Technology of drilling gas wells. Technique and technology of drilling oil wells. Well drilling design

Drilling is the impact of special equipment on the soil layers, as a result of which a well is formed in the ground, through which valuable resources will be extracted. The process of drilling oil wells is carried out according to different directions works that depend on the location of the soil or rock formation: it can be horizontal, vertical or inclined.

As a result of work, a cylindrical void is formed in the ground in the form of a straight shaft, or well. Its diameter may vary depending on the purpose, but it is always less than the length parameter. The beginning of the well is located on the soil surface. The walls are called the trunk, and the bottom of the well is called the bottom.

Key milestones

If medium and light equipment can be used for water wells, then only heavy equipment can be used for oil well drilling. The drilling process can only be carried out with the help of special equipment.

The process itself is divided into the following stages:

• Delivery of equipment to the site where the work will be done.
• The actual drilling of the mine. The process includes several works, one of which is the deepening of the shaft, which occurs with the help of regular flushing and further destruction of the rock.
• So that the wellbore is not destroyed and does not clog it, the rock layers are strengthened. For this purpose, a special column of interconnected pipes is laid in space. The place between the pipe and the rock is fixed with cement mortar: this work is called plugging.
• Last work is development. The last layer of rock is opened on it, a bottomhole zone is formed, and the mine is perforated and fluid is drained.

Site preparation

To organize the process of drilling an oil well, it will also be necessary to carry out a preparatory stage. If the development is carried out in the forest area, it is required, in addition to the preparation of the main documentation, to obtain consent to work in the forestry. The preparation of the site itself includes the following steps:

1. Cutting down trees in the area.
2. The division of the zone into separate parts of the earth.
3. Drawing up a work plan.
4. Establishment of a settlement to house the labor force.
5. Ground preparation for the drilling station.
6. Carrying out marking at the place of work.
7. Creation of foundations for the installation of tanks in a warehouse with combustible materials.
8. Arrangement of warehouses, delivery and debugging of equipment.

After that, it is necessary to start preparing equipment directly for drilling oil wells. This stage includes the following processes:

• Installation and testing of equipment.
• Wiring lines for power supply.
• Installation of bases and auxiliary elements for the tower.
• Installing the tower and lifting to the desired height.
• Debugging of all equipment.

When the oil drilling equipment is ready for operation, it is necessary to obtain a conclusion from a special commission that the equipment is in good condition and ready for work, and the personnel have sufficient knowledge in the field of safety rules in this kind of production. When checking, it is clarified whether lighting devices have the correct design (they must have an explosion-resistant casing), whether lighting with a voltage of 12V is installed along the depth of the mine. Notes regarding the quality of work and safety must be taken into account in advance.

Prior to drilling a well, it is necessary to install a hole, bring in pipes to strengthen the drill shaft, a chisel, small special equipment for auxiliary work, casing pipes, instruments for measuring during drilling, provide water supply and resolve other issues.

The drilling site contains accommodation facilities for workers, technical facilities, a laboratory building for analysis of soil samples and the results obtained, warehouses for inventory and small working tools, as well as medical aid and safety facilities.

Features of drilling an oil well

After installation, the processes of re-equipment of the traveling system begin: in the course of these works, equipment is installed, and small mechanical means are also tested. Installation of the mast opens the process of drilling into the soil; the direction should not diverge from the axial center of the tower.

After the centering is completed, a well is created for the direction: this process means installing a pipe to strengthen the wellbore and pouring the initial part with cement. After setting the direction, the centering between the tower itself and the rotary axes is re-adjusted.

Pit drilling is carried out in the center of the shaft, and in the process, casing is made using pipes. When drilling a hole, a turbodrill is used; to adjust the rotation speed, it is necessary to hold it with a rope, which is fixed on the tower itself, and is physically held by the other part.

A couple of days before the launch of the drilling rig, when the preparatory stage has passed, a conference is held with the participation of members of the administration: technologists, geologists, engineers, drillers. The issues discussed at the conference include the following:

• The scheme of occurrence of layers in an oil field: a layer of clay, a layer of sandstone with water carriers, a layer of oil deposits.
• Design features of the well.
• The composition of the rock at the point of research and development.
• Accounting for possible difficulties and complicating factors that may arise when drilling an oil well in a particular case.
• Consideration and analysis of the map of standards.
• Consideration of issues related to trouble-free wiring.

Documents and equipment: basic requirements

The process of drilling a well for oil can begin only after a number of documents have been issued. These include the following:

• Permission to start the operation of the drilling site.
• Map of standards.
• Journal of drilling fluids.
• Journal of Occupational Safety at Work.
• Accounting for the functioning of diesel engines.
• Watch log.

Back to main mechanical equipment And consumables which are used in the process of drilling a well, include the following types:

• Cementing equipment, cement mortar itself.
• Safety equipment.
• Logging mechanisms.
• Technical water.
• Reagents for various purposes.
• Water for drinking.
• Pipes for casing and actual drilling.
• Helicopter pad.

Well types

In the process of drilling an oil well, a mine is formed in the rock, which is checked for the presence of oil or gas by perforating the wellbore, which stimulates the inflow of the desired substance from the productive area. After that, the drilling equipment is dismantled, the well is sealed with the start and end dates of drilling, and then the debris is removed, and the metal parts are recycled.

At the beginning of the process, the diameter of the trunk is up to 90 cm, and by the end it rarely reaches 16.5 cm. In the course of work, the construction of a well is done in several stages:

1. The deepening of the day of the well, for which drilling equipment is used: it crushes the rock.
2. Removal of debris from the mine.
3. Fixing the trunk with pipes and cement.
4. Works during which the obtained fault is investigated, productive locations of oil are revealed.
5. Descent of depth and its cementing.

Wells can vary in depth and are divided into the following varieties:

• Small (up to 1500 meters).
• Medium (up to 4500 meters).
• Deep (up to 6000 meters).
• Super deep (more than 6000 meters).

Drilling a well involves crushing an entire rock formation with a chisel. The resulting parts are removed by washing with a special solution; the depth of the mine becomes greater when the entire bottomhole area is destroyed.

Problems during oil drilling

During the drilling of wells, a number of technical problems can be encountered that will slow down or make work almost impossible. These include the following events:

• The destruction of the trunk, landslides.
• Departure into the soil of a liquid for washing (removal of parts of the rock).
• Emergency conditions of equipment or mine.
• Drilling errors.

Most often, wall collapses occur due to the fact that the rock has an unstable structure. Signs of collapse are increased pressure, higher viscosity of the fluid that is used for flushing, and an increased number of rock pieces that come to the surface.

Fluid absorption most often occurs if the underlying formation completely takes the solution into itself. Its porous system or high absorbency contributes to this phenomenon.

In the process of drilling a well, a projectile that moves clockwise reaches the bottom hole and rises back. The drilling of the well reaches the bedrock formations, into which a tie-in takes place up to 1.5 meters. To prevent the well from being washed out, a pipe is immersed at the beginning, it also serves as a means of carrying the flushing solution directly into the gutter.

The drilling tool, as well as the spindle, can rotate at different speeds and frequencies; This figure depends on the types rocks it is required to punch what diameter of the crown will be formed. The speed is controlled by a regulator that regulates the level of load on the bit used for drilling. In the process of work, the necessary pressure is created, which is exerted on the walls of the face and the cutters of the projectile itself.

Well drilling design

Before starting the process of creating an oil well, a project is drawn up in the form of a drawing, which indicates the following aspects:

• Properties of the discovered rocks (resistance to destruction, hardness, degree of water content).
• The depth of the well, the angle of its inclination.
• The diameter of the shaft at the end: this is important for determining the extent to which the hardness of the rocks influences it.
• Well drilling method.

The design of an oil well must begin with determining the depth, the final diameter of the mine itself, as well as the level of drilling and design features. Geological analysis allows you to resolve these issues, regardless of the type of well.

Drilling methods

The process of creating a well for oil production can be carried out in several ways:

• Shock-rope method.
• Work with the use of rotary mechanisms.
• Drilling a well using a downhole motor.
• Turbine drilling.
• Drilling a well using a screw motor.
• Drilling a well with an electric drill.

The first method is one of the most well-known and proven methods, and in this case the shaft is pierced by chisel strikes, which are produced at regular intervals. Impacts are made through the influence of the weight of the chisel and the weighted rod. The lifting of the equipment is due to the balancer of the drilling equipment.

Work with rotary equipment is based on the rotation of the mechanism with the help of a rotor, which is placed on the wellhead through the drilling pipes, which act as a shaft. Drilling of small wells is carried out by participating in the process of the spindle motor. The rotary drive is connected to the cardan and the winch: such a device allows you to control the speed at which the shafts rotate.

Turbine drilling is performed by transmitting torque to the string from the motor. The same method allows you to transfer the energy of hydraulics. With this method, only one channel of energy supply at the bottomhole level functions.

A turbodrill is a special mechanism that converts hydraulic energy in solution pressure into mechanical energy, which provides rotation.

The process of drilling an oil well consists of lowering and raising the string into the mine, as well as holding it in the air. A column is a prefabricated structure made of pipes that are connected to each other by means of special locks. The main task is to transfer various types of energy to the bit. Thus, a movement is carried out, leading to the deepening and development of the well.

Design of wells for oil and gas are developed and refined in accordance with the specific geological conditions of drilling in a given area. It must ensure the fulfillment of the task, i.e. achievement of the design depth, opening of the oil and gas deposit and carrying out the entire planned complex of studies and work in the well, including its use in the field development system.

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

The initial data for the design of the well design include the following information:

purpose and depth of the well;

design horizon and characteristics of the reservoir rock;

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

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.

Selected bottom hole design . The design of the well in the reservoir interval should provide best conditions oil and gas flows into the well and the most efficient use of the reservoir energy of the oil and gas deposit.

The required number of casing strings and depths of their descent. For this purpose, a graph of the change in the coefficient of anomaly of reservoir pressures k, and the absorption pressure index kabl is plotted.

The choice is substantiated diameter of the production string and the diameters of casing strings and bits are coordinated. Diameters are calculated from bottom to top.

Cementing intervals are selected. From the casing shoe to the wellhead, the following are cemented: 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; in a section with a length of at least 500 m from the shoe of the intermediate column in oil wells up to 3004) m deep (provided that all permeable and unstable rocks are covered with cement slurry).

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

All casing strings in wells constructed in water areas are cemented along the 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 range of adjustable parameters is as follows: indicators of drilling fluid properties, flow rate of drilling pumps, diameter and number of nozzles of jet bits.

When drawing up a hydraulic program, it is assumed:

Eliminate fluid shows from the formation and loss of drilling mud;

To prevent erosion of the well walls and mechanical dispersion of the transported cuttings in order to exclude drilling fluid production;

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

Create conditions for maximum use of the jet effect;

Rationally use the hydraulic power of the pumping unit;

Exclude emergencies during shutdowns, circulation and start-up of drilling pumps.

The listed requirements for the hydraulic program are satisfied under the condition of formalization and solution of a multifactorial optimization problem. The well-known schemes for designing the flushing process of drilling wells are based on the calculations of hydraulic resistance in the system according to the given pump flow and indicators of the properties of drilling fluids.

Similar hydraulic calculations are carried out according to the following scheme. First, based on empirical recommendations, the velocity of the drilling fluid in the annulus is set and the required flow of mud pumps is calculated. According to the passport characteristics of mud pumps, the diameter of the bushings is selected that can provide the required flow. Then, according to the appropriate formulas, hydraulic losses in the system are determined without taking into account pressure losses in the bit. The area of ​​nozzles of jetting bits is selected based on the difference between the maximum passport discharge pressure (corresponding to the selected bushings) and the calculated pressure loss due to hydraulic resistance.

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

The choice of a drilling method, the development of more efficient methods for the destruction of rocks at the bottom of a well, and the solution of 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 influence of these conditions on the properties of the rocks.

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

The choice of 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, may have crucial.

The choice of well drilling method is also influenced by the intended 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 its depth, and the amount of work to develop the reservoir.

Combination of BHA parameters.

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

Dependence of the deflecting force on the bit on the curvature of the hole for a stabilizing BHA with two centralizers.

When choosing a drilling method, in addition to technical and economic factors, it should be taken into account that, compared to 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 justify the choice of drilling method in post-salt deposits and confirm the above conclusion about the rational drilling method, the technical indicators of turbine and rotary drilling of wells were analyzed.

In the case of choosing a drilling method with downhole hydraulic motors, after calculating the axial weight on bit, it is necessary to select the type of downhole motor. This choice is made taking into account the specific torque on bit rotation, axial load on bit and mud density. The technical characteristics of the selected downhole motor are taken into account when designing the bit RPM and the hydraulic well cleanout 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 m of penetration. [ 1 ]

Before proceeding to choice of drilling method for deepening the hole using gaseous agents, it should be borne in mind that their physical and mechanical properties introduce quite certain limitations, since some types of gaseous agents are not applicable for a number of drilling methods. On fig. 46 shows possible combinations of various types of gaseous agents with modern drilling techniques. As can be seen from the diagram, the most universal in terms of the use of gaseous agents are the methods of drilling with a rotor and an electric drill, the 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 installation for drilling on land, since, in addition to the drilling equipment itself, the PBU is equipped with auxiliary equipment necessary for its operation and retention at the drilling point. In practice, drilling and auxiliary equipment work alternately. The minimum required power-to-weight ratio of the MODU is determined by the energy consumed by the auxiliary equipment, which is more than necessary for the drilling drive. [ 3 ]

Eighth, section technical project dedicated choice of drilling method, standard 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 MODU does not depend on the metal consumption and power-to-weight ratio of the equipment and does not affect choice of drilling method, as it is towed without dismantling the equipment. [ 6 ]

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

The rolling parameters of the floating base should be determined by calculation already at the initial stages of the hull design, since this determines the operating range of sea waves, in which normal and safe operation is possible, as well as choice of drilling method, systems and devices to reduce the impact of pitching on the workflow. Roll reduction can be achieved by rational selection of hull sizes, their mutual arrangement and the use of passive and active anti-roll means. [ 8 ]

The most common method of exploration and exploitation of groundwater remains the drilling of wells and wells. Choice of drilling method determine: the degree of hydrogeological knowledge 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 drilling method under consideration, the cost of 1 m3 of produced water, the life of the well. The choice of well drilling technology is influenced by the temperature of groundwater, the degree of their mineralization and aggressiveness in relation to concrete (cement) and iron. [ 9 ]

When drilling ultra-deep wells, the prevention of wellbore curvature is very important due to the negative consequences of wellbore curvature when it is deepened. Therefore, when choosing 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 question of choosing a 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 ]

Thus, the speed of rotary drilling with mud flushing exceeds the speed of percussion drilling by 3–5 times. Therefore, the decisive factor in choice of drilling method it should be economic analysis. [12 ]

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

The application of the results of solving the problem creates a wide opportunity to conduct a deep, extensive analysis of the development of bits in a large number of objects with a wide variety of drilling conditions. At the same time, it is also possible to prepare recommendations for choice of drilling methods, downhole motors, drilling pumps and drilling fluid. [ 14 ]

In the practice of constructing wells for water, the following drilling methods have become widespread: rotary with direct flushing, rotary with reverse flushing, rotary with air purge and shock-rope. Application conditions various ways drilling are 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 when choice of well drilling method on water, it is necessary to take into account not only the speed of drilling 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 rocks in the bottomhole zone is observed to a minimum degree and its permeability does not decrease in comparison with the formation one. [ 1 ]

It is much more difficult to choose a drilling method for deepening a vertical wellbore. If, when drilling out an interval selected based on the practice of drilling with drilling fluids, a curvature of the vertical hole can be expected, then, as a rule, air 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 shales, gypsum, chalk, anhydrites, salt and soft limestones), it is advisable to use electric drill drilling with bit speeds up to 325 rpm. As the hardness of rocks increases, the drilling methods are arranged in the following sequence: displacement engine, rotary drilling and rotary percussion drilling. [ 2 ]

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

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

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

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

To extract the core to the surface, core bits are used (Fig. 2.7). Such a bit consists of a drill head 1 and a core set attached to the body of the drill head with a thread.

Rice. 2.7. Scheme of the core bit device: 1 - drill head; 2 - core; 3 - soil carrier; 4 - body of the core set; 5 - ball valve

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

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

Pd [kN] – weight on the bit, n [rpm] – bit rotation frequency, Q [l/s] – flow rate (feed) of ind. well, H [m] - penetration per bit, Vm [m / h] - mech. penetration rate, Vav=H/tB – average,

Vm(t)=dh/dtB – instantaneous, Vr [m/h] – route drilling speed, Vr=H/(tB + tSPO + tB), C [rub/m] – operating costs per 1m of penetration, C=( Cd+Sch(tB + tSPO + tB))/H, Cd – cost of the bit; Cch - the cost of 1 hour of work drill. rev.

Stages of finding the optimal mode - at the design stage - operational optimization of the drilling mode - adjustment of the design mode, taking into account the information obtained during the drilling process.

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

region, in analog. cond., data on goelog. section wells., recommendations of the manufacturer drill. instr., working characteristics of downhole motors.

2 ways to select a bit at the bottom: graphical and analytical.

The cutters in the drill head are mounted in such a way that the rock in the center of the bottom of the well 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 drilling with coring in various rocks. The location of rock-cutting elements in diamond and hard-alloy drill heads also makes it possible to destroy rock only along the periphery of the bottom hole.

When the well is deepened, the resulting rock column enters the core set, which consists of a body 4 and a core barrel (ground carrier) 3. The core set body serves to connect the drill head to the drill string, place the soil carrier and protect it from mechanical damage, as well as to pass flushing fluid between him and the soil carrier. The gruntonoska is designed to receive the core, save it during drilling and when lifting to the surface. To perform these functions, core breakers and core holders are installed in the lower part of the soil carrier, and at the top - a ball valve 5, which passes through itself the liquid displaced from the soil carrier when it is filled with a core.

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

Core barrels with a removable dredger allow you to lift the 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 soil carrier is removed from the core set and raised to the surface. Then, using the same catcher, an empty soil carrier is lowered and installed in the body of the core set, and drilling with coring continues.

Core bits with a removable soil carrier are used in turbine drilling, and with a fixed one - in rotary drilling.

Principal diagram of testing a productive horizon using a formation tester on pipes.

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

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

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

The final stage of drilling operations is accompanied by a process that involves well cementing. 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 fluid with cement, which has another name - cement slurry. Cementing wells involves the introduction of a composition that must harden, turning into stone. To date, there are several ways to carry out the process of cementing wells, the most commonly used of them is more than 100 years old. This is a single-stage casing cementing, introduced to the world in 1905 and used today with only a few modifications.

Scheme of cementing with one plug.

cementing process

Well cementing technology involves 5 main types of work: the first is mixing the cement slurry, the second is pumping the composition into the well, the third is feeding the mixture into the annulus by the selected method, the fourth is the cement mixture hardening, the fifth is checking the quality of the work performed.

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

Figure 1—Scheme of a single-stage cementing process.

On fig. 1 you can see the image of the schemes of the single-stage cementing process. "I" - start of feeding the mixture into the barrel. "II" is the supply of the mixture injected into the well, when the fluid moves down the casing, "III" is the start of the plugging composition into the annulus, "IV" is the final stage of the mixture is forced through. In scheme 1 - a pressure gauge, which is responsible for controlling the pressure level; 2 – cementing head; 3 - plug located on top; 4 - bottom plug; 5 – casing string; 6 - borehole walls; 7 - stop ring; 8 - liquid intended for pushing the cement mixture; 9 – drilling fluid; 10 - cement mixture.

Schematic diagram of two-stage cementing with discontinuity in time. Advantages and disadvantages.

Stepwise cementing with discontinuity in time. The cementing interval is divided into two parts, and a special cementing sleeve is installed in the ok at the interface. Outside the column, above the coupling and below it, centering lights are placed. First cement the lower part of the column. To do this, 1 portion of CR is pumped into the column in the volume necessary to fill the compressor from the column shoe to the cementing sleeve, then the displacement fluid. For cementing the 1st stage, the volume of the displacement fluid must be equal to the internal volume of the string. Having downloaded pzh, they drop a ball into the column. Under gravity, the ball descends down the string and sits on the lower sleeve of the cementing sleeve. Then the RV is pumped into the column again: the pressure in it increases above the plug, the bushing moves down to the stop, and the RV through the opened holes goes beyond the column. Through these holes, the well is flushed until the cement mortar hardens (from several hours to a day). After that, 2 portions of CR are pumped in, freeing the top plug and the solution is displaced with 2 portions of PG. The plug, having reached the sleeve, is strengthened with the help of pins in the body of the cementing sleeve, shifts it down; at the same time, the sleeve closes the openings of the coupling and separates the cavity of the column from the gearbox. After hardening, the plug is drilled out. The installation location of the coupling is chosen depending on the reasons that prompted the resort to cementing mortars. In gas wells, the cementing sleeve is installed 200-250m above the top of the productive horizon. If there is a risk of absorption during well cementing, the location of the sleeve is calculated so that the sum of hydrodynamic pressures and the static pressure of the solution column in the annulus is less than the fracturing pressure of the weak formation. The cement sleeve should always be placed against stable impermeable formations and centered with lanterns. Apply: a) if the absorption of the solution is unavoidable during single-stage cementing; b) if a formation with high-pressure pressure is opened and during the setting period of the solution after one-stage cementing, cross-flows and gas shows may occur; c) if single-stage cementing requires the simultaneous participation in the operation of a large number of cement pumps and mixing machines. Disadvantages: a large gap in time between the end of the cementing of the lower section and the beginning of the cementing of the upper one. This shortcoming can be largely eliminated by installing an external packer on the ok, below the cemented sleeve. If, after cementing the lower stage, the annular space of the well is sealed with a packer, then you can immediately start cementing the upper section.

Principles of casing string calculation for axial tensile strength for vertical wells. The specificity of the calculation of columns for inclined and deviated wells.

Casing Calculation begin with the determination of excess external pressures. [ 1 ]

Calculation of casing strings are carried out during design in order to select wall thicknesses and strength groups of the casing pipe material, as well as to check 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 for tension is carried out based on the allowable load. When lowering casing strings in sections, the length of the section is taken as the length of the string. [ 3 ]

Casing Calculation includes determining the factors that affect casing damage and selecting the most appropriate steel grades for each specific operation in terms of reliability and economy. The design of the casing string must meet the requirements for the string during the completion and operation of the well. [ 4 ]

Calculation of casing strings for directional wells differs from that adopted for vertical wells by the choice of tensile strength depending on the intensity of the curvature of the wellbore, as well as by the determination of external and internal pressures, in which the position of the points characteristic of an inclined 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, repair of wells), while taking into account their separate and joint action.

Main difference casing string calculation for directional wells from the calculation for vertical wells is to determine the tensile strength, which is produced depending on the intensity of the curvature of the wellbore, as well as the calculation of external and internal pressures, taking into account the elongation of the wellbore

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

The main loads in the calculation of the string for strength are axial tensile loads from its own 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 the period of unsteady movement of the column;

· axial loads due to the forces of friction of the string against the walls of the well during its descent;

· compressive loads from part of its own weight when unloading the column to the bottom;

· bending loads arising in deviated wells.

Calculation of the production string for an oil well

Conventions adopted in the formulas:

Distance from wellhead to string shoe, m L

Distance from the wellhead to the cement slurry, m h

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

Crimping liquid density, g/cm 3 r coolant

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

The density of the liquid in the column r B

Density of cement slurry behind the column r CR

Excessive internal pressure at depth z, MPa R WIz

Excessive external pressure at 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 weight of the column of selected sections, N (MN) Q

Cement ring unloading factor k

Safety factor when calculating for external overpressure n KR

Tensile strength factor n STR

Figure 69—Scheme of well cementing

At h > H We determine the excess external pressure (at the stage of completion of operation) for the following characteristic points.

1: z = 0; Р n.i.z = 0.01ρ b.r. * z; (86)

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

3: z = h; P n.i z \u003d (0.01 [ρ b.p h - ρ in (h - H)]), (MPa); (88)

4: z = L; R n.i z \u003d (0.01 [(ρ c.r - ρ c) L - (ρ c. r - ρ b. r) h + ρ in H)] (1 - k), (MPa). (89)

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

Figure 70. Diagrams of external and internal

excess pressure

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

Wellhead pressure: P y \u003d P pl - 0.01 ρ in 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) composition and properties of cement slurry; c) method of cementing; d) completeness of displacement fluid replacement with cement slurry in the annular space of the well; e) the strength and tightness of the adhesion of the cement stone to the casing string and the walls of the well; 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 rest mode during the period of thickening and setting of the cement slurry.

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

It is necessary to calculate cementing for the following conditions:

- reserve coefficient at the height of the rise of the cement slurry, introduced to compensate for factors that cannot be taken into account (determined statistically according to the cementing data of previous wells); and - respectively, the average diameter of the well and the outer diameter of the production string, m; - the length of the cementing section, m; - the average inner diameter of the production string, m; - the height (length) of the cement glass left in the column, m; , taking into account its compressibility, - = 1.03; - - coefficient taking into account the loss of cement during loading and unloading operations and the preparation of the solution; - - - density of the cement slurry, kg / m3; - drilling mud 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 well interval (m3): Vc.p.=0.785*kp*[(2-dn2)*lc+d02*hc]

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

Buffer liquid volume: Vb=0.785*(2-dn2)*lb;

Mass of oil-well Portland cement: Мц= - **Vцр/(1+n);

The volume of water for the preparation of cement slurry, m3: Vw = Mts*n/(kts*pv);

Before cementing, dry cementing material is loaded into the hoppers of mixing machines, the required number of which is: nc = Mts/Vcm, where Vcm is the volume of the mixer hopper.

Methods for equipping the lower section of the well in the zone of the productive formation. Conditions under which each of these methods can be used.

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

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

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

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 entire length and then perforated against a predetermined interval. With this method, significant contamination of the reservoir can be avoided by choosing the 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 after drilling out the productive deposit, a casing string is lowered into the well, the lower section of which is previously made up of pipes with slotted holes, and in that it is cemented only above the roof of the productive deposit. The perforated section of the column is placed against the productive deposit. With this method, it is impossible to ensure the selective exploitation of one or another interlayer.

Factors taken into account when choosing a cementing material for cementing a particular well interval.

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, hydraulic fracturing pressure, the presence of salt deposits, the type of fluid, etc. general case grouting slurry consists of grouting cement, mixing medium, reagents-accelerators and retarders of the setting time, reagents-reducers of the filtration index and special additives. Oil-well cement is selected as follows: according to the temperature interval, according to the interval for 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 chosen depending on the presence of salt deposits in the well section or the degree of formation water salinity. 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, gipan, CMC, PVA-TR are used as reducers of this indicator. Clay, caustic soda, calcium chloride and chromates are used to increase the thermal stability of chemical additives, to structure dispersion systems and to remove side effects when using certain reagents.

Selection of a core set for obtaining a high-quality core.

Core receiving tool - a tool that provides reception, separation from the massif of the g / p and preservation of the core during the drilling process and during transportation through the well. up to extracting it on the pov-Th 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 non-removable core receiver. Types: - for core sampling from an array of dense g / s (double core barrel with a core receiver, isolated from the pancreatic ducts and rotating with the body of the projectile), - for coring in g / c fractured, crumpled, or alternating in density and hardness (non-rotating core receiver, suspended on one or more bearings and reliable core extractors and core holders), - for core sampling in bulk g / n, easily cut. and washout. PZH (should provide complete sealing of the core and blocking of the core receiving hole at the end of drilling)

Design features and applications of drill pipes.

Leading drill pipes serve 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 solid. Drill pipes with upset ends come with upsets inside and outside. Drill pipes with welded connecting ends are made in two types: TBPV - with welded connecting ends along the upset part and TBP - with welded connecting ends along the non-upset part. at the ends of the pipe, cylindrical thread with a pitch of 4 mm, thrust 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 sections of the pipe directly behind the screwed-on nipple and collar of the lock and stabilizing sealing bands on the locks, tapered (1:32) trapezoidal thread with a pitch of 5.08 mm with mating along the inner diameter……….

Principles of calculation of the drill string when drilling with a downhole motor .

Calculation of BC when drilling a SP of a straight-inclined section of a directional well

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

Pprod=Qprod+Ftr=Q(sinα+μsinα)

LI>=Lsp+Lbt+Lnc+lI1+…+l1n

Calculation of BC when drilling a 3D curved section of a directional well.

II

Pi=FIItr+QIIproject QIIproject=|goR(sinαk-sinαn)|

Pi=μ|±2goR2(sinαk-sinαn)-goR2sinαkΔα±PnΔα|+|goR2(sinαk-sinαn)|

Δα=-- If>, then cos “+”

“-Pn” – when curvature is set “+Pn” – when curvature is reset

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

Principles of calculation of the drill string in 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 norms. conv. Kz=1.45 - with complications. conv.

for slopes

;

;

drilling mode. Method of its optimization

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

Pd [kN] – weight on the bit, n [rpm] – bit rotation frequency, Q [l/s] – flow rate (feed) of ind. well, H [m] - penetration per bit, Vm [m / h] - mech. penetration rate, Vav=H/tB – average, Vm(t)=dh/dtB – instantaneous, Vr [m/h] – line drilling speed, Vr=H/(tB + tSPO + tB), C [rub/m ] – operating costs per 1m of penetration, C=(Cd+Sch(tB + tSPO + tB))/H, Cd – cost of the bit; Cch - the cost of 1 hour of work drill. rev. Drilling mode optimization: maxVp – recon. well, minC – exp. well..

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

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

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

In the design process, we use inf. obtained by drilling wells. in this region, in analog. cond., data on goelog. section wells., recommendations of the manufacturer drill. instr., working characteristics of downhole motors.

2 ways to choose top bits at bottomhole:

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

Classification of inflow stimulation methods during well development.

The development means a set of works to cause the influx of fluid from the productive formation, clean the near-wellbore zone from pollution and provide conditions for obtaining the highest possible productivity of the well.

In order to obtain an inflow from the productive horizon, it is necessary to reduce the pressure in the well significantly below the formation pressure. There are different ways to reduce pressure, based either on replacing heavy drilling fluid with a lighter one, or on a gradual or sharp decrease in the liquid level in the production string. To induce inflow from a reservoir composed of weakly stable rocks, methods are used to gradually reduce pressure or with a small amplitude of pressure fluctuations in order to prevent reservoir destruction. If the productive formation is composed of a very strong rock, then often the greatest effect is obtained with a sharp creation of large depressions. When choosing a method of inducing inflow, the magnitude and nature of creating a drawdown, it is necessary to take into account the stability and structure of the reservoir rock, the composition and properties of the fluids saturating it, the degree of contamination during opening, the presence of permeable horizons located nearby above and below, the strength of the casing string and the state of the well support. With a very sharp creation of a large drawdown, a violation of the strength and tightness of the support is possible, and with a short-term but strong increase in pressure in the well, the absorption of fluid into the productive formation.

Replacing a heavy fluid with a lighter one. The tubing string is lowered almost to the bottomhole if the productive formation is composed of well-stable rock, or approximately to the upper perforations if the rock is not sufficiently stable. The liquid is usually replaced by the reverse circulation method: a liquid is pumped into the annular space by a mobile piston pump, the density of which is less than the density of the flushing liquid 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 at the moment when the light liquid approaches the tubing shoe. p wmt =(p pr -r cool)qz nkt +p nkt +p mt, where p pr and p exp are the densities of heavy and light liquids, kg/m; z tubing - depth of descent of the tubing string, m; p nkt and p mt - hydraulic losses in the tubing string and in the annulus, Pa. This pressure should not exceed the production casing pressure test pressure p< p оп.

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

When pumping a lighter liquid, the state of the well is monitored according to the pressure gauge readings and the ratio of the flow rates of the liquids injected into the annulus and flowing out of the tubing. If the flow rate of the outgoing fluid increases, this is a sign that the inflow from the reservoir has begun. 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 outgoing flow is directed through a line with a choke.

If replacing the heavy drilling fluid with clean water or dead oil is not sufficient to obtain a steady flow from the reservoir, other methods of increasing drawdown or stimulation are resorted to.

When the reservoir is composed of weakly 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 regulated so that the pressure in it is significantly lower than that allowed for the compressor, and the downward flow rate is at the level of about 0.8-1 m/s, and the compressor is turned on. The air flow injected by the compressor is mixed in the aerator with the water flow supplied by the pump, and a gas-liquid mixture enters the annulus; the pressure in the compressor and pump will then 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 non-carbonated 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 the completion of one or two circulation cycles so that the pressure in the annular space at the mouth does not exceed the allowable for the compressor.

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

Reducing the pressure in the well with a compressor. To induce inflow from formations composed of strong, stable rocks, the compressor method of reducing the liquid level in the well is widely used. The essence of one of the varieties of this method is as follows. A mobile compressor pumps air into the annular space in such a way as to push the liquid level in it as far as possible, aerate the liquid in the tubing and create a depression necessary to obtain inflow from the reservoir. If the static level of the liquid in the well before the start of the operation is at the mouth, the depth to which the level in the annulus can be pushed back when air is injected.

If z cn > z tubing, then the air injected 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 beforehand, when lowering 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" sn - 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, the air will begin to exit through the valve in the tubing and aerate the liquid, and the pressure in the annular space and in the tubing will decrease. If, after the pressure in the well is reduced, the inflow from the formation does not start and almost all the liquid from the tubing above the valve is displaced by air, the valve will close, the pressure in the annulus will increase again, and the liquid 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 \u003d z "" + 20 and z st \u003d z" sn.

If before the start of the operation the static level of the liquid in the well is located significantly below the wellhead, then when air is injected into the annular space and the liquid level is pushed back to a depth of z cn, the pressure on the productive formation increases, which can cause absorption of part of the liquid into it. It is possible to prevent the 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 string and using these devices to separate the productive formation zone 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 formation fluid inflow, the valve will rise and the formation fluid will begin to rise along the tubing.

After receiving the influx 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 that have entered there, as well as other silt particles, can be removed from the near-wellbore zone; at the same time, the flow rate is regulated so that the destruction of the reservoir does not begin. Periodically, samples are taken of the fluid flowing from the well in order to study its composition and properties and control the content of solid particles in it. By reducing the content of solid particles, the course of cleaning the near-stem zone from pollution is judged.

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

Classification of inflow stimulation methods in the process of well development.

Based on the analysis of controlled factors, it is possible to build a classification of artificial stimulation methods both on the reservoir as a whole and on the bottomhole 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. Physical and chemical.

3. Thermal.

4. Combined.

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

Field development analysis shows that if the reservoir pressure is low, the feed loop is sufficiently removed from the wells, or the drainage regime is not active, the oil recovery rates may be quite low; the oil recovery factor is also low. In all these cases, the use of one or another PPD system is necessary.

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

Methods of artificial impact on bottom-hole zones of a well have a significantly wider range of possibilities. The impact on the bottomhole zone is carried out already at the stage of the initial opening of the productive horizon during the construction of the well, 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 intensification of inflow or injectivity and methods of limiting or isolating water inflow (repair and isolation work - RIR).

The classification of methods of influencing the bottomhole zone with the aim of intensifying the inflow or injectivity is presented in tab. one, and to limit 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 impact on the CCD. They do not exclude, but on the contrary, suggest the need for additions both in terms of exposure methods and materials used.

Before proceeding to the consideration of methods for managing the development of reserves, we note that the object of study is a complex system consisting of a deposit (oil-saturated zone and recharge area) with its reservoir properties and saturating fluids and a certain number of wells systematically placed on the deposit. This system is hydrodynamically unified, which implies 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 self-adjusting.

Describe the technical means to obtain operational information in the process of 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 putting into development and development of new oil and gas fields.

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

ground control technological parameters and selection of the most optimal drilling modes (for example, selection of optimal weights on bit, providing high speed penetrations);

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

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

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 mud logging service is to study the geological structure of the well section, identify and evaluate productive strata and improve the quality of well construction based on the geological, geochemical, geophysical and technological information obtained during the drilling process. Operational information received by the GTI service is of great importance when drilling exploratory wells in little-studied regions with difficult mining and geological conditions, as well as when drilling directional and horizontal wells.

However, due to new requirements for information support of the drilling process, the tasks solved by the mud logging service can be significantly expanded. The highly qualified operator staff of the GTI party, working at the drilling rig, throughout the entire well construction cycle, in the presence of appropriate hardware and methodological tools and software, is able to solve practically a full range of tasks for information support of the drilling process:

geological, geochemical and technological research;

maintenance and operation with telemetry systems (MWD and LWD-systems);

maintenance of autonomous measurement and logging systems run on pipes;

drilling mud parameters control;

well casing quality control;

studies of reservoir fluid during testing and testing of wells;

wireline logging;

supervising services, etc.

In a number of cases, the combination of these works in the GTI parties is economically more profitable and allows saving on unproductive costs for the maintenance of specialized, narrowly focused geophysical parties, and minimizing transportation costs.

However, at the present time, there are no technical and software-methodological means that allow 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 informativeness.

Station structure shown in fig. 1. It is built on the principle of distributed remote collection systems, which are interconnected using a standard serial interface. The main downstream collection systems are concentrators designed to decouple the serial interface and connect individual components of the station through them: a gas logging module, a geological instrument module, digital or analog sensors, and information displays. Through the same hubs, other autonomous modules and systems are connected to the collection system (to the operator’s recording computer) - a well casing quality control module (manifold block), ground-based modules for downhole telemetry systems, geophysical data recording systems of the Hector or Vulcan type, and etc.

Rice. 1. Simplified structural scheme GTI stations

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

Process Variable Sensors

Technological parameters sensors used in GTI stations are one of the most important components of the station. The efficiency of the GTI service in solving problems of monitoring and operational management drilling process. However, due to 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 gas logging.

Most of the sensors used in production batches of GTIs were developed in the early 90s using domestic element base 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 working in a drilling rig. This explains the insufficiently high reliability of the sensors used.

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

It follows from the foregoing 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 accuracy sensors and highly integrated small-sized microprocessors allows the development of high-precision, programmable sensors with great functionality. The sensors have a unipolar supply voltage and both digital and analog outputs. Calibration and adjustment of sensors are carried out programmatically from a computer from the station, the possibility of software compensation for temperature errors and linearization of sensor characteristics are provided. The digital part of the electronic board for all types of sensors is of the same type and differs only in the setting of the internal program, which makes it unified and interchangeable during repair work. Appearance sensors is 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 drilling line at the "dead" end using a strain gauge force sensor. The sensor has a built-in processor and non-volatile memory. All information is registered and stored in this memory. The amount of memory allows you to save a monthly amount of information. The sensor can be equipped with an autonomous power supply, which ensures the operation of the sensor when the external power supply is disconnected.

Rice. 3. Hook weight sensor

Driller's information board is 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 the parameters: torque on the rotor, SF pressure at the inlet, SF density at the inlet, SF level in the tank, SF flow at the inlet, SF flow at the exit. The parameters of weight on the hook, WOB are displayed on two circular scales with additional duplication in digital form, by analogy with the GIV. In the lower part of the board there is one linear scale for displaying drilling speed, three digital indicators for displaying parameters - bottomhole depth, position above the bottomhole, gas content. The alphanumeric indicator is designed to display text messages and warnings.

Rice. 4. The appearance of the information board

Geochemical module

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

The most important part of the geochemical module is the gas chromatograph. For unmistakable, clear identification of productive intervals in the process of their opening, a very reliable, accurate, highly sensitive instrument is needed that allows determining 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 the article in this issue of NTV).

Rice. 5. Field chromatograph "Rubin"

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

To isolate the bottomhole gas dissolved in the drilling fluid, two types of degassers(Fig. 6):

float degassers of passive action;

active degasifiers with forced flow splitting.

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

Rice. 6. Mud degassers

a) passive float degasser; b) active degasser

Continuous analysis of the total gas content is performed 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 placed directly at the drilling rig and the delay time for transporting gas from the drilling rig to the station is eliminated. In addition, to complete the stations developed gas sensors to measure 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, core and reservoir fluid in the process of drilling a well, registration and processing of the data obtained.

Studies performed by the operators of the GTI station make it possible to solve the following main geological tasks:

lithological division of the section;

selection 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 based on this, a complex of geological instruments was developed (Fig. 8).

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

Carbonatometer microprocessor KM-1A designed to determine the mineral composition of rocks in carbonate sections by cuttings and core. 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 the monitor screen. A modification of the carbonate meter has been developed, which makes it possible to determine the content of the siderite mineral 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 porosity values.

Sludge density meter ПШ-1 is designed for express measurement of density and assessment of the total porosity of rocks using cuttings and core. The measurement principle of the device is hydrometric, based on weighing the studied sample of sludge in air and in water. Using the PSh-1 density meter, it is possible 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 bulk, mineralogical density and total porosity. The measurement principle of the device is thermogravimetric, based on high-precision measurement of the weight of the studied rock sample, previously saturated with water, and continuous monitoring of the change in the weight of 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 assessment of the nature of saturation of rock reservoirs by cuttings and core, filtration and density properties, and also allows you to determine the residual oil and water saturation by core and drill cuttings directly at the drilling site due to the use of a new approach in the distillate cooling system. The plant uses a condensate cooling system based on a Peltier thermoelectric element instead of the water heat exchangers used in such devices. This reduces condensate loss by providing controlled cooling. The principle of operation of the plant is based on the displacement of reservoir fluids from the pores of rock samples due to excess pressure that occurs during thermostatically controlled heating from 90 to 200 ºС ( 3 ºС), vapor condensation in a heat exchanger and separation of the condensate formed during the distillation process, by density into oil and water.

Thermal desorption and pyrolysis plant allows to determine the presence of free and sorbed hydrocarbons by small samples of rocks (sludge, core pieces), as well as to assess the presence and degree of transformation of organic matter, and on the basis of interpretation of the data obtained, to identify intervals of reservoirs, caps of producing deposits in well sections, and also to assess the nature collector saturation.

IR spectrometer created for determining the presence and quantification of the presence of hydrocarbons 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 photographic device is designed to study drill cuttings and core samples under ultraviolet light in order to determine the presence of bituminous substances in the rock, as well as to quantify them. The measurement 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 allow visually determining the presence, qualitative and quantitative composition of bitumoid in the studied rock in order to assess the nature of reservoir saturation. The device for photographing extracts is intended for documenting the results of luminescent analysis and helps to eliminate the subjective factor when evaluating the results of the analysis. A remote illuminator allows for a preliminary inspection of a large-sized core at the drilling rig in order to detect the presence of bitumoids.

Sludge dryer OSH-1 designed for express drying of sludge samples under the influence of 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 information capabilities of the described GTI station meet modern requirements and allow the implementation of 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 drilling process arise for the following reasons: complex 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 well construction.

When drilling is complicated, accidents are more likely to occur.

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

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

Overburden pressure (Pg) is the hydrostatic (geostatic) pressure at the considered depth from the overlying GP strata.

The static level of reservoir fluid in the well, determined by the equality of the pressure of this column with the reservoir 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) Рpl=rgz.

The dynamic level of the liquid in the well is set above the static level when adding to the well and below it - when withdrawing liquid, for example, when pumping out with a submersible pump.

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

Repression Р=Рskv-Рpl>0 – the pressure in the well is not higher than the formation pressure. Absorption takes place.

Reservoir pressure anomaly coefficient Ka=Рpl/rwgzpl (1), where zpl is the depth of the top of the reservoir under consideration, rv is the water density, g is the free fall acceleration. Ka<1=>ANPD; Ka>1=>AVPD.

Loss or hydraulic fracturing pressure Рp - pressure at which losses of all phases of drilling or cementing fluid occur. The value of Pp is determined empirically according to observations during the drilling process, or with the help of special studies in the well. The data obtained is used in the drilling of other similar wells.

Combined pressure graph for complications. Choice of the first well design option.

Combined pressure graph. Choice of the first well design option.

To correctly draw up a technical project for the construction of wells, it is necessary to know exactly the distribution of reservoir (pore) pressures and absorption pressures (hydraulic fracturing) 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 in depth z.

· Design of the well (1st option), which is then specified.

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

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

After opening the absorbing interval, insulation works are carried out, due to which Kp increases (artificially), making it possible, for example, to cement the column.

Scheme of the circulation system of wells

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

Scheme: 1. Bit, 2. Downhole motor, 3. Drill collar, 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. Hydrostatic pressure distribution line.

2. Line of hydraulic pressure distribution in the gearbox.

3. Line of hydraulic pressure distribution in BT.

The pressure of the flushing fluid on the formation must always be within the shaded area between Ppl and Pp.

Through each threaded connection of the BC, the liquid tries to flow from the pipe to the annular space (during circulation). This trend is caused by pressure drop in pipes and gearbox. Leakage causes the destruction of the threaded connection. Ceteris paribus, an organic disadvantage of drilling with a hydraulic downhole motor is an increased pressure drop on each threaded connection, since in the downhole motor

The circulation system is used to supply the drilling fluid from the wellhead to the receiving tanks, clean it from cuttings and degas.

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

A simplified design of the circulating system is a trough system, which consists of a trough for the movement of mortar, a deck near the trough for walking and cleaning the troughs, railings and base.

The gutters can be wooden from 40 mm boards and metal from 3-4 mm iron 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 sludge falls out of it, partitions and drops 15-18 cm high are installed in the gutters. Manholes with valves are installed at the bottom of the gutter in these places, through which the settled rock is removed. The total length of the gutter system depends on the parameters of the fluids used, drilling conditions and technology, as well as on the mechanisms used to clean and degas the fluids. The length, as a rule, can be within 20-50 m.

When using sets of mechanisms for cleaning and degassing the solution (vibrating screens, sand separators, desilters, degassers, centrifuges), the trough system is used only to supply the 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 having a length of 8-10 m and a height of up to 1 m. Such sections are installed on steel telescopic racks that adjust the installation height of the gutter, which facilitates the dismantling of the gutter system in winter. So, when cuttings accumulate and freeze under the gutters, the gutters together with the bases can be removed from the racks. Mount the gutter system with a slope towards the movement of the solution; the gutter system is connected to the wellhead with a pipe or gutter of a smaller cross section and with a large slope to increase the speed of the solution and reduce the dropout of the sludge in this place.

In modern well drilling technology, special requirements are imposed on drilling fluids, according to which mud cleaning equipment must ensure high-quality cleaning of the mud from the solid phase, mix and cool it, and remove from the mud the gas 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 mechanisms of the circulation system 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 sump, the solution passes into the compartment of the circulation system and is fed by a centrifugal slurry pump to the degasser if it is necessary to degas the solution, and then to the sand separator, where it passes the second stage of purification from rocks up to 0.074-0.08 mm in size. After that, the solution is fed into the desilter - the third stage of purification, where rock particles up to 0.03 mm are removed. Sand and silt are dumped into a tank, from where it is fed into a centrifuge for additional separation of the solution from the rock. The purified solution from the third stage enters the receiving tanks - into the receiving unit of the mud pumps to feed it into the well.

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

solution purification unit;

intermediate block (one or two);

receiving block.

The basis for the assembly of blocks are rectangular containers mounted on sled bases.

Hydraulic pressure of clay and cement mortars after stopping circulation.

Takeovers. The reasons for their occurrence.

Byabsorption of drilling or grouting slurries - a type of complication, which is manifested by the departure of fluid from the well into the rock formation. Unlike filtration, absorption is 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 loss of drilling fluid into the formation in excess of the natural loss due to filtration and cuttings. Each region has its own standard. Usually several m3 per day is allowed. Absorption is the most common type of complications, especially in the regions of the Ural-Volga region of eastern and southeastern Siberia. Absorption occurs in sections in which there are usually fractured GPs, the greatest deformations of rocks are located, and their erosion is due to tectonic processes. For example, in Tatarstan, 14% of the calendar time is annually spent on the fight against takeovers, which exceeds the time spent on fur. drilling. As a result of losses, the conditions of well drilling worsen:

1. The sticking hazard of the tool increases, because the speed of the upward flow of the flushing fluid above the absorption zone decreases sharply, if large particles of cuttings do not go into the formation, then they accumulate in the wellbore, causing puffs and sticking of the tool. The probability of tool sticking by settling sludge especially increases after the pumps (circulation) stop.

2. Screes and collapses in unstable rocks are intensifying. GNWP can occur from fluid-bearing horizons present 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, there may be overflows, which complicate the isolation work and subsequent cementing of the well.

A lot of time and material resources (inert fillers, grouting materials) are lost for isolation, downtime and accidents that cause losses.

Reasons for takeovers

The qualitative role of the factor that determines the amount of solution escape 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 the absorbed liquid in a porous circular formation is 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 flow rate, current pressure, formation radius, viscosity, respectively.

2. Mass conservation equation (continuity)

V=Q/F (2) where Q, F=2πrh , h are, respectively, the flow rate of absorption of the liquid, the area variable along the radius, 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(Pfrom-Ppl))/Mln(rk/rc) (4)formula Dupii

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

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

δ- opening (height) of the gap;

m is the number of cracks (slits);

M is the effective viscosity.

It is clear that in order to reduce the flow rate of the absorbed liquid according to 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) can be conditionally divided into 3 groups according to their origin at the time of opening of the absorption zone.

1. group - geological parameters;

2nd group - technological parameters;

3. group - mixed.

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

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

Feature of indicator curves.

Next, we will consider line 2.

Approximately, the indicator curve for rocks with artificially opened closed fractures can be described by the following formula: Рс = Рb + Рpl + 1/А*Q+BQ2 (1)

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

Рс-Рpl= ΔР=1/А*Q=А*ΔР

Thus, in rocks with open fractures, absorption will begin at any values ​​of repression, and in rocks with closed fractures, only after a pressure equal to the hydraulic fracture pressure Рс* is created in the well. The main measure to combat losses in rocks with closed fractures (clays, salts) is to prevent 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 in the course of insulation work. If, in this case, the obtained injectivity A turns out to be lower than some technologically acceptable value of injectivity Aq, which is characterized for each region, then the insulation work can be considered successful. Thus, the isolation condition can be written as А≤Аq (1) А=Q/Рс- Р* (2) For rocks with artificially opened fractures Р* = Рb+Рpl+Рр (3) where Рb is the lateral rock pressure, Рр - tensile strength g.p. In particular cases Рb and Рр = 0 for rocks with natural open fractures А= Q/Pc - Рpl (4) if the slightest absorption is not allowed, then Q=0 and А→0,

then Rs<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.

Ways to combat absorptions in the process of opening the absorption zone.

Traditional methods of loss prevention are based on reducing the pressure drops on the absorbing formation or changing the a/t) of the filtered fluid. If, instead of reducing the pressure drop across the formation, the viscosity is increased by adding plugging materials, bentonite or other substances, the loss rate will change inversely with the increase in viscosity, as follows from formula (2.86). In practice, if the solution parameters are controlled, the viscosity can be changed only within relatively narrow limits. Loss prevention 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 reservoir. Improvement of lost circulation prevention methods based on pressure drop reduction on absorbing formations is inextricably linked with a deep study and development of well drilling methods in equilibrium in the well-formation system. The drilling fluid, 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 fluid from the wellbore into the formation. The property of the solution to create resistance to the movement of fluid inside 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 on the depth of penetration of the solution into the reservoir.

In order to formulate requirements for the rheological properties of drilling fluids during the passage of absorbing formations, we consider the curves (Fig. 2.16) that reflect the dependence of shear stress and strain 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 t0. Curve 2 characterizes the behavior of pseudoplastic fluids, in which, with increasing shear rate, the rate of stress growth slows down, and the curves flatten out. Straight 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 sharply increases with strain rate. Viscoelastic fluids, in particular, include weak solutions of some polymers (polyethylene oxide, guar gum, polyacrylamide, etc.) in water, which exhibit the ability to sharply reduce (by 2-3 times) hydrodynamic resistances during the flow of fluids with high Reynolds numbers (Toms effect). At the same time, the viscosity of these liquids during their movement 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 the set of measures and methods designed to prevent and eliminate losses when drilling deep wells. Aeration of the drilling fluid reduces hydrostatic pressure, thereby contributing to its return in sufficient quantities to the surface and, accordingly, normal cleaning of the wellbore, as well as the selection of representative samples of passable rocks and formation fluids. Technical and economic indicators when drilling wells with bottomhole flushing with an aerated solution are higher compared to those when water or other flushing fluids are used as drilling fluid. The quality of drilling in productive formations is also significantly improved, especially in fields where these formations have abnormally low pressures.

An effective measure to prevent loss of drilling fluid is the introduction of fillers into the circulating drilling fluid. The purpose of their application is to create tampons in absorption channels. These tampons serve as the basis for the deposition of a filtration (clay) cake and isolation of absorbing layers. V.F. Rogers believes that a bridging agent can be virtually any material that is small enough to be pumped into the drilling fluid by mud pumps. In the USA, more than a hundred types of fillers and their combinations are used to plug absorbing channels. As plugging agents, wood chips or bast, fish scales, hay, rubber waste, gutta-percha leaves, cotton, cotton bolls, sugar cane fibers, walnut shells, granulated plastics, perlite, expanded clay, textile fibers, bitumen, mica, asbestos, cut paper, moss, cut hemp, cellulose flakes, leather, wheat bran, beans, peas, rice, chicken feathers, lumps of clay, sponge, coke, stone, etc. These materials can be used separately and in combinations made by industry or made up before use . It is very difficult to determine the suitability of each bridging material in the laboratory due to the ignorance of the size of the holes to be occluded.

In foreign practice, special attention is paid to ensuring the "dense" packing of fillers. The opinion of Furnas is held, according to which the most dense packing of particles corresponds to the condition of their size distribution according to the law of geometric progression; when eliminating loss, the greatest effect can be obtained with the most compacted plug, especially in the case of instantaneous drilling fluid loss.

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

Lamellar materials are suitable for plugging coarse gravel beds 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 beds with grain diameters up to 9-12 mm. Nut shells of 2.5 mm or less plug cracks up to 3 mm in size, and larger (up to 5 mm) and crushed rubber plug cracks up to 6 mm in size, i.e. they can plug cracks 2 times more than when using fibrous or lamellar materials.

In the absence of data on the size of grains and cracks in the absorbing horizon, mixtures of fibrous with lamellar or granular materials, cellophane with mica, fibrous with scaly and granular materials are used, as well as when mixing granular materials: perlite with rubber or walnut shells. The best mixture to eliminate absorption at low pressures is a highly colloidal clay solution with the addition of fibrous materials and mica sheets. Fibrous materials, being deposited on the wall of the well, form a grid. Mica sheets reinforce this network and clog larger channels in the rock, and on top of all this, a thin and dense clay cake is formed.

Gas water and oil shows. Their reasons. Signs of formation fluids inflow. Classification and recognition of types of manifestations.

When lost, the fluid (flushing or grouting) flows from the well into the formation, and when it appears, vice versa - from the formation into the well. Causes of inflow: 1) influx into the well in place with cuttings of fluid-containing formations. In this case, the pressure in the well is not necessarily higher and lower than in the reservoir; 2) if the pressure in the well is lower than the formation pressure, i.e. there is drawdown on the formation, the main reasons for the occurrence of depression, i.e., the decrease in pressure on the formation in the well, are as follows: 1) not adding drilling fluid to the well when lifting the tool. A device for auto-filling 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 surfactants. 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 Kp2. first layer should be drilled with 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 it will be lost in the second layer; 4) sharp fluctuations in hydrodynamic pressure during pump shutdown, tripping, and other works, aggravated by an increase in static shear stress and the presence of stuffing boxes on the column;

5) underestimated density of p.l accepted 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) low level of operational refinement of reservoir pressures by predicting them during the deepening of the well. Not using the methods of predicting the d-exponent, σ (sigma)-exponent, etc.; 7) loss of weighting agent from the drilling fluid and a decrease in hydraulic pressure. Signs of formation fluid inflow are: 1) increase in the level of circulating fluid in the pump intake tank. Need a level gauge? 2) gas is released from the solution leaving the well at the wellhead, the solution is boiling; 3) after stopping the circulation, the solution continues to flow out of the well (the well overflows); 4) the pressure rises sharply with an unexpected opening of the reservoir with AHFP. When oil flows from the reservoirs, its film remains on the walls of the gutters or flows over the solution in the gutters. When formation water enters, the properties of the wells change. Its density usually drops, the viscosity may decrease, or it may increase (after salt water enters). Water loss usually increases, pH changes, electrical resistance usually decreases.

Fluid inflow classification. It is produced according to the complexity of the measures necessary for their liquidation. They are divided into three groups: 1) manifestation - non-hazardous inflow of reservoir fluids that do not violate the drilling process and the accepted work technology; 2) release - the influx of fluids that can be eliminated only by a special purposeful change in drilling technology with the tools and equipment available at the drilling site; 3) fountain - fluid entry, the elimination of which requires the use of additional tools and equipment (except for those available at the rig) and which is associated with the occurrence of pressures in the well-formation system that threaten the integrity of the well. , wellhead equipment and formations in the loose part of the well.

Installation of cement bridges. Features of the choice of formulation and preparation of cement slurry for the installation of bridges.

One of the serious varieties of cementing process technology is the installation of cement bridges for various purposes. Improving the quality of cement bridges and the efficiency of their work is an integral part of improving the processes of 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 cases of installation of low-strength and leaky bridges, premature setting of cement slurry, sticking of string pipes, etc. are often noted. These complications are caused not only and not so much by the properties of the grouting materials used, but by the specifics of the works themselves during the installation of bridges.

In deep high-temperature wells, during these works, accidents quite often occur associated with intensive thickening and setting of a mixture of clay and cement mortars. 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 the installation of bridges is to obtain a stable water-gas-impermeable glass of cement stone of a certain strength for moving to the overlying horizon, drilling a new wellbore, strengthening the unstable and cavernous part of the wellbore, testing the horizon with the help of a formation tester, overhaul and conservation or liquidation of wells.

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

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

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

The bearing capacity of cement bridges largely depends on their height, the presence (or absence) and the condition of the mud cake or mud residue on the string. When removing the loose part of the clay cake, the shear stress is 0.15-0.2 MPa. In this case, even when maximum loads occur, a bridge height of 18–25 m is sufficient. The presence of a layer of drilling (clay) mud 1–2 mm thick on the column walls leads to a decrease in shear stress and an increase in the required height to 180–250 m. In this regard, the height of the bridge should be calculated according to the formula Nm ≥ Ho – 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 pressure drop and unloading of the tubing string or formation tester; Dc - well diameter; [τm] - specific bearing capacity of the bridge, the values ​​of which are determined both by the adhesive properties of the backfill material and by the way the bridge is installed. The tightness of the bridge also depends on its height and the condition 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 string 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 ≥ No – Pm/[∆r] (2) where Pm is the maximum value of the pressure difference acting on the bridge during its operation; [∆p] - allowable fluid breakthrough pressure gradient along the contact zone of the bridge with the borehole wall; this value is also determined mainly depending on the method of installing the bridge, on the applied backfill materials. From the values ​​of the height of cement bridges, determined by formulas (1) and (2), choose more.

Bridge installation has much in common with the column cementing process and has the following features:

1) a small amount of backfill materials is used;

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

3) rubber separating plugs are not used;

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

5) the bridge is not limited by anything from below and can spread under the action of the difference in the density of cement and drilling fluids.

The installation of a bridge is a simple operation in terms of concept and method, which in deep wells is significantly complicated by such factors as temperature, pressure, gas, water and oil shows, etc. The length, diameter and configuration of the pouring pipes, the rheological properties of cement and drilling fluids are also of no small importance. wellbore cleanliness and downflow and upflow modes. The installation of the bridge in the open part of the wellbore is significantly affected by the cavernousness of the wellbore.

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

When installing bridges for drilling a new shaft, they are subject to an additional height requirement. This is due to the fact that the strength of the upper part (H1) of the bridge should provide the possibility of drilling a new wellbore with an acceptable curvature intensity, and the lower part (H0) - reliable isolation of the old wellbore. Nm \u003d H1 + No \u003d (2Dc * Rc) 0.5 + No (3)

where Rc is the radius of curvature of the trunk.

An analysis of the available data shows that obtaining reliable bridges in deep wells depends on a complex 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 intrusions and losses).

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

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

An increase in temperature and pressure contributes to the intensive acceleration of all chemical reactions, causing rapid thickening (loss of pumpability) and setting of cement slurries, which, after short-term circulation stops, are sometimes impossible to push through.

Until now, the main method of installing cement bridges is to pump cement slurry into the well to the design depth interval along a pipe string lowered to the level of the bottom 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 controlling their movement. The process is controlled by the volume of the displacement fluid, calculated from the condition of equal levels of cement slurry in the pipe string and the annular space, and the volume of 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 cementing 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 the binder solution and other factors are to some extent due to incorrect selection of the binder solution formulation according to the thickening (setting) time or deviations from the recipe selected in the laboratory, made when preparing the binder solution.

It has been established 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 the bridge installation by at least 25%. In a number of cases, when selecting the formulations of binder solutions, they do not take into account the specifics of the work on the installation of bridges, which consists in stopping the circulation to raise the casting pipe string and sealing the wellhead.

Under conditions of high temperatures and pressure, the shear resistance of the cement slurry, even after short stops (10-20 min) of circulation, can increase dramatically. Therefore, the circulation cannot be restored and in most cases the pouring pipe string is stuck. As a result, when selecting a cement mortar 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 on preparing, pumping and pushing the cement slurry into the well, respectively; T4, T5, T6 - the time spent on lifting the pouring pipe string to the bridge cutting point, sealing the wellhead and performing preparatory work on cutting the bridge; Tm is the time spent on cutting the bridge.

According to a similar program, it is necessary to study mixtures of cement slurry with drilling slurry 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 adherence to 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 averaging tank.

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

When drilling in the intervals of distribution of permafrost, as a result of the combined physical and chemical impact and erosion on the borehole walls, ice-cemented sandy-argillaceous deposits are destroyed and easily washed away by the drilling fluid flow. This leads to intense cavern formation and related collapses and screes of rocks.

The rocks with low ice content and weakly compacted rocks are destroyed most intensively. 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 layers of thawed rocks, many of which are prone to loss of drilling fluid at pressures slightly exceeding the hydrostatic pressure of the water column in the well. Losses in such layers are very intense and require special measures to prevent or eliminate them.

In permafrost sections, rocks of the Quaternary age are usually the most unstable in the range of 0 - 200 m. With traditional drilling technology, the actual volume of the trunk in them can exceed the nominal volume by 3 - 4 times. As a result of strong cavern formation. which is accompanied by the appearance of ledges, sliding of cuttings and collapses of rocks, conductors in many wells were not lowered to the design depth.

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

In the interval of distribution of permafrost, it is difficult to provide cementing and fixing the wellbore due to the creation of stagnant zones of drilling fluid in large caverns, from where it cannot be displaced by cement slurry. Cementing is often unilateral, and the cement ring is not continuous. This creates favorable conditions for inter-layer cross-flows and the formation of griffins, for collapse of columns during reverse freezing of rocks in the case of long-term "interlayers" of the well.

The processes of destruction of permafrost are quite complex and little studied. 1 The drilling fluid circulating in the well interacts thermo- 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) - crust on the well wall - flushing 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. tend to equalize concentrations, temperatures, pressures. The role of a semi-permeable partition can be performed by both the filter cake and the downhole race 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 by the empirical formula

w = aT~ b .

1pa = 0.2618 + 0.55191nS;

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

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

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

If the degree of mineralization of the drilling fluid and the pore water of the permafrost are the same, then the well-rock system will be in isotonic equilibrium, and the destruction of the permafrost under physical and chemical influence is unlikely.

With an increase in the degree of mineralization of the flushing agent, conditions arise under which pore water with a lower mineralization 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 collapse, 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 salty washing liquid has been noted in the works of many researchers. Experiments carried out at the Leningrad Mining Institute showed that with an increase in the salt concentration in the fluid surrounding the ice, the destruction of ice intensifies. So. when the content in the circulating water is 23 and 100 kg / m - NaCl, 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 affected by the duration of exposure to salt washing liquid. 1.0 h 0.96 g: after 1.5 h 1.96 g.

As the near-wellbore permafrost zone thaws, a part of its burrow space is released, where the flushing fluid or its dispersion medium can also be filtered. This process may turn out to be another physico-chemical factor contributing to the destruction of the MMP. It can be accompanied by an osmotic flow of fluid from wells into the rock if the concentration of some soluble salt in the MMP fluid is greater than in the fluid. filling the wellbore.

Therefore, in order to minimize the negative impact of physical and chemical processes on the state of the wellbore drilled in permafrost, it is necessary, first of all, to ensure an equilibrium concentration on the well wall of the components of the drilling mud and interstitial fluid in permafrost.

Unfortunately, this requirement is not always feasible in practice. Therefore, it is more often resorted to protecting the cementing permafrost ice from the physical and chemical impact of the drilling fluid with films of viscous liquids that cover not only the ice surfaces exposed by the borehole, but also the interstitial 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, in the transition from flushing wells with salt water to flushing with a more viscous clay solution, the intensity of ice destruction decreased by 3.5–4 times at the same concentration of NaCl in them. It decreased even more when the drilling fluid was treated with protective colloids (CMC, CSB|. The positive role of additions to the drilling fluid of highly colloidal bentonite clay powder and hypan was also confirmed.

Thus, to prevent cavern formation, destruction of the wellhead zone, screes and collapses when drilling wells in permafrost. drilling fluid must meet the following basic requirements:

have a low filtration rate:

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

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

form a filtrate that does not form true solutions with the liquid;

be hydrophobic to the ice surface.

Zavgorodny Ivan Alexandrovich

2nd year student, mechanical department, majoring in Oil and Gas Well Drilling, Astrakhan State Polytechnic College, Astrakhan

Email:

Kuznetsova Marina Ivanovna

teacher of special disciplines, Astrakhan State Polytechnic College, Astrakhan

Email:

Introduction. Since ancient times, mankind has been extracting 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 appeared, at about the same time drilling began in Russia. In 1864 and 1866, the first wells were drilled in the Kuban with a flow rate of 190 tons per day.

Initially, oil wells were drilled using a manual rotary rod method, soon they switched to drilling using a manual rotary rod method. The shock-rod method is widely used 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 Russian mining engineers G.D. Romanovsky and S.G. Voislav. In 1901, for the first time in the United States, rotary drilling with flushing of the bottomhole with a circulating fluid flow (using drilling mud) was used, and the French engineer Fauvel invented the lifting of cuttings with a circulating water flow back in 1848. From that moment, the period of development and improvement of the rotary drilling method began. In 1902, in Russia, the first well was drilled with a rotary method in the Grozny region, with a depth of 345 m.

To date, the United States occupies a leading position in the oil industry, 2 million wells are drilled annually, a quarter of them are productive, Russia still occupies only the second place. In Russia and abroad, the following are used: manual drilling (water extraction); mechanical; controlled 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 Institute of Mines has developed a laser drilling technology based on rock burning.

Drilling technology. The mechanical method of drilling is the most common, it is carried out by percussive, rotary and percussive-rotary drilling methods. With the impact 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, crown) pressed against the bottom is called the rotary drilling method.

When drilling oil and gas wells in Russia, only rotary drilling 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 brought 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 engine, rotary drilling is divided into rotary drilling and turbodrilling. In rotary drilling, the rotator (rotor) is located on the surface, driving the bit at the bottomhole with the help of a drill string, the rotation frequency is 20-200 rpm. When drilling with a downhole motor (turbodrill, screw drill or electric drill), the torque is transmitted from the downhole motor mounted above the bit.

The drilling process consists of the following main operations: lowering drill pipes with a bit into the well to the bottom and lifting drill pipes with a used bit from the well and operating the bit at the bottom, i.e., destruction of the drilling rock. These operations are periodically interrupted to run casing pipes into the well in order to protect the walls from collapses and to separate the oil (gas) and water horizons. Simultaneously, in the process of drilling wells, a number of auxiliary works are performed: core sampling, preparation of flushing fluid (drilling mud), logging, curvature measurement, well development in order to cause oil (gas) inflow into the well, etc.

Figure 1 shows the technological scheme of the drilling rig.

Figure 1. Scheme of a drilling rig for rotary drilling: 1 - drilling line; 2 - traveling block; 3 - tower; 4 - hook; 5 - drilling hose; 6 - leading pipe; 7 - gutters; 8 - drilling pump; 9 - pump motor; 10 - pump piping; 11 - receiving tank (capacity); 12 - drilling lock; 13 - drill pipe; 14 - hydraulic downhole motor; 15 - chisel; 16 - rotor; 17 - winch; 18 - winch and rotor engine; 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 raising the drill string, as well as maintaining it on weight. 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 tackle system. The traveling system consists of a stationary part of the crown block installed at the top of the tower lantern and the movable part of the traveling block, traveling rope, hook and slings. The traveling system is designed to convert the rotational movement of the winch drum into the translational movement of the hook. The drilling rig 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 its uniform feeding and placement of the traveling system, drill pipes and equipment in it. Tripping operations are carried out with the help of a drilling winch. The drawworks consists of a base on which the winch shafts are fixed and interconnected by gears, all shafts are connected to a gearbox, and the gearbox, in turn, is connected to the engine.

Ground 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 fluid from cuttings. And a number of ancillary facilities.

The drill string connects the drill bit (rock breaking tool) to the surface equipment, i.e. the drilling rig. The top tube in the drill string is square, it can be hexagonal or grooved. The leading pipe passes through the opening of the rotor table. The rotor is placed in the center of the drilling rig. The top end of the kelly is connected to a swivel designed to ensure rotation of the drill string suspended on the hook and supply of 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 fixed.

Consider the technology of the drilling process (Figure 1). A flexible hose 5 is connected to the hole of the fixed part of the swivel 19, through which flushing fluid is pumped into the well using drilling 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 liquid enters the bit 15. Leaving the holes of the bit, the liquid flushes the bottomhole, picks up the particles of drilled rock and together with them through the annular space between the walls of the well and the drill pipes rises up and goes to the pump intake. On the surface, the drilling fluid is cleaned of drilled rock using special equipment, after which it is again fed into the well.

The technological process of drilling largely depends on the drilling fluid, which, depending on the geological features 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 rocks, pressures, etc.), should be selected based on geological and climatic conditions. Since, from the well-conducted opening of the productive horizon in the field, the operational characteristics of the well, namely its flow rate and productivity, depend in the future.

Bibliography:

1.Vadetsky Yu.V. Drilling of oil and gas wells: a textbook for the beginning. prof. education. M.: Publishing Center "Academy", 2003. - 352 p. ISB No. 5-7695-1119-2.

2.Vadetsky Yu.V. Driller's Handbook: textbook. allowance for the beginning prof. education. M.: Publishing Center "Academy", 2008. - 416 p. ISB No. 978-5-7695-2836-1.

Offshore drilling is one of the most striking technical breakthroughs of recent decades in the field of well construction. We will tell you about the main technological processes associated with drilling offshore wells, types of offshore drilling platforms, design features of offshore wells, measures to induce fluid flow from the reservoir into the well, and also talk about environmental complications and their solutions.

Offshore well drilling requires fundamentally new designs of drilling equipment and technologies that would guarantee the drilling of wells in compliance with safety, environmental friendliness and would provide high quality work with limited space and at the lowest cost.

About the course

The purpose of studying the course is to acquire knowledge in the field of the theory of basic technological processes associated with the construction of oil and gas wells from floating drilling rigs and offshore fixed platforms on the shelf of the World Ocean.

Taking into account the specifics of well construction on the shelf of the world ocean, this online course will be of interest not only among students in the field of "Oil and Gas Business", but also among a wide range of technical specialists in a number of related areas.

The course presents the most modern technologies for the construction, development and operation of offshore wells, based on the colossal experience of highly qualified specialists of the State Unitary Enterprise of the Republic of Kazakhstan "Chernomorneftegaz".

Format

The course includes video lectures, divided into fragments from 5 to 10 minutes. After each studied section, an intermediate control is planned for further transition to the next module; at the end of the course, a final exam is provided for all the material covered. The course also includes practical assignments in this area.

Informational resources

1. Ovchinnikov, V.P. Construction of wells on the fields of the shelf of the seas and oceans: textbook / V.P. Ovchinnikov [and others]. - Tyumen: TIU, 2018. - 370 p.

2. Features of well drilling on the shelf: textbook / V. G. Kuznetsov, Yu. V. Lavrentiev, A. E. Kazantsev et al.; under total ed. V. G. Kuznetsova. - Tyumen: Tsogu, 2013. - 80 p.

Requirements

To master the discipline, knowledge of general and organic chemistry, physics, mathematics is required, as well as primary knowledge in the field of oil and gas business (well design, well operation methods, geological sections of fields, field development methods, hydrocarbon transport).

Course program

1. Introduction to the discipline

This section will contain the following definitions: what is a shelf; oil and gas field geology; onshore drilling technology, well design, oil production methods, oil and gas processing, transportation of oil products and gases.

2. Types of offshore platforms

This section provides detailed information about the types of offshore platforms, as well as their characteristics.

3. Construction of offshore wells

This section provides concepts about / about the well, well design, the main elements of the well, casing, methods for choosing the design of wells on the shelf

4. Offshore well construction technology

This section provides detailed information about the properties, types and types of drilling fluids, as well as methods for completing offshore wells and measures to induce fluid inflow from the formation into the well.

5. Equipment of the offshore drilling platform

This section provides detailed information about the equipment used to control drilling.

6. Operation of offshore wells

This section provides information on the technique and technology of offshore wells operation. The main differences between the operation of offshore and onshore wells are given.

7. Complications when drilling offshore wells

This section describes the causes of complications during offshore drilling, as well as the types of complications and ways to prevent them.

Learning Outcomes

As a result of completing the course, the student:

He will master the conceptual and terminological apparatus in the field of drilling wells in the waters of the seas and oceans.

Will be able to set goals and formulate tasks related to the implementation of professional functions on floating and stationary drilling rigs;

Will be able to use the principles of operation of drilling equipment, equipment for the operation and workover of wells on offshore platforms

Will be able to design designs of wells with an underwater wellhead.

Formed competencies

As a result of completing the course, the student learns:

Basic technologies of oil and gas production on the shelf of the world ocean;

Safety rules in the oil and gas industry during the construction of wells from offshore hydraulic structures;

The main process equipment used on offshore drilling rigs.

Will learn:

Set goals and formulate tasks related to the implementation of professional functions on floating and stationary drilling rigs;

Use the principles of operation of drilling equipment, equipment for the operation and workover of wells on offshore platforms

Design well structures with an underwater wellhead.

will master :

Conceptual and terminological apparatus in the field of drilling wells in the waters of the seas and oceans.

The course "Technique and technology of drilling offshore wells" includes video lectures, practical exercises, intermediate control in the form of test tasks and final control.

Mining is the extraction of natural resources from the depths of the earth. The development of solid minerals is carried out by a quarry or mine method. Wells are drilled to extract liquid and gaseous natural resources. Modern well drilling technologies make it possible to develop oil and gas fields at a depth of more than 12,000 meters.

The importance of hydrocarbon production in the modern world is difficult to overestimate. Fuel is made from oil (see) and oils, rubber is synthesized. The petrochemical industry produces household plastics, dyes and detergents. For oil and gas exporting countries, fees from the sale of hydrocarbons abroad are a significant, and often the main method of replenishing the budget.

Field exploration, installation of drilling rigs

In the proposed location of the mineral deposit, a geological survey is carried out and a location for a research well is determined. Within a radius of 50 meters from the exploration well, the site is leveled and a drilling rig is mounted. The diameter of the research well is 70-150 mm. During the drilling process, samples of drill cuttings are taken from different depths for subsequent geological survey. Modern complexes for geological research make it possible to accurately answer the question of whether it is worth starting the extraction of energy resources through this well on an industrial scale.

When the geological study of the drill cuttings showed the prospects for industrial development, the construction of the drilling site begins. The previously cleared site is concreted and fenced, a grader road is laid (a road without a hard surface). On the created one they build a tower, mount a winch, drilling pumps, install a generator and everything necessary. The assembled equipment is tested, gradually brought to the planned capacity, and put into operation.

The most commonly used technology mechanical well drilling, which is carried out in a rotational, percussion or combined way. The drill is attached to a square drill string and lowered into the well with the help of a traveling system. The rotor, located above the wellhead, transmits the rotary motion to the drill.

As the well is drilled, the drill string grows. Simultaneously with the process of drilling a production well, special pumps are used to flush the well. To flush the well from broken rock particles, a flushing liquid is used, which can be industrial water, an aqueous suspension, clay solutions or hydrocarbon-based solutions. After pumping the drilling fluid into special containers, it is cleaned and used again. In addition to cleaning the bottomhole from cuttings, flushing fluids provide cooling of the drill, reduce the friction of the drill string against the borehole walls and prevent collapse.

At the final stage of drilling, the production well is cemented.

There are two cementing methods:

• direct method- the solution is pumped into the drill string and forced into the annulus.
• reverse method- the solution is pumped into the annulus from the surface.

A number of specialized machines and mechanisms are used for drilling wells. On the way to the design depth, areas of rock with increased hardness often come across. For their passage, it is necessary to give an additional load to the drill string, therefore quite serious requirements are imposed on the production equipment.

Drilling rig equipment is expensive and designed for long-term use. In the event of a stop in production due to a breakdown of any mechanism, it will be necessary to wait for a replacement, which will seriously reduce the profitability of the enterprise. Equipment and mechanisms for hydrocarbon production must be made of high quality and wear-resistant materials.

The drilling platform equipment can be divided into three parts:

• Drilling part- drill and drill string.
• Power part– rotor and travel system, providing rotation of the drill string and tripping manipulations.
• Auxiliary part- generators, pumps, tanks.

The smooth operation of the drilling rig depends on the correct operation of the equipment and the maintenance of the mechanisms, within the time limits prescribed by the manufacturer. It is equally important to change consumables in a timely manner, even if everything looks fine with them. Without compliance with the operating rules, it is impossible to guarantee the safety of the personnel of the drilling platform, the prevention of environmental pollution and the uninterrupted production of oil or gas.

Methods for drilling production wells

Well drilling methods are divided depending on the method of impact on the rock.

Mechanical:

• Shock.
• Rotational.
• Combined.

Non-mechanical:

• Hydraulic fracturing.
• high temperature exposure.
• Undermining.

It should be noted that the main drilling method is rotational and rotational-impact, other methods are rarely used in practice.

 

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