US20230332485A1

US20230332485A1 - Device and method of productive formation selective processing

Info

Publication number: US20230332485A1
Application number: US17/639,080
Authority: US
Inventors: Salavat Anatolyevich Kuzyaev
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-08-21
Filing date: 2021-08-23
Publication date: 2023-10-19
Also published as: RU2747495C1; WO2022039627A1

Abstract

There are proposed a method for selective processing of a productive formation and a device for implementation thereof coupled with a tubing. The device is lowered to the formation’s lowest interval and fixed therein. Working fluid is supplied into the device’s hydraulic fracturing port, the interval is isolated with sealing elements, and hydraulic fracturing is executed. An annular gap is flushed with flush fluid, the lower packer is activated and debris is washed out of the gap through a hydraulic fracturing port. The device is turned to the transport position. The tubing is moved shifting the device’s hollow rod and flushing holes are opened. Flush fluid is then fed into the tubing, the sealing elements are activated and debris is washed out of the gap’s lower area pushing the mixture along the device’s inner cavity into the well. Then the device is moved to the next interval for further processing.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national stage application of an international application PCT/RU2021/00362 filed on 23 Aug. 2021, published as WO/2022/039627, which international application claims priority of a Russian Federation patent application RU2020128064 filed on 21 Aug. 2020.

FIELD OF THE INVENTION

The invention relates to mining and is used to repair and operate oil wells. It is designed for productive formation selective processing within one tripping with real-time annular space flushing during well work.

BACKGROUND OF THE INVENTION

One of the main problems affecting the efficiency of repair and operation of oil wells is the one occurring during their processing - downhole equipment sticking. It is often the result of the tool jamming when moving up the well, because the annular space between the downhole equipment and the production string is sprinkled with various solids, in particular, compressed proppant. It is difficult, time-consuming and expensive to eliminate accidents caused by sticking.
To solve this problem, well-known preventive technologies are used, which capture and remove solids from the well, including the adjacent areas.
One of the ways to prevent an accident in the well due to the downhole equipment sticking is to ensure high-quality flushing of the cavities between the equipment and the production string, especially in the area of the productive formation, as well as the internal cavities of the equipment used for process fluids.
To remove solids (granular debris or formation sand) from the annulus, tools containing various filtration devices, trapping elements and storage tanks are used.
A method of oil-well jet pump operation is to be mentioned, which involves productive formation area clean-up performed after hydraulic fracturing using oil-well jet pump (patent of the Russian Federation No. 2273772, published 10.04.2006, bulletin 10). According to this method, downhole equipment being part of a jet pump with a stepped through channel in its casing, as well as a packer with a through channel and a shank with an inlet funnel positioned below the jet pump are descended into the well on the tubing string (hereinafter referred to as tubing). Then the packer positioned above the productive formation is unpacked. Next, a blocking insert with a central through channel is installed in the stepped through channel of the jet pump, and frac fluid or a mixture of frac fluid with chemical reagents is injected into the productive formation. After that, the blocking insert is removed and lifted to the surface, and a flexible tube is lowered through the tubing into the well through the seal assembly, so that the tube could be moved. The seal assembly is installed while lowering the flexible tube in the stepped through channel of the jet pump. The lower end of the flexible tube is installed below or at the level of the lower perforation interval of the productive formation.
Next, a working liquid medium is fed into the nozzle of the jet pump through the annular space of the well. The productive formation is drained by creating a depression on the productive formation. At the same time or after a stable depression is created, liquid for washing the well bottom is fed through the flexible tube. The ratio between the fluid pressure in the flexible tube and the fluid pressure in the annular space of the well is maintained at (Pr:Pp)≤0.98.
After pumping fluid of a volume equal to at least two volumes of frac fluid or a mixture of frac fluid with chemical reagents out of the productive formation, the fluid stops to be fed into the flexible tube for flushing the bottom of the well.
No sooner than after 5 minutes, the supply of the working liquid medium to the nozzle of the jet pump is stopped and the flexible tube with the seal 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, the well is placed into operation.
The well jet device used to implement the described method comprises a packer and a through channel on a tubing string, as well as a jet pump, in the body of which an active nozzle and a mixing chamber with a diffuser are arranged. In addition, the jet pump is equipped with a stepped through channel. Below the jet pump, there is a shank with an inlet funnel. A seal assembly or, alternatively, a blocking insert is installed in the stepped through channel. A flexible tube is put through the seal assembly. The lower end of the flexible tube is installed below or at the level of the lower perforation interval of the productive formation. The well jet device is placed in the well in such a way that the jet pump and packer are located above the productive formation.
The disadvantage of this method and the well jet device itself is the high probability of emergency extraction from the well in the event of jamming due to the sprinkling of mechanical debris in the annular space between the tool and casing. Cleaning and extracting solids, in particular, flushing the annular space from the proppant, is not performed according to the method described in the patent. Due to the packer being sprinkled on top, which cannot be avoided, the design of the jet device does not allow fluid to flow in a reverse direction to wash debris out from the well, for example, through the annulus space.
Another disadvantage of this system is that it is impossible to use when processing several intervals of the productive formation within one tripping, since after washing the bottom of the well, the device is immediately lifted to the surface.
The patent US 10280713 (published 2019-05-07) describes systems and methods for managing debris, including proppant, in the well, providing flushing of the annular gap between casing and the downhole tool.
These technical solutions are aimed at the passive removal of large and small debris and precipitated fluid chemicals from a rig’s circulation system and blow out preventers at the wellhead, as well as at preventing sand from reaching the annular space between casing and the downhole tool. The description to the patent contains information about the variants of separate assemblies of the annular space cleaning system in the wellbore, which contains a reversing tool installed on the tubing and debris traps with a built-in filter. The system can also be equipped with a washpipe where debris traps may be located being an indicator of cleaning efficiency.
The trap consists of two separate assemblies - the upper and lower ones positioned in the workstring at some distance from each other. The upper assembly comprises a screen resembling a sieve, a bull plug and a 3-way adapter. The lower assembly comprises a screen, a 3-way adapter and a ball check valve. The upper and lower assemblies are fixed in the workstring using known means of connection. The trap works together with the sand control tool in the well.
The process fluid with the proppant enters the tubing for hydraulic fracturing, while the proppant begins to accumulate in the annular space between the tool and casing. The fluid passes through the screen built into the tubing and enters the washpipe. Then the fluid passes through the lower assembly of the trap and the ball valve, and enters the washpipe area between the assemblies and then the upper assembly of the trap. Moving forward, the fluid is additionally filtered in the trap assemblies. This prevents the further spread of the proppant. The proppant is separated from the fluid by the filter of the lower assembly and is blocked by the ball check valve. When removing equipment from the well, the degree of contamination is determined by the amount of proppant in the washpipe between the trap assemblies. If not removing equipment from the well, it is the loss or reduction of fluid on its return to the surface which may indicate the degree of contamination.
The reversing tool is designed to carry fluid and debris out of the well, especially when there are large annular cross-sectional areas. The tool permits reverse circulation of the riser at reduced pump rates without compromising debris carrying capacity. The reversing tool consists of a cylindrical component with cup sealing elements that hermetically separate the casing and create two separate annular gaps: one above and one under the sealing elements. In addition, the cylindrical element is equipped with an internal partition forming two channels in the internal cavity of the tubing. One channel is descending, the other is ascending. Through the descending channel, the flow of fluid or other material is removed from the tubing into the annular space under the sealing element. Through the ascending channel, the flow of fluid or other material rises along the tubing below the sealing element and is removed into the annular space above the sealing element. The flow rate decreases, since the cross-sectional area of the tubing is smaller than the annular space. The annular space above the sealing element can be used for collecting debris that cannot be carried by the flow at a reduced speed, while debris collectors should not prevent the flow from flowing at a technological speed.
The reversing tool is part of the fluid circulation system. The fluid flows from the tank through the suction line to the pump, which belongs to the surface system. The pump moves the flush fluid through the pipeline to the upper tubing string above the cup sealing element.
The flush fluid flows down the upper part of the tubing to the reversing tool, where it is diverted to the annular space under the cup sealing element. The mixture of the flush fluid and debris continues to flow down the annular space to the bottom of the well and returns to the tubing again. Next, moving up the tubing, the filtered mixture reaches the reversing tool and again diverts and enters the annular space above the cup seal. Then, flowing up the upper part of the tubing, the flush fluid enters the tank. Thus, a full cycle of the flush fluid circulation is performed. The reversing tool can continuously operate for more than two years, performing more than 4000 cycles during its lifetime.
There is an alert system comprising pressure gauges, which monitor the pressure differential and indicate a risk of blockage to alert a well operator that the traps have filled or contain significant amount of debris.
The disadvantage of this system is the limited scope of use, mainly in offshore wells, and does not involve simultaneous technological operations for processing productive formations. In addition, the operation of the system is based on multiple filtration stages, and contains complex equipment for washing these devices that should be replaced periodically.
The closest to the claimed technical solution is the invention presented in the patent US 10494900 (published 2019-12-03), which presents options for a well stimulation system performing hydraulic fracturing with a flushing device 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 arrangement of the main components of the system are similar for all the versions presented in the patent and include an anchor installed on the tubing (from bottom to top), lower packer, hydraulic fracturing unit, upper packer, mechanically operated valve, sand control assembly and pressure activated injection assembly. Below the anchor there is a valve that is closed during hydraulic fracturing and a hole for removing excess fluid.
The anchor fixes the device to the wellbore and can be installed by axial movement up and down. The upper and lower packers are designed to isolate the area of the productive formation. The mechanically operated valve is part of the sand control assembly and participates in creating a pressure difference in the annulus below the sand control assembly to ensure the annular gap flushing. The sand control assembly is positioned above the hydraulic fracturing unit and is designed to remove the extracted sand and gravel from the annulus when moving to another processing zone or to the surface. A flushing device is used together with the sand control assembly during the annular gap flushing. It provides hydraulic communication with the annular space in the annular gap zone through radial ports.
In addition, to ensure a significant pressure difference determined by the condition in the wellbore, for example, when the pressure of the flushing fluid exceeds 2-5 times the pressure of the hydraulic fracturing process fluid, the sand control assembly is additionally equipped with a check valve and one or more additional packers.
The patent presents three versions of the flushing device, one of which can be activated several times, which ensures flushing of the annular gap when processing several productive formations within one tripping.
The flushing device is located above the hydraulic fracturing unit, is connected to the valve and opens when the flushing fluid is fed at an appropriate pressure, which is significantly higher than the hydraulic fracturing pressure. That is why the device is closed during hydraulic fracturing.
The flushing device comprises a sliding sleeve installed in the housing, a piston and a return spring. A spring force from a return spring opposes the net pressure force exerted on the net piston area. Radial ports are made in the housing, blocked by the piston when the flushing device is closed. Radial ports have nozzles to ensure the jet flows at a given angle into the wellbore to flush the annular space in different directions.
The advantage of this version of the flushing device is that it returns the sliding sleeve and covers radial ports when the pressure on the piston is released after the annular gap is flushed.
The system is also equipped with a release mechanism that activates and deactivates the packers sealing the productive formation area and the hydraulic fracturing unit.
The release mechanism is made in the form of a housing, which is part of the system, with an axially movable inner sleeve inside. The inner sleeve is provided with a radial port. Between the housing and the inner sleeve, there is a removable sleeve with axially extending conduits hydraulically connected to the annular space.
When the system is idling, the inner sleeve is in the working position, while the packers sealing the productive formation area and the hydraulic fracturing unit are not active. The radial port of the inner sleeve is closed by a removable sleeve. The position of the inner sleeve ensures the passage of fluid through the piston inside and closes the hydraulic connection with the annulus through the radial ports in the housing. The removable sleeve is fixed within the housing by a retainer.
When pressure is applied to the piston inside, the inner sleeve, overcoming the force of the return spring, performs an axial movement until the hydraulic connection is restored through radial ports in the inner sleeve and in the housing, which communicate with the space between the housing and the sleeve. The pressure in the piston inside partially drops, the spring forces the inner sleeve to return to the idle position. Under the pressure, the retainer moves into the seat where it is installed, freeing the removable sleeve. This sleeve covers the radial port in the housing, maintaining the hydraulic connection of the piston cavity with the area between the housing and the inner sleeve. The increasing flushing pressure does not exceed the one with which the return spring influences the inner sleeve. In this condition of the release mechanism, the hydraulic fracturing unit is closed, the packers sealing the productive formation area are not activated.
The system is designed to be used in emergencies when it is impossible to remove the drilling tool from the well, as the upper packer is sprinkled with debris and it is impossible to flush the annular gap in the annular inter-packer space. This makes it impossible to control the flushing circulation unit and extract the tool from the well. Additional units are required to flush the space above the second-from-the-bottom packer.
Another disadvantage of the system is its complicated structure caused by additional elements for various purposes (packers, valves), the use of spring mechanisms for controlling the flushing device, which are prone to instability, changes in elastic properties and subsequent deformation.
One more disadvantage of the device is the use of high pressures that exceed the hydraulic fracturing pressure by 2-5 times when flushing.
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 significantly higher than 1000 atmospheres - the pressure for which standard hydraulic fracturing equipment is designed. Using pressures which are several times higher than the one of hydraulic fracturing during annular space flushing requires non-standard wellhead equipment, a non-standard tubing hanger, non-standard pumping equipment for hydraulic fracturing, which significantly reduces the manufacturability of the system and limits its scope of use.

OBJECTS AND BRIEF SUMMARY OF THE INVENTION

The objective of the invention is to increase the efficiency of a productive formation processing within one tripping, reduce the accident rate and increase the lifetime of the proposed device (herein further referred to as the ‘inventive device’). Typically, a borehole usable in the mining industry is associated with the productive formation, and a well casing is mounted within the borehole. A tubing (also known as ‘tubing string’) is typically inserted into the well casing. An annulus space is herein defined as a space between an outer surface of the inventive device / tubing and, on the other hand, an inner surface of the well casing. The inventive device, essentially coupled with the tubing, comprises: a mechanical anchor, a collar locator, a lower feedthrough packer, a hydraulic fracturing port, an upper feedthrough packer and a centralizer sequentially installed from bottom to top on the tubing. An inter-packer annular gap is herein defined as a portion of the annulus space located between the outer surface of said inventive device and the inner sidewall surface of said well casing, vertically limited by positions of the upper feedthrough packer and the lower feedthrough packer.
The technical result is to ensure simultaneous flushing of the inter-packer annular gap between the well casing and the inventive device, as well as internal cavities of the inventive device after each processed interval of the productive formation and to increase the reliability and manufacturability of the inventive device by simplifying its design.
The technical result is achieved due to the fact that the method of selective processing of the productive formation includes sequential hydraulic fracturing and flushing of the inter-packer annular gap of each interval of the productive formation, using the inventive device which is lowered into the well casing to the level of the lowest interval of the productive formation.
When the inventive device reaches the level at which the interval of the productive formation to be processed is located in the inter-packer annular gap, the inventive device is fixed to the well casing with the mechanical anchor. Next, the working fluid is fed under pressure to the tubing, then to the hydraulic fracturing port, and the interval of the productive formation is isolated with the packers which include cup sealing elements. Then hydraulic fracturing is carried out.
After hydraulic fracturing is finished, the inter-packer annular gap is flushed. During the first cycle, flush fluid is fed to the annular space, then the lower feedthrough packer is activated and debris is washed out of the upper area of the inter-packer annular gap through windows of the hydraulic fracturing port and up the tubing.
During the second cycle, the inventive device is turned to the transport position. Then the tubing is axially moved to shift a hollow rod of the inventive device and flushing holes of the hydraulic fracturing port are opened. After that, the flush fluid is fed under pressure into the tubing, the cup sealing elements of the upper and lower feedthrough packers are activated and the debris is washed out of the lower area of the inter-packer annular gap and the cup seals, pushing the mixture along an inner cavity of the inventive device into the well casing.
Then the inventive device is moved to the next interval, where processing and cleanup are carried out likewise.
The flush fluid is supplied by a pumping unit positioned on the surface.
To turn the inventive device to the transport position, the mechanical anchor is deactivated by longitudinal movement of the inventive device.
Debris from the upper area of the inter-packer annular gap is disposed of on the surface in any known way.
The technical result is also achieved due to the fact that the inventive device comprises a mechanical anchor, a lower feedthrough packer, a hydraulic fracturing port, and an upper feedthrough packer sequentially installed on the tubing. The feedthrough packers with cup sealing elements are directed towards the hydraulic fracturing port. A hollow rod is located in the inner cavity of the inventive device.
A casing of the hydraulic fracturing port is divided by a partition into an upper part with the aforementioned windows and a lower part with the aforementioned flushing holes, providing hydraulic connection of the annular inter-packer gap with the inner cavity in the lower part of the partition. The lower feedthrough packer has a longitudinal cavity on the inner surface thereof, and the hollow rod features protrusions that interact with the longitudinal cavity while moving alongside. The distance between the lower feedthrough packer and the flushing holes does not exceed two diameters of the well casing.
The sealing capacity of the flushing holes is ensured by seals placed above and below the flushing holes. The inner cavities of the hollow rod, the lower feedthrough packer and the mechanical collar locator form a single flushing channel. The hollow rod is rigidly bound to the mechanical anchor.
The device can be additionally equipped with a collar locator positioned under the lower feedthrough packer as well as with a centralizer.
Annulus flushing carried out in two cycles, during which debris is removed from the upper or lower area of the annulus space, ensures high-quality cleanup.
Transporting debris from the inter-packer annular gap and disposing of it at the surface during the first cycle, as well as removing debris out of the inventive device into a waste area of the well casing during the second cycle completely eliminates any solids.
The sequence of hydraulic fracturing, the first and second cycles of the inter-packer annular gap flushing ensures a smooth movement of the device along the casing.
The simple and reliable design of the device ensures the flow of the flush fluid through two unconnected debris removal channels, which are managed by a simple longitudinal movement (activation/deactivation) of the mechanical anchor and due to the interaction of two elements - the hollow rod and the body of the lower feedthrough packer.

DRAWINGS OF THE INVENTION

FIG. 1 - general view of the device;

FIG. 2 - enlarged view of the hydraulic fracturing port;

FIG. 3 - longitudinal section of the device in the transport position;

FIG. 4 - longitudinal section of the device with an activated mechanical anchor;

FIG. 5 - enlarged view of the hydraulic fracturing port in the position of the device shown in FIG. 3 ;

FIG. 6 - longitudinal section of the device during hydraulic fracturing;

FIG. 7 - working fluid flow diagram with an activated anchor; and

FIG. 8 - working fluid flow diagram with a deactivated mechanical anchor.

DETAIL DESCRIPTION OF PREFERRED EMBODIMENT THE INVENTION

The present invention is designed for selective processing of a productive formation in the oil mining industry. Generally, a borehole associated with the productive formation is provided and a well casing 23 is mounted within the borehole. A tubing 22 is typically inserted into the well casing 23. The inventive device essentially coupled with the tubing 22 comprises: a mechanical anchor 1, a collar locator 2, a lower feedthrough packer 3, a hydraulic fracturing port 4, an upper feedthrough packer 5 and a centralizer 6 sequentially installed from bottom to top on the tubing 22 (FIG. 1 , FIG. 2 ). The mechanical anchor 1 and the collar locator 2 each defines an inner cavity located therein. An annulus space is herein defined as a space between an outer surface of the inventive device / tubing 22 and, on the other hand, an inner surface of the well casing 23.
Pipes 7 are connected to the centralizer 6, the installation of which is determined by the need and conditions for processing intervals of the productive formation of variable length.
The lower feedthrough packer 3 includes cup sealing elements 8 directed towards the hydraulic fracturing port 4. The upper feedthrough packer 5 includes cup sealing elements 9 also directed towards the hydraulic fracturing port 4.
The following well-known devices can be used as functional parts:

mechanical collar locator, which can be similar to the collar locator A 1025-2, e.g. presented in the catalog “Tools for current and major repairs of wells”, p. 31 <https://www.slb.ru/upload/iblock/d8e/katalog-instrumentov-dla-tekushego-i-kapitalnogo-remonta-skvaiin.pdf>);
centralizer e.g. presented in <http://www.coilsolutions.com/products/downhole-tools/drill-and-milling-tools/fluted-centralizers/> or <http://petrolibrary.ru/preduprezhdenie-iskrivleniya-vertikalnyix-skvazhi-skvazhin.html>;
mechanically operated axial anchor (YAMO-3, YAMO-2), e.g. presented in <https://npf-paker.ru/catalog/type/yakorya/mekhanicheskie/yamo3-yamo2-yam3-yam2>.

A casing of the hydraulic fracturing port 4 includes windows 10 (FIG. 2 ). The hydraulic fracturing port 4 contains a partition 11 located inside the casing of the hydraulic fracturing port with a recess 12 in its lower part, and a divider 13 in the upper part (FIG. 3 ). In addition, radial flushing holes 14 are made in the lower part of the hydraulic fracturing port 4, connecting the recess 12 with the annulus space.
The lower feedthrough packer 3 defines an inner cavity 19 within thereof (FIG. 7 ). A hollow rod 15 is at least partially located in the inner cavity 19 of the lower feedthrough packer 3, with the possibility of axial movement, rigidly connected to the mechanical anchor 1 with a cone 16. The hollow rod 15 defines its own inner cavity within thereof.
Sealing capacity of the radial flushing holes 14 is ensured by seals 18 installed on an inner surface of the partition 11 above the holes 14 and on an inner surface of the lower feedthrough packer 3 below the holes 14.
On a side of an outer surface of the hollow rod 15, it is equipped with limiting protrusions 17 that perform axial movement along the cavity 19 on the inner surface of the lower packer 3, the longitudinal size of which determines a size S of a stroke of the hollow rod 15 (FIG. 3 and FIG. 4 ).
The inner cavity of the rod 15, the inner cavity of the lower feedthrough packer 3, the inner cavity of the collar locator 2 and the inner cavity of the mechanical anchor respectively communicate with each other and form a single flushing channel 20 (FIG. 3 ).
When the device is set in a transport position, the hollow rod 15 is in a lower position, where the protrusions 17 rest against a lower horizontal wall of the cavity 18. The radial flushing holes 14 provide communication of the recess 12 with the annular inter-packer space (FIG. 2 and FIG. 3 ).
The cup seals 8 of the lower feedthrough packer 3 are located at a distance H1 (FIG. 3 ) from the flushing holes 14 of the hydraulic fracturing port 4; the distance H1 depends on a diameter of the well casing 23 and does not exceed two diameters of the well casing 23.
The device for implementing the described method works as follows:
Before lowering into the well casing 23, the device is assembled at the wellhead and installed on the tubing 22.
When descending, the mechanical anchor 1, the lower 3 and upper 5 feedthrough packers are in the transport position, the hollow rod 15 is in the lower position and is fixed by the limiting protrusions 17 to prevent its axial downward movement.
Before processing the productive formation, the device is placed in a blank section of the well casing 23 and the feedthrough packers are pressed.
Next, the device is installed in such a way that the interval to be processed is located in the inter-packer space and the mechanical anchor 1 is activated, ensuring that the device is fixed to the well with anchor elements 21 (FIG. 4 ). Then part of the tubing 22 weight is unloaded onto the mechanical anchor 1, while the hollow rod 15 enters the recess 12, hermetically closing the flushing holes 14 with the help of seals 18 (FIG. 5 ).
Next, hydraulic fracturing fluid is supplied to the tubing 22 under pressure and, due to the counterflow from the hydraulic fracturing port 4, the cup sealing elements 8 and 9 of the feedthrough packers 3 and 5 open and hermetically align to the inner wall of the well casing 23, reliably isolating the inter-packer space. Then, hydraulic fracturing is performed (FIG. 6 ).
Upon hydraulic fracturing, the tubing 22, the inventive device and the annulus space between the device and the well casing 23 are flushed to remove proppant and other debris, ensuring a smooth and safe movement of the device to the next interval of the productive formation or during its removal from the well casing 23.
Flushing of the annular space of the well casing 23 and the cavities of the device is carried out in two cycles as follows.
During the first cycle, the pumping unit located on the surface feeds the flush fluid under pressure into the annular space, while the cup sealing elements 8 of the lower feedthrough packer 3 are in the active position. The flush fluid enters the inner cavity of the hydraulic fracturing port 4 through the windows 10 and then flows through the upper feedthrough packer 5 and up the tubing 22 to the surface, carrying the proppant and other solids from the upper area of the inter-packer space (FIG. 7 ). When the flushing technological period ends, the supply of the flush fluid is stopped.
At the beginning of the second flushing cycle, the device is turned 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 limiting protrusions 17 rest against the wall of the cavity 19 and opens the flushing holes 14.
Then, the flush fluid is again fed under pressure into the tubing 22 (FIG. 8 ). The flush fluid enters the internal cavities of the upper feedthrough packer 5 and the hydraulic fracturing port 4. Then, it exits through the windows 10 into the inter-packer space, activating the upper 5 and lower feedthrough packers 3, thoroughly washing the proppant and other solids out of the lower area of the inter-packer space. Next, the mixture enters the flushing holes 14 and the inner cavity of the rod 15. It then flows through a single flushing channel 20 outside the device into the well casing 23.
The method is implemented as follows.
The inventive device assembled at the wellhead is lowered into the well casing 23, which is oppressed by a pressure of 15 MPa. The total length of the wellbore is 3250 m, including the sidetrack of 450 m. The device is lowered at a velocity of no more than 0.25 m/s when moving along the well casing 23 with a diameter of 168 mm, a length of 2800 m, and at a velocity of 0.1 m/s when moving along a sidetrack with a diameter of 114 mm (strength group N80 API 5CT).
First, the device is placed in a blank area of the sidetrack and the feedthrough cup packers 5 and 3 are put under 12 MPa pressure.
The sequence of productive formation interval processing is set in such a way that the lowest interval at the level of 3200 - 3215 m is processed first.
The inventive device is installed in the well casing 23 in such a way that the interval to be processed is located between the cup packers 5 and 3. The inventive device is then fixed to the well casing 23 with anchor elements 21 when the mechanical anchor 1 is activated (FIG. 4 ).
Next, the hydraulic fracturing fluid is pumped through the tubing 22 and packers 5 and 3 with cup seals 8 and 9 are activated, ensuring a tight fit to the inner wall of the well casing 23 and reliably isolating the annular gap between the well casing 23 and the inventive device in the inter-packer space. Then hydraulic fracturing is carried out at 46 MPa. (FIG. 6 ).
At the end of hydraulic fracturing, the hydraulic fracturing fluid supply is stopped. Meanwhile, debris, including proppant, accumulates in the inter-packer annular gap and in the cup seals, which can lead to the inventive device jamming when moving to the next formation interval to be processed.
To prevent an emergency, the inter-packer annular gap is flushed to remove debris (mechanical particles, proppant) after hydraulic fracturing.
The first cycle begins with supplying the flush fluid at 100 atmospheres by a pumping unit located on a ground surface surrounding a top entrance (top mouth) of the well casing 23. Ensuring the flow rate of the flush fluid of 6 1/s, the cup seals 8 of the lower feedthrough packer 3 are activated. The debris is washed out of the upper area of the inter-packer annular gap through the windows 10 of the hydraulic fracturing port 4, being pushed along the tubing to the surface for disposal (FIG. 7 ).
After removing debris from the upper area of the inter-packer annulus, the flush fluid supply is stopped.
During the second washing cycle, the mechanical anchor 1 is deactivated by longitudinal movement of the device, and the device is turned to the transport position. Next, the tubing 22 is axially moved to shift the hollow rod 15 of the device until the limiting protrusions 17 rest against the wall of the cavity 19 opening the flushing holes 14. Then, the flush fluid is supplied at a pressure of 12 MPa and at a flow rate of 1.5 1/s, activating the lower 3 and upper 5 packers.
Moving through the opened flushing holes 14 through a single flushing channel 20, the flush fluid cleans the lower area of the inter-packer annulus. It washes out small debris from the cup seals 8 of the lower packer 3 and all the internal cavities of the device below the hydraulic fracturing port, while all the debris is pushed down outside the device into the well casing 23. The cleanup period of the second cycle is determined by the presence or absence of resistance to the movement of the device in the well casing 23.
After it is flushed, the device is lifted to process the second interval of the productive formation at the level of 3035 - 3050 m observing the sequence of actions for hydraulic fracturing and flushing of the annular inter-packer space and the elements of the device.
After the third interval (2870 - 2885 m) is processed and flushed, the inventive device is removed from the well casing 23.
Thus, the claimed invention makes it possible to provide high-quality, technological cleanup of the inter-packer annulus space, trouble-free movement of the downhole tool for processing several intervals of the productive formation within one tripping, using a simple and reliable device.

Claims

1. A device for selective processing of a productive formation essentially coupled with a tubing insertable into a well casing associated with the productive formation; said well casing defines an inner sidewall surface thereof and has a diameter; said tubing defines an outer surface thereof; said device defines an outer surface thereof; wherein an annulus space is defined to include:

a space between the outer surface of said device and the inner surface of said well casing, and

a space between the outer surface of said tubing and the inner surface of said well casing;

wherein said device comprises sequentially mounted on the tubing from bottom to top:

a mechanical anchor;

a collar locator;

a lower feedthrough packer equipped with a number of cup seals; said lower feedthrough packer defines a lower packer inner cavity provided therein; said lower feedthrough packer has a hollow rod capable of axial movement at least within the inner cavity of said lower feedthrough packer; said hollow rod is partially passed through the collar locator, and partially passed through and rigidly connected to the mechanical anchor;

a hydraulic fracturing port divided by a partition into an upper part including an upper cavity provided with windows and a lower part provided with a recess and flushing holes communicated with the recess; said number of cup seals of the lower feedthrough packer are directed towards the hydraulic fracturing port;

an upper feedthrough packer equipped with a number of cup seals directed towards the hydraulic fracturing port; and

a centralizer;

wherein: an inter-packer annular gap is defined as a portion of the annulus space located between the outer surface of said device and the inner sidewall surface of said well casing, vertically limited by positions of the upper feedthrough packer and the lower feedthrough packer; said flushing holes provide for hydraulic connection of the inter-packer annular gap with said recess in the partition lower part; and

wherein: a distance between the lower feedthrough packer and the flushing holes does not exceed said diameter of the well casing multiplied by two.

2. The device according to claim 1 wherein seals placed above and below the flushing holes.

3. The device according to claim 1, wherein said hollow rod defines a rod inner cavity within thereof; said collar locator defines a collar inner cavity within thereof, and wherein the rod inner cavity, the lower packer inner cavity and the collar inner cavity form a single flushing channel.

4. A method for selective processing of the productive formation using the device according to claim 1; wherein the productive formation includes a number of intervals; said method comprising the steps of:

lowering the tubing with the device to a lowest interval chosen from said number of intervals;

setting up the lowest interval within the inter-packer annular gap;

fixing the device to the well casing by the mechanical anchor;

supplying working fluid under pressure into the tubing and into the hydraulic fracturing port;

isolating the lowest interval by said number of cup seals of the lower feedthrough packer and said number of cup seals of the upper feedthrough packer;

providing hydraulic fracturing of the lowest interval by the working fluid;

feeding the flush fluid into the inter-packer annular gap;

activating the lower feedthrough packer and washing debris out of an upper portion of the inter-packer annular gap through said windows of the hydraulic fracturing port and up the tubing;

turning the device into a transport position;

axially moving up the tubing thereby shifting the hollow rod and opening the flushing holes;

feeding the flush fluid under pressure into the tubing;

activating said number of cup seals of the lower feedthrough packer and said number of cup seals of the upper feedthrough packer and washing debris out of a lower portion of the inter-packer annular gap and pushing a mixture of the flush fluid and the debris mixture along said inner cavity of the device into the well casing;

moving up the device to a next interval chosen from said number of intervals, and repeating the steps above.

5. The method according to claim 4 wherein said well casing defines a top entrance thereof and a ground surface surrounding the top entrance, and wherein the flush fluid is supplied by a pumping unit positioned on the ground surface.

6. The method according to claim 4 wherein the step of turning the device into the transport position is provided by deactivation of the mechanical anchor.

7. The method according to claim 4 wherein said well casing defines a top entrance thereof and a ground surface surrounding the top entrance; and wherein the debris froman upper portionof the inter-packer annular gap is pushed up along the tubing and being disposed of on the ground surface.

8-9. (canceled)