WO2022039627A1

WO2022039627A1 - Method for selectively treating a producing formation and device for carrying out same

Info

Publication number: WO2022039627A1
Application number: PCT/RU2021/000362
Authority: WO
Inventors: Салават Анатольевич Кузяев
Original assignee: Салават Анатольевич Кузяев
Priority date: 2020-08-21
Filing date: 2021-08-23
Publication date: 2022-02-24
Also published as: RU2747495C1; US20230332485A1

Abstract

A method for selectively treating a producing formation comprises sequentially carrying out hydraulic fracturing and flushing of the annulus in a space between packers in each interval of a producing formation. At the interval to be treated, a device is secured in the well using a mechanical anchor, and a working fluid is fed under pressure into the cavity of the production tubing and into a hydraulic fracturing port, and the interval is isolated by packers with cup sealing elements. Hydraulic fracturing is carried out. The annulus is flushed in two cycles. In a first cycle, debris is flushed from the upper region of the annulus via apertures in the hydraulic fracturing port and upwards along the production tubing. In a second cycle, debris is flushed from the lower region of the annulus and from the cup seals, moving the mixture into the well. The claimed device comprises, mounted in succession on the production tubing, a mechanical anchor (1), a lower feed-through packer (3), a hydraulic fracturing port (4), an upper feed-through packer (5), and a centralizer (6). The feed-through packers (3 and 5) are provided with cup seals (8 and 9) that are oriented toward the hydraulic fracturing port (4). The housing of the hydraulic fracturing port (4) is divided by a partition into an upper part with apertures and a lower part with flushing openings.

Description

Method for selective treatment of a productive formation and device for its implementation.

Technical field

The invention relates to mining, is used in the repair and operation of oil wells, is intended for selective processing of a productive formation in one round-trip operation with flushing the annulus in real time during downhole operations.

Prior Art

One of the main problems that affect the efficiency of repair and operation of oil wells is the complication that occurs during their processing, in particular, sticking of downhole equipment. A common cause of such a complication is the jamming of the tool when moving up the well due to the sprinkling of various mechanical impurities in the annular space between the downhole equipment and the production string, in particular, compressed proppant. Elimination of accidents associated with sticking is a complex, time-consuming and expensive operation.

To solve this problem, well-known technologies are used to prevent accidents, based on the capture and removal of mechanical impurities from the well, including from areas adjacent to it.

One of the measures to avoid an emergency in the well due to stuck downhole equipment is to ensure high-quality flushing of the cavities between the downhole tool and the production string, especially in the productive formation zone, as well as the internal cavities of the equipment used for process fluids.

To remove mechanical impurities (granular debris or reservoir sand) from the annulus, devices are used that contain various filtration devices, trapping elements and storage containers.

A known method of operation of a downhole jet installation, which involves flushing the area of the productive formation after hydraulic fracturing (hereinafter hydraulic fracturing) using a downhole jet unit (RF patent No. 2273772, published April 10, 2006, bull. 10). The method consists in lowering into the well on a string of tubing (hereinafter tubing) a downhole installation consisting of a jet pump with a stepped through passage in its body and, located below the jet pump, a packer with a through passage and a liner with an inlet funnel. Then the packer is unpacked, which is installed above the productive formation. Next, a blocking insert with a central passage channel is installed in the stepped flow channel of the jet pump, and a hydraulic fracturing fluid or a mixture of hydraulic fracturing fluid with chemical reagents is pumped into the productive formation. After that, the blocking insert is removed to the surface and a flexible pipe is lowered through the tubing into the well, which is passed through the sealing assembly with the possibility of its movement. The sealing assembly is installed during the descent of the flexible pipe in the stepped flow channel of the jet pump. The lower end of the coiled tubing is installed below or at the level of the lower perforation interval of the productive formation.

Further, a liquid working medium is fed into the nozzle of the jet pump through the annulus of the well, and the productive formation is drained by creating drawdown on the productive formation in the under-packer space of the well. Simultaneously or after creating a stable drawdown on the productive formation, liquid is supplied to the well through a flexible pipe to flush the bottom hole. The ratio between fluid pressure in coiled tubing and fluid pressure in the well annulus is maintained in the range (Pg:Pp) < 0.98.

After fluid is pumped out of the productive formation with a volume equal to at least two volumes of hydraulic fracturing fluid or a mixture of hydraulic fracturing fluid and chemical reagents pumped into the productive formation, the fluid supply to the coiled tubing is stopped to flush the bottom of the well.

Not earlier than after 5 minutes, the supply of liquid working medium to the nozzle of the jet pump is stopped and a flexible pipe with a sealing assembly is removed from the well. Then, using a jet pump, hydrodynamic and geophysical studies of the productive formation are carried out to assess its productivity. After that, work is carried out to put the well into operation. The downhole jet installation used for the implementation of the method comprises a packer with a passage channel installed on the tubing string, a jet pump, in the body of which a nozzle and a mixing chamber with a diffuser are located. In addition, the jet pump has a stepped flow channel. Below the jet pump is a shank with an inlet funnel. A sealing assembly or, alternatively, a blocking insert is installed in the stepped passageway. A flexible pipe is passed through the sealing unit, the lower end of which is installed below or at the level of the lower perforation interval of the productive formation. The downhole jet unit is placed in the well so that the jet pump and packer are located above the reservoir.

The disadvantage of the known method and the downhole jet installation is the high probability of emergency extraction from the well in case of jamming due to the dusting of the annular space between the tool and the casing string with mechanical debris. Cleaning and extraction of foreign inclusions, in particular flushing the annulus from proppant, is not provided by the method according to the mentioned patent. The design of the jet unit does not allow reverse circulation of the fluid to remove mechanical debris from the well, for example, through the annulus due to the packer being sprinkled on top, which cannot be deactivated.

Another disadvantage of this system is that it cannot be used when processing several intervals of a productive formation in one trip, since after flushing the bottom of the well, the installation is immediately removed to the surface.

From the description to patent US 10280713 (published May 7, 2019), systems and methods for managing debris, including proppant, in a well are known, providing flushing of the annulus between the casing string and the downhole tool.

Technical solutions are aimed at solving problems of passive removal of large and small debris, chemical precipitated liquids from the drilling rig circulation system, blowout control equipment at the wellhead, as well as preventing sand from entering the annulus between the casing string and downhole equipment. The description of the patent contains information on options for individual components of the system for cleaning the annulus in the wellbore, which contains a reversible tool installed on the tubing and debris traps with an integrated filter, and the system can be equipped with a flush pipe, in which, as an option, traps for debris, which is an indicator of the degree of cleaning.

The trap consists of two separate nodes - the upper and lower ones, fixed in the pipe at some distance from each other. The top assembly is equipped with a screen in the form of a sieve, a plug and a three-way adapter. The bottom assembly consists of a screen, a three-way adapter and a ball check valve. The top and bottom assemblies are fixed in the flush tube by known means of connection. The trap works in conjunction with the sand control element in the well.

Process fluid with proppant enters the tubing for hydraulic fracturing, while the proppant begins to accumulate in the annulus between the casing string and equipment. The liquid passes through a screen-sieve built into the tubing and enters the wash pipe. The liquid then passes through the lower trap assembly, the ball valve and enters the space of the wash pipe between the nodes and further into the upper trap assembly. Moving, the liquid is additionally filtered in the bonds of the trap. This prevents further propagation of the proppant. The proppant is separated from the fluid by the lower assembly filter and retained by the check valve ball. When removing the equipment from the well, the amount of proppant in the cavity of the flushing tube between the trap nodes is used to judge the degree of contamination. Without extraction from the well, an indicator of the degree of contamination may be the loss of fluid volume during its return.

The reversible tool is designed to remove fluid and debris from the well, especially with large annular gaps. The tool allows reverse flow at reduced pump speeds without compromising debris throughput. The reversible tool contains a cylindrical element with cup-shaped sealing elements that hermetically separate the casing and create two separate annular gaps: one above the sealing elements, the other below the sealing elements. Besides, the cylindrical element is equipped with an internal baffle forming two channels in the inner cavity of the tubing, one channel is descending, the other is ascending. Through the descending channel, the flow of liquid or other material is removed from the tubing cavity into the annular space under the sealing element. Through the ascending channel, the flow of liquid or other material rises through the tubing below the sealing element and is discharged into the annular space above the sealing element, while the flow rate decreases, since the cross-sectional area of the tubing is less than the annular space. The annular space above the sealing element can be used to collect debris that cannot be carried by the reduced flow rate, while the debris collectors should not impede flow at the process speed.

The reversible tool is part of the fluid circulation system that flows from the tank through the suction line to the pump, which are on the above ground part of the equipment. The pump moves the flushing fluid through the pipeline to the upper tubing string above the cup sealing element.

The flushing fluid moves down the upper part of the tubing to the reversing tool, through which it is discharged to the annular space under the cup sealing element. The mixture of drilling fluid and debris then continues to move down the annulus to the bottom of the well and returns to the tubing again. Further, the filtered mixture, moving up the tubing, reaches the reversing tool and is deflected again, enters the annular space above the cup seal. Then, rising along the upper part of the tubing, the flushing fluid enters the reservoir. Thus, a complete cycle of circulation of the flushing liquid is ensured. The reversible tool can work for more than two years of continuous operation, performing more than 4000 cycles during the service life.

The system is equipped with alarms in the form of pressure gauges that monitor sudden pressure drops and the ability to block the system to warn the well operator that the traps are full or contain a lot of debris.

The disadvantage of this system is the limited area of use, mainly in offshore wells, and does not involve the simultaneous implementation of technological operations for the treatment of productive formations. In addition, work The system is based on many levels of filtration, and contains sophisticated equipment for flushing these devices that require periodic replacement.

The closest to the claimed technical solution is the invention according to US patent No. 10494900 (published on December 3, 2019), which presents options for a system for treating wells that performs hydraulic fracturing (hereinafter referred to as hydraulic fracturing), with a flushing unit and describes a method for flushing the annulus, in particular in the area of the annular gap between the string and the wellbore.

The composition and relative position of the main components of the system are similar for all options presented in the patent and includes an anchor, a lower packer, a hydraulic fracturing unit, an upper packer, a mechanical valve, a sand control unit, and an injection unit installed on the tubing (from bottom to top), providing pressure activation in the system. Below the anchor there is a valve that is in the closed position during hydraulic fracturing and a hole for dumping excess fluid.

The anchor is designed to fix the device in the well and can be installed by axial movement up and down. The top and bottom packers are designed to isolate the reservoir area. The mechanical valve is an element of the sand control unit and is involved in creating a pressure drop in the annulus below the sand control unit to ensure flushing of the annulus. The sand control unit is located above the hydraulic fracturing unit and is designed to remove produced sand and gravel from the annulus when moving to another treatment zone or to the surface. In the annular space flushing operation, together with the sand control unit, a flushing device is involved, which provides hydraulic communication with the annular space in the annular gap zone through radial channels.

In addition, to ensure a significant pressure drop determined by the conditions in the well, for example, when the pressure of the flushing fluid exceeds the pressure of the hydraulic fracturing fluid by 2-5 times, the sand control unit is additionally equipped with a check valve and one or more additional packers.

The patent presents three variants of the flushing device, one of which can be activated several times, which ensures flushing of the annular gap when processing several productive formations in one trip. The flushing device is located above the hydraulic fracturing unit, is connected to a mechanical valve and opens when flushing fluid is supplied at an appropriate pressure, which is much higher than the hydraulic fracturing pressure, therefore, during hydraulic fracturing, the flushing device is closed.

The flushing device contains a sliding sleeve installed in the housing, a piston and a return spring. The pressure exerted on the piston counteracts the compression force of the spring. Radial holes are made in the housing, blocked by a piston in the closed position of the flushing device. Nozzles are installed in the radial holes, providing a given angle of jet supply to the wellbore for the possibility of flushing the annulus in different directions.

The advantage of this version of the flushing device is that, due to the action of the spring, the return of the sliding sleeve closes the radial holes when the pressure on the piston is released after flushing the annular gap is completed.

The system is also equipped with a release mechanism that activates and deactivates the reservoir packers and the hydraulic fracturing unit.

The release mechanism is made in the form of a housing, which is an element of the system, inside which an internal sleeve is installed with the possibility of axial movement. The inner sleeve is provided with a radial hole. In the cavity between the body and the inner sleeve there is a removable sleeve with grooves forming axially longitudinal cavities hydraulically connected with the annulus.

When the system is idle, the inner sleeve is in the working position, the packers sealing the reservoir area and the hydraulic fracturing unit are not active. The radial hole of the inner sleeve is closed with a removable sleeve. The position of the inner sleeve ensures the passage of fluid through the internal cavity of the piston and closes the hydraulic connection with the annulus through the radial holes in the body. The removable sleeve is kept from displacement relative to the housing by a retainer.

When pressure is applied to the inner cavity of the piston, the inner sleeve, overcoming the action of the return spring, performs axial movement until the hydraulic connection is restored through the radial holes in the inner sleeve and in the housing, which communicate with the cavity between the housing and the sleeve. The pressure in the piston cavity partially drops, the inner sleeve returns to the idle position under the action of the spring. Under the action of pressure in the piston area, the retainer is displaced into the seat in which it is installed, releasing the removable sleeve. This bushing closes the radial hole in the housing, maintaining the hydraulic connection of the piston cavity with the cavity between the housing and the inner bushing, while the increasing flushing pressure does not exceed the force of the return spring on the inner bushing. In this state of the release mechanism, the hydraulic fracturing unit is closed, the packers sealing the formation area are not activated.

The known system is designed to operate in emergency conditions, when it is impossible to remove the drilling tool from the well, due to the dusting of the upper packer with mechanical debris and the impossibility of flushing the annulus in the annulus between the packers. This leads to the impossibility of controlling the circulating flushing unit, removing the tool from the well, and requires additional units that provide this function for flushing the space above the second packer from the bottom.

Another disadvantage of the system is the design complexity due to the presence of additional elements for various purposes (packers, valves), the use of spring mechanisms to control the flushing device, which are characterized by instability, changes in elastic properties and subsequent deformation.

Another disadvantage of the device is the use of high pressures during flushing, exceeding the hydraulic fracturing pressure by 2-5 times.

In the fields of Western Siberia, where the depth of wells can reach 3500 m, and the hydraulic fracturing pressure can reach 700 atmospheres, the flushing pressure will be 1400-3500 atmospheres, which is much higher than the value of 1000 atmospheres - the pressure for which standard hydraulic fracturing equipment is designed. The use of pressure during the operation of the device when flushing the annulus of the well, which is several times higher than the hydraulic fracturing pressure, entails the need to use non-standard wellhead equipment, non-standard tubing hanger, non-standard pumping equipment for hydraulic fracturing, which significantly reduces the manufacturability of the known system and significantly limits its use. The objective of the inventions is to increase the efficiency of the treatment of the productive formation in one round trip, to reduce the accident rate and increase the service life of the downhole tool.

The technical result is to ensure simultaneous flushing of the inter-packer annular gap between the casing string and the tool, as well as the internal cavities of the tool after each treated interval of the productive formation and to increase the reliability and manufacturability of the device used by simplifying its design.

The technical result is achieved by the fact that the method of selective treatment of a productive formation includes successive hydraulic fracturing and flushing of the annular gap in the interpacker space of each interval of the productive formation, using a device for its implementation, which is lowered into the tubing to the level of the lowest interval of the productive formation.

When the device reaches a level at which the interval of the productive formation to be processed is located in the inter-packer space, the device is fixed in the well with a mechanical anchor. Next, the working fluid is supplied under pressure to the tubing cavity, the hydraulic fracturing port, and the productive formation interval is isolated by packers with cup sealing elements. Then hydraulic fracturing is carried out.

After hydraulic fracturing, flushing of the annular gap in the inter-packer space is carried out. The first cycle, which begins with the injection of flushing fluid into the annulus, then activates the lower packer and flushes out debris from the upper area of the inter-packer annulus through the fracturing port windows up the tubing.

The second cycle begins with the transfer of the device to the transport position, then the axial movement of the tubing leads to the displacement of the hollow rod of the device and opens the flushing holes. After that, flushing fluid is supplied under pressure to the tubing, the cup sealing elements of the packers are activated and debris is washed out from the lower region of the interpacker annular gap and the cup seals, moving the mixture along the internal cavity of the device beyond its limits into the well.

Next, the device is moved to the next interval and processing and washing are carried out in the same sequence. The flushing liquid is supplied by a pumping unit located on the surface.

To transfer the device to the transport position, the mechanical anchor is deactivated by the longitudinal movement of the device.

Debris from the upper region of the interpacker annulus is disposed of at the surface by any known method.

The technical result is also achieved by the fact that the device for implementing the method contains a mechanical anchor, a lower pass-through packer, a hydraulic fracturing port, and an upper pass-through packer installed in series on the tubing. Drift packers equipped with cup seals are directed to the hydraulic fracturing port. A hollow rod is located in the internal cavity of the device.

The body of the hydraulic fracturing port is divided by a partition into the upper part, in which windows are made, and the lower part, in which flushing holes are located, providing hydraulic connection between the packer annulus with a cavity made in the lower part of the partition. The lower pass packer is provided with a longitudinal cavity on the inner surface, and the hollow rod is provided with protrusions that interact with the cavity, moving along it. The distance between the bottom drift packer and the flush holes does not exceed two casing diameters.

The tightness of the flushing holes is ensured by seals placed above and below the flushing holes. The internal cavities of the hollow rod, the lower pass-through packer and the mechanical sleeve locator form a single flushing channel. The hollow rod is rigidly connected to the mechanical anchor.

The device can be additionally equipped with a sleeve locator located under the lower drift packer and a centralizer.

Flushing of the annulus, carried out in two cycles, in each of which debris is removed from the upper or lower region of the annulus, provides high-quality cleaning.

Transport of mechanical debris from the inter-packer annular gap and disposal on the surface in the first wash cycle, as well as removal and removal of debris outside limits of the device into the worked-out space of the well in the second flushing cycle, excludes the presence of even a minimum volume of mechanical particles.

The sequence of hydraulic fracturing, the first and subsequent second cycles of flushing the inter-packer annulus annulus ensures unhindered movement of the tool along the casing string.

The simple and reliable design of the device for implementing the method ensures the movement of the flushing fluid through two unconnected channels for removing debris, which are controlled by a simple longitudinal movement (activation / deactivation) of the mechanical anchor and due to the interaction of only two elements - a hollow rod and a body of the lower through packer .

In FIG. 1 shows a general view of the device; in fig. 2 - enlarged view of the hydraulic fracturing port; in fig. 3 is a longitudinal section of the device in the transport position; in fig. 4 is a longitudinal section of a device with an activated mechanical anchor; in fig. 5 is an enlarged view of the hydraulic fracturing port in the position of the device shown in FIG. 3; in fig. 6 - longitudinal section of the device in the position of hydraulic fracturing; in fig. 7 - a diagram of the movement of the working fluid with an activated anchor; in fig. 8 - a diagram of the movement of the working fluid with a deactivated mechanical anchor.

The device contains a mechanical anchor (1), a sleeve locator (2), a lower pass-through packer (3), a hydraulic fracturing port (4) and an upper pass-through packer (5) with a centralizer (6) mounted from the bottom up on the tubing string (Fig.1, Fig. .2).

Remote nozzles (7) are connected to the centralizer b, the installation of which is determined by the need and conditions for processing intervals of the formation of variable length.

Cup sealing elements (8) of the lower floating packer (3) are directed to the hydraulic fracturing port (4). Cup sealing elements (9) of the upper floating packer (5) are also directed to the hydraulic fracturing port.

The following known devices can be used as functional parts: mechanical sleeve locator, similar to sleeve locator A 1025-2, presented in the catalog "Tool for maintenance and workover of wells", p. 31 https://www.slb.ru/upload/iblock/d8e/katalog-instrumentov-dla- tekushego-i-kapitalnogo" repair-skvaiin.pdf ):

- centralizer - (http://www.coilsolutions.com/products/downhole-tools/drill-and-milling-tools/fluted-centralizers/) or (http://petrolibrary.ru/preduprezhdenie-iskriyleniya-vertikalnyix-skvazhi -skvazhin.html); axial mechanical anchor (YAMO-3, YAMO-2) (https://npf-paker.ru/catalog/tvpe/yakorya/mekhanicheskie/vamo3-yamo2-yam3-yam2).

Windows (10) are made in the body of the hydraulic fracturing port (Fig. 2). The hydraulic fracturing port 4 contains a partition (11) placed inside the body, in the lower part of which a recess (12) is made, and a divider (1)3 is installed in the upper part (Fig. 3). In addition, through the radial holes (14) are made in the lower part of the port, connecting the recess (12) with the annulus.

In the inner cavity of the lower pass-through packer (3), a hollow rod (15) is placed with the possibility of axial movement, rigidly connected to the mechanical anchor 1 by means of a cone (16).

The tightness of the radial flushing holes (14) is ensured by seals (18) installed on the side of the inner surface of the baffle (12) above the holes (14) and on the side of the inner surface of the lower pass-through packer 3 below them.

On the side of the outer surface, the hollow rod (15) is provided with limiting protrusions (17) that move axially along the cavity (1)9 made on the inner surface of the packer (3), the longitudinal dimension of which determines the stroke “S” of the rod (15) (Fig. 3 and Fig. 4).

The internal cavities of the rod (15), the lower pass-through packer (3), the sleeve locator (2) and the mechanical anchor communicate and form a single flushing channel (20) (Fig. 2).

In the transport position of the device, the hollow rod (15) is in the lower position, in which the protrusions (17) abut against the lower horizontal wall of the cavity (18), the radial flushing holes (14) provide communication between the recess (12) and the annulus between the packers (Fig. 2 and Fig. 3). The cup seals (8) of the lower pass-through packer (3) are located at a distance H1 from the flush holes (14) of the hydraulic fracturing port (4), the value of which depends on the well diameter and does not exceed two casing string diameters.

The device for implementing the method works as follows:

Before running into the well, the device is assembled at the wellhead and installed on the tubing.

When lowering into the well, the mechanical anchor (1), lower (3) and upper (5) pass-through packers are in the transport position, the hollow rod (15) is in the lower position and is fixed from axial downward movement by limiting ledges (17).

Before treatment of the formation, the device is placed in a blind section of the production casing and pressure testing of the through-flow packers is carried out.

Next, the device is installed in such a way that the processing interval is located in the inter-packer space and the mechanical anchor (1) is activated, ensuring that the device is fixed in the well with anchor elements (21) (Fig. 4). Then part of the weight of the tubing is unloaded onto a mechanical anchor (1), while the hollow rod (15) enters the recess (12), hermetically blocking the flushing holes (14) with the help of seals (18) (Fig. 5).

Further, hydraulic fracturing fluid is supplied under pressure to the tubing pipes (1) and, due to the counter flow from the hydraulic fracturing port (4), the cup sealing elements (8) and (9) of the through-flow packers (3) and (5) open, providing a tight fit to the the inner wall of the casing pipe, reliably isolating the inter-packer space. Then hydraulic fracturing is performed (Fig. 6).

After the fracturing is completed, the tubing, the device and the space between the device and the production string are flushed, freeing it from proppant and other mechanical inclusions, ensuring unhindered and saving movement of the device to the next formation interval or recovery from the well.

Flushing of the annular space of the well and the cavities of the device is carried out in two cycles as follows.

The first cycle begins with the pumping unit, located on the surface, supplying the flushing fluid under pressure into the annulus, while cup sealing elements (8) of the lower pass-through packer (3) are in the active position. The flushing fluid through the windows (10) enters the internal cavity of the hydraulic fracturing port (4), the upper pass-through packer (5) and rises to the surface along the tubing, taking with it the proppant and other inclusions from the upper region of the inter-packer space (Fig. 7). After the technological period of washing, the supply of washing liquid is stopped.

The second washing cycle begins with the transfer of the device to the transport position. To do this, the mechanical anchor (1) is deactivated by longitudinal movement of the device. The hollow rod (15) moves down until the stop of the limiting projections (17) against the wall of the cavity (19) and opens the flushing holes (14).

Next, the flushing fluid is again fed under pressure into the tubing (Fig. 8). The flushing fluid enters the internal cavities of the upper pass-through packer (5), the hydraulic fracturing port (4), exits through the windows (10) into the inter-packer space, activating the upper (5) and lower pass-through packer (3) thoroughly washing out the proppant and other inclusions from the lower area interpacker space. Further, the mixture enters the flush holes (14) and into the internal cavity of the rod (15) and is discharged outside the device into the well through a single flush channel (20).

The method is carried out as follows.

Assembled at the wellhead, the device is installed on the tubing and lowered into the well, the production string of which is pre-pressurized to 15 MPa. The total length along the shaft is 3250 m, including the side shaft - 450 m. The descent is carried out at a speed of not more than 0.25 m/s when moving in a production string with a diameter of 168 mm, a length of 2800 m and at a speed of 0.1 m/s when moving along a sidetrack with a diameter of 114 mm (strength group "E").

The device is preliminarily placed in a blind section of the sidetrack and the through-cup packers (5) and (3) are pressure tested with a pressure of 12 MPa.

The sequence of processing intervals of the productive formation is set in such a way as to initially carry out the processing of the lowest interval at the level of 3200 - 3215m.

The device is installed in the well in such a way that the interval to be treated is located between the cup packers (5) and (3) and fixed device in the well with anchor elements 21 when the mechanical anchor (1) is activated (Figure 4).

Further, the hydraulic fracturing fluid is pumped through the internal cavity of the tubing and the packers (5) and (3) with cup seals (8) and (9) are activated, providing a tight fit to the inner wall of the casing and reliably isolating the annular gap between the wall of the casing string and the device in interpacker space. Then hydraulic fracturing is carried out at a burst pressure of 46 MPa. (Fig.6).

After hydraulic fracturing, the hydraulic fracturing fluid supply is stopped, while mechanical debris accumulates in the annulus and cup seals, including proppant particles, which can lead to jamming of the device when moving to the next formation interval to be treated.

To prevent an emergency after hydraulic fracturing, the annulus annulus is flushed to remove the resulting debris (mechanical particles, proppant).

The first cycle of flushing the inter-packer annulus begins with a pressure feed of 100 atm. flushing liquid by a pumping unit located on the surface. Providing a flushing fluid flow rate of 6 l/s, the cup seals 8 of the lower pass-through packer (3) are activated and debris is washed out from the upper area of the annular gap through the windows (1)0 of the hydraulic fracturing port (4), moving it along the tubing to the surface for disposal (Fig. 7).

After removal of debris from the upper region of the interpacker annulus, the supply of flushing fluid is stopped.

In the second washing cycle, the mechanical anchor (1) is deactivated by the longitudinal movement of the device and the device is transferred to the transport position. Next, axial displacement of the tubing is carried out, while the hollow rod (15) of the device is displaced until the stop of the limiting protrusions (17) into the wall of the cavity (19), opening the flushing holes (14). Then, flushing fluid is supplied under pressure of 12 MPa at a flow rate of 1.5 l/s, activating the lower (3) and upper (5) packers.

Moving through the open flushing holes (14) along a single flushing channel (20), the flushing fluid cleans the lower area of the inter-packer annulus, flushes out small debris from the cup seals (8) of the lower packer (3) and all internal cavities of the device below the hydraulic fracturing port, while all debris is brought down outside the device into the well.

The flushing period of the second cycle is determined by the presence or absence of resistance to movement of the device in the well.

After flushing is completed, the device is moved upwards to treat the second interval of the productive formation (level 3035-3050m), maintaining the sequence of actions for hydraulic fracturing and flushing the annulus between the packers and device elements.

After finishing the processing of the third interval (2870-2885 m.) and flushing, the device is removed from the well.

Thus, the claimed inventions make it possible to provide high-quality, technological cleaning of the inter-packer annular space, accident-free movement of the downhole tool for processing several intervals of the productive formation in one trip, using a simple and reliable device.

Claims

Claim

1. The method of selective treatment of the productive formation, including the sequential hydraulic fracturing and flushing of the annular gap in the inter-packer space of each interval of the productive formation by the device according to claim 5; at the same time, the device is lowered onto the tubing to the level of the lowest interval of the productive formation, when the interval is located in the inter-packer space, the device is fixed in the well with a mechanical anchor, then the working fluid is supplied under pressure to the tubing cavity, the hydraulic fracturing port, and the interval of the productive formation is isolated by packers with cup sealing elements , then hydraulic fracturing is carried out; after that, flushing of the annular gap in the interpacker space is carried out, the first cycle of which begins with the supply of flushing fluid to the annulus, then the lower pass-through packer is activated and debris is washed out from the upper area of the interpacker annular gap through the fracturing port windows up the tubing; the second cycle begins with the transfer of the device to the transport position, then the axial movement of the tubing leads to the displacement of the hollow rod of the device and opens the flushing holes; after that, flushing liquid is supplied under pressure to the tubing, the cup sealing elements of the packers are activated and debris is washed out from the lower region of the inter-packer annular gap and the cup seals, moving the mixture along the internal cavity of the device beyond its limits into the well, then the device is moved to the next interval and processing is carried out and washing in the same order.

2. A method for selective treatment of a productive formation according to claim 1, characterized in that the flushing liquid is supplied by a pumping unit located on the surface.

3. The method of selective treatment of the productive formation according to claim 1, characterized in that the transfer of the device to the transport position is carried out by deactivating the mechanical anchor.

4. The method of selective treatment of the productive formation according to claim 1, characterized in that the debris from the upper region of the inter-packer annular gap is disposed of on the surface.

5. A device for implementing the method according to claim 1, containing a mechanical anchor installed in series on the tubing, at least a lower pass-through packer, hydraulic fracturing port, the upper pass-through packer, while the pass-through packers are equipped with cup seals, which are directed to the hydraulic fracturing port, a hollow rod is located in the internal cavity of the device, characterized in that the body of the hydraulic fracturing port is divided by a partition into the upper part, in which windows are made, and the lower part , in which flushing holes are located, providing hydraulic connection between the annular gap between the packers and the cavity made in the lower part of the baffle; the lower pass packer is provided on the inner surface with a longitudinal cavity, and the hollow rod is provided with protrusions that interact with the cavity, moving along it; the distance between the bottom drift packer and the flush holes does not exceed two casing diameters.

6. The device according to claim. 1, characterized in that the device can be additionally equipped with a sleeve locator located under the lower pass-through packer and centralizer.

7. The device according to claim 1, characterized in that the hollow rod is rigidly connected to the mechanical anchor.

8. The device according to claim. 1, characterized in that the tightness of the flushing holes is ensured by seals placed above and below the flushing holes.

9. The device according to claim. 1, characterized in that the internal cavities of the hollow rod, the lower pass-through packer and the mechanical sleeve locator form a single flushing channel.