Fixed gas lift working barrel for operation under pressure

Abstract

The invention relates to the technical field of oil and gas field production and exploitation equipment, in particular to a fixed gas lift working barrel for under-pressure operation, which comprises a working barrel body, a casing pressure operating valve, a check valve head and a piston assembly, and the lower part of the working barrel body is provided with an overflowing hole communicated with the gas lifting channel and the overflowing channel. The working barrel is reasonable and compact in structure and convenient to use, by arranging the piston assembly, the pressure of liquid in the annulus between the outer side of the working barrel body and the inner side of a shaft can be changed so that the piston assembly can move downwards, and communication and separation of the overflowing hole and the annulus are achieved through the position change of the piston assembly; therefore, the difficulty of installing a rupture disk and a blanking plug on each stage of working barrel body is reduced when the working barrel body works under pressure, so that the working is simpler and safer, the working efficiency is improved, the production cost is reduced, and the phenomenon of polluting a shaft can be avoided.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas field production and exploitation equipment, and is a fixed gas lift working cylinder used for pressure operation. Background Art

[0002] In the production of oil and gas fields, tubing is often raised and lowered. To ensure the safety of the operation, it is necessary to perform hydraulic well pumping. After the well is pumped, irreparable damage will be caused to the reservoir, which will seriously affect the recovery rate of oil and gas resources.

[0003] Lifting the tubing string under pressure can avoid reservoir damage and has been widely used. However, when lowering the tubing string with a gas lift valve, according to the principle of the gas lift valve, the gas lift valve will open under the action of the high-pressure fluid in the wellbore, allowing the high-pressure fluid to enter the inner cavity of the tubing string, resulting in a leakage accident. The current solution is to install a rupture disk on each stage of the gas lift mandrel. The rupture disk can withstand a reverse pressure of more than 50MPa and a positive pressure difference of 7 to 15MPa. Even if the gas lift valve is opened during the well entry process, the tubing string can be effectively blocked. By positive injection of liquid or gas, the rupture disks at all levels can be broken to achieve normal production of oil and gas wells. Since a set of rupture disks must be installed on each stage of the gas lift valve mandrel, the cost is relatively high; the rupture disk is made of ceramic material, which is easy to cause accumulation in the wellbore, posing a risk to subsequent wireline operations. In addition, when the tubing string needs to be lifted out, a set of tubing plugs must be installed on the mandrel of each stage of the fixed gas lift valve, which is difficult to operate and has high tool and operation costs. Summary of the invention

[0004] The present invention provides a fixed gas lift mandrel for pressure operation, which overcomes the deficiencies of the above-mentioned prior art and can effectively solve the problems of difficult operation and high operation cost when using the existing fixed mandrel.

[0005] The technical solution of the present invention is achieved through the following measures: a fixed gas lift working cylinder for pressurized operation, comprising a working cylinder body, a casing pressure operating valve, a check valve head and a piston assembly, a flow channel and a gas lift channel which are connected vertically at intervals on the left and right sides of the upper end of the working cylinder body, a flow hole connecting the gas lift channel and the flow channel is provided at the lower part of the working cylinder body, a casing pressure operating valve is fixedly installed on the inner side of the upper part of the gas lift channel corresponding to the position above the flow hole, a check valve head whose upper end is in sealing contact with the casing pressure operating valve outlet is installed on the inner side of the middle part of the gas lift channel, the inner side of the lower part of the gas lift channel and the outer side of the piston assembly are sealed together, the upper end of the piston assembly is abutted against the lower end of the check valve head, and the upper end of the check valve head can be connected to the flow hole and the casing pressure operating valve outlet after the upper end of the check valve head moves downward.

[0006] The following are further optimizations and / or improvements to the above technical solutions: The above-mentioned piston assembly may include a piston rod, a first shear pin, a second shear pin, a locking sleeve and a support sleeve. An inner ring platform is fixed on the inner side of the gas lift channel corresponding to the position above the flow hole. The piston rod is installed in the sealing sleeve of the inner ring platform. The upper end of the piston rod abuts against the lower end of the check valve head and makes the upper end of the check valve head close the sleeve pressure operation valve outlet. A sealing ring platform is fixed on the outer side of the lower end of the piston rod corresponding to the position below the flow hole and is in sealing contact with the inner side of the gas lift channel. A push-pull rod is fixed at the center of the lower end of the sealing ring platform. A first shear pin is fixedly installed on the inner side of the right part of the gas lift channel corresponding to the lower end of the sealing ring platform, a second shear pin is fixedly installed on the inner side of the gas lift channel corresponding to the position below the first shear pin, and a support sleeve is fixedly installed on the inner side of the lower part of the gas lift channel corresponding to the position below the second shear pin. The inner side of the support sleeve is tapered with a small upper part and a large lower part. A locking sleeve is installed between the inner side of the support sleeve and the outer side of the push-pull rod. The outer side of the upper part of the locking sleeve matches the inner side of the support sleeve, and the locking sleeve can prevent the push-pull rod from moving upward.

[0007] The above-mentioned piston assembly may also include a compression sleeve, which is threadedly connected to the inner side of the gas lift channel corresponding to the lower end of the support sleeve, and the inner side of the upper end of the compression sleeve is provided with a first connecting hole, a second connecting hole and a third connecting hole which are connected in sequence from top to bottom. The inner diameter of the first connecting hole is not less than the inner diameter of the lower end of the support sleeve, the inner diameter of the second connecting hole is between the inner diameter of the first connecting hole and the outer diameter of the push-pull rod, and the projection of the third connecting hole on the horizontal plane is located on the projection of the second connecting hole on the horizontal plane.

[0008] The cross section of the third connecting hole may be a regular polygon.

[0009] A plurality of tapered locking ring platforms with a larger upper portion and a smaller lower portion may be arranged at intervals on the outer side of the push-pull rod, and a plurality of tapered ring grooves with a larger upper portion and a smaller lower portion matching the locking ring platforms may be arranged at intervals on the inner side of the locking sleeve.

[0010] A limiting ring platform located above the sealing ring platform may be fixed to the outer side of the piston rod corresponding to the lower end of the inner ring platform.

[0011] At least two sealing members may be evenly spaced up and down between the outer side of the piston rod and the inner side of the inner ring platform, and between the outer side of the upper part of the sealing ring platform and the inner side of the gas lift passage.

[0012] The above-mentioned check valve head may include a first valve head, a second valve head and an elastic reset component. The first valve head and the second valve head are symmetrically installed in the gas lift channel corresponding to the position above the inner ring platform. An elastic reset component is installed between the lower part of the first valve head and the lower part of the second valve head. The outer side of the upper part of the first valve head is spherical crown shape, the outer side of the upper part of the first valve head is abutted against the inner side of the outlet of the casing pressure operating valve, and the lower end of the second valve head is abutted against the upper end of the piston rod.

[0013] The present invention has a reasonable and compact structure and is easy to use. By arranging a piston assembly, the pressure of the liquid in the annulus between the outer side of the working cylinder body and the inner side of the wellbore can be changed to move the piston assembly downward, and the connection and isolation between the flow hole and the annulus can be achieved by changing the position of the piston assembly. Through such an arrangement, the difficulty of installing a rupture disk and a plug on each stage of the working cylinder body is reduced when the working cylinder body is operated under pressure, making the operation simpler and safer, improving the operation efficiency, reducing the production cost, and avoiding the pollution of the wellbore. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Attached Figure 1 It is a schematic diagram of the front cross-sectional structure of the first embodiment.

[0015] Attached Figure 2 For attachment Figure 1 Schematic diagram of the enlarged structure at point A in the middle.

[0016] The codes in the accompanying drawings are: 1 is the working cylinder body, 2 is the sleeve pressure operating valve, 3 is the flow channel, 4 is the gas lift channel, 5 is the flow hole, 6 is the piston rod, 7 is the first shear pin, 8 is the second shear pin, 9 is the locking sleeve, 10 is the support sleeve, 11 is the inner ring platform, 12 is the sealing ring platform, 13 is the push-pull rod, 14 is the clamping sleeve, 15 is the first connecting hole, 16 is the second connecting hole, 17 is the third connecting hole, 18 is the locking ring platform, 19 is the limit ring platform, 20 is the sealing element, 21 is the first valve head, 22 is the second valve head, and 23 is the elastic reset element. DETAILED DESCRIPTION

[0017] The present invention is not limited by the following embodiments, and specific implementation methods can be determined based on the technical solution of the present invention and actual conditions.

[0018] In the present invention, for the convenience of description, the relative position relationship of each component is described according to the attached Figure 1 The positional relationships such as front, back, top, bottom, left, and right are described according to the layout directions of the drawings in the specification.

[0019] The present invention will be further described below in conjunction with embodiments and drawings: Embodiment 1: As shown in the attached Figure 1 , 2As shown, the fixed gas lift working cylinder for pressurized operation includes a working cylinder body 1, a casing pressure operating valve 2, a check valve head and a piston assembly. A flow channel 3 and a gas lift channel 4 which pass through the working cylinder body 1 are provided at intervals on the left and right sides of the upper end. A flow hole 5 connecting the gas lift channel 4 and the flow channel 3 is provided at the lower part of the working cylinder body 1. A casing pressure operating valve 2 is fixedly installed on the inner side of the upper part of the gas lift channel 4 above the flow hole 5. A check valve head whose upper end is in sealing contact with the outlet of the casing pressure operating valve 2 is installed on the inner side of the middle part of the gas lift channel 4. The inner side of the lower part of the gas lift channel 4 and the outer side of the piston assembly are sealed together. The upper end of the piston assembly abuts against the lower end of the check valve head, and the upper end of the check valve head can be connected to the flow hole 5 and the outlet of the casing pressure operating valve 2 after the upper end of the check valve head moves downward.

[0020] According to the needs, the casing pressure operating valve 2 is an existing well-known technology. There is an inlet on the upper part of the casing pressure operating valve 2, and a notch opening upward is provided on the right part of the gas lift channel 4 corresponding to the position above the check valve head. In this way, the liquid between the working cylinder body 1 and the wellbore annulus can quickly pass through the inlet of the casing pressure operating valve 2 into the flow channel 3, and it is also convenient for the disassembly and assembly of the casing pressure operating valve 2.

[0021] During use, by setting the piston assembly, the lower end of the working cylinder body 1 is closed and then lowered into the wellbore. At this time, the upper end of the check valve head is in sealing contact with the outlet of the casing pressure operating valve 2, and the piston assembly is sealed and installed on the inner side of the lower part of the gas lift passage 4. In this way, the flow hole 5 and the annulus are isolated. During normal gas lift operations, pressure is applied to the working cylinder body 1, and the high-pressure fluid acts on the piston assembly through the flow hole 5, causing the piston assembly to move downward, and the high-pressure gas in the annulus acts on the upper end of the check valve head, causing the check valve head to After the upper end moves downward, the outlet of the casing pressure operating valve 2 is opened, thereby connecting the outlet of the casing pressure operating valve 2 and the flow hole 5, that is, connecting the flow hole 5 and the annulus. When the working cylinder body 1 is pulled out, the pressure is continuously applied to the working cylinder body 1, so that the piston assembly continues to move downward. At this time, the gas in the annulus acts on the lower end of the check valve head after passing through the outlet of the casing pressure operating valve 2, so that the lower end of the check valve head moves and contacts the gas lift channel 4 above the flow hole 5 in a sealed manner, thereby isolating the flow hole 5 from the annulus, thereby lifting the working cylinder body 1. Through such an arrangement, the pressure of the liquid in the annulus between the outer side of the working cylinder body and the inner side of the wellbore can be changed to cause the piston assembly to move downward, and the flow hole and the annulus can be connected and isolated by changing the position of the piston assembly, so that the difficulty of installing a rupture disk and a plug on each stage of the working cylinder body 1 is reduced when the working cylinder body 1 is operated under pressure, making the operation simpler and safer, improving the operation efficiency, reducing the production cost, and avoiding the phenomenon of wellbore pollution.

[0022] The above-mentioned fixed gas lift mandrel for pressurized operation can be further optimized and / or improved according to actual needs: Embodiment 2: As an optimization of the above embodiment, as shown in the attached Figure 1 , 2 As shown, the piston assembly includes a piston rod 6, a first shear pin 7, a second shear pin 8, a locking sleeve 9 and a supporting sleeve 10. An inner ring platform 11 is fixed to the inner side of the gas lift channel 4 corresponding to the position above the flow hole 5. The inner sealing sleeve of the inner ring platform 11 is equipped with the piston rod 6. The upper end of the piston rod 6 abuts against the lower end of the check valve head and makes the upper end of the check valve head close the outlet of the sleeve pressure operation valve 2. A sealing ring platform 12 is fixed to the outer side of the lower end of the piston rod 6 corresponding to the position below the flow hole 5, which is in sealing contact with the inner side of the gas lift channel 4. A push-pull rod 13 is fixed to the center of the lower end of the sealing ring platform 12. A first shear nail 7 is fixedly installed on the inner side of the right part of the gas lift channel 4 corresponding to the lower end position of the sealing ring platform 12, a second shear nail 8 is fixedly installed on the inner side of the gas lift channel 4 corresponding to the position below the first shear nail 7, and a support sleeve 10 is fixedly installed on the inner side of the lower part of the gas lift channel 4 corresponding to the position below the second shear nail 8. The inner side of the support sleeve 10 is a cone with a small upper part and a large lower part. A locking sleeve 9 is installed between the inner side of the support sleeve 10 and the outer side of the push-pull rod 13. The outer side of the upper part of the locking sleeve 9 matches the inner side of the support sleeve 10, and the locking sleeve 9 can prevent the push-pull rod 13 from moving upward.

[0023] According to the requirements, the piston rod 6 is in a stepped shape with a small top and a large bottom. The first shear nail 7 is a copper shear nail, which can prevent the working cylinder body 1 from moving downward due to external force during transportation or downhole operation, and then the upper part of the piston rod 6 is separated from the inner ring platform 11, thereby connecting the inner ring platform 11 with the flow hole 5, causing the plugging to fail. The second shear nail 8 is a steel shear nail, which can ensure that the sealing ring platform 12 no longer moves downward during the normal production stage. The inner side of the support sleeve 10 is a cone with a small top and a large bottom. The outer side of the locking sleeve 9 is connected to the inner side of the support sleeve 10. Matching, during use, through such an arrangement, the inner conical surface of the support sleeve 10 and the outer conical surface of the locking sleeve 9 cooperate with each other, and when the push-pull rod 13 moves downward, it drives the locking sleeve 9 to move downward, so that the lower end of the locking sleeve 9 opens radially, allowing the push-pull rod 13 to move downward smoothly, and the push-pull rod 13 moves upward so that the lower end of the locking sleeve 9 contracts under the action of the inner conical surface of the support sleeve 10, which can prevent the push-pull rod 13 from continuing to move upward, so that the locking sleeve 9 can reliably fix the push-pull rod 13, and can play a positioning role for the sealing ring platform 12.

[0024] During the stage of entering the wellbore, the piston rod 6 is in a high position, the outer side of the upper part of the piston rod 6 is in sealing contact with the inner ring platform 11, and the outer side of the upper part of the sealing ring platform 12 is in sealing contact with the inner side of the gas lift channel 4, so that the flow hole 5 can be blocked. During the normal production stage, the piston rod 6 is in a middle position after moving downward, and there is a gap between the upper part of the piston rod 6 and the inner ring platform 11. At the same time, the upper end of the piston rod 6 contacts the lower end of the check valve head to prevent the check valve head from moving downward, so that the inner side of the inner ring platform 11 is connected with the flow hole 5, and the gas in the working cylinder body 1 and the wellbore annulus flows out of the casing pressure operating valve 2 outlet through the inlet of the casing pressure operating valve 2. The gas acts on the upper part of the check valve head, so that the outlet of the casing pressure operating valve 2 is opened. At this time, the lower part of the check valve head is lifted by the upper part of the piston rod 6, and the gas flows into the flow channel 3 after passing through the gap between the inner side of the inner ring platform 11 and the piston rod 6 and the flow hole 5. During the pipe string extraction stage, the sealing ring platform 12 continues to move downward and is in a low position. The upper end of the piston rod 6 moves downward and is located inside the lower part of the inner ring platform 11. At this time, the lower part of the check valve head moves downward under the action of the gas in the working cylinder body 1 and the wellbore annulus and is in sealing contact with the inner side of the upper part of the inner ring platform 11, thereby completing the plugging operation of the flow hole 5.

[0025] Preparation for the production phase begins. Clean water is injected into the flow channel 3. When the pressure reaches 7 to 9 MPa, the sealing ring platform 12 cuts off the first shear pin 7 and moves downward. At the same time, the push-pull rod 13 moves downward and drives the locking sleeve 9 to move downward. After the lower end of the locking sleeve 9 opens radially, the sealing ring platform 12 quickly moves to the second shear pin 8 and stops. The piston rod 6 is in the middle position. The gas in the working cylinder body 1 and the wellbore annulus flows out of the casing pressure operating valve 2 outlet through the inlet of the casing pressure operating valve 2, and then flows into the flow channel 3 through the gap between the inner side of the inner ring platform 11 and the piston rod 6 and the flow hole 5, and gas lift production can be carried out.

[0026] When the tubing is pulled out, when the pressure is increased to 10 to 12 MPa, the sealing ring platform 12 shears off the second shear nail 8, so that the second shear nail 8 falls into the screen installed at the lower end of the working cylinder body 1, and then the pressure is stopped. The sealing ring platform 12 continues to move downward after shearing off the second shear nail 8. The sealing ring platform 12 is in a low position, and the upper end of the piston rod 6 is located on the inner side of the inner ring platform 11. At this time, the outer side of the working cylinder body 1 and the gas in the wellbore annulus act on the lower end of the check valve head through the outlet of the casing pressure operating valve 2, so that the lower part of the check valve head moves downward and contacts with the inner side of the inner ring platform 11 in a sealed manner. At this time, the flow hole 5 is closed and the tubing can be smoothly pulled out.

[0027] When the push-pull rod 13 drives the locking sleeve 9 to move upward, and the locking sleeve 9 moves upward by 4 to 6 mm, the outer side of the locking sleeve 9 contacts the inner side of the support sleeve 10, and the piston rod 6 is in the middle position. At this time, the lower end of the locking sleeve 9 contracts under the action of the inner cone of the support sleeve 10 to prevent the push-pull rod 13 from continuing to move upward, so that the locking sleeve 9 can reliably fix the push-pull rod 13 and play a positioning role for the sealing ring platform 12.

[0028] Embodiment 3: As an optimization of the above embodiment, as shown in the attached Figure 1 , 2 As shown, the piston assembly also includes a compression sleeve 14, and the compression sleeve 14 is threadedly connected to the inner side of the gas lift passage 4 corresponding to the lower end of the support sleeve 10. The inner side of the upper end of the compression sleeve 14 is provided with a first connection hole 15, a second connection hole 16 and a third connection hole 17 which are connected in sequence from top to bottom. The inner diameter of the first connection hole 15 is not less than the inner diameter of the lower end of the support sleeve 10, and the inner diameter of the second connection hole 16 is between the inner diameter of the first connection hole 15 and the outer diameter of the push-pull rod 13. The projection of the third connection hole 17 on the horizontal plane is located at the projection of the second connection hole 16 on the horizontal plane. During use, the step surfaces of the first connection hole 15 and the second connection hole 16 can limit the locking sleeve 9 to prevent the locking sleeve 9 from falling after moving downward, and the second connection hole 16 can guide the push-pull rod 13 and prevent the locking sleeve 9 from falling.

[0029] Embodiment 4: As an optimization of the above embodiment, as shown in the attached Figure 1 , 2 As shown, the cross section of the third connecting hole 17 is a regular polygon. According to the requirements, the cross section of the third connecting hole 17 is a regular hexagon. In the process of use, such a setting facilitates the disassembly and assembly of the compression sleeve 14.

[0030] Embodiment 5: As an optimization of the above embodiment, as shown in the attached Figure 1 , 2 As shown, a plurality of tapered locking ring platforms 18 with a larger upper portion and a smaller lower portion are provided at intervals on the outer side of the push-pull rod 13, and a plurality of tapered ring grooves with a larger upper portion and a smaller lower portion matching the locking ring platforms 18 are provided at intervals on the inner side of the locking sleeve 9.

[0031] According to the requirements, the material of the locking sleeve 9 is the existing well-known spring steel. During use, the locking ring 18 on the outside of the push-pull rod 13 cooperates with the conical ring groove. When the push-pull rod 13 moves downward, it can drive the locking sleeve 9 to move downward. When the lower end of the locking sleeve 9 moves to the step surface of the first connecting hole 15 and the second connecting hole 16, the push-pull rod 13 continues to move downward to make the lower end of the locking sleeve 9 radially open. The push-pull rod 13 can continue to move downward and contact with the upper end of the second shear nail 8. When the pressure on the upper end of the sealing ring 12 increases, the second shear nail 8 can be cut off, which is convenient for switching the position of the sealing ring 12. In this way, the piston rod 6 is driven to move downward, so that the check valve head seals the inner ring 11, thereby disconnecting the flow hole 5 and the outlet of the sleeve pressure operating valve 2. The setting of the conical ring groove, after the outer side of the locking sleeve 9 contacts the inner side of the support sleeve 10, the locking sleeve 9 radially contracts so that the locking ring 18 cooperates with the conical ring groove to prevent the push-pull rod 13 from moving upward.

[0032] Embodiment 6: As an optimization of the above embodiment, as shown in the attached Figure 1 , 2 As shown, a limiting ring stage 19 located above the sealing ring stage 12 is fixed to the outer side of the piston rod 6 corresponding to the lower end position of the inner ring stage 11. During use, through such a setting, after the sealing ring stage 12 moves upward, the upper end of the limiting ring stage 19 contacts the lower end of the inner ring stage 11, so that when the sealing ring stage 12 moves upward too far, the upper end of the piston rod 6 can be prevented from squeezing the check valve head and damaging the check valve head.

[0033] Embodiment 7: As an optimization of the above embodiment, as shown in the attached Figure 1 , 2 As shown, at least two seals 20 are evenly spaced between the outer side of the piston rod 6 and the inner side of the inner ring platform 11, and between the outer side of the upper part of the sealing ring platform 12 and the inner side of the gas lift channel 4. According to the requirements, the seal 20 is a known technology, such as an O-ring. The outer side of the upper part of the piston rod 6 and the outer side of the upper part of the sealing ring platform 12 are provided with a ring groove matching the seal 20, and the seal 20 is installed in the ring groove. During use, through such an arrangement, the processing accuracy and installation difficulty between the outer side of the piston rod 6 and the inner side of the inner ring platform 11, the outer side of the upper part of the sealing ring platform 12 and the inner side of the gas lift channel 4 can be reduced, and the sealing performance between the piston rod 6 and the inner side of the gas lift channel 4 can be improved, thereby ensuring the reliability of the action of the piston rod 6.

[0034] Embodiment 8: As an optimization of the above embodiment, as shown in the attached Figure 1 , 2As shown, the check valve head includes a first valve head 21, a second valve head 22 and an elastic reset member 23. The first valve head 21 and the second valve head 22 are symmetrically installed in the gas lift channel 4 corresponding to the position above the inner ring platform 11, and an elastic reset member 23 is installed between the lower part of the first valve head 21 and the lower part of the second valve head 22. The outer side of the upper part of the first valve head 21 is spherical crown-shaped, and the outer side of the upper part of the first valve head 21 abuts against the inner side of the outlet of the casing pressure operating valve 2, and the lower end of the second valve head 22 abuts against the upper end of the piston rod 6.

[0035] According to the requirements, the elastic reset member 23 is an existing well-known technology, such as a compression spring, and the lower end of the second valve head 22 is located above the inner ring stage 11. During use, the first valve head 21 and the inner side of the outlet of the sleeve pressure operation valve 2 can be abutted to close the sleeve pressure operation valve 2, and the lower end of the second valve head 22 and the inner side of the inner ring stage 11 can be abutted to seal the inner ring stage 11, thereby disconnecting the flow hole 5 and the outlet of the sleeve pressure operation valve 2. By setting the elastic reset member 23, the relative movement between the first valve head 21 and the second valve head 22 can play a buffering role, thereby reducing the failure rate.

[0036] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

Claims

1. A fixed gas lift mandrel for pressure operation, characterized in that It includes a working cylinder body, a casing pressure operating valve, a check valve head and a piston assembly. A flow channel and a gas lift channel which pass through the working cylinder body are provided at intervals on the left and right sides of the upper end. A flow hole connecting the gas lift channel and the flow channel is provided at the lower part of the working cylinder body. A casing pressure operating valve is fixedly installed on the inner side of the upper part of the gas lift channel above the flow hole. A check valve head whose upper end is in sealing contact with the casing pressure operating valve outlet is installed on the inner side of the middle part of the gas lift channel. The inner side of the lower part of the gas lift channel and the outer side of the piston assembly are sealed together. The upper end of the piston assembly abuts against the lower end of the check valve head, and the upper end of the check valve head can be connected to the flow hole and the casing pressure operating valve outlet after the upper end of the check valve head moves downward.

2. The fixed gas lift mandrel for pressure operation according to claim 1, characterized in that The piston assembly includes a piston rod, a first shear pin, a second shear pin, a locking sleeve and a supporting sleeve. An inner ring platform is fixed to the inner side of the gas lift channel corresponding to the position above the flow hole. The piston rod is sealed in the inner ring platform. The upper end of the piston rod abuts against the lower end of the check valve head and makes the upper end of the check valve head close the sleeve pressure operation valve outlet. A sealing ring platform is fixed to the outer side of the lower end of the piston rod corresponding to the position below the flow hole and is in sealing contact with the inner side of the gas lift channel. A push-pull rod is fixed to the center of the lower end of the sealing ring platform. The first shear pin is fixed to the inner side of the right part of the gas lift channel corresponding to the lower end of the sealing ring platform. The second shear pin is fixed to the inner side of the gas lift channel corresponding to the position below the first shear pin. The supporting sleeve is fixed to the inner side of the lower part of the gas lift channel corresponding to the position below the second shear pin. The inner side of the supporting sleeve is tapered with a small top and a large bottom. A locking sleeve is installed between the inner side of the supporting sleeve and the outer side of the push-pull rod. The outer side of the upper part of the locking sleeve matches the inner side of the supporting sleeve, and the locking sleeve can prevent the push-pull rod from moving upward.

3. The fixed gas lift mandrel for pressure operation according to claim 2, characterized in that The piston assembly also includes a compression sleeve, which is threadedly connected to the inner side of the gas lift channel corresponding to the lower end of the support sleeve. The inner side of the upper end of the compression sleeve is provided with a first connecting hole, a second connecting hole and a third connecting hole which are connected in sequence from top to bottom. The inner diameter of the first connecting hole is not less than the inner diameter of the lower end of the support sleeve, the inner diameter of the second connecting hole is between the inner diameter of the first connecting hole and the outer diameter of the push-pull rod, and the projection of the third connecting hole on the horizontal plane is located on the projection of the second connecting hole on the horizontal plane.

4. The fixed gas lift mandrel for pressure operation according to claim 3, characterized in that The cross section of the third connecting hole is a regular polygon.

5. The fixed gas lift mandrel for pressure operation according to claim 2, 3 or 4, characterized in that A plurality of tapered locking ring platforms with a larger upper portion and a smaller lower portion are arranged at intervals on the outer side of the push-pull rod, and a plurality of tapered ring grooves with a larger upper portion and a smaller lower portion matching the locking ring platforms are arranged at intervals on the inner side of the locking sleeve.

6. The fixed gas lift mandrel for pressure operation according to claim 2, 3 or 4, characterized in that A limiting ring platform located above the sealing ring platform is fixed on the outer side of the piston rod corresponding to the lower end position of the inner ring platform.

7. The fixed gas lift mandrel for pressure operation according to claim 5, characterized in that A limiting ring platform located above the sealing ring platform is fixed on the outer side of the piston rod corresponding to the lower end position of the inner ring platform.

8. The fixed gas lift mandrel for pressure operation according to claim 2, 3, 4 or 7, characterized in that At least two sealing components are evenly distributed between the outer side of the piston rod and the inner side of the inner ring platform, and between the outer side of the upper part of the sealing ring platform and the inner side of the gas lift channel; or / and, the check valve head includes a first valve head, a second valve head and an elastic reset component, and the first valve head and the second valve head are symmetrically installed in the gas lift channel corresponding to the position above the inner ring platform, and an elastic reset component is installed between the lower part of the first valve head and the lower part of the second valve head. The outer side of the upper part of the first valve head is spherical crown shape, the outer side of the upper part of the first valve head abuts against the inner side of the outlet of the casing pressure operating valve, and the lower end of the second valve head abuts against the upper end of the piston rod.

9. The fixed gas lift mandrel for pressure operation according to claim 5, characterized in that At least two sealing components are evenly distributed between the outer side of the piston rod and the inner side of the inner ring platform, and between the outer side of the upper part of the sealing ring platform and the inner side of the gas lift channel; or / and, the check valve head includes a first valve head, a second valve head and an elastic reset component, and the first valve head and the second valve head are symmetrically installed in the gas lift channel corresponding to the position above the inner ring platform, and an elastic reset component is installed between the lower part of the first valve head and the lower part of the second valve head. The outer side of the upper part of the first valve head is spherical crown shape, the outer side of the upper part of the first valve head abuts against the inner side of the outlet of the casing pressure operating valve, and the lower end of the second valve head abuts against the upper end of the piston rod.

10. The fixed gas lift mandrel for pressure operation according to claim 6, characterized in that At least two sealing components are evenly distributed between the outer side of the piston rod and the inner side of the inner ring platform, and between the outer side of the upper part of the sealing ring platform and the inner side of the gas lift channel; or / and, the check valve head includes a first valve head, a second valve head and an elastic reset component, and the first valve head and the second valve head are symmetrically installed in the gas lift channel corresponding to the position above the inner ring platform, and an elastic reset component is installed between the lower part of the first valve head and the lower part of the second valve head. The outer side of the upper part of the first valve head is spherical crown shape, the outer side of the upper part of the first valve head abuts against the inner side of the outlet of the casing pressure operating valve, and the lower end of the second valve head abuts against the upper end of the piston rod.

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