Device and method for replacing a valve under pressure in a flowing well

Abstract

The application discloses a device for replacing a valve of a self-flowing oil well under pressure, which comprises a valve matching connector connected with a valve of a self-flowing oil well to be disassembled, a blowout preventer pipe connected with the other end of the valve matching connector, a setting tool and a setting push cylinder connected in sequence on the blowout preventer pipe from the end close to the valve matching connector to the end far from the valve matching connector, and the other end of the setting push cylinder extending out of the blowout preventer pipe; or the setting tool and an unsetting tool are arranged on the blowout preventer pipe from the end close to the valve matching connector to the end far from the valve matching connector, and the other end of the unsetting tool extends out of the blowout preventer pipe. The device for replacing the valve of the self-flowing oil well under pressure solves the problem of long operation period and large difficulty in replacing the valve of the self-flowing oil well by adopting a pressure relief and well killing mode in the prior art. The application further discloses a method for replacing the valve of the self-flowing oil well under pressure.

Description

Technical Field

[0001] This invention belongs to the technical field of auxiliary devices for flowing oil wells, and relates to a device for replacing valves in flowing oil wells under pressure; this invention also relates to a method for replacing valves in flowing oil wells under pressure. Background Technology

[0002] Currently, many oil wells in oilfields achieve increased production through acidizing, fracturing, and other operations. Under scientifically controlled pressure, they can maintain flowing production for extended periods, achieving low-cost production. However, during long-term use, flowing wells experience problems such as internal leakage, rust, and inflexible operation of the main valves due to fluid erosion and natural aging of seals. These issues severely impact the safe production of flowing wells. Replacing valves by depressurizing or killing the well is not only time-consuming and difficult, but also inefficient. Furthermore, it poses risks of environmental pollution, reservoir contamination, and even wellhead loss of control during the process. Summary of the Invention

[0003] The purpose of this invention is to provide a device for replacing valves in flowing oil wells under pressure, which solves the problems of long operation cycles and high difficulty in replacing valves in flowing oil wells by depressurization and well control in the prior art.

[0004] Another object of the present invention is to provide a method for replacing valves under pressure in a self-flowing oil well.

[0005] The technical solution adopted in this invention is a device for replacing valves in a self-flowing oil well under pressure, including a valve fitting joint connected to the valve of the self-flowing oil well to be disassembled, and a blowout preventer connected to the other end of the valve fitting joint. The blowout preventer is provided with a setting tool and a setting pusher connected in sequence from the end near the valve fitting joint to the end away from the valve fitting joint, and the other end of the setting pusher extends out of the blowout preventer.

[0006] Alternatively, the blowout preventer is equipped with a setting tool and a release tool from the end closest to the valve fitting to the end furthest from the valve fitting, with the other end of the release tool extending out of the blowout preventer.

[0007] The invention is further characterized in that,

[0008] A pressure relief valve is installed at the position between the valve fitting and the setting tool on the blowout preventer.

[0009] The pressure relief valve is connected to a pressure gauge for monitoring the internal pressure of the blowout preventer.

[0010] The setting tool includes an outer tube coaxially mounted with the blowout preventer. The outer tube is fitted with, in sequence from the end closest to the valve fitting to the end furthest from the valve fitting, a lower support ring for the rubber sleeve, a setting rubber sleeve, an upper support ring for the rubber sleeve, a movable cone, a setting slip, and a thrust ring. The outer circumference of the setting slip is inlaid with setting slip teeth through heat treatment. The side of the movable cone closest to the setting slip is a conical surface. The side of the setting slip and the movable cone closest to each other has an inner conical hole that mates with the conical surface of the movable cone. The setting slip extends into the inner conical hole of the setting slip. The setting pusher can be sheared to the end of the outer tube furthest from the valve fitting. An inner tube coaxial with the outer tube is also installed inside the outer tube. The inner tube can be sheared to the outer tube. The inner wall of the other end of the inner tube is inlaid with retrieval teeth through heat treatment, and the retrieval teeth extend beyond the end of the outer tube where the setting pusher is installed.

[0011] A spring assembly is provided radially along one end of the inner tube and the outer tube. Holes are provided on the tube walls at the connection points of the inner tube and the outer tube, corresponding to the two ends of the spring assembly. The inner tube and the outer tube are connected by shearable pins a through the corresponding holes. The two ends of the spring assembly are fixed on the shearable pins a on the corresponding sides.

[0012] The setting pusher includes a hollow tube that can be sheared and connected to the outer tube at one end away from the valve fitting. The hollow tube is coaxial with the outer tube, and the other end of the hollow tube extends out of the blowout preventer. A pusher head, a pusher body, and a pusher rear end are sequentially fitted on the hollow tube from the direction closest to the outer tube to the direction furthest from the outer tube. The section of the pusher body furthest from the outer tube is located outside the blowout preventer and is provided with a pusher body step. The pusher rear end is connected to the end of the hollow tube furthest from the outer tube by a thread. The end of the pusher rear end closest to the outer tube is also provided with a pusher rear end step. The pusher rear end step and the pusher body step cooperate to limit the movement of the pusher body. A closed hydraulic cavity is formed between the outer wall of the hollow tube, the end face of the pusher body near the pusher rear end, and the inner wall of the pusher rear end. An inlet pipe and a drain pipe are connected to the hydraulic cavity.

[0013] A sealing ring is installed at the end of the blowout preventer that is away from the valve fitting. The pusher head passes through the sealing ring and extends out of the blowout preventer. Holes are correspondingly opened on the pipe wall at the connection between the outer pipe and the hollow pipe. The outer pipe and the hollow pipe are sheared together by passing a shearable pin b through the corresponding holes.

[0014] The unsealing tool includes an unsealing tool body. One end of the unsealing tool body is inlaid with retrieval teeth through heat treatment. The retrieval teeth and retrieval teeth interlock with each other. The end of the unsealing tool body away from the retrieval teeth passes through the sealing ring and extends out of the blowout preventer.

[0015] Another technical solution adopted in this invention is a method for replacing valves in a flowing oil well under pressure, using the aforementioned device for replacing valves in a flowing oil well under pressure, specifically implemented according to the following steps:

[0016] Step 1, the valve setting and replacement process, is completed by connecting the setting tool and the setting pusher.

[0017] Step 2: The unsealing process is completed by connecting the sealing tool and the unsealing tool.

[0018] Step 1 is as follows:

[0019] Step 1.1: Connect the valve fitting to the valve of the self-flowing well to be replaced. At this time, the setting tool and the setting pusher are connected, the pressure relief valve is in the closed state, and there is no pressure inside the blowout preventer.

[0020] Step 1.2: Slowly open the valve of the self-flowing oil well to be replaced;

[0021] Step 1.3: Push the setting pusher to make the setting tool pass through the valve to be replaced and reach the predetermined position at the front end of the self-flowing oil well valve to be replaced, that is, in the wellhead body pipeline connected to the front end of the self-flowing oil well valve to be replaced.

[0022] Step 1.4: High-pressure hydraulic oil is injected into the hydraulic chamber through the inlet pipe, pushing the pusher body forward. The pusher body pushes the pusher head and thrust ring forward, forcing the setting slips, movable cone, upper support ring of the rubber sleeve, and setting rubber sleeve to move forward synchronously. Since there is no room for movement at the front end of the setting rubber sleeve, the sealing annulus expands under the compression of the upper and lower support rings. After the annulus is completely sealed, the setting rubber sleeve cannot be compressed further, the movable cone cannot move forward further, and the setting slips are forced to slide relative to the outside of the movable cone due to the continued movement of the thrust ring, thus opening up. The teeth of the setting slips embed into the wellhead. The inner wall of the pipe is anchored. After the setting slip and thrust ring move into place, the limiting shearable pin a is ejected outward from the hole on the inner and outer pipe walls by the action of the spring assembly, completing the pressure isolation before and after the setting tool and limiting the thrust ring. High-pressure hydraulic oil continues to be injected into the hydraulic chamber through the inlet pipe. Since the push cylinder body can no longer move forward, the rear end of the push cylinder begins to move backward under force, which at the same time drives the hollow tube to move backward. The backward movement of the hollow tube causes the shearable pin b to be sheared, realizing the separation of the setting push cylinder and the setting tool. Then, the high-pressure hydraulic oil in the hydraulic chamber is recovered through the drain pipe, completing the pressure release in the hydraulic chamber.

[0023] Step 1.5: Open the pressure relief valve to release pressure until the internal pressure of the blowout preventer is 0 MPa, then replace it with a new valve. The new valve should be in the normally open position. At the same time, remove the blowout preventer equipped with the setting pusher.

[0024] Step 2 is as follows:

[0025] Step 2.1: Connect the valve fitting to the new valve that has been replaced, and pass the end of the unsealing tool with the retrieval teeth through the dynamic seal ring;

[0026] Step 2.2, close the pressure relief valve;

[0027] Step 2.3: Push the unsealing tool body through the new valve to the position of the inner tube at the rear end of the setting tool, and continue to push so that the retrieval teeth enter the inner tube and mesh with each other, so that the setting tool is retrieved by the unsealing tool;

[0028] Step 2.4: Pull out the unsealing tool body to move the inner tube backward, causing the shearable pin a to be sheared, resulting in the release of the thrust ring limit. Continue to move the unsealing tool backward, giving the setting tool a backward force. At the same time, since the setting rubber sleeve is in a compressed state, it has a rebound force. After the thrust ring limit is released, the movable cone has a backward force. Under the action of the dual forces, the setting slips contract and release the anchor. Continue to pull out the unsealing tool to move the thrust ring and movable cone backward until the setting state is released. Continue to pull out the unsealing tool and retrieve the unsealing tool and setting tool into the blowout preventer.

[0029] Step 2.5: Close the new valve, open the pressure relief valve to release pressure until the pressure inside the blowout preventer is 0 MPa, disassemble the blowout preventer, and recover the device used for replacing valves under pressure in a self-flowing oil well.

[0030] The beneficial effects of this invention are:

[0031] (1) The present invention enables the replacement of the main valve or inner valve of the self-flowing oil well without depressurization or well control, reducing the workflow and shortening the construction cycle. Moreover, the present invention is simple to operate, requires no manpower or material resources, and saves the maintenance cost of the self-flowing oil well.

[0032] (2) Since the present invention does not depressurize or kill the self-flowing oil well, it will not cause environmental pollution, oil layer pollution or even wellhead loss of control, and has the advantages of safety and environmental protection, and improves the production efficiency of oil wells.

[0033] (3) The setting tool and setting pusher of the present invention can be reused after the pin is replaced, thus reducing costs. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the device for replacing valves under pressure in a self-flowing oil well according to the present invention;

[0035] Figure 2 yes Figure 1 A magnified view of a section at point A in the middle;

[0036] Figure 3 yes Figure 1 A magnified view of a section at point B in the middle;

[0037] Figure 4 yes Figure 1 A magnified view of a section at point C;

[0038] Figure 5This is a schematic diagram of the setting tool after setting and removal of the setting pusher in the method for replacing valves in a self-flowing oil well under pressure according to the present invention.

[0039] Figure 6 This is a schematic diagram illustrating the use of the unsealing tool in the method for replacing valves in a self-flowing oil well under pressure, as described in this invention. Detailed Implementation

[0040] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0041] Example 1

[0042] The device for replacing valves on pressurized surfaces in flowing oil wells has the following structure: Figure 1-4 As shown, it includes a valve fitting 1 connected to the self-flowing oil well valve 8 to be dismantled. The other end of the valve fitting 1 is connected to a blowout preventer 2. The blowout preventer 2 is provided with a setting tool 4 and a setting pusher 5 connected in sequence from one end near the valve fitting 1 to the end away from the valve fitting 1. The other end of the setting pusher 5 extends out of the blowout preventer 2.

[0043] Alternatively, the blowout preventer 2 is equipped with a setting tool 4 and a release tool 7 from one end near the valve fitting 1 to the other end away from the valve fitting 1, with the other end of the release tool 7 extending out of the blowout preventer 2.

[0044] A pressure relief valve 3 is installed at the position between the valve fitting 1 and the setting tool 4 on the blowout preventer 2.

[0045] A pressure gauge is connected to the pressure relief valve 3 to monitor the internal pressure of the blowout preventer 2.

[0046] The setting tool 4 includes an outer tube 411 coaxially arranged with the blowout preventer 2. The outer tube 411 is fitted with, in sequence from the end closest to the valve fitting 1 to the end furthest from the valve fitting 1, a lower support ring 401, a setting rubber tube 402, an upper support ring 403, a movable cone 404, a setting slip 405, and a thrust ring 407. The outer circumference of the setting slip 405 is inlaid with setting slip teeth 406 through heat treatment. The side of the movable cone 404 closest to the setting slip 405 is set as a conical surface. The setting slip 405... An inner conical hole is provided on one side near the movable cone 404, which mates with the conical surface of the movable cone 404. The setting slip 405 extends into the inner conical hole of the setting slip 405. The setting push cylinder 5 and the outer tube 411 can be cut-connected at the end away from the valve matching connector 1. The outer tube 411 is also provided with an inner tube 410 coaxial with the outer tube 411. The inner tube 410 and the outer tube 411 can be cut-connected. The inner wall of the other end of the inner tube 410 is inlaid with a retrieval tooth 412 by heat treatment, and the retrieval tooth 412 extends out of the end of the outer tube 411 where the setting push cylinder 5 is installed.

[0047] A spring assembly 408 is provided radially along the inner end of the inner tube 410 and the outer tube 411. Holes are provided on the tube walls at the connection points of the inner tube 410 and the outer tube 411 corresponding to the two ends of the spring assembly 408. The inner tube 410 and the outer tube 411 are sheared together by shearable pins a409 provided in the corresponding holes. The two ends of the spring assembly 408 are respectively fixed on the shearable pins a409 on the corresponding side.

[0048] The setting pusher 5 includes a hollow tube 502 that can be sheared and connected to the outer tube 411 at one end away from the valve fitting 1. The hollow tube 502 is coaxially arranged with the outer tube 411, and the other end of the hollow tube 502 extends out of the blowout preventer 2. A pusher head 501, a pusher body 503, and a pusher rear end 505 are sequentially fitted on the hollow tube 502 from the direction closest to the outer tube 411 to the direction furthest from the outer tube 411. The section of the pusher body 503 furthest from the outer tube 411 is located outside the blowout preventer 2 and is provided with a pusher body step 5031. The pusher rear end 505 is connected to the hollow tube. The end of 502 away from the outer tube 411 is connected by a thread. The end of the pusher cylinder 505 near the outer tube 411 is also provided with a pusher cylinder rear end step 5051. The pusher cylinder rear end step 5051 and the pusher cylinder body step 5031 cooperate with each other to limit the movement of the pusher cylinder body 503. A closed hydraulic cavity 506 is formed between the outer wall of the hollow tube 502, the end face of the pusher cylinder body 503 near the pusher cylinder rear end 505, and the inner wall of the pusher cylinder rear end 505. The hydraulic cavity 506 is connected to an inlet pipe 507 and an outlet pipe 508.

[0049] A sealing ring 6 is provided at the end of the blowout preventer 2 away from the valve fitting 1. The pusher head 501 extends out of the blowout preventer 2 after passing through the sealing ring 6. Holes are correspondingly opened on the pipe wall at the connection between the outer pipe 411 and the hollow pipe 502. The outer pipe 411 and the hollow pipe 502 are shearably connected by passing a shearable pin b504 through the corresponding holes.

[0050] The unsealing tool 7 includes an unsealing tool body 702. One end of the unsealing tool body 702 is inlaid with a retrieval tooth 701 by heat treatment. The retrieval tooth 701 and the retrieval tooth 412 mesh with each other. The end of the unsealing tool body 702 away from the retrieval tooth 412 passes through the sealing ring 6 and extends out of the blowout preventer 2.

[0051] Example 2

[0052] Based on Example 1, the valve fitting connector 1 is connected to the blowout preventer 2 via threads, and the blowout preventer 2 is connected to the pressure relief valve 3 with connectivity via threads. The pressure relief valve 3 can be connected to a pressure gauge via threads to monitor the internal pressure of the blowout preventer 2; and the pressure gauge installed on the pressure relief valve 3 should be greater than the highest production pressure at the wellhead of the self-flowing oil well.

[0053] The present invention incorporates annular steps between the components of the lower support ring 401, the setting rubber tube 402, the upper support ring 403, the movable cone 404, and the setting slip 405, which allow for accurate connection and sealing of each component during installation. The present invention requires design to ensure that the moving distance of each component on the setting tool matches the limit of the shearable pin a when the setting rubber tube 402 expands and seals.

[0054] The front sections of the inlet pipe 507 and the outlet pipe 508 are internally connected to the hydraulic chamber 506 by threads, and have pressure-bearing capacity.

[0055] The blowout preventer 2 is designed with a sealing ring 6 at the tail end, which can withstand the high pressure inside the well of the self-flowing oil well;

[0056] The inlet pipe 507 and outlet pipe 508 are connected to a bidirectional hydraulic pump. When the hydraulic pump is turned on in the forward direction, high-pressure hydraulic oil can be injected through the inlet pipe 507. When the hydraulic pump is turned on in the reverse direction, the high-pressure hydraulic oil in the hydraulic chamber 506 can be recovered to the hydraulic pump through the outlet pipe 508, thus releasing the pressure in the hydraulic chamber 506. The maximum force for setting the sealing tool is P1, which is injected with hydraulic oil through the inlet pipe 507. The force for shearing the shearable pin a is P2, which is continued to be injected with hydraulic oil. It is required that P1 < 0.8P2 through design to prevent the shearable pin a from being sheared before the setting tool sets.

[0057] Example 3

[0058] Based on Example 2, the present invention provides a method for replacing valves in a self-flowing oil well under pressure, which is implemented according to the following steps:

[0059] Step 1, the valve setting and replacement process, is completed by connecting the setting tool 4 and the setting pusher 5;

[0060] Step 2, the unsealing process is completed by connecting the sealing tool 4 and the unsealing tool 7.

[0061] Step 1 is as follows:

[0062] Step 1.1: Connect the valve fitting connector 1 to the self-flowing well valve 8 to be replaced. At this time, the setting tool 4 and the setting pusher 5 are connected, the pressure relief valve 3 is in the closed state, and there is no pressure inside the blowout preventer 2.

[0063] Step 1.2: Slowly open the valve 8 of the self-flowing oil well to be replaced;

[0064] Observe the pressure gauge during the process and record the details to facilitate risk identification and prevention;

[0065] Step 1.3: Push the setting pusher 5 to make the setting tool 4 pass through the valve to be replaced and reach the predetermined position at the front end of the self-flowing oil well valve 8 to be replaced, that is, in the wellhead body pipeline connected to the front end of the self-flowing oil well valve 8 to be replaced.

[0066] Step 1.4: High-pressure hydraulic oil is injected into the hydraulic chamber 506 through the inlet pipe 507, pushing the pusher body 503 forward. The pusher body 503 pushes the pusher head 501 and the thrust ring 407 forward, forcing the setting slip 405, the movable cone 404, the upper support ring 403 of the rubber sleeve, and the setting rubber sleeve 402 to move forward synchronously. Since there is no room for movement at the front end of the setting rubber sleeve 402, the sealing annulus is expanded under the compression of the upper support ring 403 and the lower support ring 401 of the rubber sleeve. After the annulus is completely sealed, the setting rubber sleeve 402 cannot be compressed further, the movable cone 404 cannot move forward further, and the setting slip 405 is forced to move outside the movable cone 404 due to the continued movement of the thrust ring 407. The relative sliding propagation opens the setting slip 406, which embeds into and anchors the inner wall of the wellhead pipe. After the setting slip 405 and thrust ring 407 move into place, the limiting shearable pin a409, under the action of spring assembly 408, pops out from the holes in the inner tube 410 and outer tube 411, completing the pressure isolation before and after the setting tool 4 and limiting the thrust ring 407. High-pressure hydraulic oil continues to be injected into the hydraulic chamber 506 through the inlet pipe 507. Since the pusher body 503 cannot move forward, the rear end 505 of the pusher begins to move backward under force, simultaneously driving the hollow tube 502 to move backward. The backward movement of the hollow tube 502 shears the shearable pin b504, realizing the separation of the setting pusher 5 from the setting tool 4. Figure 5 As shown, the high-pressure hydraulic oil in the hydraulic chamber 506 is then recovered through the drain pipe 508, thus completing the pressure release in the hydraulic chamber 506.

[0067] Step 1.5: Open the pressure relief valve 3 to release pressure until the internal pressure of the blowout preventer 2 is 0 MPa, then replace it with a new valve. The new valve should be in the normally open state. At the same time, disassemble the blowout preventer 2 equipped with the setting pusher 5.

[0068] Step 2 is as follows:

[0069] Step 2.1: Connect the valve fitting connector 1 to the new valve that has been replaced, and pass one end of the unsealing tool 7 with the retrieval tooth 701 through the dynamic seal ring 6;

[0070] Step 2.2, close pressure relief valve 3;

[0071] Step 2.3, as follows Figure 6 As shown, the unsealing tool body 702 is pushed through the new valve to the position of the rear inner tube 410 of the setting tool 4. The push continues to make the retrieval tooth 701 enter the inner tube 410 and mesh with the retrieval tooth 412, so that the setting tool 4 is retrieved by the unsealing tool 7.

[0072] Step 2.4: Pull out the unsealing tool body 702 to move the inner tube 410 backward, causing the shearable pin a409 to be sheared, resulting in the release of the limit of the thrust ring 407. Continue to move the unsealing tool 7 backward, so that the setting tool 4 has a backward force. At the same time, since the setting rubber sleeve 402 is in a compressed state, it has a rebound force. After the limit of the thrust ring 407 is released, the movable cone 404 has a backward force. Under the action of the dual forces, the setting slip 405 contracts and releases the anchor. Continue to pull out the unsealing tool 7 to move the thrust ring 407 and the movable cone 404 backward until the setting state is released. Continue to pull out the unsealing tool 7, and retrieve the unsealing tool 7 and the setting tool 4 into the blowout preventer 2.

[0073] Step 2.5: Close the new valve, open the pressure relief valve 3 to release pressure until the pressure inside the blowout preventer 2 is 0 MPa, disassemble the blowout preventer 2, and recover the device used for replacing valves under pressure in a self-flowing oil well.

Claims

1. A device for replacing valves under pressure in a self-flowing oil well, characterized in that, Includes a valve fitting joint (1) connected to the self-flowing well valve (8) to be dismantled, and a blowout preventer (2) connected to the other end of the valve fitting joint (1). The blowout preventer (2) is provided with a setting tool (4) and a setting pusher (5) connected in sequence from the end near the valve fitting joint (1) to the end away from the valve fitting joint (1). The other end of the setting pusher (5) extends out of the blowout preventer (2). The setting tool (4) includes an outer tube (411) coaxially arranged with the blowout preventer (2). The outer tube (411) is fitted with, in sequence from the end closest to the valve fitting (1) to the end furthest from the valve fitting (1), a lower support ring (401), a setting rubber sleeve (402), an upper support ring (403), a movable cone (404), a setting slip (405), and a thrust ring (407). The outer circumference of the setting slip (405) is inlaid with setting slip teeth (406) through heat treatment. The side of the movable cone (404) closest to the setting slip (405) is set as a conical surface. The setting slip (405) and the movable cone (404) are connected... 04) An inner conical hole is provided near one side to mate with the conical surface of the movable cone (404). The setting slip (405) extends into the inner conical hole of the setting slip (405). The setting push cylinder (5) and the outer tube (411) can be sheared connected at one end away from the valve matching connector (1). The outer tube (411) is also provided with an inner tube (410) coaxial with the outer tube (411). The inner tube (410) and the outer tube (411) can be sheared connected. The inner wall of the other end of the inner tube (410) is inlaid with a retrieval tooth (412) by heat treatment. The retrieval tooth (412) extends out of the end of the outer tube (411) where the setting push cylinder (5) is installed. A spring assembly (408) is provided radially at one end of the inner tube (410) and the outer tube (411). Holes are provided on the tube walls at both ends of the spring assembly (408) at the connection position of the inner tube (410) and the outer tube (411). The inner tube (410) and the outer tube (411) are connected by shearable pins a (409) provided in the corresponding holes. The two ends of the spring assembly (408) are respectively fixed on the shearable pins a (409) on the corresponding side. The setting pusher (5) includes a hollow tube (502) that can be sheared and connected to the outer tube (411) away from the valve fitting joint (1). The hollow tube (502) is coaxially arranged with the outer tube (411). The other end of the hollow tube (502) extends out of the blowout preventer (2). The hollow tube (502) is provided with a pusher head (501), a pusher body (503), and a pusher rear end (505) in sequence from the direction close to the outer tube (411) to the direction away from the outer tube (411). The section of the pusher body (503) away from the outer tube (411) is located outside the blowout preventer (2) and is provided with a pusher body step (5031). The pusher rear end ( 505) is connected to the end of the hollow tube (502) away from the outer tube (411) by a thread. The end of the pusher cylinder (505) near the outer tube (411) is also provided with a pusher cylinder rear end step (5051). The pusher cylinder rear end step (5051) and the pusher cylinder body step (5031) cooperate with each other to limit the movement of the pusher cylinder body (503). A closed hydraulic cavity (506) is formed between the outer wall of the hollow tube (502), the end face of the pusher cylinder body (503) near the pusher cylinder rear end (505), and the inner wall of the pusher cylinder rear end (505). The hydraulic cavity (506) is connected to an inlet pipe (507) and a drain pipe (508). A sealing ring (6) is provided at the end of the blowout preventer (2) away from the valve fitting (1). The pusher head (501) passes through the sealing ring (6) and extends out of the blowout preventer (2). Holes are correspondingly opened on the pipe wall at the connection between the outer pipe (411) and the hollow pipe (502). The outer pipe (411) and the hollow pipe (502) are shearably connected by passing a shearable pin b (504) through the corresponding holes.

2. The device for replacing valves under pressure in a self-flowing oil well according to claim 1, characterized in that, The blowout preventer (2) is equipped with a pressure relief valve (3) located between the valve fitting (1) and the setting tool (4).

3. The device for replacing valves under pressure in a self-flowing oil well according to claim 2, characterized in that, The pressure relief valve (3) is connected to a pressure gauge for monitoring the internal pressure of the blowout preventer (2).

4. The device for replacing valves under pressure in a self-flowing oil well according to claim 3, characterized in that, It also includes a release tool (7), and the blowout preventer (2) is provided with a setting tool (4) and a release tool (7) from one end near the valve fitting (1) to the other end away from the valve fitting (1), with the other end of the release tool (7) extending out of the blowout preventer (2).

5. The device for replacing valves under pressure in a self-flowing oil well according to claim 4, characterized in that, The unsealing tool (7) includes an unsealing tool body (702), one end of which is inlaid with a retrieval tooth (701) by heat treatment. The retrieval tooth (701) and the retrieval tooth (412) mesh with each other. The end of the unsealing tool body (702) away from the retrieval tooth (412) passes through the sealing ring (6) and extends out of the blowout preventer (2).

6. A method for replacing valves under pressure in a self-flowing oil well, characterized in that, The device for replacing valves in a flowing oil well under pressure, as described in claim 5, is implemented according to the following steps: Step 1, the valve setting and replacement process, is completed by connecting the setting tool (4) and the setting pusher (5); Step 2, the unsealing process is completed by connecting the sealing tool (4) and the unsealing tool (7).

7. The method for replacing valves in a flowing oil well under pressure according to claim 6, characterized in that, Step 1 specifically involves: Step 1.1: Connect the valve fitting connector (1) to the self-flowing well valve (8) to be replaced. At this time, the setting tool (4) and the setting pusher (5) are connected, the pressure relief valve (3) is in the closed state, and there is no pressure inside the blowout preventer (2). Step 1.2: Slowly open the valve (8) of the self-flowing oil well to be replaced; Step 1.3, push the setting pusher (5) so that the setting tool (4) passes through the valve to be replaced and reaches the predetermined position at the front end of the self-flowing oil well valve (8) to be replaced, that is, in the wellhead body pipeline connected to the front end of the self-flowing oil well valve (8) to be replaced. Step 1.4: High-pressure hydraulic oil is injected into the hydraulic chamber (506) through the inlet pipe (507), pushing the pusher body (503) forward. The pusher body (503) pushes the pusher head (501) and thrust ring (407) forward, forcing the setting slips (405), movable cone (404), upper support ring (403) of the rubber sleeve, and setting rubber sleeve (402) to move forward synchronously. Since there is no room for movement at the front end of the setting rubber sleeve (402), the sealing annulus is expanded under the compression of the upper support ring (403) and lower support ring (401) of the rubber sleeve. After the annulus is completely sealed, the setting rubber sleeve (402) cannot be compressed further, the movable cone (404) cannot move forward further, and the setting slips (405) are forced to slide relative to the outside of the movable cone (404) and open due to the continued movement of the thrust ring (407). The setting slip teeth (406) are embedded in the wellhead. After the inner wall of the pipe is anchored and the setting slip (405) and the thrust ring (407) are moved into place, the limiting shearable pin a (409) is ejected outward from the hole on the inner tube (410) and outer tube (411) by the action of the spring assembly (408), thus completing the pressure isolation before and after the setting tool (4) and the limiting of the thrust ring (407); continue to inject high pressure hydraulic oil into the hydraulic chamber (506) through the inlet pipe (507). Since the push cylinder body (503) cannot move forward, the rear end (505) of the push cylinder begins to move backward under force, and at the same time drives the hollow tube (502) to move backward. The backward movement of the hollow tube (502) causes the shearable pin b (504) to be sheared, thus realizing the separation of the setting push cylinder (5) from the setting tool (4). Then, the high pressure hydraulic oil in the hydraulic chamber (506) is recovered through the drain pipe (508), thus completing the pressure release in the hydraulic chamber (506). Step 1.5: Open the pressure relief valve (3) to release pressure until the internal pressure of the blowout preventer (2) is 0 MPa, then replace it with a new valve. The new valve should be in the normally open state. At the same time, disassemble the blowout preventer (2) equipped with the setting pusher (5). Step 2 specifically involves: Step 2.1: Connect the valve fitting connector (1) to the new valve that has been replaced, and pass one end of the unsealing tool (7) with the retrieval teeth (701) through the dynamic seal ring (6). Step 2.2, close the pressure relief valve (3); Step 2.3, push the unsealing tool body (702) through the new valve to the position of the rear inner tube (410) of the setting tool (4), and continue to push so that the retrieval teeth (701) enter the inner tube (410) and mesh with the retrieval teeth (412), so that the setting tool (4) is retrieved by the unsealing tool (7); Step 2.4, pull the unsealing tool body (702) to move the inner tube (410) backward, so that the shearable pin a (409) is sheared, causing the limit of the thrust ring (407) to be released. Continue to move the unsealing tool (7) backward, so that the setting tool (4) has a backward force. At the same time, since the setting rubber tube (402) is in a compressed state, it has a rebound force. After the limit of the thrust ring (407) is released, the movable cone (404) has a backward force. Under the action of the dual forces, the setting slip (405) contracts and releases the anchor. Continue to pull the unsealing tool (7) to move the thrust ring (407) and the movable cone (404) backward until the setting state is released. Continue to pull the unsealing tool (7) and retrieve the unsealing tool (7) and the setting tool (4) into the blowout preventer (2). Step 2.5: Close the new valve, open the pressure relief valve (3) to release pressure until the pressure inside the blowout preventer (2) is 0 MPa, disassemble the blowout preventer (2), and recover the device used for replacing valves under pressure in a self-flowing oil well.

Images