A resettable, segmented pressure-driven water injection process tubing and method

Abstract

A resettable, segmented pressure-driven water injection process string and method, belonging to the field of oilfield engineering technology, comprises, from bottom to top, a seated sliding sleeve connected sequentially to a lower reset sliding sleeve, packer I, a middle reset sliding sleeve, packer II, an upper reset sliding sleeve, packer III, a high-pressure well-washing valve, and tubing threads. The water injection string is lowered into the casing. The upper end of the tubing is suspended above the lower four-way valve at the water injection wellhead via a self-sealing core. A ball-dropped blowout preventer is located above the test gate at the water injection wellhead. An annular pressure self-balancing device is connected to the left-side production valve. The lower balancing hole, drain hole I, and inlet hole I of the annular pressure self-balancing device are connected to the left-side casing gate valve at the water injection wellhead via a connecting pipe. This invention is applicable to segmented pressure-driven water injection in oilfield water injection wells, meeting the needs of segmented formation water injection. The injection string can be reused, improving the qualification rate of the injection segments and saving operating costs.

Description

Technical Field

[0001] This invention relates to the field of oil production engineering technology, specifically to a repositionable stratified and segmented pressure-driven water injection process tubing and method. Background Technology

[0002] China possesses abundant shale oil resources, with currently exploitable reserves of approximately 5.5 billion tons, accounting for 9.7% of the world's total recoverable resources. Shale oil, with its unique advantages, has become an important component of the world's energy strategy, playing a significant role in ensuring national energy security. my country's development and utilization of oil shale started relatively late. Although China has become one of the world's largest shale oil producers, a significant gap remains compared to the United States, and several problems urgently need to be addressed. With the gradual depletion of oil and gas resources, my country will vigorously develop the shale oil industry, which has promising prospects.

[0003] Shale oil is an unconventional oil and gas resource, referring to petroleum resources contained in shale formations, primarily composed of shale. This includes oil in the pores and fractures of mudstone and shale, as well as oil resources in adjacent and interlayered layers of tight carbonate or clastic rocks within the mudstone and shale formations. The main characteristics of these reservoirs are tight rock, belonging to low-permeability and ultra-low-permeability oil and gas reservoirs; deep burial of oil and gas, characterized by high temperature and high pressure. Typically, effective development methods include horizontal wells and staged fracturing technology. In recent years, Shengli Oilfield has been exploring water injection development technology for such reservoirs. This technology employs water injection at pressures exceeding or approaching formation fracturing pressure (30-70 MPa) and with large displacements (200-2880 m³ / d), defined as pressure-driven water injection technology. Field applications have yielded good results. However, many problems also exist, one of which is the issue of staged pressure-driven water injection.

[0004] Because wells requiring pressure-driven water injection are often deep-buried with high reservoir temperatures (100-150℃), the four conventional types of water injection tubing are insufficient for pressure-driven water injection needs. The first type uses downhole nozzles for throttling injection; however, due to the large flow rate and high pressure of pressure-driven water injection, the nozzles suffer severe wear, and the throttling pressure differential is limited, making it unsuitable for pressure-driven water injection. The second type uses intelligent injection tubing with smart switches; however, because the smart switches employ electronic circuitry, they are also unsuitable for high-temperature environments. The third type uses concentric double-tube injection tubing; due to the large flow rate of pressure-driven water injection, the concentric double-tube tubing has a very small diameter, and a tubing length of several kilometers would generate significant friction, also failing to meet the requirements of large-volume injection. The fourth method is to use a sliding sleeve switch in the well, which can achieve segmented and layered water injection. However, the sliding sleeve switch in the well is a one-time use device and cannot be closed after it is opened downhole. First, it cannot be used again for the next water injection, and the injection string can only be used once. Second, if it is not closed in time after the lower layer is injected, it is easy to communicate with the upper layer, and the purpose of segmented and layered injection cannot be achieved.

[0005] The following comparison was made with existing patent technologies based on the search results:

[0006] A secondary opening and dispensing device for oilfield water injection wells (application number: 202120707838.X) is disclosed. Its main body has a small-diameter borehole with an internal clearance fit connecting to a sliding sleeve. In the small-diameter section of the main body, the sleeve wall has intermittent fluid outlet holes. Below the fluid outlet holes, the main body wall has several fluid passage holes. The sliding sleeve is connected to the main body below the fluid passage holes via a lower shear pin. The bottom of the sliding sleeve has a constricting ball seat cone hole. This invention achieves two-stage operations—opening and closing the fluid passage holes—with a single ball insertion, reducing the number of times the water injection string needs to be pulled out of the well, significantly lowering production costs and reducing the operational risks and post-processing difficulties associated with pulling out the string. It also improves the qualification rate of the injection well layers and enables segmented water injection. However, the purpose of this invention is to facilitate well washing. By throwing the ball twice, the well washing channel is opened the first time. After washing, the ball is thrown again to pressurize and close the well washing channel. The sliding sleeve can only be pushed in one direction and is disposable and cannot be reused. By throwing the ball twice, the first time is to open the water injection channel and the second time is to close the water injection channel. The pressure of the water injection layer is used to push back and close the channel to achieve the purpose of resetting.

[0007] A tiered water injection process tubing and method, application number 201611221209.6, describes a tubing string comprising a central pipe lowered into a casing, a setting valve, at least three packers placed inside the casing and spaced apart outside the central pipe, water injection pipes positioned between the central pipe and the casing, and a water injection mechanism located on the ground. The setting valve includes a pressure relief valve seat fixed to the bottom of the central pipe and a valve ball resting on the pressure relief valve seat. A through hole is provided on the pressure relief valve seat, and the valve ball can seal the through hole. Water injection layers are formed between adjacent set packers. The number of water injection pipes is the same as the number of water injection layers, and the lower opening of each water injection pipe is connected to the corresponding water injection layer. The water injection mechanism includes ground pipelines; the upper opening of the central pipe is connected to the outlet of one of the ground pipelines, and the upper openings of each water injection pipe are connected to the outlets of the remaining ground pipelines. This invention allows each water injection layer to be injected independently, avoiding inter-layer interference, and allows adjustment of the water injection volume of each water injection layer on the ground. The patent uses a water injection pipe (actually a capillary steel pipe) to be lowered into the corresponding layer for water injection. The water injection pipe must be tied to the outer wall of the central oil pipe and lowered into the well together with the oil pipe.

[0008] The present invention has the following shortcomings:

[0009] 1. The small outer diameter of the injection pipe (13-25mm) cannot meet the requirements of pressure-driven injection, large diameter, and large displacement water injection. Because the inner diameter of the injection well is small, the frictional resistance of water injection is large, which limits the increase of water injection displacement. Moreover, the wall thickness of only 1-2mm cannot meet the requirements of ultra-high pressure (above 30-70MPa) for pressure-driven water injection.

[0010] 2. If the water injection pipe is not properly protected when going down into the well, there is a risk of it being worn through.

[0011] 3. If the water injection pipe breaks off after being in the well for a long time, it may fall into the well and cause an accident, which is difficult to retrieve.

[0012] An automatic reversing water distributor for stratified injection wells and its usage method, application number: 201610968450.9, comprises an upper connector and a lower connector. An outer pipe connects the upper and lower connectors, and an inner pipe connects to the inner cavity of the upper connector, forming an injection annular cavity between the inner and outer pipes. Injection holes are radially arranged in the injection annular cavity. The inner pipe has an upper flow hole and a lower flow hole on its wall, and an upper valve and a lower valve are installed in the cavity. A lower valve slow-closing device is installed in the inner pipe between the upper and lower valves. This water distributor corresponds to the injection layer and is connected in the injection string. This invention can be used in conjunction with other injection tools in the injection string, can be switched on and off according to geological requirements, improves the feasibility of rotational injection operations, and achieves the purpose of targeted subdivision of injection.

[0013] However, due to the excessive friction of the water injection flow hole, the flow rate of this invention is small and cannot meet the needs of pressure-driven water injection with large discharge capacity.

[0014] Therefore, it is necessary to develop a repositionable stratified and segmented pressure-driven water injection process string and method that can meet the needs of large-volume and high-temperature resistance of stratified and segmented water injection in formations, and can reuse the injection string to save operating costs. Summary of the Invention

[0015] To address the shortcomings of the prior art, this invention provides a repositionable stratified and segmented pressure-driven water injection process string and method. This string not only meets the needs of stratified and segmented water injection in formations but also allows for the reuse of the injection string, thereby saving costs.

[0016] The objective of this invention is achieved through the following technical solution:

[0017] This invention comprises: casing, seated sliding sleeve, lower reset sliding sleeve, packer I, middle reset sliding sleeve, packer II, upper reset sliding sleeve, packer III, high-pressure resistant well-washing valve, tubing, water injection wellhead, ball-operated blowout preventer, and casing annular pressure self-balancing device; characterized in that: the resettable, segmented pressure-driven water injection process tubing string, from bottom to top, consists of the seated sliding sleeve, lower reset sliding sleeve, packer I, middle reset sliding sleeve, packer II, upper reset sliding sleeve, and packer III, sequentially connected to the lower reset sliding sleeve, packer I, middle reset sliding sleeve, packer II, and packer III. Device III, high-pressure well-washing valve, and tubing thread connection are included. The water injection process tubing is lowered into the casing. The upper end of the tubing is suspended above the lower four-way valve at the water injection wellhead via a self-sealing core. The ball-dropping blowout preventer is located above the test gate at the water injection wellhead. The casing annular pressure self-balancing device is connected to the left-side production valve. The lower balance hole, drain hole I, and inlet hole I of the casing annular pressure self-balancing device are connected to the left-side casing gate at the water injection wellhead via a connecting pipe.

[0018] Furthermore, the seat seal sleeve is cylindrical, with its outer cylinder I having a sealed bottom and 2 to 4 symmetrical circulation holes at the bottom. The upper part of the circulation holes has an inner cylinder I, and a pin I is provided between the inner cylinder I and the outer cylinder I. The upper part has external threads.

[0019] Furthermore, the lower reset sleeve is cylindrical, with external threads at both the upper and lower ends of the outer cylinder II. The lower part of the outer cylinder II has an outer cylinder water injection hole, and the inner cylinder II is located inside the outer cylinder II. A limiting ball is located at the lower part between the two. A small metal ball is located on the small ball seat at the lower part of the inner cylinder II. The inner cylinder II wall above the small metal ball has symmetrical inner cylinder water injection holes. A large metal ball is located on the large ball seat at the upper part of the inner cylinder II. A blocking ring is located at the upper end of the inner cylinder II, and a threaded limiting pressure cap is located at the upper end of the outer cylinder II.

[0020] Furthermore, the upper inner wall of the lower outer cylinder water injection hole of the outer cylinder II is provided with an inner blind hole, and a limiting spring and a limiting ball are provided in the inner blind hole.

[0021] Furthermore, the lower outer wall of the inner cylinder II is provided with a limiting hole corresponding to the position of the limiting ball.

[0022] Furthermore, the middle reset sleeve, upper reset sleeve, and lower reset sleeve have the same structure.

[0023] Furthermore, the high-pressure resistant well-washing valve is cylindrical, with external threads at both the upper and lower ends of the working cylinder, a flared hole in the middle, the larger hole of the flared hole facing inward, a sealing plug inside the flared hole, a sealing ring between the flared hole and the sealing plug, and a pin between the outer flared hole and the sealing plug.

[0024] Furthermore, the oil jacket annular pressure self-balancing device is a combination of a transverse cylindrical self-balancing hydraulic cylinder and a vertical "L"-shaped connecting pipe. The self-balancing hydraulic cylinder is provided with a drain valve in the upper middle part. The lower part of the self-balancing hydraulic cylinder is provided with a balance hole, a drain hole I, and an inlet hole I in sequence from left to right. The lower parts of the balance hole, drain hole I, and inlet hole I are connected to the upper part of the connecting pipe. The self-balancing hydraulic cylinder is provided with a constant pressure spring on the left side and a balance piston on the right side. The left end of the balance piston is provided with a drain hole II, and the right end of the balance piston is provided with an "L"-shaped inlet hole II.

[0025] A resettable, segmented, pressure-driven water injection process:

[0026] ①. Connecting the water injection tubing string: from bottom to top, seated sliding sleeve + lower reset sliding sleeve + packer I + middle reset sliding sleeve + packer II + upper reset sliding sleeve + packer III + high-pressure resistant well washing valve + tubing;

[0027] ②. Lowering the water injection string: Lower the water injection string into the casing to the oil layer position. The lower reset sleeve, middle reset sleeve, and upper reset sleeve are all in the closed state, and the seated sleeve is in the open state.

[0028] ③. Sealing: Insert the small metal ball of the lower reset sleeve. The ball falls into the ball seat, and the oil pipe is pressurized from the production valve to the set sealing pressure of packer I, thus completing the sealing of packer I.

[0029] ④. Opening the lower reset sleeve and closing the seated sleeve: Continue pressurizing to cut off pin I of the seated sleeve. The inner cylinder II of the lower reset sleeve pushes the inner cylinder I of the seated sleeve to fall. The inner cylinder II squeezes the limiting ball and opens the limiting mechanism. After the reset inner cylinder II and the seated sleeve inner cylinder I are in place, the seated sleeve inner cylinder I closes the circulation hole and closes the well washing channel. The water injection hole of the lower reset sleeve inner cylinder is aligned with the water injection hole of the outer cylinder, and the water injection channel is opened. The opening of the lower reset sleeve and the closing of the seated sleeve are completed. The next step is to inject water into the water injection layer III as required.

[0030] ⑤. Operate the middle reset sliding sleeve and the upper reset sliding sleeve in the same way as above to realize the water injection of water injection layer II and water injection layer I;

[0031] ⑥. Recovery and Reset of the Lower Reset Sleeve: The large metal ball of the lower reset sleeve is deployed to recover the sleeve. Under pressure, the large metal ball is pushed into the large ball seat at the upper part of the inner cylinder II of the lower reset sleeve. The blocking ring seals and blocks the large metal ball. By controlling the pressure release, the inner cylinder II is forced to move upward and into position, blocking the water injection hole of the outer cylinder, closing the water injection channel. The limiting ball falls back into the limiting hole, locking the inner cylinder II. The lower reset sleeve returns to its initial state, completing the recovery and reset of the sleeve. The large and small metal balls are completely melted under the action of the high-temperature liquid in the well.

[0032] ⑦. Other layer opening and closing: By inserting the corresponding large and small metal balls, the opening and closing operation of the corresponding reset sliding sleeve can be realized, so as to achieve the purpose of multi-layer segmented injection;

[0033] ⑧. Connect the high-pressure well-washing valve above the packer and put it in the closed and locked state. Rely on the two sealing rings to seal the pressure from the tubing. After water injection is completed, when the water injection string in the well is to be pulled out, release the pressure of the tubing, pressurize from the right casing gate valve, cut the pin, remove the sealing plug, connect the tubing and the annular space of the casing, and complete the establishment of the well-washing channel.

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] This invention is applicable to layered and segmented pressure-driven water injection in oilfield water injection wells, which can meet the needs of layered and segmented water injection in formations. The injection tubing can be reused, improving the qualification rate of the injection layer and saving operating costs.

[0036] In the description of this invention, it should be understood that the terms "coaxial," "bottom," "one end," "top," "middle," "other end," "upper," "side," "top," "inner," "front," "center," "both ends," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0037] Furthermore, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first," "second," "third," or "fourth" may explicitly or implicitly include at least one of those features.

[0038] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "setting," "connection," "fixing," "screw connection," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components or the interaction between two components. Unless otherwise explicitly limited, those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Throughout the drawings, the same reference numerals are used to denote the same components. The drawings are only used to illustrate preferred embodiments and are not intended to limit the present invention. Obviously, the drawings described below are only some embodiments of the present invention. Through the detailed description of preferred embodiments, various other advantages and benefits will become clear to those skilled in the art. Other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a partial sectional view of the drive mechanism of the present invention.

[0041] Figure 2 This is a schematic diagram of the main sectional view of the seat seal sleeve 1 of the present invention.

[0042] Figure 3 This is a schematic diagram of the main sectional view of the lower reset sleeve 2 of the present invention.

[0043] Figure 4This is a schematic diagram of the main view of the high-pressure well-washing valve 8 of the present invention.

[0044] In the diagram: 0. Casing; 1. Sealing sleeve; 1-1. Inner cylinder I; 1-1-1. Inner cylinder water injection hole; 1-2. Pin I; 1-3. Circulation hole; 1-4. Outer cylinder I; 2. Lower reset sleeve; 2-1. Outer cylinder II; 2-2. Large ball seat; 2-3. Inner cylinder II; 2-4. Small ball seat; 2-5. Limiting cap; 2-6. Blocking ring; 2-7. Large metal ball; 2-8. Limiting ball; 2-9. Limiting spring; 2-9-1. Inner blind hole; 2-9-2. Limiting hole; 2-10. Small metal ball; 2-11. Outer cylinder water injection hole; 3. Packer I; 4. Middle reset sleeve; 5. Packer II; 6. Upper reset sleeve; 7. Packer III; 8. High-pressure resistant well washing valve; 8-1. Sealing... 8-2. Sealing ring, 8-3. Sealing plug, 8-4. Working cylinder; 9. Tubing, 10. Water injection wellhead, 10-0. Large four-way valve, 10-1. Casing gate valve, 10-2. Main valve, 10-3. Production valve, 10-4. Test gate valve, 11. Ball-dropping blowout preventer; 12. Oil casing annulus pressure self-balancing device, 12-0. Drain hole II, 12-1. Connecting pipe, 12-2. Constant pressure spring, 12-3. Self-balancing hydraulic cylinder, 12-4. Drain valve, 12-5. Balance piston, 12-6. Inlet hole II, 12-7. Inlet hole I, 12-8. Drain hole I, 12-9. Balance hole; 13. Water injection layer I, 14. Water injection layer II, 15. Water injection layer III. Detailed Implementation

[0045] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a resettable, segmented pressure-driven water injection process proposed by the present invention. In the following description, different "embodiments" or "embodiments" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0046] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three relationships, such as A and / or B. Specifically, it can mean that A and B can be included at the same time, A can exist alone, or B can exist alone, and any of the above three situations can be met.

[0047] The implementation of the present invention will be further described below with reference to the accompanying drawings: Example 1

[0048] like Figure 1As shown in Figure 4, a resettable, segmented pressure-driven water injection process string includes: casing 0, seated sliding sleeve 1, lower reset sliding sleeve 2, packer I 3, middle reset sliding sleeve 4, packer II 5, upper reset sliding sleeve 6, packer III 7, high-pressure resistant well-washing valve 8, tubing 9, water injection wellhead 10, ball-dropped blowout preventer 11, and casing annular pressure self-balancing device 12; characterized in that: the resettable, segmented pressure-driven water injection process string, from bottom to top, consists of seated sliding sleeve 1 sequentially connected to lower reset sliding sleeve 2, packer I 3, middle reset sliding sleeve 4, packer II 5, upper reset sliding sleeve 6, and packer III 7. The high-pressure well-washing valve 8 and tubing 9 are threaded together. This water injection process string is lowered into the casing 0. The upper end of the tubing 9 is suspended above the lower large four-way valve 10-0 of the water injection wellhead 10 via a self-sealing core. The ball-dropping blowout preventer 11 is located above the test gate 10-4 of the water injection wellhead 10. The annular pressure self-balancing device 12 is connected to the left-side production valve 10-3. The lower balancing hole 12-9, drain hole I 12-8, and inlet hole I 12-7 of the annular pressure self-balancing device 12 are connected to the left-side casing gate valve 10-1 of the water injection wellhead 10 via a connecting pipe 12-1. These different tools are connected with tubing 9 of a certain length according to design requirements to form a downhole pressure-driven injection string.

[0049] Specifically, the sealing sleeve 1 is cylindrical, with its outer cylinder I1-4 having a sealed bottom and two symmetrical circulation holes 1-3 at the bottom. An inner cylinder I1-1 is located above the circulation holes 1-3, and a pin I1-2 is provided between the inner cylinder I1-1 and the outer cylinder I1-4. The upper part of the inner cylinder I1-1 has external threads. The circulation holes 1-3 are exposed on the sealing sleeve 1, facilitating well flushing after it is lowered into the well.

[0050] Specifically, the lower reset sleeve 2 is cylindrical, and the outer cylinder II2-1 has external threads at both the upper and lower ends. The lower part of the outer cylinder II2-1 has an outer cylinder water injection hole 2-11. The inner cylinder II2-3 is located inside the outer cylinder II2-1, and a limiting ball 2-8 is located at the lower part between the two. The lower part of the inner cylinder II2-3 has a small metal ball 2-10 on the small ball seat 2-4. The inner cylinder II2-3 wall above the small metal ball 2-10 has symmetrical inner cylinder water injection holes 1-1-1. The upper part of the inner cylinder II2-3 has a large metal ball 2-7 on the large ball seat 2-2. The upper end of the inner cylinder II2-3 has a blocking ring 2-6. The upper end of the outer cylinder II2-1 has a threaded limiting cap 2-5.

[0051] Specifically, the upper inner wall of the lower outer cylinder water injection hole 2-11 of the outer cylinder II 2-1 is provided with an inner blind hole 2-9-1, and a limiting spring 2-9 and a limiting ball 2-8 are provided in the inner blind hole 2-9-1.

[0052] Specifically, the lower outer wall of the inner cylinder II 2-3 is provided with a limiting hole 2-9-2 corresponding to the position of the limiting ball 2-8.

[0053] Specifically, the structures of the middle reset sleeve 4 and the upper reset sleeve 6 are the same as those of the lower reset sleeve 2. The diameter of the small metal ball in the middle reset sleeve 4 is equal to the diameter of the large metal ball in the lower reset sleeve 2; the diameter of the small metal ball in the upper reset sleeve 6 is equal to the diameter of the large metal ball in the middle reset sleeve 4.

[0054] The inner cylinder II2-3 of the aforementioned lower reset sleeve 2 is installed inside the outer cylinder II2-1. The limiting ball 2-8, under the action of the limiting spring 2-9, is pressed into the limiting hole 2-9-2, thereby fixing the inner cylinder II2-3 and preventing movement. The inner cylinder II2-3 is fixed inside the outer cylinder II2-1 by the limiting cap 2-5. The large metal ball 2-7 and the small metal ball 2-10 are high-temperature soluble metal balls.

[0055] The aforementioned lower reset sleeve 2 has four states: First, the inner cylinder II 2-3 blocks the outer cylinder water injection hole 2-11, which is the initial closed state, and also the reset state; Second, when the small metal ball 2-10 is inserted into the inner cylinder II 2-3, it pushes open the limiting ball 2-8, thereby opening the limiting mechanism and aligning the inner cylinder water injection hole 1-1-1 with the outer cylinder water injection hole 2-11, which is the open state; Third, when the large metal ball 2-7 is inserted and squeezed into the large ball seat 2-2, the limiting cap 2-5 seals and blocks the large metal ball 2-7, and by controlling the pressure release, the inner cylinder II 2-3 is forced to move upward, which is the recovery state; Fourth, the inner cylinder II 2-3 moves upward and blocks the outer cylinder water injection hole 2-11, the limiting ball 2-8 falls back into the limiting hole 2-9-2, locking the inner cylinder II 2-3, and the reset sleeve returns to the initial state, which is also the reset state.

[0056] Specifically, the high-pressure well-washing valve 8 is cylindrical, with external threads at both the upper and lower ends of the working cylinder 8-4, and a flared hole in the middle. The larger hole of the flared hole faces inward, and a sealing plug 8-2 is provided inside the flared hole. A sealing ring 8-1 is provided between the flared hole and the sealing plug 8-2, and a pin 8-3 is provided between the outer flared hole and the sealing plug 8-2.

[0057] Specifically, the oil jacket annular pressure self-balancing device 12 is a combination of a transverse cylindrical self-balancing hydraulic cylinder 12-3 and a vertical "L"-shaped connecting pipe 12-1. A drain valve 12-4 is located in the upper middle part of the self-balancing hydraulic cylinder 12-3. From left to right, the lower part of the self-balancing hydraulic cylinder 12-3 has a balance hole 12-9, a drain hole I 12-8, and an inlet hole I 12-7. The lower parts of the balance hole 12-9, drain hole I 12-8, and inlet hole I 12-7 are connected to the upper part of the connecting pipe 12-1. A pressure-regulating spring 12-2 is located on the left side of the self-balancing hydraulic cylinder 12-3, and a balance piston 12-5 is located on the right side. A drain hole II 12-0 is located at the left end of the balance piston 12-5, and an "L"-shaped inlet hole II 12-6 is located at the right end of the balance piston 12-5. The pressure limit value is set by adjusting the pressure-regulating spring 12-2.

[0058] The steps of a resettable, stratified, segmented pressure-driven water injection process are as follows:

[0059] Step 1. Connect the water injection tubing string: from bottom to top, seated sliding sleeve 1 + lower reset sliding sleeve 2 + packer I 3 + middle reset sliding sleeve 4 + packer II 5 + upper reset sliding sleeve 6 + packer III 7 + high pressure resistant well washing valve 8 + tubing 9;

[0060] Step 2. Lowering the water injection string: Lower the water injection string into the casing 0 to the oil layer position. The lower reset sleeve 2, the middle reset sleeve 4, and the upper reset sleeve 6 are all in the closed state, and the seated sleeve 1 is in the open state.

[0061] Step 3. Sealing: Insert the small metal ball 2-10 of the lower reset sleeve 2. The ball falls into the ball seat 2-4. Pressurize the oil pipe 9 from the production valve 10-3 to the set sealing pressure of packer I3 to complete the sealing of packer I3.

[0062] Step 4. Open the lower reset sleeve 2 and close the seated sleeve 1: Continue pressurizing, cut the pin I1-2 of the seated sleeve 1, the inner cylinder II2-3 of the lower reset sleeve 2 pushes the inner cylinder I1-1 of the seated sleeve 1 to fall, the inner cylinder II2-3 squeezes the limiting ball 2-8, opens the limiting mechanism, after the reset inner cylinder II2-3 and the inner cylinder I1-1 of the seated sleeve 1 are in place, the inner cylinder I1-1 of the seated sleeve 1 closes the circulation hole 1-3, closes the well washing channel, the water injection hole 1-1-1 of the inner cylinder of the lower reset sleeve 2 is aligned with the water injection hole 2-11 of the outer cylinder, the water injection channel is opened, the opening of the lower reset sleeve 2 and the closing of the seated sleeve 1 are completed, the next step is to inject water into the water injection layer III15 as required;

[0063] Step 5. Operate the middle reset sliding sleeve 4 and the upper reset sliding sleeve 6 in the same way as above to realize the water injection of water injection layer II 14 and water injection layer I 13;

[0064] Step 6. Recovery and Reset of Lower Reset Sleeve 2: The large metal ball 2-7 of the lower reset sleeve 2 is inserted to recover the sleeve. Under pressure, the large metal ball 2-7 is pushed into the large ball seat 2-2 at the top of the inner cylinder II 2-3 of the lower reset sleeve 2. The blocking ring 2-6 seals and blocks the large metal ball 2-7. By controlling the pressure release, the inner cylinder II 2-3 is forced to move upward and into place, blocking the water injection hole 2-11 of the outer cylinder and closing the water injection channel. The limiting ball 2-8 falls back into the limiting hole 2-9-2, locking the inner cylinder II 2-3. The lower reset sleeve 2 returns to its initial state, completing the recovery and reset of the lower reset sleeve 2. The large metal ball 2-7 and the small metal ball 2-10 are completely melted under the action of the high-temperature liquid in the well.

[0065] Step 7. Opening and closing of other layers: Inserting the corresponding large and small metal balls can realize the opening and closing operation of the corresponding reset sliding sleeve, so as to achieve the purpose of multi-layer segmented injection;

[0066] Step 8. Connect the high-pressure well-washing valve 8 to the packer Ⅲ7 or above, and put it in the closed and locked state. Rely on the two sealing rings 8-1 to seal the pressure from the tubing 9. After water injection is completed, when the water injection string in the well is to be pulled out, release the pressure of the tubing 9, pressurize from the right casing gate valve 10-1, cut the pin 8-3, remove the sealing plug 8-2, connect the tubing 9 and the annular space of the casing, and complete the establishment of the well-washing channel.

[0067] Working process of oil jacket annular pressure self-balancing device 12:

[0068] (1) Connect the right end of the oil casing annular pressure self-balancing device 12 to the production valve 10-3 of the water injection wellhead 10, and the lower end to the left casing gate valve 10-1. Open the production valve 10-3, the casing gate valve 10-1 and the drain valve 12-4.

[0069] (2) Water is injected into oil pipe 9, and the pressure in oil pipe 9 gradually increases;

[0070] (3) Pressure self-balancing during the pressurization process: When the pressure in oil pipe 9 exceeds the pressure set by the constant pressure spring 12-2, the pressure pushes the balance piston 12-5, compressing the constant pressure spring 12-2 to the left. When the inlet hole I 12-7 and the inlet hole II 12-6 are aligned, the inlet channel is opened, thus realizing liquid inlet into the casing 0 and increasing the casing pressure. At the same time, the liquid enters the self-balancing liquid cylinder 12-3 through the connecting pipe 12-1 until the pressure difference between the oil and casing stabilizes. The stable pressure is the pressure set by the constant pressure spring 12-2, and it no longer changes with the increase of oil pressure and casing pressure. Thus, the automatic balance of the annular pressure of the oil and casing is achieved during the pressurization process.

[0071] (4) Pressure self-balancing during pressure reduction: When water injection in tubing 9 stops, the pressure in tubing 9 gradually decreases as the oil layer pressure diffuses. The constant pressure spring 12-2 pushes the balance piston 12-5 to the right, aligning drain hole I 12-8 and drain hole II 12-0, opening the drain channel. As excess liquid is discharged, the casing annular pressure decreases. When the pressure set by the constant pressure spring 12-2 plus the casing pressure equals the oil pressure, establishing a new balance, the balance piston 12-5 returns to the left, closing drain hole II 12-0, thus completing the automatic balance of the oil-casing annular pressure during the pressure reduction process. As the oil pressure continues to decrease, the self-balancing piston repeats the above actions to complete a new pressure balance.

[0072] Working principle of the invention:

[0073] By deploying small and large metal balls of different diameters in conjunction with the reset sleeve, the opening and closing operation of the reset sleeve is controlled, enabling multiple repeated layered water injection functions of the tubing string, thereby meeting the requirements of pressure-driven injection (large diameter, high temperature resistance, and reusability). The pressure-balancing casing 12 enables automatic pressurization of the casing and automatically adjusts according to the oil pressure, ensuring sufficient pressure differential for the packer slips to pass through the wellhead blowout preventer, thus enabling the deployment of small and large metal balls of different diameters during the water injection process. The use of the seated sliding sleeve 1 enables a resettable, layered, segmented pressure-driven water injection process that connects the oil and casing circulation channels during downhole operation and closes them during water injection. The use of the high-pressure resistant well-washing valve 8 enables well-washing functionality of the tubing string during tripping operations.

[0074] While preferred embodiments of the present invention have been described above, those skilled in the art, upon learning the basic inventive concept, can make further changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the present invention without departing from its spirit and scope. Thus, if these modifications and modifications fall within the scope of the claims and their equivalents, the present invention also intends to include these modifications and modifications.

Claims

1. A resettable, segmented pressure-driven water injection process tubing, comprising: The casing (0), seated sliding sleeve (1), lower reset sliding sleeve (2), packer I (3), middle reset sliding sleeve (4), packer II (5), upper reset sliding sleeve (6), packer III (7), high-pressure resistant well-washing valve (8), tubing (9), water injection wellhead (10), ball-dropped blowout preventer (11), and oil casing annular pressure self-balancing device (12) are characterized in that: the resettable layered and segmented pressure-driven water injection process tubing is connected from bottom to top by the seated sliding sleeve (1) in sequence with the lower reset sliding sleeve (2), packer I (3), middle reset sliding sleeve (4), packer II (5), and upper reset sliding sleeve (6). Packer III (7), high-pressure well-washing valve (8), and tubing (9) are threaded together. The water injection process tubing is lowered into the casing (0). The upper end of the tubing (9) is suspended above the lower large cross-connector (10-0) of the water injection wellhead (10) by a self-sealing core. The ball-dropping blowout preventer (11) is located above the test gate (10-4) of the water injection wellhead (10). The annular pressure self-balancing device (12) is connected to the left-side production valve (10-3). The lower balance hole (12-9), drain hole I (12-8), and inlet hole I (12-9) of the annular pressure self-balancing device (12) are connected together. 7) Connected to the left casing gate (10-1) of the injection wellhead (10) via a connecting pipe (12-1); the seated sliding sleeve (1) is cylindrical, its outer cylinder I (1-4) is provided with a sealed bottom, and the lower part is provided with 2 to 4 symmetrical circulation holes (1-3), the upper part of the circulation hole (1-3) is provided with an inner cylinder I (1-1), and a pin I (1-2) is provided between the inner cylinder I (1-1) and the outer cylinder I (1-4), and the upper part is provided with an external thread; the lower reset sliding sleeve (2) is cylindrical, the upper and lower ends of the outer cylinder II (2-1) are provided with external threads, and the lower part of the outer cylinder II (2-1) is provided with an outer cylinder injection Water hole (2-11), inner cylinder II (2-3) is provided inside outer cylinder II (2-1), a limiting ball (2-8) is provided at the lower part between the two, a small metal ball (2-10) is provided on the small ball seat (2-4) at the lower part of inner cylinder II (2-3), an inner cylinder water injection hole (1-1-1) is symmetrically provided on the upper part of inner cylinder II (2-3) wall above the small metal ball (2-10), a large metal ball (2-7) is provided on the large ball seat (2-2) at the upper part of inner cylinder II (2-3), a blocking ring (2-6) is provided at the upper end of inner cylinder II (2-3), and a threaded limiting cap (2-5) is provided at the upper end of outer cylinder II (2-1).

2. The repositionable, segmented pressure-driven water injection process tubing according to claim 1, characterized in that: The lower outer cylinder II (2-1) has an inner blind hole (2-9-1) on the upper inner wall of the water injection hole (2-11). The inner blind hole (2-9-1) is provided with a limiting spring (2-9) and a limiting ball (2-8).

3. The resettable, segmented pressure-driven water injection process tubing according to claim 2, characterized in that: The lower outer wall of the inner cylinder II (2-3) is provided with a limiting hole (2-9-2) corresponding to the position of the limiting ball (2-8).

4. The repositionable layered segmented pressure-driven water injection process tubing according to claim 3, characterized in that: The high-pressure well-washing valve (8) is cylindrical. The upper and lower ends of the working cylinder (8-4) are provided with external threads, and the middle is provided with a horn hole. The larger hole of the horn hole faces inward, and a sealing plug (8-2) is provided inside the horn hole. A sealing ring (8-1) is provided between the horn hole and the sealing plug (8-2), and a pin (8-3) is provided between the outer horn hole and the sealing plug (8-2).

5. A resettable, segmented pressure-driven water injection process tubing string according to claim 1, characterized in that: The oil jacket annular pressure self-balancing device (12) is a combination of a transverse cylindrical self-balancing hydraulic cylinder (12-3) and a vertical "L"-shaped connecting pipe (12-1). The self-balancing hydraulic cylinder (12-3) is provided with a drain valve (12-4) in the upper middle part. The lower part of the self-balancing hydraulic cylinder (12-3) is provided with a balance hole (12-9), a drain hole I (12-8), and an inlet hole I (12-7) from left to right. The lower part of the balance hole (12-9), the drain hole I (12-8), and the inlet hole I (12-7) are connected to the upper part of the connecting pipe (12-1). The self-balancing hydraulic cylinder (12-3) is provided with a constant pressure spring (12-2) on the left side and a balance piston (12-5) on the right side. The balance piston (12-5) is provided with a drain hole II (12-0) on the left end and an "L"-shaped inlet hole II (12-6) on the right end.

6. A resettable, segmented pressure-driven water injection process method, implemented using the resettable, segmented pressure-driven water injection process tubing as described in claim 4, comprising the following steps: Step 1. Connect the water injection tubing string: from bottom to top, seated sliding sleeve (1) + lower reset sliding sleeve (2) + packer I (3) + middle reset sliding sleeve (4) + packer II (5) + upper reset sliding sleeve (6) + packer III (7) + high pressure resistant well washing valve (8) + tubing (9). Step 2. Lowering the water injection string: Lower the water injection string into the casing (0) to the oil layer position. The lower reset sleeve (2), the middle reset sleeve (4), and the upper reset sleeve (6) are all in the closed state, and the seated sleeve (1) is in the open state. Step 3. Sealing: Insert the small metal ball (2-10) into the lower reset sleeve (2), the ball falls into the ball seat (2-4), and the oil pipe (9) is pressurized from the production valve (10-3) to the set sealing pressure of packer I (3) to complete the sealing of packer I (3); Step 4. Open the lower reset sleeve (2) and close the seated sleeve (1): Continue to pressurize and cut the pin I (1-2) of the seated sleeve (1). The inner cylinder II (2-3) of the lower reset sleeve (2) pushes the inner cylinder I (1-1) of the seated sleeve (1) to fall. The inner cylinder II (2-3) squeezes the limiting ball (2-8) and opens the limiting mechanism. After the inner cylinder II (2-3) and the inner cylinder I (1-1) of the seated sleeve (1) are in place, the inner cylinder I (1-1) of the seated sleeve (1) closes the circulation hole (1-3) and closes the well washing channel. The water injection hole (1-1-1) of the inner cylinder of the lower reset sleeve (2) is aligned with the water injection hole (2-11) of the outer cylinder. The water injection channel is opened, and the opening of the lower reset sleeve (2) and the closing of the seated sleeve (1) are completed. The next step is to inject water into the water injection layer III (15) as required. Step 5. Operate the middle reset sleeve (4) and the upper reset sleeve (6) in the same way as above to realize the water injection of water injection layer II (14) and water injection layer I (13); Step 6. Recovery and Reset of Lower Reset Sleeve (2): The large metal ball (2-7) of the lower reset sleeve (2) is put into the recovery sleeve. Under the pressure, the large metal ball (2-7) is squeezed into the large ball seat (2-2) at the top of the inner cylinder II (2-3) of the lower reset sleeve (2). The blocking ring (2-6) seals and blocks the large metal ball (2-7). By controlling the pressure release, the inner cylinder II (2-3) is forced to move upward and into place, blocking the water injection hole (2-11) of the outer cylinder, closing the water injection channel. The limiting ball (2-8) falls back into the limiting hole (2-9-2), locking the inner cylinder II (2-3). The lower reset sleeve (2) returns to the initial state, completing the recovery and reset of the sleeve. The large metal ball (2-7) and the small metal ball (2-10) are completely melted under the action of the high temperature liquid in the well. Step 7. Opening and closing of other layers: Inserting the corresponding large and small metal balls can realize the opening and closing operation of the corresponding reset sliding sleeve, so as to achieve the purpose of multi-layer segmented injection; Step 8. Connect the high-pressure well-washing valve (8) to packer III (7) and lock it in a closed state. Use two sealing rings (8-1) to seal the pressure from the tubing (9). After water injection is completed, when the water injection string in the well is to be pulled out, release the pressure of the tubing (9), pressurize from the right casing gate (10-1), cut off the pin (8-3), remove the sealing plug (8-2), connect the tubing (9) and the annular space of the casing, and complete the establishment of the well-washing channel.

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