Process pipe column with well killing function and blowout prevention function and construction method

Abstract

The invention discloses an under-pressure well process pipe column with a blowout prevention function and a construction method of the under-pressure well process pipe column. The under-pressure well process pipe column sequentially comprises a screwed plug, a screen pipe, a multifunctional under-pressure ball seat, a blowout prevention tail pipe valve, a first water distributor, a first packer, a second water distributor, a second packer and a third water distributor from bottom to top; normal water injection of the first to third water distributors is ensured; during plugging, the multifunctional under-pressure ball seat is automatically opened, so that no dead cavity is generated at the lower end of the tubular column. During normal well washing, the ball seat is closed, and water is injected into the water distributors normally. During inverse well flushing, the center channel of the ball seat is opened, and it can be guaranteed that setting can be conducted again during normal water injection. When the underground pipe column needs to be lifted, the strong magnetic ball suction pipe is put, and the lower end of the pipe column does not form a dead cavity, so that the strong magnetic ball suction pipe can smoothly move downwards; the bottom reversely seals the lower end opening of the inner sliding sleeve of the blowout prevention tail pipe valve, reliable blocking is achieved, and then 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 process pipe string with a well-killing function and a blowout prevention function; the present invention also relates to a construction method of a process pipe string with a well-killing function and a blowout prevention function, belonging to the technical field of downhole pipe strings for oil production wells. 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 formation energy of the surrounding oil wells decreases. At the same time, it breaks 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 pressure difference changes greatly and damages 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 to throw a strong magnetic suction ball tube; 2. Gravity free throw of a strong magnetic suction ball tube.

[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 pressurized operations cause wellhead overflow and environmental pollution, and to provide a process tubing string with a blowout prevention function for pressurized wells. Under the premise of pressurized operations, the bottom of the water injection well can be reliably sealed, and the internal overflow of the oil pipe during the process of raising and lowering the tubing string in the water injection well operation can be reduced, thereby achieving environmentally friendly construction.

[0009] In order to solve the above technical problems, the present invention provides a process pipe string with a blowout prevention function for a pressure well, which comprises, from bottom to top, a thread plug, a screen pipe, a multifunctional pressure ball seat, a blowout prevention tail pipe valve, a water distributor 1, a packer 1, a water distributor 2, a packer 2 and a water distributor 3. When injecting water, the multifunctional pressure ball seat closes automatically to ensure normal water injection from water distributor 1 to water distributor 3; when plugging, the multifunctional pressure ball seat opens automatically to prevent dead space from being generated at the lower end of the pipe string.

[0010] As an improvement of the present invention, 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.

[0011] As a further improvement of the present invention, the multifunctional pressure ball seat comprises: The ball seat outer cylinder has an upper end which is screwed to the lower part of the blowout-prevention tail pipe valve; The ball seat body has a lower end that abuts against the inner step in the middle of the ball seat outer tube, a bell mouth is provided at the center of the upper end, and the top is limited by a retaining spring on the cylinder body embedded in the inner wall of the upper part of the ball seat outer tube; A low-density iron ball, used for sealing the bell mouth at the upper end of the ball seat body and reversely sealing the lower end of the inner sleeve; The supporting liquid inlet ring is fixed to the middle and lower inner cavity of the outer cylinder of the ball seat; An upper ejector 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 passing through the center hole of the supporting liquid inlet ring; An upper ejector rod spring is sleeved on the lower reduced diameter section of the upper ejector rod, with the upper end abutting against the lower portion of the outer step of the upper ejector rod and the lower end supported on the supporting liquid inlet ring; A lower push rod coaxial with the upper push rod is provided below the upper push rod, and the lower end of the lower push rod is screwed to the top center of the stopper, and the stopper is locked in the lower inner cavity of the ball seat outer cylinder through a stopper shear pin.

[0012] As a further improvement of the present invention, an upper push rod nut is screwed onto the lower end of the upper push rod, and the upper push rod nut abuts against the lower side of the supporting liquid inlet ring.

[0013] As a further improvement of the present invention, the lower part of the upper push rod is provided with an upper push rod long groove extending along the axis and radially penetrating, and a limiting rod is inserted in the upper push rod long groove. The limiting rod extends radially along the supporting liquid inlet ring and both ends are supported in the supporting liquid inlet ring.

[0014] As a further improvement of the present invention, an upper conical surface of the inner sleeve is provided at the upper end of the center hole of the inner sleeve for limiting the strong magnetic suction ball tube, and a lower conical surface of the inner sleeve is provided at the lower end of the center hole of the inner sleeve for reverse sealing of a low-density iron ball. The low-density iron ball is also used for positive sealing of the multifunctional pressure ball seat below.

[0015] 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.

[0016] 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.

[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 construction method for a process pipe string with a blowout prevention function for a well pressured well. Through a multifunctional pressurized ball seat, a blowout prevention tail pipe valve and a strong magnetic ball suction pipe, reliable blocking of the bottom of the pipe string is achieved, which is resistant to high pressure and does not increase additional investment.

[0019] In order to solve the above technical problems, the construction method of the process pipe string with blowout prevention function for well killing of the present invention comprises the following steps: Pressurized pipe string: The spring of the upper push rod of the multifunctional pressurized 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 port of the pipe string to prevent overflow at the wellhead; Formation water injection: The pipe string is lowered to the designed position, the wellhead is pressurized, and the low-density iron ball pushes the upper push rod downward. The upper push rod supports the lower push rod downward, cutting the shear pin of the stopper. The stopper and the lower push rod fall onto the plug, and the low-density iron ball is sealed on the ball seat, so that each water distributor can inject water into the corresponding formation normally.

[0020] When not injecting water: the upper ejector spring pushes the upper ejector upward to separate the low-density iron ball from the ball seat body, avoiding the formation of a dead cavity under the ball seat body, ensuring that when plugging, the strong magnetic ball suction tube can move down to its position under the action of gravity to achieve the plugging function.

[0021] As a further improvement of the present invention, backwashing well circulation: downhole pressure pushes the low-density iron ball to make it rise, the lower end of the inner sleeve of the blowout-preventing tail pipe valve is sealed by the low-density iron ball, and the well-washing fluid enters the central hole from the outer sealing sleeve drainage hole and the inner sleeve drainage hole, and is normally discharged and circulated toward the wellhead; when normal water injection is restored, the low-density iron ball can be re-sealed.

[0022] As a further improvement of the present invention, the pipe string is lifted under pressure: 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 upper push rod spring is reset and pushes the low-density iron ball to move upward, so that the lower end of the pipe string is not a dead cavity, so that the strong magnetic ball suction pipe can smoothly descend, and stop after being inserted into the blowout prevention tail pipe valve. Under the action of magnetic attraction, the top of the low-density iron ball is adsorbed on the lower port 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 It is a schematic diagram of the structure of the process pipe string with well killing and blowout prevention function 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.

[0026] In the figure: A. Water distributor 3; B. Oil pipe; C. Packer 2; D. Water distributor 2; E. Packer 1; F. Water distributor 1; G. Blowout preventer tail pipe valve; H. Multifunctional pressure ball seat; J. Screen pipe; K. Thread plug; Blowout-proof tail pipe valve: 1. Joint on valve body; 2. Outer cylinder of valve body; 3. Circlip of outer cylinder; 4. Inner sleeve; 4a. Upper conical surface of inner sleeve; 4b. Outer convex ring of inner sleeve; 4c. Circlip groove of inner sleeve; 4d. Drain hole of inner sleeve; 4e. Lower conical surface of inner sleeve; 5. Outer sealing sleeve; 5a. Expanded hole of outer sealing sleeve; 5b. Drain hole of outer sealing sleeve; 5c. Annular channel in valve; 6. Outer sealing ring of sealing sleeve; 7. Circlip of outer sealing sleeve; 8. Inner sealing ring of outer sealing sleeve; 9. Shear pin of inner sleeve; 10. Nut of inner sleeve; Multifunctional pressure ball seat: 11. Ball seat outer cylinder; 11a. Upper retaining spring of the cylinder; 11b. Lower retaining spring of the cylinder; 12. Ball seat body; 12a. Ball seat body sealing ring; 13. Low-density iron ball; 14. Upper ejector rod; 14a. Upper ejector rod nut; 15. Upper ejector rod spring; 16. Support liquid inlet ring; 17. Limit rod; 18. Lower ejector rod; 19. Stopper; 19a. Stopper seal ring; 20. Stopper shear pin; Strong magnetic ball suction tube: 21. Magnetic isolation jacket; 21a. Outer cone surface of the magnetic isolation jacket; 21b. Inner cone surface of the magnetic isolation jacket; 22. Strong magnetic core; 23. Strong magnetic ball suction seat. 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 As shown, the process string with blowout prevention function for the pressure well of the present invention includes from top to bottom: a water distributor 3A, an oil pipe B, a packer 2C, a water distributor 2D, an oil pipe B, a packer 1E, a water distributor 1F, a blowout prevention tail pipe valve G, a multifunctional pressure ball seat H, a screen pipe J, and a screw plug K.

[0031] like Figure 2 As shown, the blowout-proof tail pipe valve G 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 H.

[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 expansion 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 13 with a pressure ball seat H.

[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 13 abuts against the lower conical surface 4e of the inner sleeve, the inner sleeve nut 10 withstands 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 G is located above the multifunctional pressurized ball seat H and is pre-lowered into the well with the pipe string. The internal diameter of the blowout-preventing tail pipe valve G is 42 mm, while the internal diameters of the water distributor F, water distributor D, and water distributor A are all 46 mm.

[0043] like Figure 3 As shown, the multifunctional pressurized ball seat H includes a ball seat outer tube 11, a ball seat body 12, a low-density iron ball 13, an upper push rod 14, a supporting liquid inlet ring 16, an upper push rod spring 15, a lower push rod 18, a block 19 and a block shear pin 20. The conical female thread at the upper end of the ball seat outer tube 11 is screwed with the male thread at the lower end of the valve body outer tube 2 of the blowout-proof tail pipe valve G.

[0044] The lower end of the ball seat body 12 rests on the inner step in the middle of the ball seat outer tube 11. There are two ball seat body sealing rings 12a in front of the outer periphery of the ball seat body 12 to achieve sealing with the inner wall of the ball seat outer tube 11. A bell mouth is provided in the center of the upper end of the ball seat body 12, and a cylinder upper retaining spring 11a is pressed on the top. The cylinder upper retaining spring 11a is embedded in the annular groove on the inner wall of the upper part of the ball seat outer tube 11.

[0045] The low-density iron ball 13 is used to seal the bell mouth at the upper end of the ball seat body 12 and the lower end of the reverse sealing inner sleeve 4; a hollow iron ball can be used to control the density at 2g / cm³.

[0046] The top of the supporting liquid inlet ring 16 is supported under the inner step of the ball seat outer cylinder 11 , and the bottom of the supporting liquid inlet ring 16 is supported on the lower retaining spring 11 b of the cylinder body, and the lower retaining spring 11 b of the cylinder body is embedded in the annular groove of the ball seat outer cylinder 11 .

[0047] The upper push rod 14 passes through the center hole of the ball seat body 12, and a gap is left between the center hole of the ball seat body 12. The upper end of the upper push rod 14 abuts against the bottom of the low-density iron ball 13, and the lower end passes through the center hole of the supporting liquid inlet ring 16 and can slide up and down.

[0048] The lower reduced diameter section of the upper ejector rod 14 is sleeved with an upper ejector rod spring 15 , the upper end of the upper ejector rod spring 15 abuts against the lower side of the outer step of the upper ejector rod 14 , and the lower end is supported on the supporting liquid inlet ring 16 .

[0049] A lower push rod 18 coaxial with the upper push rod 14 is provided below the upper push rod 14, with a gap between the two. The lower end of the lower push rod 18 is screwed to the top center of the stopper 19, and the middle part of the circumference of the stopper 19 is locked in the lower inner cavity of the ball seat outer tube 11 by symmetrically arranged stopper shear pins 20; two stopper sealing rings 19a are embedded in the outer periphery of the upper and lower ends of the stopper 19 to achieve sealing with the inner wall of the ball seat outer tube 11.

[0050] The lower end of the upper push rod 14 is screwed with an upper push rod nut 14 a, which abuts against the bottom of the supporting liquid inlet ring 16 to prevent the upper push rod 14 from sliding out of the center hole of the supporting liquid inlet ring 16 and bear the tension of the upper push rod spring 15.

[0051] The lower part of the upper ejector rod 14 is provided with an upper ejector rod long groove extending along the axis and radially penetrating, and a limit rod 17 is inserted in the upper ejector rod long groove, and the limit rod 17 extends along the radial direction of the support liquid inlet ring 16 and is supported at both ends in the support liquid inlet ring 16. The distance of the upper ejector rod long groove in the height direction is the up and down floating stroke of the upper ejector rod 14, and the floating of the upper ejector rod 14 can be guided.

[0052] 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 to be sealed.

[0053] 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 .

[0054] 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 13 and is easy to cooperate with the low-density iron ball 13.

[0055] 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 body of the magnetic isolation jacket 21 is less than 30 mm, the maximum diameter of the bell mouth of the magnetic isolation jacket is less than 38 mm, and the inner diameter of each water distributor is 46 mm. The strong magnetic suction ball tube can easily pass through the water distributor and go down smoothly.

[0056] During construction, the pipe string is screwed into the well in the following order from bottom to top: thread plug K + screen pipe J + multifunctional pressurized ball seat H + blowout-proof tail pipe valve G + 1 tail pipe + water distributor F + oil pipe B + packer E + oil pipe B + water distributor D + oil pipe B + packer C + oil pipe B + water distributor A + oil pipe B to the wellhead.

[0057] Lowering the pipe string with pressure: The upper push rod spring 15 of the multifunctional pressure ball seat H pushes the upper push rod 14 to lift the low-density iron ball 13 and detach it from the bell mouth of the ball seat body 12. The lower block 19 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.

[0058] Formation water injection: The pipe column goes down to the designed position, and the water distributor 1F, water distributor 2D, and water distributor 3A correspond to the corresponding water injection layers respectively. The wellhead is pressurized, and the low-density iron ball 13 presses the upper push rod 14 downward until it is seated on the bell mouth of the ball seat body 12 to achieve sealing; the lower step of the upper push rod 14 compresses the upper push rod spring 15, and the lower end head pushes the lower push rod 18 downward, and the lower push rod 18 pushes the block 19 downward, cutting off the block shear pin 20. The block 19 and the lower push rod 18 fall to the position of the screw plug K. The 1-2MPa pressure difference during water injection pushes the low-density iron ball 13 downward, the upper push rod spring 15 is compressed, and the low-density iron ball 13 is seated on the bell mouth of the ball seat body 12, closing the lower channel of the ball seat body 12, ensuring the normal water injection of the water distributor 1F, water distributor 2D, and water distributor 3A.

[0059] Backwashing circulation: Downhole pressure pushes the low-density iron ball 13 away, causing it to rise. The lower end of the inner sleeve 4 of the blowout-proof tail pipe valve G blocks the low-density iron ball 13, and the lower port of the inner sleeve 4 is sealed by the low-density iron ball 13. The well-washing fluid enters the outer sealing sleeve drainage hole 5b from the annular channel 5c inside the valve, and then enters the central hole through the inner sleeve drainage hole 4d, achieving normal drainage. 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 13 can be re-sealed.

[0060] When no water is injected: the upper push rod spring 15 is released and reset, pushing the upper push rod 14 upward for a distance, so that the low-density iron ball 13 leaves the bell mouth of the ball seat body 12 for a distance, and the liquid column at the lower part of the pipe string can pass through the ball seat body 12, and then communicate with the oil casing annulus through the screen pipe J, 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.

[0061] Lifting the pipe string with pressure: 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 upper push rod spring 15 is reset, pushing the low-density iron ball 13 to move upward, and the lower pipe string is connected with the oil casing annulus through the ball seat body 12 and the screen pipe J. The lower end of the pipe string is not a dead cavity. Since the interior of the strong magnetic ball suction pipe is a through hole, it is smooth to go down. After the strong magnetic ball suction pipe enters the blowout tail pipe valve G under the action of gravity, the outer conical surface 21a of the magnetic isolation jacket of the strong magnetic ball suction pipe 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 pipe reaches the lower limit. At this time, the lower end of the strong magnetic ball suction pipe extends out 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 13 is adsorbed at the bell mouth of the strong magnetic ball suction seat 23 at the lower end of the strong magnetic ball suction pipe, and the lower port of the strong magnetic ball suction pipe is closed.

[0062] Then, a steel ball is dropped from the wellhead, and the steel ball falls on the inner conical surface 21b of the magnetic isolation jacket at the top of the strong magnetic ball suction tube and is sealed. Then, the wellhead is pressurized, and the steel ball pushes the inner sleeve 4 and the strong magnetic ball suction tube downward, shearing the sleeve shear pin, and the inner sleeve 4 and the strong magnetic ball suction 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.

[0063] After the wellhead is depressurized, the downhole pressure pushes the strong magnetic ball suction tube upward through the low-density iron ball 13 and the lower conical surface of the strong magnetic ball suction tube. When the low-density iron ball 13 is blocked by the lower end of the inner sleeve 4, the low-density iron ball 13 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 13 in sealing the lower end of the inner sleeve 4.

[0064] 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 13, 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.

[0065] 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 process pipe string with well killing and blowout prevention function, characterized in that: From bottom to top, they include thread plug, screen pipe, multifunctional pressurized ball seat, blowout-proof tail pipe valve, water distributor 1, packer 1, water distributor 2, packer 2 and water distributor 3. When injecting water, the multifunctional pressurized ball seat closes automatically to ensure normal water injection from water distributor 1 to water distributor 3; when plugging, the multifunctional pressurized ball seat opens automatically to prevent dead space at the lower end of the pipe string.

2. The process pipe string with blowout prevention function for well pressure control according to claim 1 is characterized in that: 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.

3. The process pipe string with blowout prevention function for well pressure control according to claim 2 is characterized in that: The multifunctional pressure ball seat comprises: The ball seat outer cylinder has an upper end which is screwed to the lower part of the blowout-prevention tail pipe valve; The ball seat body has a lower end that abuts against the inner step in the middle of the ball seat outer tube, a bell mouth is provided at the center of the upper end, and the top is limited by a retaining spring on the cylinder body embedded in the inner wall of the upper part of the ball seat outer tube; A low-density iron ball, used for sealing the bell mouth at the upper end of the ball seat body and reversely sealing the lower end of the inner sleeve; The supporting liquid inlet ring is fixed to the middle and lower inner cavity of the outer cylinder of the ball seat; An upper ejector 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 passing through the center hole of the supporting liquid inlet ring; An upper ejector rod spring is sleeved on the lower reduced diameter section of the upper ejector rod, with the upper end abutting against the lower portion of the outer step of the upper ejector rod and the lower end supported on the supporting liquid inlet ring; A lower push rod coaxial with the upper push rod is provided below the upper push rod, and the lower end of the lower push rod is screwed to the top center of the stopper, and the stopper is locked in the lower inner cavity of the ball seat outer cylinder through a stopper shear pin.

4. The process pipe string with blowout prevention function for well pressure control according to claim 3 is characterized in that: The lower end of the upper push rod is screwed with an upper push rod nut, and the upper push rod nut is against the lower side of the supporting liquid inlet ring.

5. The process pipe string with blowout prevention function for well killing according to claim 3 is characterized in that: The lower part of the upper push rod is provided with an upper push rod long groove extending along the axis and radially penetrating, and a limit rod is inserted in the upper push rod long groove. The limit rod extends radially along the supporting liquid inlet ring and has two ends supported in the supporting liquid inlet ring.

6. The process pipe string with blowout prevention function for well pressure control according to claim 2, characterized in that: An upper conical surface of the inner sleeve is provided at the upper end of the center hole of the inner sleeve for limiting the strong magnetic suction ball tube, and a lower conical surface of the inner sleeve is provided at the lower end of the center hole of the inner sleeve for reverse sealing of a low-density iron ball. The low-density iron ball is also used for positive sealing of the multifunctional pressure ball seat below.

7. The process pipe string with blowout prevention function for well killing according to claim 6 is characterized in that: The lower end of the inner sliding sleeve extends out from the lower port of the outer sealing sleeve and is screwed with an inner sliding sleeve nut, and the top of the inner sliding sleeve nut abuts against the bottom of the outer sealing sleeve.

8. The process pipe string with blowout prevention function for well pressure control according to claim 2, 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.

9. The process pipe string with blowout prevention function for well killing according to claim 3, 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 construction method using the process pipe string with blowout prevention function for well killing according to claim 1, characterized in that: The steps include: Pressurized pipe string: The spring of the upper push rod of the multifunctional pressurized 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 port of the pipe string to prevent overflow at the wellhead; Formation water injection: The pipe string is lowered to the designed position, the wellhead is pressurized, and the low-density iron ball pushes the upper push rod downward. The upper push rod pushes the lower push rod downward, cutting off the shear pin of the stopper. The stopper and the lower push rod fall onto the plug, and the low-density iron ball is sealed on the ball seat, so that each water distributor can inject water into the corresponding formation normally; When not injecting water: the upper ejector spring pushes the upper ejector upward to separate the low-density iron ball from the ball seat body, avoiding the formation of a dead cavity under the ball seat body, ensuring that when plugging, the strong magnetic ball suction tube can move down to its position under the action of gravity to achieve the plugging function.

11. The construction method of the process pipe string with blowout prevention function for well killing according to claim 10, characterized in that: Backwash well circulation: Downhole pressure pushes the low-density iron ball to make it rise, and the lower end of the inner sleeve of the blowout-preventing tail pipe valve is sealed by the low-density iron ball. The well-washing fluid enters the center hole from the drainage hole of the outer sealing sleeve and the drainage hole of the inner sleeve, and circulates normally toward the wellhead; when normal water injection is restored, the low-density iron ball can be re-sealed.

12. The construction method of the process pipe string with blowout prevention function for well killing according to claim 10, characterized in that: Lifting the pipe string under pressure: 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 upper push rod spring is reset and pushes the low-density iron ball upward, so that the lower end of the pipe string is not a dead cavity, and the strong magnetic ball suction pipe moves down smoothly. After being inserted into the blowout-prevention tail pipe valve, it stops. Under the action of magnetic attraction, the top of the low-density iron ball is adsorbed on the lower port 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 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 this time, the retaining spring of the outer sealing sleeve is stuck in the retaining spring groove of the inner sleeve to lock the inner sleeve, and a seal is achieved between the inner sleeve and the outer sealing sleeve.

13. 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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