Downhole device for switching backwashing function of water injection string and switching method

Abstract

The invention provides an underground device for switching a backwashing function of a water injection string and a switching method. The underground device comprises a first liquid inlet assembly and a second liquid inlet assembly, the first liquid inlet assembly comprises a first elastic piece, a rotating sleeve and a movable inner sleeve, a fixed inner sleeve is arranged on the inner side of the movable inner sleeve, an inner liquid inlet hole is formed in the movable inner sleeve, and at least partial areas of the fixed inner sleeve and the movable inner sleeve are overlapped; the second liquid inlet assembly comprises a fixed outer sleeve, a second elastic piece and a movable outer sleeve are arranged on the outer side of the fixed outer sleeve, and an outer liquid inlet hole is formed in the fixed outer sleeve. The rotating sleeve is provided with a rail set, and when the movable inner sleeve moves in the same direction away from the fixed inner sleeve, the rail set is used for limiting the axial movement distance of the movable inner sleeve. By means of the underground device, the same water injection tubular column has the inverse well flushing function when inverse well flushing is needed, and does not have the inverse well flushing function when operations such as pressure reduction measurement and adjustment and positive pressure operation are carried out.

Description

Technical Field

[0001] The present application relates to the technical field of oilfield development, and in particular to a downhole device and a switching method for switching a backwash function of a water injection string. Background Art

[0002] Water injection is a common technical means in the process of oil field exploitation, which is implemented by lowering water injection strings into water injection wells. Nowadays, water injection is generally achieved in all sections of the water injection well through water injection strings, and then the segmented injection and water volume control of each section are achieved through layered water injection strings and deployment tools. In the process of deep water injection development of oil reservoirs, it is very difficult to allocate water volume in the layered sections of some water injection wells during high-pressure water injection. It is usually necessary to "release the pressure at the wellhead to a certain pressure value, and then lower the deployment instrument to adjust the flow of each section." However, when depressurizing, the injected water at the bottom layer will enter the water injection string from the well washing device and return to the wellhead, resulting in waste of injected water and too long depressurization time. Summary of the invention

[0003] In view of the above problems, one of the purposes of the present invention is to provide a downhole device for switching the backwash function of the water injection string, so that when the operating conditions do not require backwashing, the device does not have the backwash function, so as to avoid the injected water from entering the water injection string during the pressure reduction test and adjustment; when the operating conditions require reverse circulation well washing, the downhole device has the backwash function and can perform the backwash operation. The second purpose of the present invention is to provide a switching method to realize the switching of the two functions, so as to adapt to different operating conditions.

[0004] The first aspect of the present invention provides a downhole device for switching the backwash function of a water injection string, and the technical solution adopted is:

[0005] A downhole device for switching backwashing function of a water injection pipe string comprises: a first liquid inlet assembly and a second liquid inlet assembly radially overlapped from inside to outside; wherein:

[0006] The first liquid inlet assembly comprises a first elastic member, a rotating sleeve and a movable inner sleeve axially arranged from top to bottom, a fixed inner sleeve is arranged on the inner side of the movable inner sleeve, an inner liquid inlet hole is opened on the movable inner sleeve, wherein the fixed inner sleeve and the movable inner sleeve overlap at least partially, and the first elastic member is configured to drive the rotating sleeve and the movable inner sleeve to axially reciprocate so that the inner liquid inlet hole is inside or outside the overlapping area;

[0007] The second liquid inlet assembly comprises a fixed outer sleeve, a second elastic member and a movable outer sleeve are axially arranged on the outer side of the fixed outer sleeve from top to bottom, an outer liquid inlet hole is opened on the fixed outer sleeve, and the second elastic member is configured to drive the movable outer sleeve to axially reciprocate so that the movable outer sleeve covers or opens the outer liquid inlet hole;

[0008] Wherein, a track group is arranged on the rotating sleeve, and when the movable inner sleeve moves in the same direction away from the fixed inner sleeve, the track group is used to limit the axial movement distance of the movable inner sleeve.

[0009] As one of the preferred solutions, the track group includes a limit pin and a special-shaped track, and a plurality of the limit pins are movably embedded in the special-shaped track; wherein the special-shaped track includes:

[0010] A first track unit and a second track unit are interconnected and arranged opposite to each other, and the first track unit is located on a side away from the fixed inner sleeve; wherein,

[0011] The first track unit includes a plurality of long tracks and a first short track arranged around the circumference of the rotating sleeve, and the long tracks and the first short tracks are arranged alternately; the second track unit includes a plurality of second short tracks arranged around the circumference of the rotating sleeve, and each of the second short tracks is located between two adjacent long tracks and the first short tracks.

[0012] As one of the preferred solutions, a guide surface is respectively provided on one side where the first track unit and the second track unit are connected.

[0013] As one of the preferred schemes, the inner liquid inlet hole and the outer liquid inlet hole are at least partially overlapped and connected; and anti-overflow rings are provided in the overlapping area between the fixed inner sleeve and the movable inner sleeve, between the movable outer sleeve and the fixed outer sleeve, and between the fixed outer sleeve and the movable inner sleeve.

[0014] As one of the preferred solutions, the end surfaces of the rotating sleeve that are in contact with the first elastic member and the movable inner sleeve are both provided with bearings.

[0015] As one of the preferred solutions, a retaining ring is provided at one end of the movable sleeve away from the second elastic member.

[0016] As one of the preferred schemes, the outer diameter of the axial lower end of the fixed inner sleeve is larger than the outer diameter of the axial upper end thereof, a pressure chamber is formed between the fixed inner sleeve, the movable inner sleeve and the fixed outer sleeve, and a pressure conducting hole connected to the pressure chamber is opened on the fixed outer sleeve.

[0017] As one of the preferred solutions, the thickness of the axial lower end of the movable sleeve is greater than the thickness of the axial upper end thereof.

[0018] Compared with the prior art, this application has the following advantages:

[0019] The embodiment of the present invention provides a downhole device for switching the backwash function of a water injection column, comprising: a first liquid inlet assembly and a second liquid inlet assembly radially overlapped from inside to outside; wherein the first liquid inlet assembly comprises a first elastic member, a rotating sleeve and a movable inner sleeve axially arranged from top to bottom, a fixed inner sleeve is arranged on the inner side of the movable inner sleeve, an inner liquid inlet hole is provided on the movable inner sleeve, wherein the fixed inner sleeve overlaps with the movable inner sleeve at least partially, and the first elastic member is configured to drive the rotating sleeve and the movable inner sleeve to axially reciprocate so that the inner liquid inlet hole is inside or outside the overlapping area; the second liquid inlet assembly comprises a fixed outer sleeve, a second elastic member and a movable outer sleeve are axially arranged on the outer side of the fixed outer sleeve from top to bottom, an outer liquid inlet hole is provided on the fixed outer sleeve, and the second elastic member is configured to drive the movable outer sleeve to axially reciprocate so that the movable outer sleeve blocks or opens the outer liquid inlet hole; wherein a track group is provided on the rotating sleeve, and when the movable inner sleeve moves in the same direction away from the fixed inner sleeve, the track group is used to limit the axial movement distance of the movable inner sleeve.

[0020] By adopting the technical solution of the present application, the pressures to which the downhole device is subjected in different operating conditions are different. In normal water injection operating conditions, water in the water injection string enters the pipeline enclosed by the first liquid inlet assembly and the second liquid inlet assembly. The pressure during water injection drives the first elastic member to drive the rotating sleeve and the movable inner sleeve to move axially downward, so that the inner liquid inlet hole on the movable inner sleeve is in the overlapping area. At this time, the inner liquid inlet hole is in a closed state, and the downhole device is closed, so that the downhole device does not have a backwashing function.

[0021] When, in the operating conditions of pressure reduction, measurement and adjustment and backwashing, the casing pressure is greater than the pressure during water injection, the first elastic member is driven to drive the rotating sleeve and the movable inner sleeve to move axially upward, and the second elastic member is driven to drive the movable outer sleeve to move axially upward. Due to the action of the track group of the rotating sleeve, during the axial upward movement, the track group limits the axial movement distance of the movable inner sleeve, so that the inner liquid inlet hole on the movable inner sleeve in the operating condition of pressure reduction, measurement and adjustment is still in the overlapping area, at which time the inner liquid inlet hole is in a closed state, and the downhole device is closed, so that the downhole device does not have the backwashing function; so that the inner liquid inlet hole on the movable inner sleeve in the operating condition of the backwashing is outside the overlapping area, at which time the inner liquid inlet hole is in an open state, and the downhole device is opened, so that the downhole device has the backwashing function;

[0022] In this way, by arranging a downhole device for switching the backwash function of the water injection string at the bottom of the water injection string, the water injection string of the embodiment of the present invention simultaneously realizes "having a backwash function when a backwash operation is required, and not having a backwash function when pressure reduction, measurement and adjustment and other operations are performed". During normal water injection, the well washing device is closed; when reverse circulation well washing is required, the device has a backwash function and can perform backwash operations; when the pressure is reduced and adjusted after a period of high-pressure water injection, the device does not have a backwash function. At this time, the water injected into the formation will not enter the water injection string when the pressure is released, thereby avoiding the problems of waste of injected water and too long pressure release time.

[0023] The second aspect of the present invention further provides a switching method, which relies on the downhole device for switching the backwash function of the water injection string provided by the first aspect of the present invention, the downhole device is connected to the bottom end of the water injection string, and the method comprises:

[0024] Perform multiple water injection operations to drive the movable inner sleeve and the movable outer sleeve to perform axial reciprocating motion; each water injection operation includes a well opening water injection operation and a well closing pressure relief operation;

[0025] Based on the current number of water injection operations, determining whether the inner liquid inlet hole on the movable inner sleeve is within the overlapping area during the shut-in and pressure relief operation;

[0026] Based on the position judgment result of the inner liquid inlet hole, determining whether the downhole device has a backwashing function;

[0027] The current number of water injection operations is switched according to the operation requirements corresponding to the backwashing well function and the operation requirements corresponding to the backwashing well function.

[0028] As one of the preferred solutions, based on the current number of water injection operations, judging whether the inner liquid inlet hole on the movable inner sleeve is within the overlapping area during the shut-in and pressure relief operation includes:

[0029] Determining whether the current operation number of the water injection operation is an odd number or an even number;

[0030] Based on an odd number of water injection operations, a judgment result is obtained that the inner liquid inlet hole corresponding to the well shut-in and pressure relief operation in the current water injection operation is within the overlapping area;

[0031] Based on an even number of water injection operations, a judgment result is obtained that the inner liquid inlet hole corresponding to the well shut-in and pressure relief operation in the current water injection operation is outside the overlapping area;

[0032] The switching of the current number of water injection operations according to the operation requirements corresponding to the backwashing well function and the operation requirements corresponding to the backwashing well function not including:

[0033] According to the backwashing operation corresponding to the backwashing function, the current number of times of switching the water injection operation is an even number;

[0034] According to the pressure reduction test and adjustment operation corresponding to not having the backwash well function, the current number of times the water injection operation is switched is an odd number.

[0035] By adopting the technical solution of the present application, it is possible to switch the two functions of the water injection string, namely, backwashing function and non-backwashing function, according to the number of times the well is opened and closed at the wellhead. The same water injection string can achieve "backwashing function when backwashing is needed, and not having the backwashing function when pressure reduction measurement and adjustment, positive pressure operation, etc.", thereby avoiding the problem of "water injected into the formation flowing out of the water injection string, causing waste and long pressure release time" in the pressure release process before high-pressure well deployment in the existing backwashing well device. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solution of the present application, the drawings required for use in the description of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0037] Figure 1 It is a schematic diagram of the overall structure of a downhole device for switching the backwash function of a water injection string according to an embodiment of the present application;

[0038] Figure 2 is a schematic diagram of the expanded structure of a track group according to another embodiment of the present application;

[0039] Figure 3 This is a flow chart of the steps of the switching method described in yet another embodiment of the present application.

[0040] Description of reference numerals:

[0041] 1. Upper joint; 2. First elastic member; 3. Second elastic member; 4. First bearing; 5. Limit pin; 6. Rotating sleeve; 7. Second bearing; 8. Moving inner sleeve; 9. Inner liquid inlet hole; 10. Outer liquid inlet hole; 11. Moving outer sleeve; 12. Retaining ring; 13. Pressure-conducting hole; 14. Fixing pin; 15. Fixing inner sleeve; 16. Fixing outer sleeve; 17. Lower joint. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0043] In the related technologies, some researchers proposed the technology of "Research and Application of Offshore Oilfield Layered Water Injection Backwash Well Technology". In order to solve the problems of scaling, corrosion, oil layer pollution, blockage, and increased water injection pressure of the pipe string of the offshore oilfield layered water injection well, three types of backwash well pipe strings, namely lifting type, hydraulically controlled expansion type, and inserted sealing type, were studied and designed to implement backwash well operations without moving the water injection pipe string, so as to achieve the purpose of maintaining the wellbore of the water injection well, cleaning the water injection pipe string, and improving the effect of layered water injection. Some researchers proposed the technology of repeatable switchable pressure-conducting backwash valve, which uses metal balls to block and open the backwash channel, and increases the area of ​​the liquid channel by evenly distributing several liquid channels circumferentially to meet the requirements of large-displacement backwash wells. When backwashing the well, the casing annulus and the tool cavity can be connected, and the liquid channel is automatically closed when the backwashing is ended. Some researchers have proposed a backwashable well device technology for oilfield well repair operations. The device consists of an upper joint, a baffle, a diverter body, a check valve ball, and a diverter tube. The device is assembled with a downhole salvage string. When salvaging fallen objects and sand control strings, the fallen objects and sand on the sand control strings can be recoiled through the backwash well, avoiding the need to flush the fallen objects and sand on the sand control strings with the lower string, thereby reducing operating costs.

[0044] It can be seen that the water injection well in the related technology mainly realizes the backwashing function through the downhole backwashing device at the bottom of the water injection string. However, the backwashing device has a single function. During the pressure release process before the high-pressure well deployment, the oil pressure in the water injection string drops and the casing pressure outside the water injection string rises. The existing backwashing device cannot be closed and the backwashing phenomenon will still occur. Therefore, the same water injection string cannot achieve "backwashing function when backwashing operation is required, and not backwashing function when pressure reduction, measurement and adjustment are performed". Under the operating conditions of pressure reduction, measurement and adjustment, the backwashing function of the downhole device should be avoided, otherwise the injected formation water will flow out of the water injection string, causing waste and prolonged pressure release time.

[0045] In view of this, an embodiment of the present invention proposes a downhole device for switching the backwash function of a water injection string. The same water injection string can achieve "backwash function when backwash is needed, and not have the backwash function when pressure reduction measurement and adjustment, positive pressure operation and other operations are performed", avoiding the problem of "the injected formation water flowing out of the water injection string causing waste and long pressure release time" in the pressure release process before high-pressure well deployment in the existing backwash well device.

[0046] Reference Figure 1 As shown, Figure 1 The figure shows an exemplary downhole device for switching the backwash function of the water injection string according to some embodiments of the present disclosure. In order to clearly and concisely show the internal structure and appearance of the downhole device at the same time, the present embodiment Figure 1A partial (half) cross-sectional view of the downhole device is shown to show its internal structure. On the other side of the central axis direction of the downhole device, there is a front view of a portion of the downhole device symmetrical to the cross-sectional structure, so as to better understand the overall structure of the downhole device.

[0047] Please participate Figure 1 , a downhole device for switching backwashing function of a water injection string provided in an embodiment of the present invention comprises: a first liquid inlet assembly and a second liquid inlet assembly radially overlapped from the inside to the outside; wherein,

[0048] The first liquid inlet assembly includes a first elastic member 2, a rotating sleeve 6 and a movable inner sleeve 8 axially arranged from top to bottom, a fixed inner sleeve 15 is arranged on the inner side of the movable inner sleeve 8, and an inner liquid inlet hole 9 is provided on the movable inner sleeve 8, wherein the fixed inner sleeve 15 overlaps with the movable inner sleeve 8 at least partially, and the first elastic member 2 is configured to drive the rotating sleeve 6 and the movable inner sleeve 8 to axially reciprocate so that the inner liquid inlet hole 9 is inside or outside the overlapping area; the second liquid inlet assembly includes a fixed outer sleeve 16, and the outer side of the fixed outer sleeve 16 is axially arranged from top to bottom with a second elastic member 3 and a movable outer sleeve 11, and an outer liquid inlet hole 10 is provided on the fixed outer sleeve 16, and the second elastic member 3 is configured to drive the movable outer sleeve 11 to axially reciprocate so that the movable outer sleeve 11 blocks or opens the outer liquid inlet hole 10; wherein a track group is arranged on the rotating sleeve 6, and when the movable inner sleeve 8 moves in the same direction away from the fixed inner sleeve 15, the track group is used to limit the axial movement distance of the movable inner sleeve 8.

[0049] Specifically, Figure 1 For a downhole device placed horizontally, the radial direction referred to in this article is the direction from the inner center of the downhole device to the outside world, the radial outward direction is the direction toward the outside world or the wellbore, and the radial inward direction is the direction toward the central pipeline, and the first liquid inlet component and the second liquid inlet component together enclose the central pipeline; the axial direction referred to in this article is the height direction of the downhole device or the length direction of the pipeline, that is, Figure 1 In the left and right directions, axially upward is the direction from the lower joint 17 to the upper joint 1, or in other words, the direction from the formation to the water injection string, and the top of the downhole device is arranged at the bottom of the water injection string. Similarly, axially downward is opposite to axially upward.

[0050] An upper joint 1 is provided at the upper end of the outer side of the second liquid inlet assembly, and an internal thread is provided at the upper end of the upper joint 1, which is connected to the water injection column through the internal thread. An internal thread is designed at the lower end of the upper joint 1, and the upper joint 1 is connected to the upper end of the fixed outer sleeve 16 through a threaded connection. The outer peripheral thread sleeve of the lower end of the fixed outer sleeve 16 is provided with a lower joint 17. The overlapping first liquid inlet assembly and the second liquid inlet assembly can be understood as the innermost side of the second liquid inlet assembly being close to the outermost side of the first liquid inlet assembly. Specifically, the outermost side of the first liquid inlet assembly is the first elastic member 2, the rotating sleeve 6 and the movable inner sleeve 8 arranged in sequence axially, and the innermost side of the second liquid inlet assembly is the fixed outer sleeve 16.

[0051] Specifically, a fixed outer sleeve 16 is provided on the inner side of the movable inner sleeve 8. The fixed inner sleeve 15 overlaps with the movable inner sleeve 8 in at least part of the area, which means that the lower part of the movable inner sleeve 8 overlaps with the upper part of the fixed inner sleeve 15, so that the two have an intersecting area. The fixed inner sleeve 15 covers the movable inner sleeve 8 in the overlapping area. Since the movable inner sleeve 8 reciprocates axially with the first elastic member 2, the area of ​​the overlapping area changes accordingly. When the inner liquid inlet hole 9 is located in the overlapping area, the fixed inner sleeve 15 blocks the inner liquid inlet hole 9, and the inner liquid inlet hole 9 is in a closed state. At this time, the water in the water injection pipe can only flow from the inside of the downhole device to the formation. When the area of ​​the overlapping area becomes smaller, that is, the inner liquid inlet hole 9 is outside the overlapping area, the fixed inner sleeve 15 cannot block the inner liquid inlet hole 9, and the inner liquid inlet hole 9 is in an open state. At this time, the water in the water injection pipe can flow from the outside to the inside of the downhole device.

[0052] It can be understood that when the first elastic member 2 is in a stationary state, that is, when the first elastic member 2 is not subjected to axial upward pressure or has no axial downward elastic force, the inner liquid inlet hole 9 should be located in the overlapping area.

[0053] Specifically, the inner side of the fixed outer sleeve 16 is respectively the first elastic member 2, the rotating sleeve 6 and the movable inner sleeve 8, wherein the projection area of ​​the fixed outer sleeve 16 covers the above three, and the outer side of the fixed outer sleeve 16 is respectively the second elastic member 3 and the movable outer sleeve 11 which are axially arranged from top to bottom, wherein the movable outer sleeve 11 is located in the middle position of the fixed outer sleeve 16, and is located near the position of the movable inner sleeve 8. Among them, the inner liquid inlet hole 9 and the outer liquid inlet hole 10 can be arranged adjacently or side by side. The adjacent arrangement can be that the inner liquid inlet hole 9 and the outer liquid inlet hole 10 are at different axial positions, and the two have a vertical distance; the side by side arrangement can be that the inner liquid inlet hole 9 and the outer liquid inlet hole 10 are at the same axial position, and the center lines of the two coincide, so that the inner liquid inlet hole 9 and the outer liquid inlet hole 10 are connected. In some embodiments, the inner liquid inlet hole 9 can be closer to the water injection column than the outer liquid inlet hole 10.

[0054] It can be understood that when the second elastic member 3 is in a stationary state, that is, when the second elastic member 3 is not subjected to axial upward pressure or has no axial downward elastic force, the position of the external liquid inlet hole 10 should be where the movable sleeve 11 contacts the fixed sleeve 16 .

[0055] In some embodiments, the lower end of the fixed inner sleeve 15 and the lower end of the fixed outer sleeve 16 are connected and fixed by a plurality of fixing pins 14. In some embodiments, the sealing between the fixed inner sleeve 15 and the fixed outer sleeve 16 can be achieved by an O-ring sleeved on the fixed inner sleeve 15.

[0056] As a specific explanation of this embodiment, the driving force of the first elastic member 2 and the second elastic member 3 is derived from the pressure of the downhole device. When performing normal water injection operation, the oil pressure is greater than the casing pressure, and the first elastic member 2 can drive the rotating sleeve 6 and the movable inner sleeve 8 to move axially downward under the action of the oil pressure. When performing pressure reduction measurement and adjustment operation and backwashing operation, the oil pressure is less than the casing pressure, and the first elastic member 2 can drive the rotating sleeve 6 and the movable inner sleeve 8 to move axially upward under the action of the casing pressure, and the second elastic member 3 can drive the movable outer sleeve 11 to move axially upward. When the pressure reduction measurement and adjustment operation and the backwashing operation are stopped, the casing pressure is reduced, and the first elastic member 2 and the second elastic member 3 have a tendency to return to the initial state, so that the first elastic member 2 can drive the rotating sleeve 6 and the movable inner sleeve 8 to move axially downward, and the second elastic member 3 can drive the movable outer sleeve 11 to move axially downward, thus forming an axial reciprocating motion.

[0057] In some embodiments, a retaining ring 12 is disposed at the lower portion of the movable sleeve 11 , and the retaining ring 12 is fixedly connected to the movable sleeve 11 via threads to limit the moving distance of the movable sleeve 11 under the elastic action of the second elastic member 3 .

[0058] The first elastic member 2 and the second elastic member 3 may be springs.

[0059] It can be understood that during the axial downward movement, the area of ​​the overlapping region formed between the movable inner sleeve 8 and the fixed inner sleeve 15 increases, and the inner liquid inlet hole 9 moves into the overlapping region, at which time the inner liquid inlet hole 9 is in a closed state. During the axial upward movement, the outer liquid inlet hole 10 is in an open state, while the area of ​​the overlapping region formed between the movable inner sleeve 8 and the fixed inner sleeve 15 is reduced. By setting the track group, the upward distance of the movable outer sleeve 11 can be limited, thereby controlling the frequency of the inner liquid inlet hole 9 moving into or out of the overlapping region. In this way, the inner liquid inlet hole 9 on the movable inner sleeve 8 in the operating condition of the pressure reduction measurement and adjustment is still in the overlapping region, at which time the inner liquid inlet hole 9 is in a closed state, and the downhole device is closed, so that the downhole device does not have the backwashing function. At this time, the water injected into the formation will not enter the water injection string when the pressure is released, avoiding the problem of waste of injected water and too long pressure release time.

[0060] Therefore, the backwash channel of the embodiment of the present invention can be said to be composed of an outer liquid inlet hole 10 and an inner liquid inlet hole 9. The outer liquid inlet hole 10 is controlled by a movable outer sleeve 11 on the outside. The backwash channel is closed during positive injection. During backwashing, the external pressure pushes the movable outer sleeve 11 to move axially until the outer liquid inlet hole 10 is not blocked by the movable outer sleeve 11. The inner liquid inlet hole 9 is controlled by a fixed inner sleeve 15. When the inner liquid inlet hole 9 is blocked by the fixed inner sleeve 15, the backwash channel is blocked and does not have the backwash well function; when the inner liquid inlet hole 9 is not blocked by the fixed inner sleeve 15, it has the backwash well function and can perform backwash well operations.

[0061] In some embodiments, the sizes of the inner liquid inlet hole 9 and the outer liquid inlet hole 10 can be the same; in the present embodiment, the outer liquid inlet hole 10 can be located at the axial upper end, and when the inner liquid inlet hole 9 moves from bottom to top, the inner liquid inlet hole 9 is partially connected with the outer liquid inlet hole 10, wherein the partial connection can be that when the inner liquid inlet hole 9 stops moving upward, the inner liquid inlet hole 9 and the outer liquid inlet hole 10 are at different axial positions, and the vertical distance between the two is greater than the difference between the inner diameters of the two and less than the sum of the inner diameters of the two.

[0062] In some embodiments, the sizes of the inner liquid inlet hole 9 and the outer liquid inlet hole 10 may be different; in some embodiments, the size of the inner liquid inlet hole 9 is larger than the size of the outer liquid inlet hole 10; in some embodiments, the size of the inner liquid inlet hole 9 is smaller than the size of the outer liquid inlet hole 10. Preferably, the inner liquid inlet hole 9 and the outer liquid inlet hole 10 are at least partially overlapped and connected, wherein the overlapping connection can be that the size of the outer liquid inlet hole 10 can be larger than the distance traveled by the inner liquid inlet hole 9 during the axial reciprocating motion, so that the inner liquid inlet hole 9 is always connected with the outer liquid inlet hole 10, so that under the reverse circulation well washing operation condition, the formation water can quickly enter the downhole device for backwashing operation.

[0063] More preferably, anti-overflow rings are provided in the overlapping area of ​​the fixed inner sleeve 15 and the movable inner sleeve 8, between the movable outer sleeve 11 and the fixed outer sleeve 16, and between the fixed outer sleeve 16 and the movable inner sleeve 8. The movable inner sleeve 8 and the fixed inner sleeve 15 are sealed by the anti-overflow ring sleeved on the fixed inner sleeve 15 to prevent formation water from flowing into the downhole device from the gap between the fixed inner sleeve 15 and the movable inner sleeve 8 when the inner liquid inlet hole 9 is in a closed state; the movable outer sleeve 11 and the fixed outer sleeve 16 are sealed by the anti-overflow ring sleeved on the fixed outer sleeve 16 to prevent formation water from flowing into the outer liquid inlet hole 10 from the gap between the movable outer sleeve 11 and the fixed outer sleeve 16 when the outer liquid inlet hole 10 is in a closed state; and the upper outer wall of the fixed outer sleeve 16 and the movable inner sleeve 8 are provided with anti-overflow rings to prevent formation water from flowing into the inner liquid inlet hole 9 from the gap between the fixed outer sleeve 16 and the movable inner sleeve 8 when the inner liquid inlet hole 9 is in a closed state. In this way, an anti-overflow ring is set between two adjacent layers of the movable outer sleeve 11, the fixed outer sleeve 16, the movable inner sleeve 8 and the fixed inner sleeve 15, which are arranged sequentially from the outside to the inside. Under operating conditions where the backwash well function is not required, they can work together to effectively prevent formation water from flowing from the outside to the inside into the downhole device and causing backwashing.

[0064] It needs to be explained that the inner liquid inlet hole 9 and / or the outer liquid inlet hole 10 should be located between the anti-overflow rings of the corresponding layers. When the backwash well function is required, the formation water can be directed to the positions of the outer liquid inlet hole 10 and the inner liquid inlet hole 9, thereby flowing to the interior of the downhole device, and preventing it from discharging to other areas through the gaps between the two adjacent layers.

[0065] This embodiment is used to illustrate the track group for controlling the opening and closing state of the inner liquid inlet hole 9 during the axial upward movement. Figure 2 , Figure 2 The schematic diagram of the unfolded structure of the track group shown in the present invention. The track group includes a limit pin 5 and a special-shaped track, and a plurality of the limit pins 5 are movably embedded in the special-shaped track; wherein the special-shaped track includes: a first track unit and a second track unit that are interconnected and arranged opposite to each other, and the first track unit is located on a side away from the fixed inner sleeve 15; wherein the first track unit includes a plurality of long tracks and a first short track that are arranged circumferentially around the rotating sleeve 6, and the long tracks and the first short tracks are arranged in an alternating manner; the second track unit includes a plurality of second short tracks that are arranged circumferentially around the rotating sleeve 6, and each of the second short tracks is located between two adjacent long tracks and the first short tracks.

[0066] Specifically, the track group includes a plurality of long tracks and short tracks, the length of the long track is greater than the length of the short track, wherein the long tracks and the short tracks are evenly spaced around the rotating sleeve 6. Specifically, the track group includes a first track unit composed of a long track and a first short track, and a second track unit composed of a second short track, wherein the first track unit and the second track unit are interconnected, which means that one end of the long track, the first short track, and the second short track is open and the other end is closed, forming a strip-shaped groove structure, and the open ends of each track are opposite, so that the first track unit and the second track unit are interconnected, so that the limit pin 5 can be in different tracks (long track and the first short track, and the second short track) during the axial movement of the rotating sleeve 6. Since the special-shaped track has an axially upward and axially downward movement trajectory under the formation pressure, due to the action of the limit pin 5, the rotating sleeve 6 is spirally upward or spirally downward.

[0067] Among them, in order to fit the trajectory of the spiral reciprocating motion, the long track and the first short track are arranged alternately, that is, they are evenly arranged with a long and a short interval around the rotating sleeve 6, and the second short track is evenly arranged around the rotating sleeve 6 and is located between the adjacent long track and the first short track, forming an arrangement of the second short track, the first short track, the second short track, and the long track as units in sequence along the circumferential direction, and the interval distance between two adjacent tracks is equal, so that during the axial spiral reciprocating motion, it moves from any track in the first track unit to the corresponding track in the second track unit adjacent in the rotation direction.

[0068] Preferably, the first track unit and the second track unit are connected on one side and are respectively provided with a guide surface. In this embodiment, the first short track and the long track, as well as the second short track are all provided with a guide surface. Figure 2 The open ends of each long track and the first short track shown are in a trumpet shape with the opening facing the second short track, and one side of the open end of the second short track is an inclined surface, so that the area connected between the two is lightning-shaped, which is convenient for guiding the limit pin 5 to move from any track in the first track unit to the corresponding track in the second track unit adjacent in the rotation direction during the spiral movement of the rotating sleeve 6.

[0069] Exemplarily, when the rotating sleeve 6 moves axially upward, it enters the first short track from the second short track. The second short track first moves linearly relative to the limit pin 5 to the open end of the second short track, enters the open end of the first short track, enters the first short track along the inclined surface of the open end, and moves linearly to the closed end of the second short track.

[0070] The first track unit is located on the side close to the upper joint 1, and is used to determine whether the inner liquid inlet hole 9 of the movable inner sleeve 8 is blocked by the fixed inner sleeve 15 through the position of the limit pin 5 on the long track and the first short track outside the rotating sleeve 6 during the backwashing operation and the pressure reduction measurement and adjustment operation, that is, during the spiral upward movement. If it is blocked, it does not have the backwashing function, and if it is not blocked, it has the backwashing function. The second track unit is located on the side close to the lower joint 17, and is used to block the inner liquid inlet hole 9 by the fixed inner sleeve 15 through the position of the limit pin 5 at the second short track during the water injection operation, that is, during the spiral downward movement.

[0071] The axial movement distance is limited by the first pin. When the first pin is in the first short track, the upward distance of the moving inner sleeve 8 is less than the distance that the inner liquid inlet hole 9 moves out of the fixed inner sleeve 15. At this time, the inner liquid inlet hole 9 is still in the overlapping area and does not have the backwash well function. When the first pin is in the long track, the upward distance of the moving inner sleeve 8 is greater than the distance that the inner liquid inlet hole 9 moves out of the fixed inner sleeve 15. At this time, the inner liquid inlet hole 9 is outside the overlapping area and has the backwash well function.

[0072] The second track unit is located on one side of the lower joint 17 and is used for water injection operation, that is, during the spiral downward movement. Since the second track unit is closer to the fixed sleeve 16 than the first track unit, when the limit pin 5 is in the second short track outside the rotating sleeve 6, the inner liquid inlet hole 9 is always blocked by the fixed sleeve 16.

[0073] In this way, through the setting of the track group, the switch of the inner liquid inlet hole 9 of the movable inner sleeve 8 is realized, and the same water injection pipe string can complete the function of backwashing the well or not backwashing the well, realizing "having the backwashing well function when backwashing is needed, and not having the backwashing well function when pressure reduction measurement and adjustment are performed", avoiding the problem of "the injected formation water flowing out of the water injection pipe string causing waste and long pressure release time" in the pressure release process before the high-pressure well deployment of the existing backwashing well device.

[0074] In some embodiments, eight tracks are arranged on the outside of the rotating sleeve 6, that is, the first track unit has two first short tracks and a long track arranged in an alternating manner, and the second track unit has four second short tracks. Under the track group of eight tracks, four operations can be performed. Under each normal water injection operation, the rotating sleeve 6 goes down into the second track unit, and the rotating sleeve 6 goes up from the second short track into the first short track to achieve pressure relief before high-pressure well deployment; or the rotating sleeve 6 goes up from the second short track into the long track to achieve backwashing operation. In this way, two backwashing operations and two pressure reduction and measurement operations can be performed for each rotation of the rotating sleeve 6.

[0075] In a further technical solution, the first elastic member 2 is placed inside the outer sleeve, the first elastic member 2 is provided with a first bearing 4 at the bottom, the first bearing 4 is provided with a rotating sleeve 6 at the bottom, the second bearing 7 is provided with a rotating sleeve 6 at the bottom, and the second bearing 7 is provided with a movable inner sleeve 8 at the bottom. The first elastic member 2, the first bearing 4, the rotating sleeve 6, the second bearing 7, the movable inner sleeve 8, and the fixed inner sleeve 15 are all located inside the fixed outer sleeve 16. The bearing can reduce the friction between the components during use, and the rotating sleeve 6 can operate flexibly and extend the working cycle.

[0076] In some embodiments, the outer diameter of the axial lower end of the fixed inner sleeve 15 is greater than the outer diameter of the axial upper end thereof, and a pressure chamber is formed between the fixed inner sleeve 15, the movable inner sleeve 8 and the fixed outer sleeve 16, and a pressure-conducting hole 13 communicating with the pressure chamber is provided on the fixed outer sleeve 16. Among them, the upper part of the fixed inner sleeve 15 has a smaller outer diameter, the lower part has a larger outer diameter, and has the same inner diameter, forming an inverted T-shaped structure, the upper side of the vertical section of the T-shaped structure is in active contact with the movable inner sleeve 8, and a space is formed between the middle and lower sides and the fixed outer sleeve 16, and the transverse section of the T-shaped structure is connected to the fixed outer sleeve 16 through the above-mentioned fixed pin 14, so that a pressure chamber is formed between the three. Several pressure-conducting holes 13 are designed on the fixed outer sleeve 16 at the position where the pressure chamber is formed. When the backwash function is required, the formation water enters the pressure chamber from the pressure-conducting hole 13 under the formation pressure, pushing the movable inner sleeve 8 and the rotating sleeve 6 axially upward, and controlling the position of the limit pin 5 on the long and short tracks of the rotating sleeve 6.

[0077] In some other embodiments, the thickness of the axial lower end of the movable jacket 11 is greater than the thickness of the axial upper end thereof. In this embodiment, the thickness can be the difference between the outer diameter and the inner diameter of the movable jacket 11. The thickness of the movable jacket 11 is proportional to its pressure area, wherein the thickness of the axial lower end of the movable jacket 11 is greater, and the axial pressure it bears is greater. Thus, when the backwashing operation is performed, the pressures at both ends of the movable jacket 11 are different, so that the movable jacket 11 has a tendency to move from bottom to top, pushing the movable jacket 11 axially upward, thereby opening the external liquid inlet 10.

[0078] Specifically, the movable outer sleeve 11 may be arranged with a larger inner diameter at the upper portion and a smaller inner diameter at the lower portion, with the same outer diameter, and is sleeved on the middle portion of the fixed outer sleeve 16 .

[0079] Reference Figure 3 As shown, Figure 3 Another aspect of the present invention is to propose a switching method, which relies on the downhole device for switching the backwash function of the water injection string proposed in the first aspect of the present invention, and the downhole device is connected to the bottom end of the water injection string, and the method comprises:

[0080] S1, perform multiple water injection operations to drive the movable inner sleeve 8 and the movable outer sleeve 11 to perform axial reciprocating motion; each water injection operation includes a well opening water injection operation and a well closing pressure relief operation;

[0081] S2. Based on the current number of water injection operations, determine whether the inner liquid inlet hole 9 on the movable inner sleeve 8 is within the overlapping area during the shut-in and pressure relief operation;

[0082] S3, based on the position judgment result of the inner liquid inlet hole 9, determining whether the downhole device has a backwashing function;

[0083] S4. Switching the current number of water injection operations according to the operation requirements corresponding to the backwashing well function and the operation requirements corresponding to the backwashing well function.

[0084] Specifically, first, according to the structure of the special-shaped track on the outside of the rotating sleeve 6, the number of water injection operations matching the number of tracks of the special-shaped track is set. The water injection operation includes the well opening water injection operation and the well closing pressure relief operation, that is, each water injection operation requires the participation of two tracks, that is, moving from any track in the first track unit to the corresponding track in the second track unit adjacent in the rotation direction. In this embodiment, eight tracks are arranged on the outside of the rotating sleeve 6, that is, the first track unit has two first short tracks and a long track arranged in an alternating manner, and the second track unit has four second short tracks. For ease of understanding, the tracks are named in order (e.g., clockwise) along the circumferential direction as 1 (the first short track under the first operation), 2 (the second short track under the first operation), 3 (the first short track under the second operation), 4 (the long track under the second operation), 5 (the second short track under the third operation), 6 (the first short track under the third operation), 7 (the second short track under the third operation), 8 (the long track under the fourth operation), and 1 (the first short track entered in the fourth operation). That is, the second track units (1, 3, 5, 7) are all located at the lower end, the second track units (2, 4, 6, 8) are all located at the upper end, the rotating sleeve 6 descends into the second track unit, and the rotating sleeve 6 ascends from the second short track into the first short track or the long track.

[0085] When eight tracks are set up, four water injection operations (opening the well for water injection and closing the well for pressure relief) are required for each rotation of the rotating sleeve 6. During normal water injection, the limit pin 5 is located at position 1, 3, 5 or 7 in the track. When the well is closed for pressure relief or backwashing after a period of water injection, the formation pressure drives the movable inner sleeve 8 to move axially, and the rotating sleeve 6 rotates and moves axially upward under the limit of the limit pin 5, and the first pin is located at position 2, 4, 6 or 8 in the track.

[0086] Therefore, during the shut-in and pressure relief operation in the water injection operation under adjacent operation times, the limit pin 5 is in different tracks. When in the long track, the inner liquid inlet hole 9 on the movable inner sleeve 8 is outside the overlapping area during the shut-in and pressure relief operation, and the outer liquid inlet hole 10 is in an open state, and the backwash operation can be performed; when in the first short track, the inner liquid inlet hole 9 on the movable inner sleeve 8 is in the overlapping area during the shut-in and pressure relief operation, and the outer liquid inlet hole 10 is in an open state, and the pressure reduction measurement and adjustment operation can be performed. Therefore, it can be obtained whether the downhole device has the backwash function according to the current operation times.

[0087] For example, under the operational requirements of backwashing, during normal water injection, the limit pin 5 is at position 3 or 7 in the track. If the wellhead process is reversed under this condition to perform backwashing, the formation pressure pushes the movable inner sleeve 8 and the rotating sleeve 6 upward through the pressure-conducting hole 13 until the limit pin 5 is at position 4 or 8 in the track of the rotating sleeve 6, and finally the movable inner liquid inlet hole 9 is blocked by the fixed inner sleeve 15. At this time, the liquid enters the water injection string from the outside of the water injection string through the external liquid inlet hole 10 and the internal liquid inlet hole 9, and flows out of the wellhead, and the reverse circulation well washing operation can be carried out.

[0088] However, if the high-pressure water injection well is shut down and depressurized before testing and adjustment under this condition, the water injected into the formation will enter the water injection string through the external inlet hole 10 and the internal inlet hole 9, and flow out of the wellhead, resulting in a waste of injected water and an extension of the depressurization time. Based on the above process analysis, in order to meet the needs of backwashing the water injection well, it is sufficient to obtain the judgment result that the position of the limit pin 5 in the track is at position 3 or position 7 during the normal water injection process; in order to meet the needs of shutting down and depressurizing the high-pressure water injection well before testing and adjustment, it is sufficient to obtain the judgment result that the position of the limit pin 5 in the track is not at position 3 or position 7 during the normal water injection process.

[0089] Under the operational requirements that do not require the backwash function, during the normal water injection process, the limit pin 5 is at position 1 or 5 in the track. If under this condition, the high-pressure water injection well is shut down and depressurized before measurement and adjustment, the formation pressure pushes the movable inner sleeve 8 and the rotating sleeve 6 to move axially upward through the pressure-conducting hole 13, and the limit pin 5 is at position 2 or 6 in the track. At this time, the inner liquid inlet hole 9 is blocked by the fixed inner sleeve 15, and the water injected into the formation will not enter the water injection column through the outer liquid inlet hole 10 and the inner liquid inlet hole 9, which will not cause waste of injected water. The internal pressure of the water injection column will drop rapidly and meet the requirements of low-pressure measurement and adjustment. However, if the wellhead process is reversed under this condition to backwash the well, since the inner liquid inlet hole 9 is blocked by the fixed inner sleeve 15, the liquid will not enter the water injection column from the outside to the inside of the water injection column, and the backwash operation cannot be completed. Based on the above process analysis, in order to meet the need of shutting down and relieving pressure before measuring and adjusting the high-pressure water injection well, it is sufficient to obtain the judgment result that the limit pin 5 is at position 1 or 5 in the track during the normal water injection process; in order to meet the needs of backwashing wells, it is necessary to obtain the judgment result that the limit pin 5 is not at position 1 or 5 in the track during the normal water injection process.

[0090] Wherein, step S2 comprises:

[0091] S21, determining whether the current operation number of the water injection operation is an odd number or an even number;

[0092] S22, based on an odd number of water injection operations, obtaining a judgment result that the inner liquid inlet hole 9 corresponding to the well shut-in and pressure relief operation in the current water injection operation is within the overlapping area;

[0093] S23, based on an even number of water injection operations, obtaining a judgment result that the inner liquid inlet hole 9 corresponding to the well shut-in and pressure relief operation in the current water injection operation is outside the overlapping area;

[0094] Step S4 includes:

[0095] S41, according to the backwashing operation corresponding to the backwashing function, switching the current number of the water injection operation to an even number;

[0096] S42. According to the pressure reduction test and adjustment operation corresponding to the non-backwashing well function, the current number of times of switching the water injection operation is an odd number.

[0097] Through steps S1-S4, the water injection string can be controlled to backwash the well or not according to the number of well opening and closing at the wellhead (opening the well for water injection, closing the well for pressure relief), so as to achieve "having the backwash function when backwashing is needed, and not having the backwash function when performing pressure reduction measurement and adjustment operations". According to the order of the number of operations, the first operation can be set as the second short track at point 1 entering the first short track at point 2, then the second operation is the second short track at point 3 entering the long track at point 4, and so on... That is, it can be obtained that when odd-numbered operations such as 1, 3, ... are performed, the water injection string does not have the backwash function, the well can be closed and pressure relieved before the high-pressure water injection well is measured and adjusted, and the backwash operation cannot be performed. When even-numbered operations such as 2, 4, ... are performed, the water injection string has the backwash function, the well can be backwashed, and the well cannot be closed and pressure relieved before the high-pressure water injection well is measured and adjusted.

[0098] The relationship between the switch state of the inner liquid inlet hole 9 and the backwash function switching corresponding to each rotation of the rotating sleeve 6 is shown in Table 1:

[0099]

[0100] Table 1

[0101] It can be seen that if the current water injection well is an odd-numbered operation, a backwash well operation corresponding to the backwash well function is required, and an injection operation of "opening the well to inject water and closing the well to release pressure" is added at the wellhead, so that the current water injection well is switched to an even-numbered operation. After that, the water injection string has the backwash well function, and the backwash well operation can be performed at this time.

[0102] If the current water injection well is an even-numbered operation, and a pressure reduction and testing and adjustment operation corresponding to a well without backwashing function is required, an injection operation of "opening the well to inject water, closing the well to release pressure" is added at the wellhead, so that the current water injection well is switched to an odd-numbered operation. At this time, the tubing string has a non-backwashing function, which meets the requirement of closing the well and releasing pressure before testing and adjustment of the high-pressure water injection well, that is, the requirement that the injected water at the lowest level will not enter the water injection tubing string from the well washing device during the pressure reduction and testing and adjustment.

[0103] If you are not sure whether the current operation is odd or even, you can perform backwashing after “opening the well to inject water, closing the well to release pressure” for inspection. If reverse circulation well washing is possible this time, the next time “opening the well to inject water, closing the well to release pressure” the backwashing function will not be available, and you can perform pressure reduction measurement and adjustment. If reverse circulation well washing is not possible this time, the next time “opening the well to inject water, closing the well to release pressure” the backwashing function will be available, and you can perform reverse circulation well washing.

[0104] To sum up, the downhole device provided in the embodiment of the present invention includes an upper joint 1, an outer sleeve, a fixed inner sleeve 15, a pressure guide hole 13, a retaining ring 12, a movable outer sleeve 11, an outer sleeve liquid inlet hole, a movable inner sleeve 8 liquid inlet hole, a movable inner sleeve 8, a bearing, a rotating sleeve 6, a spring, and a lower joint 17. The invention is installed at the bottom of the water injection string. The position of the pin on the long and short tracks of the rotating sleeve 6 can be controlled by the number of operations of "opening the well to inject water, closing the well to release pressure" at the wellhead. The movable inner sleeve 8 and the movable outer sleeve 11 are pushed axially by the liquid to block or not block the inner liquid inlet hole 9. The backwashing and non-backwashing functions of the water injection string are switched according to the number of well opening and closing wells at the wellhead. The water injection string has the backwashing function when backwashing is needed, and does not have the backwashing function when pressure reduction, measurement and adjustment and other operations are being performed. The same water injection string realizes "the backwashing function when backwashing is needed, and does not have the backwashing function when pressure reduction, measurement and adjustment, positive pressure operation and other operations are being performed". The tool is simple to operate, safe and reliable to enter the well, and can be widely used in the field of oilfield water injection development technology.

[0105] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0106] It should also be noted that, in this article, the orientation or position relationship indicated by the terms "upper", "lower", "left", "right", "inside", "outside", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations, nor can they be understood as indicating or implying relative importance. Moreover, the term "include" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or terminal device.

[0107] The above is a detailed introduction to a downhole device and a switching method for switching the backwash function of a water injection string provided by the present application. This article uses specific examples to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the present application, and the content of this specification should not be understood as a limitation on the present application. At the same time, for a person of ordinary skill in the art, according to the present application, there will be different forms of changes in the specific implementation methods and application scopes. It is not necessary and impossible to list all the implementation methods here, and the obvious changes or modifications derived therefrom are still within the protection scope of the present application.

Claims

1. A downhole device for switching backwash function of water injection string, characterized in that: include: A first liquid inlet assembly and a second liquid inlet assembly are radially overlapped from the inside to the outside; wherein, The first liquid inlet assembly comprises a first elastic member, a rotating sleeve and a movable inner sleeve axially arranged from top to bottom, a fixed inner sleeve is arranged on the inner side of the movable inner sleeve, an inner liquid inlet hole is opened on the movable inner sleeve, wherein the fixed inner sleeve and the movable inner sleeve overlap at least partially, and the first elastic member is configured to drive the rotating sleeve and the movable inner sleeve to axially reciprocate so that the inner liquid inlet hole is inside or outside the overlapping area; The second liquid inlet assembly comprises a fixed outer sleeve, a second elastic member and a movable outer sleeve are axially arranged on the outer side of the fixed outer sleeve from top to bottom, an outer liquid inlet hole is opened on the fixed outer sleeve, and the second elastic member is configured to drive the movable outer sleeve to axially reciprocate so that the movable outer sleeve covers or opens the outer liquid inlet hole; Wherein, a track group is arranged on the rotating sleeve, and when the movable inner sleeve moves in the same direction away from the fixed inner sleeve, the track group is used to limit the axial movement distance of the movable inner sleeve.

2. A downhole device for switching backwashing function of a water injection string according to claim 1, characterized in that: The track group includes a limit pin and a special-shaped track, and a plurality of the limit pins are movably embedded in the special-shaped track; wherein the special-shaped track includes: A first track unit and a second track unit are interconnected and arranged opposite to each other, and the first track unit is located on a side away from the fixed inner sleeve; wherein, The first track unit includes a plurality of long tracks and a first short track arranged around the circumference of the rotating sleeve, and the long tracks and the first short tracks are arranged alternately; the second track unit includes a plurality of second short tracks arranged around the circumference of the rotating sleeve, and each of the second short tracks is located between two adjacent long tracks and the first short tracks.

3. A downhole device for switching backwashing function of a water injection string according to claim 2, characterized in that: A guide surface is respectively provided on one side where the first track unit and the second track unit are connected.

4. A downhole device for switching backwashing function of a water injection string according to claim 1, characterized in that: The inner liquid inlet hole and the outer liquid inlet hole are at least partially overlapped and connected; and anti-overflow rings are arranged in the overlapping area between the fixed inner sleeve and the movable inner sleeve, between the movable outer sleeve and the fixed outer sleeve, and between the fixed outer sleeve and the movable inner sleeve.

5. A downhole device for switching backwashing function of a water injection string according to claim 1, characterized in that: The end surfaces of the rotating sleeve that are in contact with the first elastic member and the movable inner sleeve are respectively provided with bearings.

6. A downhole device for switching backwashing function of a water injection string according to claim 1, characterized in that: A retaining ring is disposed at one end of the movable outer sleeve away from the second elastic member.

7. A downhole device for switching backwashing function of a water injection string according to claim 1, characterized in that: The outer diameter of the axial lower end of the fixed inner sleeve is greater than the outer diameter of the axial upper end thereof, a pressure chamber is formed between the fixed inner sleeve, the movable inner sleeve and the fixed outer sleeve, and a pressure conducting hole connected to the pressure chamber is provided on the fixed outer sleeve.

8. A downhole device for switching backwashing function of a water injection string according to claim 1, characterized in that: The thickness of the axial lower end of the movable outer sleeve is greater than the thickness of the axial upper end thereof.

9. A switching method, characterized in that: A downhole device for switching the backwash function of a water injection string according to any one of claims 1 to 8, wherein the downhole device is connected to the bottom end of the water injection string, and the method comprises: Perform multiple water injection operations to drive the movable inner sleeve and the movable outer sleeve to perform axial reciprocating motion; each water injection operation includes a well opening water injection operation and a well closing pressure relief operation; Based on the current number of water injection operations, determining whether the inner liquid inlet hole on the movable inner sleeve is within the overlapping area during the shut-in and pressure relief operation; Based on the position judgment result of the inner liquid inlet hole, determining whether the downhole device has a backwashing function; The current number of water injection operations is switched according to the operation requirements corresponding to the backwashing well function and the operation requirements corresponding to the backwashing well function.

10. A downhole device for switching backwashing function of a water injection string according to claim 9, characterized in that: Based on the current number of water injection operations, determining whether the inner liquid inlet hole on the movable inner sleeve is within the overlapping area during the shut-in and pressure relief operation includes: Determining whether the current operation number of the water injection operation is an odd number or an even number; Based on an odd number of water injection operations, a judgment result is obtained that the inner liquid inlet hole corresponding to the well shut-in and pressure relief operation in the current water injection operation is within the overlapping area; Based on an even number of water injection operations, a judgment result is obtained that the inner liquid inlet hole corresponding to the well shut-in and pressure relief operation in the current water injection operation is outside the overlapping area; The switching of the current number of water injection operations according to the operation requirements corresponding to the backwashing well function and the operation requirements corresponding to the backwashing well function not including: According to the backwashing operation corresponding to the backwashing function, the current number of times of switching the water injection operation is an even number; According to the pressure reduction test and adjustment operation corresponding to not having the backwash well function, the current number of times the water injection operation is switched is an odd number.

Images