Device and method for replacing valve of flowing oil well under pressure

Abstract

The invention discloses a device for replacing a valve of a self-injection oil well under pressure, which comprises a valve matching joint connected with the valve of the self-injection oil well to be disassembled, and the other end of the valve matching joint is connected with a blowout prevention pipe. A setting tool and a setting push cylinder which are connected in sequence are arranged from one end, close to the valve matching connector, of the blowout prevention pipe to one end, far away from the valve matching connector, of the blowout prevention pipe, and the other end of the setting push cylinder extends out of the blowout prevention pipe; or the setting tool and the unsetting tool are arranged from one end, close to the valve matching connector, of the anti-spraying pipe to one end, far away from the valve matching connector, of the anti-spraying pipe, and the other end of the unsetting tool extends out of the anti-spraying pipe. According to the device for replacing the valve under pressure of the flowing oil well, the problems that in the prior art, the operation period is long and the replacement difficulty is large when the valve is replaced in a pressure relief and well killing mode for the flowing oil well are solved. The invention further discloses a method for replacing the valve under pressure of the flowing oil well.

Description

Technical Field

[0001] The invention belongs to the technical field of auxiliary devices for self-flowing oil wells, and relates to a device for replacing valves under pressure in a self-flowing oil well; the invention also relates to a method for replacing valves under pressure in a self-flowing oil well. Background Art

[0002] At present, many oil wells in oil fields have achieved the purpose of increasing production through acidification, fracturing and other measures. Under the condition of scientific pressure control, they can maintain self-flowing production for a long time and achieve the purpose of low-cost production. However, due to the erosion of the wellhead of the self-flowing oil well due to the erosion of the well fluid and the natural aging of the seals during long-term production and use, the internal or main valve leaks, rusts, and inflexible switches, which seriously affects the safe production of the self-flowing oil well. If the valve is replaced by relieving the pressure and killing the well of the self-flowing oil well, not only will the operation cycle be long, the replacement is difficult, and the operation efficiency is low, but there will also be risks of environmental pollution, oil layer pollution, and even wellhead loss of control during the construction process. Summary of the invention

[0003] The purpose of the present invention is to provide a device for replacing valves under pressure in a self-flowing oil well, which solves the problem of long operation cycle and great difficulty in replacing valves in the prior art by means of pressure relief and well killing for self-flowing oil wells.

[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 by the present invention is a device for replacing valves under pressure in a self-flowing oil well, comprising a valve matching joint connected to the valve of the self-flowing oil well to be removed, a blowout preventer connected to the other end of the valve matching joint, a setting tool and a setting push tube connected in sequence are arranged on the blowout preventer from one end close to the valve matching joint to the end away from the valve matching joint, and the other end of the setting push tube extends out of the blowout preventer;

[0006] Alternatively, the blowout preventer is provided with a sealing tool and a releasing tool from one end close to the valve matching joint to one end away from the valve matching joint, and the other end of the releasing tool extends out of the blowout preventer.

[0007] The present invention is also characterized in that

[0008] A pressure relief valve is provided at a position of the blowout preventer between the valve matching joint and the sealing tool.

[0009] A pressure gauge is connected to the pressure relief valve to monitor the internal pressure of the blowout preventer.

[0010] The setting tool comprises an outer tube coaxially arranged with the blowout preventer, on which a lower support ring of a rubber sleeve, a setting rubber sleeve, an upper support ring of a rubber sleeve, a movable cone, a setting slip and a thrust ring are sequentially sleeved from one end close to the valve matching joint to the end away from the valve matching joint, and a setting slip tooth is inlaid on the outer circumference of the setting slip by means of heat treatment, a side of the movable cone close to the setting slip is arranged with a conical surface, an inner conical hole matching with the conical surface of the movable cone is arranged on the side close to the setting slip and the movable cone, the setting slip extends into the inner conical hole of the setting slip, a setting push tube and an end of the outer tube away from the valve matching joint can be shear-connected, an inner tube coaxial with the outer tube is further arranged in the outer tube, the inner tube and the outer tube can be shear-connected, the inner wall of the other end of the inner tube is inlaid with a salvage tooth by means of heat treatment, and the salvage tooth extends out of the outer tube to install one end of the setting push sleeve.

[0011] A spring assembly is arranged radially inside one end where the inner tube is connected to the outer tube, and holes are opened on the tube walls corresponding to the two ends of the spring assembly at the position where the inner tube and the outer tube are connected. The inner tube and the outer tube are shearably connected through shearable pins a arranged in the corresponding holes, and the two ends of the spring assembly are respectively fixed on the shearable pins a on the corresponding side.

[0012] The sealing push cylinder includes a hollow tube that can be shear-connected to one end of the outer tube away from the valve matching joint, the hollow tube is coaxially arranged with the outer tube, and the blowout preventer is extended from the other end of the hollow tube. A push cylinder head, a push cylinder body and a push cylinder rear end are sequentially sleeved on the hollow tube from close to the outer tube to away from the outer tube. A section of the push cylinder body away from the outer tube is located outside the blowout preventer and is provided with a push cylinder body step. The push cylinder rear end is connected to the end of the hollow tube away from the outer tube by a thread, and a push cylinder rear end step is also provided at the end of the push cylinder rear end close to the outer tube. The push cylinder rear end step and the push cylinder body step cooperate with each other to limit the movement of the push cylinder body. A closed hydraulic cavity is formed between the outer wall of the hollow tube, the end face of the push cylinder body close to the push cylinder rear end and the inner wall of the push cylinder rear end, and the hydraulic cavity is connected with a liquid inlet pipe and a liquid discharge pipe.

[0013] A sealing ring is arranged in one end of the blowout preventer away from the valve matching joint, and the push tube head extends out of the blowout preventer after passing through the sealing ring; corresponding holes are opened on the pipe wall at the connection between the outer pipe and the hollow pipe, and the outer pipe and the hollow pipe are shearably connected by passing a shearable pin b through the corresponding holes.

[0014] The unsealing tool comprises an unsealing tool body. One end of the unsealing tool body is inlaid with a salvage tooth through heat treatment. The salvage teeth are engaged with each other. The end of the unsealing tool body away from the salvage tooth passes through a sealing ring and extends out of a blowout preventer.

[0015] Another technical solution adopted by the present invention is a method for replacing a valve under pressure in a self-flowing oil well, which adopts the above-mentioned device for replacing a valve under pressure in a self-flowing oil well, and is specifically implemented according to the following steps:

[0016] Step 1, the process of setting and replacing the valve, is completed by connecting the setting tool with the setting push cylinder;

[0017] Step 2, the replacement and 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 matching joint to the self-flowing oil well valve to be replaced. At this time, the setting tool and the setting push tube are connected, the pressure relief valve is in a closed state, and there is no pressure inside the blowout preventer;

[0020] Step 1.2, slowly open the self-flowing oil well valve to be replaced;

[0021] Step 1.3, pushing the setting push tube 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, inject high-pressure hydraulic oil into the hydraulic chamber through the liquid inlet pipe to push the push cylinder body forward. The push cylinder body pushes the push cylinder head and the thrust ring forward, forcing the sealing slip, the movable cone, the upper support ring of the rubber cylinder, and the sealing rubber cylinder to move forward synchronously. Since there is no moving space at the front end of the sealing rubber cylinder, the sealing annulus is expanded under the squeeze of the upper support ring and the lower support ring of the rubber cylinder. After the annulus is completely sealed, the sealing rubber cylinder cannot be further compressed, and the movable cone cannot be further moved forward. The sealing slip is forced to slide relatively on the outside of the movable cone due to the continued movement of the thrust ring and expand, and the sealing slip teeth are embedded in the wellhead itself The inner wall of the body pipeline is anchored. After the sealing slip and the thrust ring are moved into place, the limited shear pin a is ejected outward from the holes on the inner and outer pipe walls by the spring assembly, completing the pressure isolation before and after the sealing tool and the limiting of the thrust ring; the high-pressure hydraulic oil is continuously injected into the hydraulic cavity through the liquid inlet pipe. Since the push cylinder body cannot continue to move forward, the rear end of the push cylinder begins to move backward under the force, and at the same time drives the hollow tube to move backward. The backward movement of the hollow tube causes the shear pin b to be sheared, realizing the separation of the sealing push cylinder from the sealing tool, and then the high-pressure hydraulic oil in the hydraulic cavity is recovered through the drain pipe, completing the pressure release in the hydraulic cavity;

[0023] Step 1.5, open the pressure relief valve to release the pressure until the internal pressure of the blowout preventer is 0 MPa, then replace the new valve, which should be in the normally open state, and disassemble the blowout preventer equipped with the setting push cylinder;

[0024] Step 2 is as follows:

[0025] Step 2.1, connect the valve matching joint to the replaced new valve, and pass one end of the unsealing tool with the fishing tooth through the dynamic sealing 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 rear end inner tube of the setting tool, continue to push so that the fishing teeth enter the inner tube and bite with the fishing teeth, so that the setting tool is fished out by the unsealing tool;

[0028] Step 2.4, pull the unsealing tool body to move the inner tube backward, so that the shearable pin a is sheared, resulting in the limit of the thrust ring being released, and continue to move the unsealing tool backward, so that the setting tool has the force to move backward. At the same time, since the setting rubber cylinder is in a compressed state and has a rebound force, after the limit of the thrust ring is released, the movable cone has the force to move backward. Under the action of the double force, the setting slip shrinks and releases the anchoring. Continue to pull the unsealing tool to move the thrust ring and the movable cone backward until the setting state is released, and continue to pull the unsealing tool, retract the unsealing tool and the setting tool and put them into the blowout preventer;

[0029] Step 2.5, close the new valve, open the pressure relief valve to release the pressure until the pressure in the blowout preventer is 0 MPa, disassemble the blowout preventer, and recover the device used to replace the valve under pressure in the self-flowing oil well.

[0030] The beneficial effects of the present invention are:

[0031] (1) The present invention realizes the replacement of the main valve or the inner valve of the self-flowing oil well without depressurizing or killing the well, thereby reducing the work process and shortening the construction period. The present invention is simple to operate and does not require much manpower and material resources, thus saving the maintenance cost of the self-flowing oil well.

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

[0033] (3) The setting tool and setting push tube of the present invention can be reused after the pins are replaced, thereby reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0035] Figure 2 yes Figure 1 A partial enlarged view of the middle A;

[0036] Figure 3 yes Figure 1 A partial enlarged view of point B in the middle;

[0037] Figure 4 yes Figure 1 A partial enlarged view of point C in the middle;

[0038] Figure 5It is a schematic diagram of the method for replacing a valve under pressure in a self-flowing oil well according to the present invention after the setting tool completes the setting and the setting push cylinder is removed;

[0039] Figure 6 It is a schematic diagram of the use of the unsealing tool in the method for replacing a valve under pressure in a self-flowing oil well according to the present invention. DETAILED DESCRIPTION

[0040] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0041] Example 1

[0042] The device used for replacing valves under pressure in self-flowing oil wells has a structure as follows Figure 1-4 As shown, it includes a valve matching joint 1 connected to a valve 8 to be removed from a gushing well, the other end of the valve matching joint 1 is connected to a lubricating preventer 2, the lubricating preventer 2 is provided with a setting tool 4 and a setting push tube 5 connected in sequence from one end close to the valve matching joint 1 to the end far from the valve matching joint 1, and the other end of the setting push tube 5 extends out of the lubricating preventer 2;

[0043] Alternatively, the lubricant preventer 2 is provided with a sealing tool 4 and a sealing release tool 7 from one end close to the valve matching joint 1 to one end away from the valve matching joint 1 , and the other end of the sealing release tool 7 extends out of the lubricant preventer 2 .

[0044] The blowout preventer 2 is provided with a pressure relief valve 3 at a position between the valve matching joint 1 and the setting tool 4 .

[0045] The pressure relief valve 3 is connected to a pressure gauge for monitoring 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, and the outer tube 411 is sleeved with a lower support ring 401 of a rubber cylinder, a setting rubber cylinder 402, an upper support ring 403 of a rubber cylinder, a movable cone 404, a setting slip 405, and a thrust ring 407 in sequence from one end close to the valve matching joint 1 to the end away from the valve matching joint 1. The outer circumference of the setting slip 405 is inlaid with a setting slip tooth 406 by heat treatment. The side of the movable cone 404 close to the setting slip 405 is set as a conical surface. The setting slip 405 An inner tapered hole matching the tapered surface of the movable cone 404 is provided on one side close to the movable cone 404, and the setting slip 405 extends into the inner tapered hole of the setting slip 405. The setting push tube 5 and the end of the outer tube 411 away from the valve matching joint 1 can be shear-connected, and an inner tube 410 coaxial with the outer tube 411 is also provided in the outer tube 411. The inner tube 410 and the outer tube 411 can be shear-connected, and the inner wall of the other end of the inner tube 410 is inlaid with a fishing tooth 412 by heat treatment, and the fishing tooth 412 extends out of the outer tube 411 to install one end of the setting push tube 5.

[0047] A spring assembly 408 is arranged radially inside one end where the inner tube 410 is connected to the outer tube 411, and holes are opened on the tube walls corresponding to the two ends of the spring assembly 408 at the position where the inner tube 410 and the outer tube 411 are connected. The inner tube 410 and the outer tube 411 are shearably connected through shearable pins a409 arranged in the corresponding holes, and the two ends of the spring assembly 408 are respectively fixed on the shearable pins a409 on the corresponding side.

[0048] The sealing push tube 5 includes a hollow tube 502 that can be shear-connected to one end of the outer tube 411 away from the valve matching joint 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 anti-blowout pipe 2. The hollow tube 502 is sequentially sleeved with a push tube head 501, a push tube body 503, and a push tube rear end 505 from the direction close to the outer tube 411 to the direction away from the outer tube 411. A section of the push tube body 503 away from the outer tube 411 is located outside the anti-blowout pipe 2 and is provided with a push tube body step 5031. The push tube rear end 505 is connected to the hollow tube The end of 502 away from the outer tube 411 is connected by a thread, and the end of the push cylinder rear end 505 close to the outer tube 411 is also provided with a push cylinder rear end step 5051, the push cylinder rear end step 5051 and the push cylinder body step 5031 cooperate with each other to limit the movement of the push cylinder body 503, and a closed hydraulic chamber 506 is formed between the outer wall of the hollow tube 502, the end face of the push cylinder body 503 close to the push cylinder rear end 505, and the inner wall of the push cylinder rear end 505, and the hydraulic chamber 506 is connected with a liquid inlet pipe 507 and a liquid discharge pipe 508.

[0049] A sealing ring 6 is arranged in one end of the blowout preventer 2 away from the valve matching joint 1, and the push cylinder head 501 extends out of the blowout preventer 2 after passing through the sealing ring 6; corresponding holes are opened on the pipe wall at the connection between the outer tube 411 and the hollow tube 502, and the outer tube 411 and the hollow tube 502 are shearably connected by passing the shearable pin b504 through the corresponding holes.

[0050] The unsealing tool 7 includes an unsealing tool body 702 , one end of which is inlaid with a salvage tooth 701 by heat treatment, the salvage tooth 701 is engaged with the salvage tooth 412 , and one end of the unsealing tool body 702 away from the salvage tooth 412 passes through the sealing ring 6 and extends out of the blowout preventer 2 .

[0051] Example 2

[0052] On the basis of Example 1, the valve matching joint 1 is connected to the blowout preventer 2 through a thread, and a pressure relief valve 3 with connectivity is connected to the blowout preventer 2 through a thread. A pressure gauge can be threadedly connected to the pressure relief valve 3 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 provides an annular step between the lower support ring 401 of the rubber cylinder, the setting rubber cylinder 402, the upper support ring 403 of the rubber cylinder, the movable cone 404, and the setting slip 405, so that the components can be accurately connected and sealed during installation; the present invention needs to ensure through design that when the setting rubber cylinder 402 expands and seals, the moving distance of each component on the setting tool matches the limit of the shear pin a;

[0054] The front sections of the liquid inlet pipe 507 and the liquid discharge pipe 508 are both connected to the hydraulic chamber 506 in a threaded manner and have pressure bearing capacity;

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

[0056] The rear ends of the inlet pipe 507 and the discharge pipe 508 are connected to a bidirectional hydraulic pump. After 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 discharge pipe 508 to complete the pressure release in the hydraulic chamber 506. The maximum force for sealing the sealing tool by injecting hydraulic oil through the inlet pipe 507 is P1. Continuing to inject hydraulic oil makes the shearing force of the shearable pin a to be P2. It is required that P1 must be ensured to be less than 0.8P2 through design to avoid the shearing pin a from being sheared before the sealing tool is sealed.

[0057] Example 3

[0058] On the basis of Example 2, the method for replacing a valve under pressure in a self-flowing oil well according to the present invention is specifically implemented according to the following steps:

[0059] Step 1, the process of setting and replacing the valve, is completed by connecting the setting tool 4 with the setting push cylinder 5;

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

[0061] Step 1 is as follows:

[0062] Step 1.1, connect the valve matching joint 1 to the self-flowing oil well valve 8 to be replaced, at this time, the setting tool 4 is connected to the setting push tube 5, the pressure relief valve 3 is in a closed state, and there is no pressure inside the lubricant preventer 2;

[0063] Step 1.2, slowly open the self-flowing oil well valve 8 to be replaced;

[0064] Open the process to observe the pressure gauge and record it in detail to facilitate risk identification and prevention;

[0065] Step 1.3, pushing the setting push tube 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, inject high-pressure hydraulic oil into the hydraulic chamber 506 through the liquid inlet pipe 507, push the push cylinder body 503 to move forward, and the push cylinder body 503 pushes the push cylinder head 501 and the thrust ring 407 to move forward, forcing the sealing slip 405, the movable cone 404, the upper support ring 403 of the rubber cylinder, and the sealing rubber cylinder 402 to move forward synchronously. Since there is no moving space at the front end of the sealing rubber cylinder 402, the sealing annulus is expanded and sealed under the squeezing of the upper support ring 403 and the lower support ring 401 of the rubber cylinder. After the annulus is completely sealed, the sealing rubber cylinder 402 cannot continue to be compressed, and the movable cone 404 cannot continue to move forward, while the sealing slip 405 is forced to move outside the movable cone 404 due to the continued movement of the thrust ring 407. The sealing tool 4 is opened by relative sliding, and the sealing slip tooth 406 is embedded in the inner wall of the wellhead body pipeline and anchored. After the sealing slip 405 and the thrust ring 407 are moved into place, the limiting shear pin a409 is ejected outward from the holes on the walls of the inner tube 410 and the outer tube 411 by the action of the spring assembly 408, completing the pressure isolation before and after the sealing tool 4 and limiting the thrust ring 407; continue to inject high-pressure hydraulic oil into the hydraulic chamber 506 through the liquid inlet pipe 507. Since the push tube body 503 cannot move forward further, the rear end 505 of the push tube begins to move backward under the force, and at the same time drives the hollow tube 502 to move backward. The backward movement of the hollow tube 502 causes the shear pin b504 to be sheared, so that the sealing push tube 5 is separated from the sealing tool 4. Figure 5 As shown, the high-pressure hydraulic oil in the hydraulic chamber 506 is then recovered through the drain pipe 508 to complete the pressure release in the hydraulic chamber 506;

[0067] Step 1.5, open the pressure relief valve 3 to release the pressure until the internal pressure of the lubricant preventer 2 is 0 MPa, then replace the new valve, which should be in the normally open state, and disassemble the lubricant preventer 2 equipped with the setting push tube 5;

[0068] Step 2 is as follows:

[0069] Step 2.1, connect the valve matching connector 1 to the replaced new valve, and pass one end of the unsealing tool 7 provided with the fishing tooth 701 through the dynamic sealing ring 6;

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

[0071] Step 2.3, such as Figure 6 As shown, the unsealing tool body 702 is pushed through the new valve to the position of the rear end inner tube 410 of the setting tool 4, and the fishing teeth 701 are continuously pushed to enter the inner tube 410 and engage with the fishing teeth 412, so that the setting tool 4 is fished out by the unsealing tool 7;

[0072] Step 2.4, pull the unsealing tool body 702 to move the inner tube 410 backward, so that the shearable pin a409 is sheared, resulting in the limit of the thrust ring 407 being released, and continue to move the unsealing tool 7 backward, so that the setting tool 4 has the force to move backward. At the same time, since the setting rubber cylinder 402 is in a compressed state and has a rebound force, after the limit of the thrust ring 407 is released, the movable cone 404 has the force to move backward. Under the action of the double force, the setting slip 405 shrinks and releases the anchoring, and the unsealing tool 7 is continued to be pulled to move the thrust ring 407 and the movable cone 404 backward until the setting state is released, and the unsealing tool 7 is continued to be pulled, and the unsealing tool 7 and the setting tool 4 are recovered and put into the blowout preventer 2;

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

Claims

1. A device for replacing valves under pressure in a self-flowing oil well, characterized in that: It comprises a valve matching joint (1) connected to a valve (8) to be removed from a gushing well, the other end of the valve matching joint (1) being connected to a blowout preventer (2), the blowout preventer (2) being provided with a setting tool (4) and a setting push tube (5) connected in sequence from one end close to the valve matching joint (1) to one end far from the valve matching joint (1), the other end of the setting push tube (5) extending out of the blowout preventer (2); Alternatively, the lubricant preventer (2) is provided with a sealing tool (4) and a releasing tool (7) from one end close to the valve matching joint (1) to one end far from the valve matching joint (1), and the other end of the releasing tool (7) extends out of the lubricant preventer (2).

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 provided with a pressure relief valve (3) at a position between the valve matching joint (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 1, 2 or 3, characterized in that: The setting tool (4) comprises an outer tube (411) coaxially arranged with the blowout preventer (2); the outer tube (411) is provided with a rubber sleeve lower support ring (401), a setting rubber sleeve (402), a rubber sleeve upper support ring (403), a movable cone (404), a setting slip (405), and a thrust ring (407) in sequence from one end close to the valve matching joint (1) to the end far from the valve matching joint (1); the outer circumference of the setting slip (405) is inlaid with a setting slip tooth (406) by heat treatment; the side of the movable cone (404) close to the setting slip (405) is provided with a conical surface; the setting slip (405) and the movable cone (407) are connected to each other. An inner conical hole matching the conical surface of the movable cone (404) is arranged near one side of the valve body (404), the sealing slip (405) extends into the inner conical hole of the sealing slip (405), the sealing push tube (5) and the end of the outer tube (411) away from the valve matching joint (1) can be shear-connected, an inner tube (410) coaxial with the outer tube (411) is also arranged in the outer tube (411), the inner tube (410) and the outer tube (411) can be shear-connected, the inner wall of the other end of the inner tube (410) is inlaid with a fishing tooth (412) by heat treatment, and the fishing tooth (412) extends out of the outer tube (411) to install one end of the sealing push tube (5).

5. The device for replacing valves under pressure in a self-flowing oil well according to claim 4, characterized in that: A spring assembly (408) is arranged radially inside one end of the inner tube (410) connected to the outer tube (411); holes are provided on the tube walls corresponding to the two ends of the spring assembly (408) at the position where the inner tube (410) and the outer tube (411) are connected; the inner tube (410) and the outer tube (411) are shearably connected via shearable pins a (409) arranged in the corresponding holes; and the two ends of the spring assembly (408) are respectively fixed to the shearable pins a (409) on the corresponding side.

6. The device for replacing valves under pressure in a self-flowing oil well according to claim 4, characterized in that: The sealing push tube (5) comprises a hollow tube (502) which can be shear-connected to one end of the outer tube (411) away from the valve matching 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); a push tube head (501), a push tube body (503), and a push tube rear end (505) are sequentially sleeved on the hollow tube (502) from the direction close to the outer tube (411) to the direction away from the outer tube (411); a section of the push tube body (503) away from the outer tube (411) is located outside the blowout preventer (2) and is provided with a push tube body step (5031); the push tube rear end (505) is connected to the end of the hollow tube (502) away from the outer tube (411) by a threaded connection, and the end of the push tube rear end (505) close to the outer tube (411) is also provided with a push tube rear end step (5051), and the push tube rear end step (5051) and the push tube body step (5031) cooperate with each other to limit the movement of the push tube body (503), and a closed hydraulic chamber (506) is formed between the outer wall of the hollow tube (502), the end face of the push tube body (503) close to the push tube rear end (505) and the inner wall of the push tube rear end (505), and the hydraulic chamber (506) is connected with a liquid inlet pipe (507) and a liquid discharge pipe (508).

7. The device for replacing valves under pressure in a self-flowing oil well according to claim 6, characterized in that: A sealing ring (6) is arranged in one end of the blowout preventer (2) away from the valve matching joint (1), and the push cylinder head (501) extends out of the blowout preventer (2) after passing through the sealing ring (6); corresponding holes are opened on the pipe wall at the connection between the outer pipe (411) and the hollow pipe (502), and the outer pipe (411) and the hollow pipe (502) are shearably connected by passing a shearable pin b (504) through the corresponding holes.

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

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

10. The method for replacing a valve under pressure in a self-flowing oil well according to claim 9, characterized in that: The step 1 is specifically as follows: Step 1.1, connect the valve matching joint (1) to the self-flowing oil well valve (8) to be replaced, at this time, the setting tool (4) and the setting push tube (5) are connected, the pressure relief valve (3) is in a closed state, and there is no pressure inside the blowout preventer (2); Step 1.2, slowly opening the self-flowing oil well valve (8) to be replaced; Step 1.3, pushing the setting push cylinder (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; Step 1.4, inject high-pressure hydraulic oil into the hydraulic chamber (506) through the liquid inlet pipe (507), push the push tube body (503) to move forward, and the push tube body (503) pushes the push tube head (501) and the thrust ring (407) to move forward, forcing the sealing slip (405), the movable cone (404), the upper support ring of the rubber tube (403), and the sealing rubber tube (402) to move forward synchronously. Since there is no moving space at the front end of the sealing rubber tube (402), the sealing annulus is expanded under the squeezing of the upper support ring (403) and the lower support ring (401) of the rubber tube. After the annulus is completely sealed, the sealing rubber tube (402) cannot be further compressed, and the movable cone (404) cannot be further moved forward. The sealing slip (405) is forced to slide relatively on the outside of the movable cone (404) due to the continued movement of the thrust ring (407) and is stretched open, and the sealing slip teeth (406) are embedded in the wellhead. The inner wall of the body pipeline is anchored, and after the sealing slip (405) and the thrust ring (407) are moved into place, the limiting shear pin a (409) is ejected outward from the holes on the walls of the inner tube (410) and the outer tube (411) by the action of the spring assembly (408), thereby completing the pressure isolation before and after the sealing tool (4) and the limiting of the thrust ring (407); high-pressure hydraulic oil is continuously injected into the hydraulic chamber (506) through the liquid inlet pipe (507), and since the push cylinder body (503) cannot continue to move forward, the rear end (505) of the push cylinder begins to move backward under the force, and at the same time drives the hollow tube (502) to move backward, and the backward movement of the hollow tube (502) causes the shear pin b (504) to be sheared, thereby realizing the separation of the sealing push cylinder (5) from the sealing tool (4), and then the high-pressure hydraulic oil in the hydraulic chamber (506) is recovered through the liquid discharge pipe (508), thereby completing the pressure release in the hydraulic chamber (506); Step 1.5, open the pressure relief valve (3) to release the pressure until the internal pressure of the blowout preventer (2) is 0 MPa, then replace the new valve, which should be in a normally open state, and at the same time dismantle the blowout preventer (2) equipped with the setting push cylinder (5); The step 2 is specifically as follows: Step 2.1, connect the valve matching connector (1) to the replaced new valve, and pass one end of the unsealing tool (7) provided with the fishing tooth (701) through the dynamic sealing ring (6); Step 2.2, close the pressure relief valve (3); Step 2.3, pushing the unsealing tool body (702) through the new valve to the position of the rear end inner tube (410) of the setting tool (4), and continuing to push so that the fishing teeth (701) enter the inner tube (410) and engage with the fishing teeth (412), so that the setting tool (4) is fished out 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, resulting in the limit of the thrust ring (407) being released, and the unsealing tool (7) is continued to move backward, so that the setting tool (4) has the force to move backward. At the same time, since the setting rubber cylinder (402) is in a compressed state and has a rebound force, after the limit of the thrust ring (407) is released, the movable cone (404) has the force to move backward. Under the action of the double force, the setting slip (405) shrinks and releases the anchoring. 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, and continue to pull the unsealing tool (7), retract 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 the pressure until the pressure in the blowout preventer (2) is 0 MPa, disassemble the blowout preventer (2), and recover the device for replacing the valve under pressure in the self-flowing oil well.

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