Blowout prevention operation tool for water injection well and well killing-free operation method thereof

Abstract

The upper end of a multifunctional ball seat with pressure is connected with a blowout prevention tail pipe valve in a screwed mode, the blowout prevention tail pipe valve comprises an outer sealing sleeve located in a valve body outer barrel, an expanding hole is formed in the center of the upper portion of the outer sealing sleeve, and an in-valve annular channel is arranged between the portion below an upper sealing section and the valve body outer barrel; an outer sealing sleeve liquid discharge hole is formed in the middle lower part; the inner sliding sleeve is located in the inner cavity of the outer sealing sleeve, an inner sliding sleeve outer convex ring is arranged on the periphery of the upper end of the inner sliding sleeve and supported on the inner wall of the upper portion of the outer sealing sleeve expanding hole, and an inner sliding sleeve drainage hole communicated with the outer sealing sleeve drainage hole is formed in the lower middle portion of the inner sliding sleeve; and the inner sliding sleeve shear pin fixes the inner sliding sleeve. During normal well washing, the ball seat is closed. And during inverse well flushing, the ball seat is opened. When the underground pipe columns need to be pulled out, the strong magnetic ball suction pipe is put in until the strong magnetic ball suction pipe is inserted into the blowout prevention tail pipe valve to suck up the low-density iron ball until the lower end opening of the inner sliding sleeve of the blowout prevention tail pipe valve is reversely sealed, reliable blocking is achieved, and then the underground pipe columns can be pulled out of a well mouth one by one under pressure for maintenance.

Description

Technical Field

[0001] The present invention relates to a downhole pipe string for a water injection well, in particular to a blowout prevention tool for a water injection well; the present invention also relates to a pressure-free well operation method for the blowout prevention tool for a water injection well, belonging to the technical field of oil production facilities. Background Art

[0002] In the later stage of oilfield management, water injection is often used to maintain or restore reservoir pressure and increase formation energy, so that the reservoir has a stronger driving force to improve the production speed and recovery rate of the reservoir. As the water injection pressure continues to increase, downhole pipe string failures continue, and it is an inevitable choice to lift the pipe string for downhole pipe string maintenance. In order to ensure safe production, it is necessary to release pressure or kill the well before the operation and construction, and then lift the layered water injection pipe string.

[0003] There are many problems with the above production methods. First, the use of high-density hydraulic well pressure causes an increase in the cost of operation and construction; second, well pressure can easily pollute the formation and crush the formation; third, it is necessary to release the pressure, which increases the construction period, sometimes taking 1-2 months, greatly increases the amount of sewage recovery, and the energy of the surrounding oil well formations decreases, while breaking the balance of the injection and production well network. It is time-consuming and laborious to restore the formation energy after the operation, and the large pressure difference changes damage the casing. Therefore, pressure-carrying operations are gradually promoted in oil fields, and the plugging assembly is often used to seal the pipe column. There are currently two main methods: 1. Wireline operation plugging device; 2. Gravity free plugging device.

[0004] At present, the conventional stratified water injection pressure operation process string from bottom to top is: wire plug + screen tube + pressure ball seat + water distributor 1 + oil pipe + packer 1 + oil pipe + water distributor 2 + oil pipe + packer 2 + ... + oil pipe + water distributor 3 + oil pipe to wellhead. Taking the string of 73mm oil pipe completion as an example, the inner diameter of 73mm oil pipe is 62mm, the inner diameter of water distributor is 46mm, and the inner diameter of packer is 60mm-62mm. Pressure operation technology is a downhole operation technology for lifting and lowering oil pipes without well pressure reduction. The core of the downhole pipe string internal sealing is the pipe string internal plugging technology. At present, the internal blockage of the tubing is usually sealed with a strong magnetic ball tube (minimum outer diameter 56mm). However, if there is severe scaling in the tubing (taking a 73mm tubing as an example, the tubing diameter is 62mm, and sometimes the diameter is only 30mm after scaling) and small-diameter downhole tools such as water distributors (inner diameter 46mm) have smaller actual diameters after scaling, the inner diameter of the tubing changes, resulting in the tubing strong magnetic ball tube being unable to be smoothly placed in the predetermined position, poor sealing, and unable to achieve the expected sealing effect, and even more unable to reach the bottom of the tubing through the water distributor, resulting in repeated plugging, liquid spraying, and environmental pollution. Therefore, it is urgent to solve the bottom blockage problem during pressurized operation of water injection wells.

[0005] The following problems need to be solved for high-pressure water injection well pressure operation: 1. Realize the pipe string under pressure; 2. Water can be injected normally in each formation; 3. Backwashing well operation can be carried out; 4. Realize the pipe string under pressure. The commonly used methods of using strong magnetic suction ball pipe and various valves to solve the problem of pipe string under pressure are not ideal. When the first three functions can be achieved, the most difficult problem is to realize the pipe string under pressure.

[0006] The Chinese utility model patent with the publication number CN202338277U discloses a downhole circulation switch valve. Its track cylinder with track groove is sleeved on the outside of the valve body with threaded holes, and the sliding nail is located in the track cylinder track groove and connected to the valve body threaded hole; the upper and lower ends of the track cylinder are provided with rolling bearings; the sealing sleeve with sealing ring is sleeved on the bottom end of the valve body and fixed by a limit pin; the valve body is provided with an oil hole connecting its inner cavity and the external annular cavity, and a sliding plug and a hollow plugging nail are provided in the inner cavity of the valve body; the protective cylinder is fixed on the outside of the track cylinder; the lower joint with an embedded retaining ring at the bottom is sleeved on the outside of the protective cylinder and the sealing sleeve; the valve core with a flow hole and a sealing groove is threadedly connected above the valve body, the upper joint with a throttle hole is sleeved on the outside of the valve core and threadedly connected to the lower joint, and the mesh pipe is sleeved on the outside of the upper joint. The downhole circulation switch valve is feasible in principle, but the long-term repeated movement of the seal makes the sealing effect poor, and sometimes the switch state is unclear.

[0007] The Chinese utility model patent with publication number CN202645505U discloses a pressure-operated ball seat, which is mainly composed of an upper joint, a valve ball, a valve seat, a piston rod, an intermediate joint, an O-ring, a shear pin, a lower joint, etc. The valve ball and the valve seat are located in the upper joint, the valve ball is located on the upper part of the valve seat, the upper end face of the valve seat is in contact and seal with the step end face of the upper joint, the lower end face of the valve seat is in contact and seal with the upper end face of the intermediate joint, the upper joint is threadedly connected with the intermediate joint, the intermediate joint is threadedly connected with the lower joint, the piston rod is located in the intermediate joint and is sealed with the intermediate joint through an O-ring, the piston rod lifts the valve ball through the valve seat and separates it from the valve seat, the shear pin fixes the piston rod in the outer circular threaded hole of the intermediate joint, and O-rings are provided at the upper and lower parts of the outer circular threaded hole of the intermediate joint to form a seal with the lower joint. The ball seat can effectively prevent the high-pressure liquid in the well from spraying out from the pipe string when the pipe string is lowered under pressure. After the pipe string is lowered, it can be pressed on the ground to become a ball seat in the forward direction, and can be circulated in the reverse direction to wash the well, meeting the functions of normal water injection and well washing. The existing problems are as follows: when the strong magnetic suction ball pipe is cast, the strong magnetic suction ball pipe goes down, and the entire strong magnetic suction ball pipe string is a dead cavity. The strong magnetic suction ball pipe cannot be cast in place and cannot enter the blowout-preventing tail pipe valve, resulting in blockage failure and loss of the blowout-preventing tail pipe valve function. Summary of the invention

[0008] The primary purpose of the present invention is to overcome the shortcomings of the prior art in which pressure-operated operations cause wellhead overflow and environmental pollution, and to provide a water injection well blowout prevention operation tool that can achieve reliable sealing of the bottom of the water injection well under the premise of pressure-operated operations, reduce internal overflow of the oil pipe during the process of raising and lowering the pipe string in the water injection well operation, and achieve environmentally friendly construction.

[0009] In order to solve the above technical problems, the water injection well blowout prevention tool of the present invention comprises a multifunctional pressure ball seat, the upper end of which is screwed with a blowout prevention tail pipe valve, and the blowout prevention tail pipe valve comprises: The outer tube of the valve body has an upper female thread which is screwed to the upper oil pipe through the upper joint of the valve body, and a lower male thread which is screwed to the upper end of the multifunctional pressure ball seat; An outer sealing sleeve, wherein the upper part of the center hole is provided with an outer sealing sleeve expansion hole, the outer periphery of the upper part is provided with an outer sealing sleeve sealing section, the outer sealing sleeve sealing section is fixed on the inner step of the outer cylinder of the valve body, an inner valve annular channel is provided between the lower part of the outer sealing sleeve sealing section and the inner wall of the outer cylinder of the valve body, and an outer sealing sleeve drainage hole is provided in the middle and lower part; An inner sleeve is located in the inner cavity of the outer sealing sleeve, an inner sleeve outer convex ring is provided on the outer periphery of the upper end and supported on the upper inner wall of the outer sealing sleeve expansion hole, and an inner sleeve drainage hole is provided in the middle and lower part and communicates with the outer sealing sleeve drainage hole; The inner sleeve shear pin is screwed into the screw hole at the lower end of the outer sealing sleeve, and the inner end is embedded in the countersunk hole of the inner sleeve, so that the drainage hole of the inner sleeve is opposite to the drainage hole of the outer sealing sleeve.

[0010] As an improvement of the present invention, the multifunctional pressure ball seat comprises: The ball seat outer cylinder accommodates the ball seat body, the low-density iron ball and the ejector rod; The ball seat body, the upper outer periphery of which abuts against the lower inner step of the middle part of the ball seat outer tube, the upper center is provided with a bell mouth, and the bottom is supported on the top of the lower joint of the ball seat; A low-density iron ball is seated on the bell mouth of the ball seat; A push rod passes through the center hole of the ball seat body, with its upper end abutting against the bottom of the low-density iron ball and its lower end supported in the lower joint of the ball seat; A push rod spring is sleeved on the upper part of the push rod, with the upper end extending into the bell mouth of the ball seat body and the bottom abutting against the inner step at the lower end of the center hole of the ball seat body; The upper end of the lower joint of the ball seat is screwed into the lower end internal thread of the outer tube of the ball seat and the two are sealed with each other.

[0011] As a further improvement of the present invention, the lower end of the push rod is supported on the top center of the stopper, the upper end of the stopper is against the bottom of the inner step of the lower joint of the ball seat, and the outer periphery of the stopper is fixed to the circumference of the lower joint of the ball seat by a stopper shear pin.

[0012] As a further improvement of the present invention, at least one pair of radial holes of the ball seat body is provided along the height direction of the center hole of the ball seat body, the inner ports of the radial holes of the ball seat body are communicated with the center hole of the ball seat body, the outer ports of the radial holes of the ball seat body are communicated with the axial holes of the ball seat body, and the lower ports of the axial holes of the ball seat body are communicated with the inner cavity of the lower joint of the ball seat.

[0013] As an improvement of the present invention, an inner sleeve upper conical surface is provided at the upper end of the center hole of the inner sleeve, and an inner sleeve lower conical surface is provided at the lower end of the center hole of the inner sleeve.

[0014] As a further improvement of the present invention, the lower end of the inner sleeve extends out from the lower port of the outer sealing sleeve and is screwed with an inner sleeve nut, and the top of the inner sleeve nut abuts against the bottom of the outer sealing sleeve; When the lower conical surface of the inner sleeve is reversely sealed, the inner sleeve nut bears the pressure from below and the annulus of the oil casing, ensuring that the shear pin of the inner sleeve is not sheared off.

[0015] As a further improvement of the present invention, an outer sealing sleeve retaining spring is embedded in the annular groove on the middle inner wall of the outer sealing sleeve, and an inner sleeve retaining spring groove is provided on the upper outer periphery of the inner sleeve. When the bottom of the outer convex ring of the inner sleeve abuts against the inner step of the expanded diameter hole of the outer sealing sleeve, the outer sealing sleeve retaining spring is embedded in the inner sleeve retaining spring groove to lock the inner sleeve.

[0016] As a further improvement of the present invention, the upper conical surface of the inner sleeve limits the strong magnetic ball suction tube, and the lower conical surface of the inner sleeve provides reverse sealing for the low-density iron ball, and the low-density iron ball is also used for the forward sealing of the multifunctional pressurized ball seat.

[0017] As a further improvement of the present invention, the strong magnetic ball suction tube comprises: The magnetic isolation jacket has a magnetic isolation jacket bell mouth at the upper end, and the magnetic isolation jacket bell mouth is provided with a magnetic isolation jacket outer cone surface and a magnetic isolation jacket inner cone surface, the magnetic isolation jacket outer cone surface matches the cone surface on the inner sliding sleeve, and the magnetic isolation jacket inner cone surface is used for steel ball sealing; A strong magnetic core, which is annular and has an upper end that abuts against the lower inner step of the magnetic isolation jacket; A strong magnetic ball seat is screwed into the screw hole at the lower end of the magnetic isolation jacket, with its top abutting against the bottom of the strong magnetic core and a magnetic horn mouth at its lower end; The central holes of the magnetic isolation jacket, the strong magnetic core and the strong magnetic absorption ball seat are connected and have the same diameter.

[0018] Another object of the present invention is to overcome the problems existing in the prior art and provide a pressure-free well operation method for a water injection well blowout prevention tool, which achieves reliable blocking of the bottom of the pipe column through a multifunctional pressure-blowout prevention tail pipe valve and a strong magnetic suction ball pipe, is resistant to high pressure and does not increase additional investment.

[0019] In order to solve the above technical problems, the pressure-free well operation method of the water injection well blowout prevention operation tool of the present invention can lift the pipe string with pressure, and the steps are as follows: the push rod spring of the multifunctional pressure ball seat pushes the upper push rod upward to lift the steel ball and separate it from the bell mouth of the ball seat body; the stopper blocks the lower port of the pipe string to prevent blowout or wellhead overflow; When the string is lowered to the designed position, water can be injected normally. The steps are as follows: the wellhead is pressurized, the low-density iron ball presses the push rod downward, the shear pin of the block is cut off, the push rod and the block fall down, the low-density iron ball compresses the push rod spring and continues to move downward until it is seated on the ball seat body, the lower channel of the ball seat body is closed, and the upper water distributor performs normal water injection.

[0020] When water injection stops: the push rod spring is released and reset, pushing the low-density iron ball away from the ball seat body, and the lower part of the pipe string is connected with the casing annulus through the ball seat body, ensuring that when the strong magnetic suction ball tube is dropped, the strong magnetic suction ball tube can quickly descend to the position under the action of gravity.

[0021] Furthermore, backwashing circulation can be performed, and the steps are as follows: the downhole pressure pushes the low-density iron ball to make it rise until it reversely seals the lower end of the blowout-prevention tail pipe valve, and the well-washing fluid enters the central hole through the outer sealing sleeve drainage hole and the inner sliding sleeve drainage hole to achieve normal drainage, and the well-washing fluid returns to the wellhead along the central channel for circulation; when normal water injection is restored, the low-density iron ball can be re-sealed on the ball seat body.

[0022] Furthermore, the pipe string can be lifted under pressure, and the steps are as follows: at the wellhead, a strong magnetic ball suction pipe is put into the pipe string, and then the valve at the upper end of the pipe string is closed. At this time, the push rod spring is reset and pushes the low-density iron ball to move upward, opening the dead space at the lower end of the pipe string, so that the strong magnetic ball suction pipe can smoothly descend, and the strong magnetic ball suction pipe is inserted into the blowout prevention tail pipe valve and then stops. Under the action of magnetic suction, the low-density iron ball is adsorbed on the lower end of the strong magnetic ball suction pipe; Then a steel ball is dropped from the wellhead, and the steel ball falls on the top of the strong magnetic ball suction tube to seal it; then the wellhead is pressurized, and the steel ball pushes the inner sleeve and the strong magnetic ball suction tube downward, cutting off the shear pin of the sleeve, and the inner sleeve and the strong magnetic ball suction tube continue to move downward until the inner sleeve is stuck on the limit step of the outer sealing sleeve and stops, at which time the outer sealing sleeve retaining spring is stuck in the inner sleeve retaining spring groove to lock the inner sleeve, and a seal is achieved between the inner sleeve and the outer sealing sleeve; After the wellhead is depressurized, the downhole pressure pushes the strong magnetic suction ball pipe upward until the low-density iron ball cooperates with the lower cone surface of the inner sleeve to achieve reverse sealing. Then the downhole pipes are pulled out of the wellhead one by one for maintenance.

[0023] Compared with the prior art, the present invention has achieved the following beneficial effects: 1. No need to kill the well, maintain the vitality of the formation, avoid polluting the formation, and avoid breaking the balance of the injection and production well network; 2. It saves the cost of well killing, shortens the pressure release cycle by 1-2 months, improves the safety of the wellhead, and avoids wellhead pollution; 3. During the plugging operation, the dead space of the lower pipe string is eliminated, solving the problem that the strong magnetic suction ball tube cannot be put into place and cannot enter the blowout prevention tail pipe valve, ensuring that the strong magnetic suction ball tube can be put into place smoothly and quickly; 4. The strong magnetic suction tube has a strong magnetic suction force. When the lower end of the strong magnetic suction tube attracts the low-density iron ball, the central channel of the multifunctional pressure ball seat is opened to make the bottom of the pipe column not a dead cavity, ensuring that the inner sleeve and the strong magnetic suction tube can descend smoothly, and the shear pin of the sleeve can be reliably cut off. When the inner sleeve and the strong magnetic suction tube continue to descend to the bottom of the outer convex ring of the inner sleeve and contact the limit step at the lower part of the expansion hole of the outer sealing sleeve, the low-density iron ball will not contact the bell mouth of the ball seat body, ensuring the success of the pressure. 5. The construction process is simple. Without adding additional equipment, it can realize operations such as lowering the pipe string under pressure, normal multi-layer water injection, backwashing well operations, plugging, and lifting the pipe string under pressure. No matter what kind of operation is performed, well control safety can be guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The accompanying drawings are only provided for reference and explanation and are not intended to limit the present invention.

[0025] Figure 1 This is a schematic diagram of the structure of the water injection well blowout prevention tool of the present invention; Figure 2 It is a structural schematic diagram of the blowout prevention tail pipe valve in the present invention; Figure 3 It is a structural schematic diagram of the multifunctional pressure ball seat in the present invention; Figure 4 It is a structural schematic diagram of the strong magnetic suction ball tube in the present invention; Figure 5 This is a state diagram of the present invention during normal water injection; Figure 6 It is a state diagram of the present invention when backwashing the well; Figure 7 This is a state diagram of the strong magnetic ball suction tube in the present invention when it is put into place and sucks up the low-density iron ball; Figure 8 This is a state diagram after a steel ball is put in to shear off the shear pin of the inner sleeve in the present invention; Fig. 9 This is a state diagram of the low-density iron ball in the present invention.

[0026] Figure: blowout-proof tail pipe valve: 1. valve body upper joint; 2. valve body outer cylinder; 3. outer cylinder retaining spring; 4. inner sleeve; 4a. inner sleeve upper conical surface; 4b. inner sleeve outer convex ring; 4c. inner sleeve retaining spring groove; 4d. inner sleeve drainage hole; 4e. inner sleeve lower conical surface; 5. outer sealing sleeve; 5a. outer sealing sleeve enlarged diameter hole; 5b. outer sealing sleeve drainage hole; 5c. valve inner annular channel; 6. sealing sleeve outer sealing ring; 7. outer sealing sleeve retaining spring; 8. outer sealing sleeve inner sealing ring; 9. inner sleeve shear pin; 10. inner sleeve nut; Multifunctional pressure ball seat: 11. Ball seat outer tube; 12. Low-density iron ball; 13. Ball seat body; 13a. Ball seat body radial hole; 13b. Ball seat body axial hole; 13c. Ball seat body sealing ring; 14. Push rod; 15. Push rod spring; 16. Ball seat lower joint; 16a. Lower joint sealing ring; 17. Lower joint positioning pin; 18. Stopper; 19. Stopper sealing ring; 20. Stopper shear pin; Strong magnetic ball suction tube: 21. Magnetic isolation jacket; 21a. Outer cone of magnetic isolation jacket; 21b. Inner cone of magnetic isolation jacket; 22. Strong magnetic core; 23. Strong magnetic ball suction seat; 24. Steel ball. Implementation

[0027] In the following description of the present invention, the directions or positional relationships indicated by terms such as "up", "down", "front", "back", "left", "right", "inside" and "outside" are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description, and do not mean that the device must have a specific direction.

[0028] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below with reference to specific diagrams.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0030] like Figure 1 , Figure 2 As shown, the water injection well blowout prevention tool of the present invention includes a blowout prevention tail pipe valve, a multifunctional pressurized ball seat and a strong magnetic ball suction tube. The multifunctional pressurized ball seat is screwed under the blowout prevention tail pipe valve. After the strong magnetic ball suction tube is put into the pipe string, it is inserted into the blowout prevention tail pipe valve.

[0031] The blowout-proof tail pipe valve comprises a valve body upper joint 1, a valve body outer tube 2, an outer sealing sleeve 5 and an inner sliding sleeve 4. The upper female thread of the valve body upper joint 1 is screwed to the upper oil pipe B, and the lower male thread of the valve body upper joint 1 is screwed to the upper female thread of the valve body outer tube 2. The lower male thread of the valve body outer tube 2 is screwed to the upper female thread of the multifunctional pressure ball seat.

[0032] The outer sealing sleeve 5 is located in the middle section of the inner cavity of the outer cylinder 2 of the valve body. The upper part of the center hole of the outer sealing sleeve 5 is provided with an outer sealing sleeve enlarged diameter hole 5a, and the upper outer periphery is provided with an outer sealing sleeve sealing section. Two sealing sleeve outer sealing rings 6 are embedded on the circumference of the outer sealing sleeve sealing section to achieve sealing with the inner wall of the outer cylinder 2 of the valve body. The bottom of the outer sealing sleeve sealing section is supported on the inner step of the outer cylinder 2 of the valve body, and the top of the outer sealing sleeve 5 is pressed with an outer cylinder retaining spring 3, which is embedded in the inner wall ring groove of the outer cylinder 2 of the valve body.

[0033] The inner sleeve 4 is located in the inner cavity of the outer sealing sleeve 5, and its inner surface is treated with anti-scaling to prevent the inner diameter from being affected by scaling. An inner sleeve outer convex ring 4b is provided on the outer periphery of the upper end of the inner sleeve 4, and the inner sleeve outer convex ring 4b is supported on the upper inner wall of the outer sealing sleeve enlarged diameter hole 5a, and the distance between the bottom of the inner sleeve outer convex ring 4b and the bottom step of the outer sealing sleeve enlarged diameter hole 5a is the sliding stroke of the inner sleeve 4.

[0034] An inner valve annular channel 5c is provided between the sealing section of the outer sealing sleeve and the inner wall of the valve body outer tube 2, an outer sealing sleeve drainage hole 5b is provided in the middle and lower part of the outer sealing sleeve 5, and two sealing sleeve inner sealing grooves are respectively provided on the inner walls of the outer sealing sleeve on the upper and lower sides of the outer sealing sleeve drainage hole 5b, and the outer sealing ring 8 of the outer sealing sleeve and the outer wall of the inner sliding sleeve 4 are respectively embedded in the inner sealing grooves of the sealing sleeve to achieve sealing.

[0035] An inner sleeve drainage hole 4d is provided in the middle and lower part of the inner sleeve 4, and the outer sealing sleeve drainage hole 5b is opposite to and connected with the inner sleeve drainage hole 4d, providing a radial communication channel between the inner annular channel 5c of the valve and the center hole of the valve body.

[0036] The inner sleeve shear pin 9 is screwed into the screw hole at the lower end of the outer sealing sleeve 5, and the inner end of the inner sleeve shear pin 9 is embedded in the countersunk hole of the inner sleeve 4. It not only plays the role of axial positioning of the inner sleeve 4 and the function of constant pressure shearing, but also has the role of radial positioning, ensuring that the inner sleeve drainage hole 4d of the inner sleeve 4 and the outer sealing sleeve drainage hole 5b of the outer sealing sleeve 5 are facing each other in the circumferential direction.

[0037] An outer sealing sleeve retaining ring 7 is embedded in the inner wall ring groove of the middle section of the outer sealing sleeve 5, and an inner sleeve retaining ring groove 4c is provided on the upper outer periphery of the inner sleeve 4. Before the inner sleeve shear pin 9 is sheared off, the outer sealing sleeve retaining ring 7 is located below the inner sleeve retaining ring groove 4c, and the height difference between the two is equivalent to the downward travel of the inner sleeve 4.

[0038] When the inner sleeve shear pin 9 is cut off, the inner sleeve 4 slides down, and when the bottom of the inner sleeve outer convex ring 4b abuts against the inner step of the outer sealing sleeve enlarged diameter hole 5a, the inner sleeve 4 slides down into place, and the outer sealing sleeve retaining ring 7 is embedded in the inner sleeve retaining ring groove 4c to lock the inner sleeve 4.

[0039] An inner sleeve upper conical surface 4a is provided at the upper end of the center hole of the inner sleeve 4, which is used to limit the downward movement of the strong magnetic suction ball tube.

[0040] The lower end of the center hole of the inner sleeve 4 is provided with an inner sleeve lower conical surface 4e for reverse sealing of the multifunctional low-density iron ball 12 with a pressure ball seat.

[0041] The lower end of the inner sleeve 4 extends out from the lower port of the outer sealing sleeve 5, and is screwed with the inner sleeve nut 10, the top of which abuts against the bottom of the outer sealing sleeve 5. When backwashing the well, when the top of the low-density iron ball 12 abuts against the lower conical surface 4e of the inner sleeve, the inner sleeve nut 10 bears the pressure from below and the annulus of the oil casing, ensuring that the inner sleeve shear pin 9 is not sheared off.

[0042] The blowout-preventing tail pipe valve is located above the multifunctional pressurized ball seat and is pre-lowered into the well with the pipe string. The internal diameter of the blowout-preventing tail pipe valve is 42mm, while the internal diameters of water distributor 1F, water distributor 2D, and water distributor 3A are all 46mm.

[0043] like Figure 3 As shown, the multifunctional pressure ball seat comprises a ball seat outer cylinder 11, a ball seat body 13, a push rod 14, a push rod spring 15, a stopper 18 and a ball seat lower joint 16. The ball seat body 13 is abutted against the lower step of the middle section of the ball seat outer cylinder 11. The upper center of the ball seat body 13 is provided with a bell mouth for sealing the low-density iron ball 12. The bottom of the ball seat outer cylinder 11 is supported on the top of the ball seat lower joint 16. The upper end external thread section of the ball seat lower joint 16 is screwed into the lower end internal thread of the ball seat outer cylinder 11. A lower joint positioning pin 17 is screwed on the lower end circumference of the ball seat outer cylinder 11 to further lock the ball seat lower joint 16 to prevent it from loosening.

[0044] A ball seat lower joint sealing section is provided above the upper external thread section of the ball seat lower joint 16 , and two lower joint sealing rings 16 a are embedded on the outer periphery of the ball seat lower joint sealing section to achieve sealing with the inner wall of the ball seat outer tube 11 .

[0045] The top rod 14 passes through the center hole of the ball seat body 13, and the upper end abuts against the bottom of the low-density iron ball 12; the lower end is screwed into the center screw hole of the stopper 18, and the upper end of the stopper 18 abuts against the bottom of the inner step of the lower joint 16 of the ball seat. Two stopper sealing rings 19 are embedded in the outer periphery of the stopper 18 to achieve sealing with the inner wall of the lower joint 16 of the ball seat. The outer periphery of the stopper 18 is fixed to the circumference of the lower joint 16 of the ball seat by the stopper shear pin 20, ensuring that the lower port of the pipe string is closed during the well entry process to avoid blowout or overflow at the wellhead.

[0046] The upper part of the push rod 14 is provided with a push rod spring 15, and the upper end of the push rod spring 15 extends into the bell mouth at the upper end of the ball seat body 13, and is used to push the low-density iron ball 12 out of the setting state. The lower end of the center hole of the ball seat body is provided with a reduced diameter section to form an inner step, and the bottom of the push rod spring 15 is supported on the inner step at the lower end of the center hole of the ball seat body.

[0047] At least one pair of radial holes 13a of the ball seat body is provided along the height direction of the center hole of the ball seat body, the inner port of the radial hole 13a of the ball seat body is communicated with the center hole of the ball seat body, the outer port of the radial hole 13a of the ball seat body is communicated with the axial hole 13b of the ball seat body, and the lower port of the axial hole 13b of the ball seat body is communicated with the inner cavity of the lower joint 16 of the ball seat, so as to expand the flow area when the ball seat body 13 is opened, improve the backwash efficiency, or make the plugger drop faster.

[0048] A ball seat body sealing section is provided on the upper part of the ball seat body 13 , and two ball seat body sealing rings 13 c are embedded on the outer periphery of the ball seat body sealing section to achieve sealing with the inner wall of the ball seat outer tube 11 .

[0049] A ball seat body reduction section is provided below the ball seat body sealing section to reduce the finishing length of the outer periphery of the ball seat body 13; the annular space between the ball seat body reduction section and the ball seat outer cylinder 11 is connected to the ball seat body center hole through the ball seat body radial hole 13a to avoid pressure buildup in the annular space.

[0050] like Figure 4 As shown, the strong magnetic ball suction tube includes a magnetic isolation jacket 21, a strong magnetic core 22 and a strong magnetic ball suction seat 23. The magnetic isolation jacket 21 is generally made of magnetic isolation high-chromium stainless steel material. The upper end of the magnetic isolation jacket 21 is provided with a magnetic isolation jacket bell mouth, and the magnetic isolation jacket bell mouth is provided with a magnetic isolation jacket outer cone surface 21a and a magnetic isolation jacket inner cone surface 21b. The magnetic isolation jacket outer cone surface 21a matches the upper cone surface of the inner sliding sleeve 4, and the magnetic isolation jacket inner cone surface 21b is provided for the steel ball 24 to be sealed.

[0051] The strong magnetic core 22 is made of a material with strong magnetism, is annular in shape, and its upper end abuts against the inner step of the magnetic isolation sleeve 21 .

[0052] The strong magnetic ball seat 23 is screwed into the screw hole at the lower end of the magnetic isolation jacket 21, and its top is against the bottom of the strong magnetic core 22 to limit it. The lower end of the strong magnetic ball seat 23 is provided with a magnetic suction bell mouth, which matches the shape of the low-density iron ball 12 and is easy to cooperate with the low-density iron ball 12.

[0053] The central holes of the magnetic isolation jacket 21, the strong magnetic core 22 and the strong magnetic suction ball seat 23 are connected and have equal diameters. The outer diameter of the main body of the magnetic isolation jacket 21 is less than 30mm, and the maximum diameter of the bell mouth of the magnetic isolation jacket is less than 38mm, so that the strong magnetic suction ball tube can easily pass through the water distributor with an inner diameter of 46mm and go down smoothly.

[0054] The water injection well blowout prevention tool of the present invention can perform pressure-free well operation, in the following order: Pressure down pipe string: The multifunctional pressure ball seat push rod spring 15 pushes the push rod 14 to lift the low-density iron ball 12 and detach it from the bell mouth of the ball seat body 13. The lower block 18 closes the lower port of the ball seat outer tube 11, which can avoid blowout or wellhead overflow without well killing, ensure well control safety, and protect the wellhead environment from pollution.

[0055] Formation water injection: Figure 5 As shown, the pipe string moves downward to the designed position, the wellhead is pressurized, and the low-density iron ball 12 presses the push rod 14 downward until it is seated on the bell mouth of the ball seat body 13 to achieve sealing; the lower end of the push rod 14 pushes the block 18 downward to cut off the block shear pin 20. The push rod 14 and the block 18 fall down, and the 1-2MPa pressure difference during water injection pushes the low-density iron ball 12 downward, the push rod spring 15 is compressed, and the low-density iron ball 12 is seated on the bell mouth of the ball seat body 13, closing the lower channel of the ball seat body 13 to ensure normal water injection of the upper water distributor.

[0056] Backwash well circulation: Figure 6 As shown, the downhole pressure pushes the low-density iron ball 12 away, causing it to rise, and the lower end of the inner sleeve 4 of the blowout-proof tail pipe valve blocks the low-density iron ball 12, and the lower port of the inner sleeve 4 is closed by the low-density iron ball 12. The well-washing fluid enters the outer sealing sleeve drainage hole 5b from the annular channel 5c in the valve, and then enters the central hole through the inner sleeve drainage hole 4d, achieving normal drainage, and the well-washing fluid returns to the wellhead along the central channel to ensure the circulation of the well-washing fluid. When normal water injection is restored, the low-density iron ball 12 can be re-sealed.

[0057] When no water is injected: the push rod spring 15 is released and reset, pushing the low-density iron ball 12 away from the bell mouth of the ball seat body 13 for a distance, and the liquid column at the lower part of the pipe string can be connected with the oil casing annulus through the ball seat body 13, that is, the bottom of the pipe string is not a dead cavity, ensuring that when the strong magnetic suction ball tube is cast, the strong magnetic suction ball tube can quickly descend to the position under the action of gravity.

[0058] Lifting the pipe string with pressure: Figure 7As shown, at the wellhead, a strong magnetic ball suction tube is put into the pipe string, and then the valve at the upper end of the pipe string is closed. At this time, the push rod spring 15 is reset, pushing the low-density iron ball 12 to move upward, and the lower pipe string is connected with the oil casing annulus through the ball seat body 13. The lower end of the pipe string is not a dead cavity. Since the interior of the strong magnetic ball suction tube is a through hole, it is smooth to go down. After the strong magnetic ball suction tube enters the blowout-proof tail pipe valve under the action of gravity, the outer conical surface 21a of the magnetic isolation jacket of the strong magnetic ball suction tube falls to contact the upper conical surface 4a of the inner sleeve at the upper part of the inner sleeve 4, and the strong magnetic ball suction tube reaches the lower limit. At this time, the lower end of the strong magnetic ball suction tube extends out of or is flush with the lower port of the inner sleeve 4. Under the magnetic attraction of the strong magnetic core 22, the top of the low-density iron ball 12 is adsorbed at the bell mouth of the strong magnetic ball suction seat 23 at the lower end of the strong magnetic ball suction tube, and the lower port of the strong magnetic ball suction tube is closed.

[0059] like Figure 8 As shown, a steel ball 24 is then dropped from the wellhead, and the steel ball 24 falls on the inner conical surface 21b of the magnetic isolation jacket at the top of the strong magnetic suction ball tube and is sealed. Then the wellhead is pressurized, and the steel ball 24 pushes the inner sleeve 4 and the strong magnetic suction ball tube downward, shearing the sleeve shear pin, and the inner sleeve 4 and the strong magnetic suction ball tube continue to move downward until the outer convex ring 4b of the inner sleeve abuts against the limit step at the lower part of the outer sealing sleeve expansion hole 5a, and the inner sleeve 4 no longer moves downward. At this time, the outer sealing sleeve retaining ring 7 pops out and clamps the inner sleeve retaining ring groove 4c, fixing the relative position of the inner sleeve 4 and the outer sealing sleeve 5. At this time, the outer sealing sleeve drainage hole 5b and the inner sleeve drainage hole 4d are staggered in the height direction, and the inner sealing ring 8 of the outer sealing sleeve seals the upper and lower sides of the outer sealing sleeve drainage hole 5b, and the inner sleeve 4 and the outer sealing sleeve 5 are sealed.

[0060] like Fig. 9 As shown, after the wellhead is depressurized, the downhole pressure pushes the strong magnetic ball tube upward through the low-density iron ball 12. When the low-density iron ball 12 is blocked by the lower end of the inner sleeve 4, the low-density iron ball 12 cooperates with the lower conical surface of the inner sleeve 4 to achieve reverse sealing. The higher the downhole pressure, the better the effect of the low-density iron ball 12 in sealing the lower end of the inner sleeve 4.

[0061] In this state, the downhole pipes are pulled out of the wellhead one by one for maintenance. During this process, the central channel at the bottom of the pipe is reliably blocked by the low-density iron ball 12, which will not cause a blowout of the well with pressure or cause sewage overflow at the wellhead, effectively protecting the wellhead environment and ensuring operational safety.

[0062] The above is only a preferred embodiment of the present invention, which shows and describes the basic principles, main features and advantages of the present invention, but does not limit the scope of patent protection of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. In addition to the above embodiments, the present invention may have other implementation modes without departing from the spirit and scope of the present invention. The present invention may also have various changes and improvements, and all technical solutions formed by equivalent substitution or equivalent transformation fall within the scope of protection required by the present invention. The scope of protection required by the present invention is defined by the attached claims and their equivalents. The technical features not described in the present invention can be realized by or using existing technologies, which will not be repeated here.

Claims

1. A water injection well blowout prevention tool, comprising a multifunctional pressure ball seat, characterized in that: The upper end of the multifunctional pressure ball seat is screwed with a blowout-proof tail pipe valve, and the blowout-proof tail pipe valve comprises: The outer tube of the valve body has an upper female thread which is screwed to the upper oil pipe through the upper joint of the valve body, and a lower male thread which is screwed to the upper end of the multifunctional pressure ball seat; An outer sealing sleeve, wherein the upper part of the center hole is provided with an outer sealing sleeve expansion hole, the outer periphery of the upper part is provided with an outer sealing sleeve sealing section, the outer sealing sleeve sealing section is fixed on the inner step of the outer cylinder of the valve body, an inner valve annular channel is provided between the lower part of the outer sealing sleeve sealing section and the inner wall of the outer cylinder of the valve body, and an outer sealing sleeve drainage hole is provided in the middle and lower part; An inner sleeve is located in the inner cavity of the outer sealing sleeve, an inner sleeve outer convex ring is provided on the outer periphery of the upper end and supported on the upper inner wall of the outer sealing sleeve expansion hole, and an inner sleeve drainage hole is provided in the middle and lower part and communicates with the outer sealing sleeve drainage hole; The inner sleeve shear pin is screwed into the screw hole at the lower end of the outer sealing sleeve, and the inner end is embedded in the countersunk hole of the inner sleeve, so that the drainage hole of the inner sleeve is opposite to the drainage hole of the outer sealing sleeve.

2. The water injection well blowout prevention tool according to claim 1, characterized in that: The multifunctional pressure ball seat comprises: The ball seat outer cylinder accommodates the ball seat body, the low-density iron ball and the ejector rod; The ball seat body, the upper outer periphery of which abuts against the lower inner step of the middle part of the ball seat outer tube, the upper center is provided with a bell mouth, and the bottom is supported on the top of the lower joint of the ball seat; A low-density iron ball is seated on the bell mouth of the ball seat; A push rod passes through the center hole of the ball seat body, with its upper end abutting against the bottom of the low-density iron ball and its lower end supported in the lower joint of the ball seat; A push rod spring is sleeved on the upper part of the push rod, with the upper end extending into the bell mouth of the ball seat body and the bottom abutting against the inner step at the lower end of the center hole of the ball seat body; The upper end of the lower joint of the ball seat is screwed into the lower end internal thread of the outer tube of the ball seat and the two are sealed with each other.

3. The water injection well blowout prevention tool according to claim 2, characterized in that: The lower end of the push rod is supported at the top center of the stopper, the upper end of the stopper abuts against the lower inner step of the lower joint of the ball seat, and the outer periphery of the stopper is fixed to the circumference of the lower joint of the ball seat by a stopper shear pin.

4. The water injection well blowout prevention tool according to claim 2, characterized in that: At least one pair of radial holes of the ball seat body is provided along the height direction of the center hole of the ball seat body, the inner port of the radial hole of the ball seat body is communicated with the center hole of the ball seat body, the outer port of the radial hole of the ball seat body is communicated with the axial hole of the ball seat body, and the lower port of the axial hole of the ball seat body is communicated with the inner cavity of the lower joint of the ball seat.

5. The water injection well blowout prevention tool according to claim 1, characterized in that: An inner sleeve upper conical surface is arranged at the upper end of the center hole of the inner sleeve, and an inner sleeve lower conical surface is arranged at the lower end of the center hole of the inner sleeve.

6. The water injection well blowout prevention tool according to claim 5, characterized in that: The lower end of the inner sleeve extends out from the lower port of the outer sealing sleeve and is screwed with an inner sleeve nut, and the top of the inner sleeve nut abuts against the bottom of the outer sealing sleeve; When the lower conical surface of the inner sleeve is reversely sealed, the inner sleeve nut bears the pressure from below and the annulus of the oil casing, ensuring that the shear pin of the inner sleeve is not sheared off.

7. The water injection well blowout prevention tool according to claim 1, characterized in that: An outer sealing sleeve retaining ring is embedded in the annular groove on the middle inner wall of the outer sealing sleeve, and an inner sleeve retaining ring groove is provided on the upper outer periphery of the inner sleeve. When the bottom of the outer convex ring of the inner sleeve abuts against the inner step of the enlarged diameter hole of the outer sealing sleeve, the outer sealing sleeve retaining ring is embedded in the inner sleeve retaining ring groove to lock the inner sleeve.

8. The water injection well blowout prevention tool according to claim 5, characterized in that: The upper conical surface of the inner sleeve limits the strong magnetic ball suction tube, and the lower conical surface of the inner sleeve provides reverse sealing for the low-density iron ball, and the low-density iron ball is also used for the positive sealing of the multifunctional pressure ball seat.

9. The water injection well blowout prevention tool according to claim 8, characterized in that: The strong magnetic suction ball tube comprises: The magnetic isolation jacket has a magnetic isolation jacket bell mouth at the upper end, and the magnetic isolation jacket bell mouth is provided with a magnetic isolation jacket outer cone surface and a magnetic isolation jacket inner cone surface, the magnetic isolation jacket outer cone surface matches the cone surface on the inner sliding sleeve, and the magnetic isolation jacket inner cone surface is used for steel ball sealing; A strong magnetic core, which is annular and has an upper end that abuts against the lower inner step of the magnetic isolation jacket; A strong magnetic ball seat is screwed into the screw hole at the lower end of the magnetic isolation jacket, with its top abutting against the bottom of the strong magnetic core and a magnetic horn mouth at its lower end; The central holes of the magnetic isolation jacket, the strong magnetic core and the strong magnetic absorption ball seat are connected and have the same diameter.

10. A method for pressure-free well operation using the water injection well blowout prevention tool according to claim 2, characterized in that: The pipe string can be lifted with pressure, and the steps are as follows: the push rod spring of the multifunctional pressure ball seat pushes the upper push rod upward to lift the steel ball and separate it from the bell mouth of the ball seat; the stopper closes the lower end of the pipe string to avoid blowout or wellhead overflow; When the string is lowered to the designed position, water can be injected normally. The steps are as follows: the wellhead is pressurized, the low-density iron ball presses the push rod downward, cuts the shear pin of the stopper, the push rod and the stopper fall down, the low-density iron ball compresses the push rod spring and continues to move downward until it is seated on the ball seat body, the lower channel of the ball seat body is closed, and the upper water distributor performs normal water injection; When water injection stops: the push rod spring is released and reset, pushing the low-density iron ball away from the ball seat body, and the lower part of the pipe string is connected with the casing annulus through the ball seat body, ensuring that when the strong magnetic suction ball tube is dropped, the strong magnetic suction ball tube can quickly descend to the position under the action of gravity.

11. The pressure-free well operation method of the water injection well blowout prevention tool according to claim 10, characterized in that: Backwashing can be performed, and the steps are as follows: the downhole pressure pushes the low-density iron ball to make it rise until it reversely seals the lower end of the blowout-prevention tail pipe valve, and the well-washing fluid enters the center hole through the outer sealing sleeve drainage hole and the inner sliding sleeve drainage hole to achieve normal drainage, and the well-washing fluid returns to the wellhead along the center channel for circulation; when normal water injection is restored, the low-density iron ball can be re-sealed on the ball seat body.

12. The pressure-free well operation method of the water injection well blowout prevention tool according to claim 10, characterized in that: The pipe string can be lifted under pressure. The steps are as follows: at the wellhead, a strong magnetic ball suction pipe is put into the pipe string, and then the valve at the upper end of the pipe string is closed. At this time, the push rod spring is reset and pushes the low-density iron ball upward, opening the dead space at the lower end of the pipe string, so that the strong magnetic ball suction pipe can move downward smoothly. The strong magnetic ball suction pipe is inserted into the blowout prevention tail pipe valve and stops. Under the action of magnetic suction, the low-density iron ball is adsorbed on the lower end of the strong magnetic ball suction pipe; Then a steel ball is dropped from the wellhead, and the steel ball falls on the top of the strong magnetic ball suction tube to seal it; then the wellhead is pressurized, and the steel ball pushes the inner sleeve and the strong magnetic ball suction tube downward, cutting off the shear pin of the sleeve, and the inner sleeve and the strong magnetic ball suction tube continue to move downward until the inner sleeve is stuck on the limit step of the outer sealing sleeve and stops, at which time the outer sealing sleeve retaining spring is stuck in the inner sleeve retaining spring groove to lock the inner sleeve, and a seal is achieved between the inner sleeve and the outer sealing sleeve; After the wellhead is depressurized, the downhole pressure pushes the strong magnetic suction ball pipe upward until the low-density iron ball cooperates with the lower cone surface of the inner sleeve to achieve reverse sealing. Then the downhole pipes are pulled out of the wellhead one by one for maintenance.

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