Water injection well downhole pressure control sand flow prevention pipe string

Abstract

The application discloses a downhole pressure control and sand spitting prevention pipe column for a water injection well, which comprises, from top to bottom, a tubing, a pipe-in-pipe type water injection packer, a tubing short circuit, a one-way valve, a sand settling tail pipe and a plug; wherein the pipe-in-pipe type water injection packer comprises a center pipe, a sealing cylinder, a connecting cylinder, a slip mechanism, a sealing rubber cylinder group, a rubber cylinder support seat and a support cylinder; the one-way valve is connected to the bottom end of the pipe-in-pipe type water injection packer through the tubing short circuit, and a flow hole communicating with a well bore is formed in the side wall of one side of the one-way valve; the sand settling tail pipe is connected to the bottom end of the one-way valve to collect sand in water and a bottom plug; and the plug is sealed to the opening at the bottom end of the sand settling tail pipe. The downhole pressure control and sand spitting prevention pipe column for the water injection well can realize downhole pressure control of the water injection well, can normally lift and lower the pipe column under conventional conditions, can prevent sand from being produced from the formation, can prolong a pipe inspection period, and can improve the completion rate and the construction efficiency of the water injection well construction.

Description

Technical Field

[0001] This invention relates to the field of oil and gas production technology, and in particular to a downhole pressure control and sand-prevention tubing string for water injection wells. Background Technology

[0002] In the middle and late stages of oilfield development, as the inter-layer contradictions of water injection wells become increasingly serious, the upward work-up rate of water injection wells increases, and the upward work-up problem of high-pressure water injection wells is particularly prominent.

[0003] Currently, pressure control technologies for high-pressure water injection wells both domestically and internationally include shut-in depressurization technology, high-density well-killing hydraulic well technology, and live-operation technology. Among these, shut-in depressurization technology suffers from prolonged workover cycles due to the inability to quickly release pressure at the wellhead, and some injection wells experience severe sand release after pressure release, affecting injection efficiency. High-density well-killing hydraulic well technology, on the other hand, can cause formation contamination and reservoir damage after well killing. While live-operation technology can meet the operational needs of various high-pressure water injection wells, it has high requirements for the well site, high operating costs for live-operation equipment, and is characterized by high construction difficulty and long construction periods.

[0004] Therefore, based on the various problems existing in the above-mentioned technologies, it is necessary to propose a pressure control and sand-prevention technology to overcome the existing high-pressure water injection wells and realize efficient well workover operations in water injection wells, using downhole pressure control and sand-prevention tubing. Summary of the Invention

[0005] The purpose of this invention is to provide a downhole pressure control and sand-prevention string for water injection wells that can overcome the shortcomings of existing pressure control and sand-prevention technologies for high-pressure water injection wells and achieve efficient well workover operations.

[0006] Therefore, the technical solution of the present invention is as follows:

[0007] A downhole pressure control and sand-prevention tubing string for water injection wells includes, from top to bottom, tubing, a plug-in type water injection packer, a tubing connector, a check valve, a sand-suppressing tailpipe, and a plug; wherein...

[0008] The insert-type water-filled packer includes a central insert, a sealing cylinder, a connecting cylinder, a slip mechanism, a sealing rubber sleeve assembly, a rubber sleeve support base, and a support cylinder. The central insert consists of an upper connector, an insert body, and an annular sleeve. The upper connector is connected to the top of the insert body, and its outer diameter is larger than that of the insert body, forming an annular step on the outer wall of the connection point. The annular sleeve is fitted onto the upper outer wall of the insert body in a coaxial manner, and its top end is connected and fixed to the insert body as a single unit via an inner annular boss. The bottom end of the insert body is sealed with a bottom plug. The sealing cylinder is fitted onto the outside of the annular sleeve, and there is an annular gap between its upper part and the insert body. The gap and lower part fit into the annular sleeve; the connecting cylinder is fitted onto the outside of the sealing cylinder with an annular gap between it and the sealing cylinder, and its top end is inserted into the outside of the upper connector of the central insertion tube; the top end of the sealing cylinder is located below the annular step on the outer wall of the central insertion tube, and its top outer wall has an outer annular boss that fits into the inner wall of the connecting cylinder, and its top inner wall has an inner annular boss that fits into the outer wall of the insertion tube body, so that an annular cavity is formed between the insertion tube body and the sealing cylinder; multiple radial flow holes communicating with the annular cavity are opened circumferentially on the top side wall of the insertion tube body; the sealing cylinder is connected to the insertion tube through the circumferentially arranged inner annular boss. Multiple shear pins connect the main bodies; the slip mechanism consists of a slip seat, slips, and slip blocks; the slip seat is composed of a conical cylinder and a straight cylinder connected sequentially from top to bottom; the lower inner wall of the conical cylinder has an inner annular boss, and the middle outer wall of the straight cylinder has an outer annular boss; the top of the slip seat is fixed to the bottom of the connecting cylinder, and the bottom of the annular sleeve of the central insertion tube is pressed against the upper end face of its inner annular boss; the slip block is a conical cylinder with an outer diameter that gradually increases from top to bottom, which is fitted onto the outside of the slip seat and pressed against the upper end face of the outer annular boss of the slip seat; the slip is fitted onto the outside of the slip seat, and its top inner wall and bottom inner wall are respectively machined into... A conical surface that mates with the outer wall of the conical cylinder and the outer wall of the slip block; a sealing rubber sleeve assembly fitted onto the lower outer wall of the slip seat, with its top end abutting against the lower end face of the outer annular boss of the slip seat; a support cylinder is a cylinder with an upper inner diameter larger than its lower inner diameter, with an annular gap between its upper part and the insertion tube body, and its top end inserted into the outer side of the bottom end of the slip seat, with an annular step in its middle part that is spaced from the bottom end of the slip seat, and its lower sealing sleeve fitted onto the outer side of the lower part of the insertion tube body; a rubber sleeve support seat fitted onto the outer side of the top end of the support cylinder, with the inner annular boss on its top inner wall pressed against the upper end face of the support cylinder, so that the bottom end of the sealing rubber sleeve assembly is pressed against the rubber sleeve support seat;

[0009] The check valve is connected to the bottom of the plug-in water injection packer via a short-circuit tubing. A flow hole communicating with the wellbore is opened on one side wall of the check valve. The sand settling tailpipe is connected to the bottom of the check valve to collect sand and bottom plug in the water. The plug is sealed at the bottom opening of the sand settling tailpipe.

[0010] Furthermore, the check valve includes an upper check valve connector, a flow pipe, a check valve body, and a lower check valve connector; wherein, the flow pipe is a pipe body with an inner cavity having, from top to bottom, an upper straight channel, a sloping channel, a connecting channel, an eccentric channel group, and a lower straight channel; the upper straight channel is connected to the outside of the pipe body; the sloping channel is a channel that opens axially from the bottom of the upper straight channel and whose inner diameter gradually decreases from top to bottom, and the sloping channel is connected to the upper straight channel; the connecting channel is a straight channel that opens axially from the bottom of the sloping channel, and the connecting channel is connected to the sloping channel; the eccentric channel group consists of two parallel eccentric channels, a first eccentric channel and a second eccentric channel, opening axially from the bottom of the connecting channel, the first eccentric channel being located directly below the bottom of the sloping channel and connected to the connecting channel; the top of the second eccentric channel is connected to... The connecting channels are connected and closed at the bottom; the lower straight channel is a straight channel opened axially from the bottom of the first eccentric channel, and the lower straight channel is connected to the first eccentric channel and the outside of the pipe body respectively; two flow channels connected to the outside of the pipe body are spaced apart from top to bottom on the side wall of the second eccentric channel; the one-way valve body is composed of a first ball seat, a sealing ball, a second ball seat and a spring arranged sequentially from top to bottom in the second eccentric channel; the first ball seat is an annular body fixed on the inner wall of the top of the second eccentric channel, and its bottom surface is machined into a conical surface that matches the sealing ball; the second ball seat is a cylindrical block with a conical surface machined on the top surface; the spring is arranged vertically in a compressed state, and its two ends are fixed to the bottom of the second eccentric channel and the bottom surface of the second ball seat respectively; the upper connector of the one-way valve is connected in the upper straight channel, and the lower connector of the one-way valve is connected in the lower straight channel.

[0011] Furthermore, a double sealing ring is provided on the outer wall of the outer annular boss of the sealing cylinder to form a seal between it and the inner wall of the connecting cylinder. A double sealing ring is provided on the inner wall of the inner annular boss of the sealing cylinder to form a seal between it and the outer wall of the insertion tube body. A double sealing ring is provided on the outer wall of the bottom end of the connector on the central insertion tube to form a seal between it and the inner wall of the connecting cylinder.

[0012] Furthermore, the sealing rubber sleeve assembly consists of three sets of rubber sleeves, and a spacer ring is provided between adjacent rubber sleeves.

[0013] Furthermore, a double sealing ring is installed between the upper straight channel and the upper connector of the check valve to form a sealed connection between the two; a double sealing ring is also installed between the lower straight channel and the lower connector of the check valve to form a sealed connection between the two.

[0014] Furthermore, the length of the oil pipe short connection is greater than 1m.

[0015] Compared with existing technologies, this downhole pressure control and sand-prevention tubing string for water injection wells can achieve downhole pressure control, and the tubing string can be pulled out and pulled out normally under normal conditions, preventing sand production in the formation, extending the inspection cycle, and improving the completion rate and efficiency of water injection well construction. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the downhole pressure control and sand-prevention tubing string for water injection wells according to the present invention;

[0017] Figure 2 This is a schematic diagram of the single-flow valve of the downhole pressure control and sand-expelling prevention tubing string for water injection wells according to the present invention.

[0018] Figure 3 This is a schematic diagram of the insert-type water injection packer for the downhole pressure control and sand-prevention tubing string of the present invention. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the following embodiments are by no means intended to limit the present invention.

[0020] See Figure 1 The downhole pressure control and sand-prevention string for the water injection well includes, from top to bottom, a tubing 1, a plug-in water injection packer 2, a tubing connector 3, a check valve 4, a sand-sinking tailpipe 5, and a plug 6, which are connected by threads.

[0021] See Figure 3 The insertion-type water-filled packer 2 includes a central insertion tube 2a, a sealing cylinder 2b, a connecting cylinder 2c, a slip mechanism, a sealing rubber sleeve assembly 2f, a rubber sleeve support seat 2g, a support cylinder 2h, and a bottom plug 2i;

[0022] The central cannula 2a consists of an upper connector, a cannula body, and an annular sleeve. The cannula body is a vertically arranged cylindrical tube. The upper connector is a cylindrical tube with both its inner and outer diameters larger than those of the cannula body, forming an annular step on the outer wall of the connection between the upper connector and the cannula body. The inner wall of the upper connector is provided with an internal thread. The annular sleeve is fitted onto the upper outer wall of the cannula body in a coaxial manner with the cannula body, and its top end is connected and fixed to the cannula body as one piece through an inner annular boss, so that the annular sleeve is closed at the top and open at the bottom.

[0023] The sealing cylinder 2b is a cylindrical body with an outer annular boss on its inner wall at the top and an inner annular boss on its inner wall at the top. The inner diameter of the sealing cylinder 2b is adapted to the outer diameter of the annular sleeve of the central insertion tube 2a, so that its upper part has an annular gap with the insertion tube body and its lower part fits in close contact with the annular sleeve. The connecting cylinder 2c is a cylindrical body with an inner diameter larger than the outer diameter of the sealing cylinder 2b. The connecting cylinder 2c is fitted onto the outside of the sealing cylinder 2b with an annular gap between it and the sealing cylinder 2b, and its top end is inserted into the upper connector of the central insertion tube 2a. The top of the sealing cylinder 2b is located below the annular step on the outer wall of the central insertion tube 2a. Its top outer wall is provided with an outer annular boss that fits against the inner wall of the connecting cylinder 2c, and its top inner wall is provided with an inner annular boss that fits against the outer wall of the insertion tube body, so that an annular cavity is formed between the insertion tube body and the sealing cylinder 2b. Multiple radial flow holes 2k connected to the annular cavity are opened circumferentially on the top side wall of the insertion tube body. The sealing cylinder 2b is connected to the insertion tube body by multiple shearing pins arranged circumferentially between its inner annular boss and the insertion tube body.

[0024] As a preferred technical solution of this embodiment, a double sealing ring is provided on the outer wall of the outer annular boss of the sealing cylinder 2b to form a seal between it and the inner wall of the connecting cylinder 2c; a double sealing ring is provided on the inner wall of the inner annular boss of the sealing cylinder 2b to form a seal between it and the outer wall of the insertion tube body; and a double sealing ring is provided on the outer wall of the bottom end of the connector of the central insertion tube 2a to form a seal between it and the inner wall of the connecting cylinder 2c.

[0025] The sealing cylinder 2b is fitted onto the outside of the annular sleeve, and the inner wall of the inner annular boss on its top inner wall forms a seal with the top outer wall of the insertion tube body through double sealing rings; the top of the sealing cylinder 2b is fixed to the central insertion tube 2a by multiple pins arranged in the circumferential direction.

[0026] Meanwhile, the top of the connecting tube 2c is inserted into the outside of the upper connector of the central insert tube 2a, and the two are sealed by a double sealing ring set on the outer wall of the upper connector.

[0027] The slip mechanism consists of slip seat 2e-1, slip 2d, and slip block 2e-2; among which,

[0028] The slip seat 2e-1 is composed of a conical cylinder and a straight cylinder connected sequentially from top to bottom; the lower inner wall of the conical cylinder is provided with an inner annular boss, and the middle outer wall of the straight cylinder is provided with an outer annular boss; the top of the conical cylinder of the slip seat 2e-1 is welded and fixed to the bottom of the connecting cylinder 2c, and the bottom of the annular sleeve of the central insertion tube 2a is pressed onto the upper end face of the inner annular boss on the slip seat 2e-1;

[0029] The slip block 2e-2 is a conical cylinder with a constant inner diameter and an outer diameter that gradually increases from top to bottom. It is fitted onto the outside of the slip seat 2e-1 and pressed onto the upper end face of the outer annular boss on the slip seat 2e-1.

[0030] The slip 2d is fitted onto the outside of the slip seat 2e-1. The inner wall of its top end is machined with a conical surface that mates with the outer wall of the conical cylinder, and the inner wall of its bottom end is machined with a conical surface that mates with the outer wall of the slip block 2e-2. In the initial state, the gap between the conical cylinder on the slip seat 2e-1 and the slip block 2e-2 causes the slip 2d to be in a contracted state. When the central insertion tube 2a moves downward under hydraulic pressure, the gap between the conical cylinder on the slip seat 2e-1 and the slip block 2e-2 decreases, and then the slip 2d opens outward under the compression of the conical surfaces at both ends, anchoring itself to the inner wall of the well shaft.

[0031] The sealing rubber sleeve assembly 2f consists of three rubber sleeves, and a spacer ring is provided between adjacent rubber sleeves; the sealing rubber sleeve assembly 2f is fitted on the lower outer wall of the slip seat 2e-1, and the top rubber sleeve abuts against the lower end face of the outer annular boss on the slip seat 2e-1.

[0032] The support cylinder 2h is a cylindrical body with an upper inner diameter larger than a lower inner diameter, and an annular step is formed at the connection between the upper and lower inner walls. The support cylinder 2h is fitted onto the lower outer side of the central insertion tube 2a, and its lower inner diameter is adapted to the outer diameter of the central insertion tube 2a. This allows the lower part of the support cylinder 2h to be sealed and fixed to the outside of the central insertion tube 2a by multiple sets of sealing rings 2j spaced on the lower outer wall of the central insertion tube 2a. At the same time, the top of the support cylinder 2h is fitted onto the bottom outer wall of the slip seat 2e-1. The annular step on its inner wall is spaced from the bottom of the slip seat 2e-1, and the distance between the two satisfies the following condition: when the slip seat 2e-1 descends to the annular step on the inner wall of the support cylinder 2h, the slip 2d opens outward to its maximum extent, and at the same time, the sealing rubber sleeve 2f is compressed and expanded to contact the inner wall of the wellbore, thus completing the setting seal.

[0033] The rubber tube support 2g is a cylindrical body with an inner annular boss on the inner wall of the top end. It is fitted on the outer side of the top end of the support tube 2h, and its inner annular boss is pressed against the top end face of the support tube 2h. In the initial state, the rubber tube located on the bottom side is pressed against the upper end face of the rubber tube support 2g.

[0034] The bottom plug 2i is sealed on the inner wall of the bottom end of the central cannula 2a. It is made of rubber and is inserted into the cannula body by friction. The size of the bottom plug 2i is adapted to the design pressure of being pressed away from the cannula body so that it can be pressed away from the cannula body under specific hydraulic action, thereby opening the axial channel of the cannula body.

[0035] See Figure 2 The check valve 4 includes an upper check valve connector 4a, a flow pipe 4h, a check valve body 4d, and a lower check valve connector 4i; wherein,

[0036] The upper connector 4a of the check valve is a cylindrical body with an external thread on the outer wall of its top end; the lower connector 4i of the check valve is a cylindrical body with an external thread on the outer wall of its bottom end.

[0037] The flow tube 4h is a tube body with an inner cavity that, from top to bottom, sequentially comprises an upper straight channel, a sloping channel 4b, a connecting channel 4c, an eccentric channel group, and a lower straight channel. The upper straight channel is connected to the outside of the tube body. The sloping channel 4b is an axially extending channel from the bottom of the upper straight channel, with its inner diameter gradually decreasing from top to bottom, and is connected to the upper straight channel. The connecting channel 4c is a straight channel axially extending from the bottom of the sloping channel 4b, and is connected to the sloping channel 4b. The eccentric channel group consists of a section from the connecting channel 4b... The bottom of the pipe is formed by two parallel eccentric channels 4f and 4c, which are opened along the axial direction. The first eccentric channel 4f is located directly below the bottom of the sloping channel 4b and is connected to the connecting channel 4c. The second eccentric channel is connected to the connecting channel 4c and is closed at the bottom. The lower straight channel is a straight channel opened along the axial direction from the bottom of the first eccentric channel 4f and is connected to the first eccentric channel 4f and the outside of the pipe body. Two flow passages connected to the outside of the pipe body are provided at intervals from top to bottom on the side wall of the second eccentric channel.

[0038] In the flow pipe 4h, the inner wall of the upper straight channel is provided with internal threads, so that it is fixedly connected to the bottom thread of the one-way valve upper connector 4a; the inner wall of the lower straight channel is provided with internal threads, so that it is fixedly connected to the top thread of the one-way valve lower connector 4i; in addition, as a preferred technical solution of this embodiment, a double sealing ring is provided between the upper straight channel and the one-way valve upper connector 4a to form a sealed connection between the two; a double sealing ring is also provided between the lower straight channel and the one-way valve lower connector 4i to form a sealed connection between the two; the first eccentric channel 4f serves as a sedimentation channel, and the second eccentric channel serves as a water injection channel. The first eccentric channel 4f is located directly below the slope channel 4b, so that the sand in the injected water is deposited in the sedimentation channel, and then the clean water enters the water injection channel through the connecting channel 4c to prevent sand from entering the formation;

[0039] The single-flow valve body 4d is composed of a first ball seat, a plugging ball, a second ball seat, and a spring, arranged sequentially from top to bottom within the second eccentric channel. The first ball seat is an annular body fixed to the inner wall of the top of the second eccentric channel, and the bottom surface of the annular body is machined into a conical surface that matches the plugging ball. The second ball seat is a cylindrical block with a conical top surface. The spring is vertically arranged in a compressed state, with its bottom end fixed in the center at the bottom of the second eccentric channel and its top end fixed to the bottom surface of the second ball seat. The single-flow valve body 4d is arranged within the second eccentric channel, so that it can only be compressed by hydraulic pressure to allow fluid to enter the second eccentric channel and then flow out through the flow passage to the outside of the flow pipe 4h and into the wellbore.

[0040] The oil pipe 1 is a commercially available product, and its length is adapted to the required lowering depth of the insert-type water-filled packer 2. The bottom end of the oil pipe 1 is threaded to the upper inner wall of the upper connector of the central insert 2a on the insert-type water-filled packer 2. During operation, water is injected into the central chamber of the central insert 2a through the oil pipe 1.

[0041] The oil pipe short connector 3 is a commercially available product. Its top end is connected to the bottom end of the support cylinder of the insert-type water injection packer 2, and its bottom end is connected to the inner wall of the check valve upper connector 4a of the check valve 4. Specifically, the length of the oil pipe short connector 3 is preferably greater than 1m.

[0042] Both the sedimentation tailpipe 5 and the plug 6 are commercially available products. The sedimentation tailpipe 5 is connected to the bottom of the check valve 4 to collect sediment and bottom plug 2i in the water; the plug 6 is sealed at the bottom opening of the sedimentation tailpipe 5.

[0043] The specific working process of the downhole pressure control and sand-prevention tubing string in this water injection well is as follows:

[0044] S1. After well cleaning and circulation, the assembled downhole pressure control and sand-prevention tubing string for the water injection well is lowered into the well, and the insert-type water injection packer 2 is positioned as designed. Figure 1 As shown;

[0045] S2. The tubing is pressurized. First, the wellhead pressure reaches 10 MPa and is stabilized for 5 minutes. Then, it is increased to 15 MPa and stabilized for 5 minutes. Finally, when it reaches 20 MPa, the insertion-type water-filled packer 2 is set, achieving tubing string sealing. During this process, fluid is pumped through tubing 1 into the inner cavity of the central insertion tube 2a. Because the bottom of the insertion tube is initially sealed with a bottom plug 2i, after the high-pressure fluid fills the entire inner cavity of the central insertion tube 2a, the high-pressure fluid continues to flow radially. The orifice 2k enters the annular cavity, applying hydraulic pressure to the upper surfaces of the inner and outer annular bosses of the sealing cylinder 2b, thereby pushing the sealing cylinder 2b downwards and causing the slip seat 2e-1 to move downwards synchronously. During the downward movement of the slip seat 2e-1, the slip 2d extends outwards and anchors itself to the inner wall of the wellbore, and the sealing rubber sleeve assembly compresses and expands to set itself on the inner wall of the wellbore. Since the slip seat 2e-1 cannot automatically recover after it has moved to its position, the insert-type water injection packer 2 is always in a pressurized state.

[0046] S3. After the insertion-type water injection packer 2 is set, continue to pressurize to no more than 24MPa, so that the bottom plug 2i at the bottom of the insertion body is blown off by the pressure and leaves the insertion body. At this time, the central chamber of the insertion body is connected from top to bottom, forming a water injection channel, and water is injected into the wellbore through the check valve 4. After the water injection is completed, the wellhead pressure test is qualified and normal production can begin.

[0047] S3. When the next water injection well requires an upper repair operation, only the tubing 1 needs to be raised until the lifting load is greater than 80KN (i.e., the load required to cut all shear pins). All shear pins will then cut, and the central insert 2a in the insert-type water injection packer 2 will separate from it. The tubing 1, along with the central insert 2a and the sealing cylinder 2b, will be taken out from the wellhead. The insert-type water injection packer will control the pressure in the lower part of the wellbore at the lower part of the packer. There will be no pressure in the annular space between the upper tubing and the casing, which will also protect the upper casing. The check valve will control the pressure in the tubing string at the casing below the packer. After the injection is stopped and the pressure is released, there will be no pressure inside the tubing, thus sealing the lower casing wellbore and maintaining the pressure in the lower wellbore. There will be no pressure in the upper tubing and the annulus between the tubing and the casing, and the water injection tubing string can be raised and lowered normally.

[0048] S4. After the construction work is completed, secondary water injection can be carried out by re-inserting the central insertion pipe 2a and the sealing cylinder 2b.

[0049] This pressure-controlled, sand-preventing tubing string for water injection wells has been applied in three wells in the Liuquan Oilfield. One of these wells was a potential hazard remediation well, where the wellhead was consistently under high pressure, requiring live operation at 12-15 MPa. The pressure-controlled, sand-preventing tubing string was installed upon well completion of this well, and water injection is now proceeding normally. When applied to combined water injection wells, this invention allows for simple tubing inspection to release the pressure in the casing, avoiding well kill operations and live operation, thus saving operating costs and production downtime. It controls the injection well pressure at the bottom of the well, preventing formation changes caused by pressure fluctuations and effectively maintaining the injection pressure differential. This not only prevents sand release but also reduces permeability changes caused by formation sand flow. Simultaneously, because the upper casing is not pressurized, it is protected, playing a certain role in inhibiting upper casing damage and deformation.

Claims

1. A downhole pressure control and sand-prevention tubing string for water injection wells, characterized in that, It includes, from top to bottom, an oil pipe (1), a tubing-type water injection packer (2), an oil pipe connector (3), a check valve (4), a sand-collecting tailpipe (5), and a plug (6); among which, The insertion-type water-filled packer (2) includes a central insertion tube (2a), a sealing cylinder (2b), a connecting cylinder (2c), a slip mechanism, a sealing rubber sleeve assembly (2f), a rubber sleeve support base (2g), and a support cylinder (2h). The central insertion tube (2a) consists of an upper connector, an insertion tube body, and an annular sleeve. The upper connector is connected to the top of the insertion tube body, and its outer diameter is larger than that of the insertion tube body, so that an annular step is formed on the outer wall of the connection between the two. The annular sleeve is fitted onto the upper outer wall of the insertion tube body in a manner coaxial with the insertion tube body, and its top end is connected and fixed to the insertion tube body as one piece through an inner annular boss. The bottom end of the insertion tube body is sealed with a bottom plug (2i). The sealing cylinder (2b) is fitted onto the outside of the annular sleeve, and its upper part is connected to the outer wall of the sealing cylinder. The cannula body has an annular gap and its lower part fits into the annular sleeve; the connecting sleeve (2c) is fitted onto the outside of the sealing sleeve (2b) with an annular gap between it and the sealing sleeve (2b), and its top end is inserted into the outside of the upper connector of the central cannula (2a); the top end of the sealing sleeve (2b) is located below the annular step on the outer wall of the central cannula (2a), and its top outer wall has an outer annular boss that fits into the inner wall of the connecting sleeve (2c), and its top inner wall has an inner annular boss that fits into the outer wall of the cannula body, so that an annular cavity is formed between the cannula body and the sealing sleeve (2b); the top side wall of the cannula body has multiple radial flow holes (2k) connected to the annular cavity along the circumferential direction; the sealing sleeve (2b) The connection between the inner annular boss and the cannula body is achieved by multiple shearing pins arranged circumferentially between them; the slip mechanism consists of a slip seat (2e-1), slips (2d), and slip blocks (2e-2); the slip seat (2e-1) consists of a conical cylinder and a straight cylinder connected sequentially from top to bottom; the inner wall of the lower part of the conical cylinder is provided with an inner annular boss, and the outer wall of the middle part of the straight cylinder is provided with an outer annular boss; the top of the slip seat (2e-1) is fixed to the bottom of the connecting cylinder (2c), and the bottom of the annular sleeve of the central cannula (2a) is pressed against the upper end face of its inner annular boss; the slip block (2e-2) is a conical cylinder with an outer diameter that gradually increases from top to bottom, which is fitted on the outside of the slip seat (2e-1) and pressed against the slip seat (2e-2). On the upper surface of the outer annular boss of e-1); the slip (2d) is fitted on the outside of the slip seat (2e-1), and its top inner wall and bottom inner wall are respectively processed into conical surfaces that cooperate with the outer wall of the conical cylinder and the outer wall of the slip block (2e-2); the sealing rubber sleeve assembly (2f) is fitted on the lower outer wall of the slip seat (2e-1), and its top end abuts against the lower surface of the outer annular boss of the slip seat (2e-1); the support cylinder (2h) is a cylinder with an upper inner diameter larger than the lower inner diameter, and there is an annular gap between its upper part and the insertion tube body, and its top end is inserted into the outer side of the bottom end of the slip seat (2e-1), and an annular step with a gap between its middle part and the bottom end of the slip seat (2e-1), and its lower sealing sleeve is fitted on the outer side of the lower part of the insertion tube body;The rubber sleeve support base (2g) is fitted on the outer side of the top of the support tube (2h), and the inner annular boss on the inner wall of its top is pressed against the upper end face of the support tube (2h), so that the bottom end of the sealing rubber sleeve assembly (2f) is pressed against the rubber sleeve support base (2g). A single-flow valve (4) is connected to the bottom of the plug-in water injection packer (2) via a short-circuit pipe (3), and a flow hole communicating with the wellbore is provided on one side wall; a sand-collecting tailpipe (5) is connected to the bottom of the single-flow valve (4) to collect sand and bottom plug (2i) in the water; a plug (6) is sealed at the bottom opening of the sand-collecting tailpipe (5).

2. The downhole pressure control and sand-prevention tubing string for water injection wells according to claim 1, characterized in that, The check valve (4) includes a check valve upper connector (4a), a flow pipe (4h), a check valve body (4d), and a check valve lower connector (4i); wherein, the flow pipe (4h) is a pipe body with an inner cavity having an upper straight channel, a sloped channel (4b), a connecting channel (4c), an eccentric channel group, and a lower straight channel in sequence from top to bottom; the upper straight channel is connected to the outside of the pipe body; the sloped channel (4b) is opened axially from the bottom of the upper straight channel and the inner diameter of the channel gradually decreases from top to bottom. The channel is reduced in size, and the sloping channel (4b) is connected to the upper straight channel; the connecting channel (4c) is a straight channel opened axially from the bottom of the sloping channel (4b), and the connecting channel (4c) is connected to the sloping channel (4b); the eccentric channel group consists of two parallel eccentric channels, a first eccentric channel (4f) and a second eccentric channel, opened axially from the bottom of the connecting channel (4c), with the first eccentric channel (4f) located directly below the bottom of the sloping channel (4b). It is connected to the connecting channel (4c); the top of the second eccentric channel is connected to the connecting channel (4c) and the bottom is closed; the lower straight channel is a straight channel opened axially from the bottom of the first eccentric channel (4f), and the lower straight channel is connected to the first eccentric channel (4f) and the outside of the pipe body respectively; two flow channels connected to the outside of the pipe body are spaced apart from top to bottom on the side wall of the second eccentric channel; the single-flow valve body (4d) is composed of a first ball seat, a sealing ball, a second ball seat and a spring arranged sequentially from top to bottom in the second eccentric channel; the first ball seat is an annular body fixed on the inner wall of the top of the second eccentric channel, and its bottom surface is machined into a conical surface that matches the sealing ball; the second ball seat is a cylindrical block with a conical surface machined on the top surface; the spring is arranged vertically in a compressed state, and its two ends are fixed to the bottom of the second eccentric channel and the bottom surface of the second ball seat respectively; the upper connector (4a) of the single-flow valve is connected in the upper straight channel, and the lower connector (4i) of the single-flow valve is connected in the lower straight channel.

3. The downhole pressure control and sand-prevention tubing string for water injection wells according to claim 1, characterized in that, A double sealing ring is provided on the outer wall of the outer annular boss of the sealing cylinder (2b) to form a seal between it and the inner wall of the connecting cylinder (2c). A double sealing ring is provided on the inner wall of the inner annular boss of the sealing cylinder (2b) to form a seal between it and the outer wall of the insertion tube body. A double sealing ring is provided on the outer wall of the bottom end of the connector of the central insertion tube (2a) to form a seal between it and the inner wall of the connecting cylinder (2c).

4. The downhole pressure control and sand-prevention tubing string for water injection wells according to claim 1, characterized in that, The sealing rubber sleeve assembly (2f) consists of three sets of rubber sleeves, with spacer rings between adjacent rubber sleeves.

5. The downhole pressure control and sand-prevention tubing string for water injection wells according to claim 2, characterized in that, A double sealing ring is also provided between the upper straight channel and the upper connector (4a) of the check valve to form a sealed connection between the two; a double sealing ring is also provided between the lower straight channel and the lower connector (4i) of the check valve to form a sealed connection between the two.

6. The downhole pressure control and sand-prevention tubing string for water injection wells according to claim 1, characterized in that, The length of the oil pipe short connector (3) is greater than 1m.

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