits with diamond and hard-alloy inserts are also used. They are used in drilling sections where there is an alternation of rocks of different hardness, including a combination of high-plastic with medium-hard rocks.

The moment when the bit is lowered into the hole, at which drillers use special stabilizers to ensure that the bit is accurately lowered to the center of the hole.

The bits can be used for continuous drilling, when the rock is destroyed along the entire face, or for ring drilling, when the rock is destroyed along the face ring. In the latter case, the bits are called core bits and are used to take core from the well. In this case, drilling heads are used: cone, diamond and carbide. The core bit consists of a drill head, a dredger, a core set body and a ball valve. With the help of a soil carrier, in which there are core extractors and core holders, and at the top of a wide valve, the core is selected and stored until it is raised to the surface.

The drill string is designed to carry out the process of drilling a well. It connects the bit or downhole motor to surface equipment. The drill string consists of a row of drill pipes. At the top of the shō there is a leading square tube attached to a swivel. Drill pipes are screwed together with drill joints and couplings. The task of the drill string is to transfer rotation to the bit, create a load on the bit, to raise and lower the bits, to carry out various auxiliary work in the process of drilling a well and testing formations.

To rotate the bit at the bottom of the well, the mechanisms mentioned above are used: rotors, turbodrills and electric drills.

The rotors provide rotational movement of the drill string and bit, and also support the weight of the heavy drill string. The rotor, installed at the wellhead, consists of a frame, in the inner part of which a rotating table is installed. In the center of the table there is a hole (through) for lowering bits and drill pipes through it. The diameter of the rotor table hole varies from 400 to 700 mm, which is determined by the maximum diameter of the bit that passes through it. Inserts and clips are inserted into the central hole, which provide suspension for the square section leading pipe. A subsequent drill pipe is attached to the kelly, and then others.

Turbodrills, being downhole motors, convert hydraulic energy into mechanical energy, which ensures the rotation of the turbodrill shaft and bit. The turbodrill consists of two main elements of the turbine: a stator, rigidly fastened to the body, and a rotor, fixed on the turbodrill shaft. Due to the many stages (up to 350), the hydraulic flow, flowing from stage to stage, creates a powerful mechanical energy that drives the bit. The more stages in a turbodrill, the greater the power and torque, and the more efficient the turbodrill.

Electric drills convert the electrical energy supplied from the surface into mechanical energy that rotates the bit at the bottom. Electric drills, consisting of two main parts - an electric motor and an oil-filled spindle, with a screwed bit are lowered into the well on the drill string. Power from the power transformer is supplied through an external cable and an internal cable, the latter of which is installed in the drill pipe string. In this case, the flushing liquid, having passed through the system of subs and dubricators, gets inside the hollow shaft of the electric motor and then to the bit. And then, as in rotary and turbine drilling, the drilling fluid entrains cuttings and lifts them through the annulus to the surface.

Drilling rigs differ in their characteristics depending on the depth of drilling. The hook load of the drilling rig must match the weight of the drill string, and the weight of the drill string must be greater than the weight of the casing string.

In this regard, drilling rigs differ in parameters (maximum allowable hook load), which depend on the diameter of the well and drill pipes, as well as on the mass of the latter.

Drilling rigs differ in the characteristics of drilling and power equipment.

General view of a drilling rig for drilling wells for oil and gas.

The drilling rig includes a number of mechanisms that are mounted on a common base, which makes it possible to transport the rig from one well to another in an assembled form. A typical rotary drilling rig includes: a tower, a crane block, a travel block, a hook, a swivel, a winch, diesel engines, a gearbox, a mud pump, pump receiving tanks, pneumatic control, a rotor. The installation has a metal frame, which is sheathed with shields and boards or rubberized fabric to protect mechanisms and people from precipitation and wind.

In addition, the installation kit includes a circulation system, which consists of a vibrating whitefish, gutters, receiving tanks for flushing liquid, and discharge pipelines.

More sophisticated drilling equipment and rigs are used for offshore drilling. As mentioned earlier, offshore drilling is carried out either from fixed platforms or from floating platforms and special vessels.

At the same time, stationary platforms require the construction of a metal base, rigidly fastened to the seabed. For this, support blocks are used, installed by special security units, which are reliably cemented.

The drilling bases are connected by overpasses, and all drilling facilities are located on the near-overlapping areas very compactly and are covered to protect the equipment and workers of the drilling crew. Offshore construction work on the construction of the foundation and the installation of drilling equipment is very time-consuming and is carried out by special organizations.

On the most modern drilling rigs, there is a control panel for the drilling process, where the control is carried out by buttons mounted on a compact membrane-type keyboard. So, for example, the driller's console for the Power Drill 2000 drive, supplied by the US General Electric Drive System, is made in the style of modern industrial design and has closed keys that were specially designed so that they can be accurately used by the driller in thick working areas. mittens.

Fluorescent digital displays - three programmable and one diagnostic - provide the driller with data on the status of the drilling rig and operating parameters. Automatic diagnostics and direct communication with the Power Drill 2000 drive make the console a unique tool for the driller. Each time the driller tries to set an illegal function, the console informs him of the error. The error that is most likely to cause the drilling rig to stop working is identified first.

This will give the driller instant feedback, allowing them to correct the error and resume normal work more quickly. The operator can switch diagnostic displays to get more information about detected faults. System status is permanently displayed in simple, full words on an easy-to-read programming device on a dedicated keypad mounted directly on the drive. Diagnostic alarms are delivered to the keypad using easy-to-read text, allowing rig personnel with minimal electrical skills to identify a problem at any level in a matter of minutes.

In addition to a drilling rig with a rotor, a turbodrill or an electric drill, a set of bits, the following equipment and materials are available at the drilling site:

• 1) drill rods and tubing;
• 2) casing pipes;
• 3) pumps for pumping liquids and compressors for pumping gas or air;
• 4) clay and various chemicals;
• 5) containers for mud and other flushing liquids;
• 6) cementing units and cement;
• 7) perforators and seam testers and other equipment.

Before drilling a well, the geological service, together with drilling and design organizations, draws up a geological and technical work order (GTO), which includes the geological and technical parts. Drillers start drilling the well after the approval and signing of the GTN by the heads of the organizations performing the work. In the geological part of the GTN, a predicted section of deposits at the well drilling site is given. Depths of penetration of various stratigraphic subdivisions of the section are indicated, the design section of deposits (lithological column) indicating the strength of the rocks,

the required intervals for coring and testing of formations in an open hole are given, as well as possible complications when drilling against certain intervals of the section, a set of necessary field geophysical works is given.

The technical part proposes the most optimal well design, indicates: string test conditions, fluid and chemical reserves, drilling methods, downhole motor type, type, size, number of bits, well drilling mode (axial load, rotor speed, pump feed, deprivation, number of pumps), type of drilling fluid according to drilling intervals, drilling fluid parameters, chemical treatment of the fluid, tool lifting speed, drill string layout, drilling rig parameters, etc.

The design of the well is a system of pipes of various diameters and depths of descent into the well, which ensures its rigid attachment to the walls of the wellbore and adjacent rocks. Usually, in order to block the upper part of the section, composed of loose rocks, a pit is built with a depth of 4--8 m and a large-diameter pipe with a window at the top is lowered into it. The space between the pipe and the wall of the pit is filled with rubble stone with cement mortar, which makes it possible to reliably strengthen the wellhead. Then a metal gutter is welded to the window in the pipe, through which, during the drilling of the well, the flushing fluid is directed to the gutter system. A pipe installed in a pit is called a direction.

After setting the direction, they start drilling the well. After drilling loose rocks in the upper part of the section (50--400 m), a steel pipe casing is lowered and the annulus is cemented. The first casing string is called the conductor.

Then drilling continues. If further complications arise during drilling due to unstable formations, a second casing string, called an intermediate casing, is lowered. In some cases, both the third and fourth strings have to be run in order to strengthen the wellbore.

After reaching the design depth, the production string is lowered into the well and it is cemented. It can be designed either to lift oil or gas to the surface, or to inject water (gas or air) into the reservoir to maintain pressure.

The layout of casing strings, indicating their diameters, the depth of transition from a larger diameter to a smaller one, the depth of running casing strings and their cementing intervals, allows us to imagine the design of the well.

According to the number of lowered casing strings, wells can be single-string, double-string and triple-string. Typically, the initial hole diameter ranges from 400 to 600 mm, and the final diameter is 127 mm (5").

During drilling, collapses of the upper part of the sedimentary complex, composed of clays, sandstones and pebbles, were often observed; the formation of caverns in the halogen rocks of the kungur, in which the breakage of the drilling tool occurred; abnormally high pressure occurred, requiring drilling in a weighted mud (1.7 g / cm "); absorption of clay mud (up to the loss of circulation) during the penetration of porous and fractured rocks, which, in combination with abnormally high pressure, threatens open gas emissions; the formation of oil seals against porous and fractured rocks of the productive strata, which leads to sticking and tightening of the drilling tool.

After the casing strings are lowered into the well, they are cemented (cementing). To do this, cement is poured into the annulus using special grouting cements. Cement mortars are prepared in special cement mixing machines that come to the drilling rig. Through cementing units equipped with pumps, cement is forced from the casing string into the annulus of the well up to a certain height of cement rise, specified in the GTN.

The drilling of productive horizons in exploratory wells is carried out with core bits in order to select and then study the core. After completion of drilling of productive formations, a full scope of field geophysical well surveys (GIS) is carried out.

Then the formations are tested with the help of formation testers, which are based on the induction of oil flow from the formation due to a sharp pressure drop in the formation-drill string system.

Typically, the well is drilled just below the bottom of the pay zone, run in a production string, and cemented once or twice. Then, after the cement has hardened, the wall of the string, including the cement ring, is perforated opposite the productive formation to establish a connection between the string and the formation. For this, various perforators (cumulative, torpedo or bullet) are used. The most commonly used cumulative perforators are based on the action of a cumulative jet that occurs due to the explosion of the copper lining of the charge and the shock wave. In this case, a thin metal jet is ejected at a speed of 8,000–10,000 m/s and punches holes in the column and cement stone. The perforator is lowered into the well and a calculated network of holes is produced against the productive formation.

Underground workover of wells is carried out both in the process of drilling and during their subsequent operation by special underground workover teams that perform major and current repairs of wells. Repair crews usually work in shifts, like drilling crews.