A continuous jar unjammer

Abstract

This invention belongs to the field of drilling engineering technology and discloses a continuous shock release device, including a pulse shock unit and a differential pressure unit. The upper valve of the differential pressure unit has a first state and a second state during rotation. In the first state, the upper valve covers the main hole and avoids the secondary hole, so that the mounting sleeve is under high pressure. Under high pressure, the piston assembly hammers the bottom wall of the first chamber to generate vibration. This vibration is transmitted through the cylinder assembly and the mounting sleeve to the release component below, thereby causing vibration of the fish and its stuck position. When the upper valve rotates to the second state, the upper valve covers the secondary hole and avoids the main hole, so that the mounting sleeve is under normal pressure. Under normal pressure, the piston assembly moves in the opposite direction and resets. The upper valve rotates continuously relative to the lower valve, so the piston assembly can transmit high-frequency, pulsed shock waves to the fish through the release component. The high frequency and large shock force effectively improve the success rate of release.

Description

Technical Field

[0001] This invention relates to the field of drilling engineering technology, and in particular to a continuous impact release device. Background Technology

[0002] In drilling operations, stuck pipe accidents frequently occur due to complex geological structures, inappropriate technical measures, and various reasons such as mud, tubing, and wellbore issues. Stuck pipe has a significant impact on drilling operations and can cause serious damage. If not handled properly, it can not only prolong the process but also worsen the accident, potentially even leading to the abandonment of the oil and gas well.

[0003] In recent years, oil and gas fields have begun large-scale development of horizontal wells, directional wells, extended reach wells, and geothermal wells, and are continuously expanding towards shale gas and shale oil. However, during oil development drilling, factors such as downhole tools, drill string quality, formation variations, and drilling fluid properties frequently lead to stuck pipe and fish-falling accidents. Furthermore, in later stages of production, stuck downhole tubing tools (due to incomplete recovery of slips or rubber sleeves), stuck downhole debris, stuck sand, stuck wax, stuck scale, stuck casing, and stuck corrosion are common problems encountered in oil and water well production and well workover operations.

[0004] Shock absorbers are one of the effective tools for relieving stuck drill pipe and preventing larger accidents. When designing complex well drilling or anticipating the possibility of stuck drill pipe in a certain section, the best approach is to use a shock absorber in the drill string assembly beforehand. When the drill string gets stuck, the shock absorber applies a strong upward or downward impact to the stuck point, loosening the stuck point and thus quickly relieving the stuck drill pipe. Hydraulic shock absorbers are the most commonly used in current technology.

[0005] However, when using existing hydraulic shock absorbers to provide upward or downward vibrations, the shock absorber can only strike once at a time, and there is a long waiting period before the next strike can be performed, limiting the number of vibrations per minute. This also limits the impact energy transmitted to the stuck drill string. In highly deviated or horizontal wells, where the drill string is against the wellbore, most of its stored elastic potential energy is dissipated by friction between the drill string and the wellbore, resulting in a significant reduction in the impact force reaching the stuck point and a substantial decrease in the success rate of unblocking. Increasing the impact force and the number of strikes would increase damage to the drilling tools and equipment, and also increase the risk of secondary accidents.

[0006] Therefore, there is an urgent need for a continuous shock card releaser to solve the above problems. Summary of the Invention

[0007] The purpose of this invention is to provide a continuous shock-type fish release device that can continuously shock a fallen fish and transmit the shock wave directly to the fish. It has a high frequency and a large shock force, which effectively improves the success rate of fish release and has a high safety factor.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] A continuous shock card release device is provided, comprising:

[0010] The pulse shock unit includes a hammer base, a cylinder assembly, and a piston assembly. The hammer base is provided with a first chamber, in which flowing liquid can be introduced. The cylinder assembly is a cylindrical structure with openings at both ends and is connected to the hammer base. One end of the piston assembly is movably inserted into the first chamber, and the other end is movably inserted into the inner cavity of the cylinder assembly.

[0011] The differential pressure unit includes an installation sleeve, a release mechanism, an upper disc valve, and a lower disc valve. The installation sleeve is open at both ends, with one end connected to the end of the cylinder assembly away from the hammer seat, and the other end connected to the release mechanism. The release mechanism is configured to connect with a fish. A second chamber is vertically provided along the upper edge of the release mechanism. The upper disc valve is rotatably disposed within the installation sleeve, and the lower disc valve is fixedly disposed within the installation sleeve. The lower disc valve has a main hole and a secondary hole vertically provided along its upper edge, with the diameter of the main hole being larger than the diameter of the secondary hole.

[0012] The upper valve has a first state and a second state. When the upper valve is rotated to the first state, the upper valve covers the main hole and avoids the secondary hole, so that the mounting sleeve is under high pressure and the piston assembly hammers the bottom wall of the first chamber under high pressure. When the upper valve is rotated to the second state, the upper valve covers the secondary hole and avoids the main hole, so that the mounting sleeve is under normal pressure and the piston assembly moves in the opposite direction and resets under normal pressure.

[0013] As a preferred embodiment of the continuous vibration card releaser provided by the present invention, two main holes and two secondary holes are provided on the lower plate valve. The two main holes are spaced apart along the first diameter of the lower plate valve, and the two secondary holes are spaced apart along the second diameter of the lower plate valve. The first diameter is perpendicular to the second diameter. The upper plate valve includes a valve body for covering the main holes and the secondary holes, and the cross-section of the valve body is rectangular.

[0014] As a preferred embodiment of the continuous shock unlocking device provided by the present invention, an elastic element is provided inside the cylinder assembly. When the piston assembly strikes the bottom wall of the first chamber, it can compress the elastic element. When the upper valve rotates to the second state, the piston assembly can move away from the second chamber under the elastic force of the elastic element.

[0015] As a preferred embodiment of the continuous vibration unlocking device provided by the present invention, the upper end of the cylinder assembly is threaded onto the hammer seat, and the piston assembly is sequentially fitted with a limiting sleeve, an upper stop ring, the elastic element, and a lower stop ring from top to bottom. The limiting sleeve can abut against the bottom surface of the hammer seat, and the inner wall of the cylinder assembly is provided with a first limiting step. The side of the lower stop ring facing away from the elastic element can abut against the first limiting step.

[0016] As a preferred embodiment of the continuous vibration card releaser provided by the present invention, it further includes a ball bearing. The outer wall of the piston assembly is recessed with a limiting groove, and the ball bearing is disposed in the limiting groove and can roll and cooperate with the inner wall of the limiting sleeve.

[0017] As a preferred embodiment of the continuous vibration unlocking device provided by the present invention, the cylinder assembly includes a first-stage cylinder liner, a second-stage cylinder liner, and a third-stage cylinder liner connected sequentially from top to bottom. The piston assembly includes a main hammer rod, a first-stage piston rod, a second-stage piston rod, and a third-stage piston rod connected sequentially from top to bottom. One end of the main hammer rod is movably inserted into the first chamber, and the other end is movably inserted into the first-stage cylinder liner. One end of the first-stage piston rod is movably inserted into the first-stage cylinder liner, and the other end is movably inserted into the second-stage cylinder liner. One end of the second-stage piston rod is movably inserted into the second-stage cylinder liner, and the other end is movably inserted into the third-stage cylinder liner. The third-stage piston rod is movably inserted into the third-stage cylinder liner.

[0018] As a preferred embodiment of the continuous vibration unlocking device provided by the present invention, the upper end of the first-stage piston rod is threaded onto the bottom end of the main hammer rod, and the limiting sleeve, the upper stop ring, the elastic element and the lower stop ring are all sleeved on the main hammer rod. The top surface of the first-stage piston rod is used to push the lower stop ring to move, so as to compress the elastic element.

[0019] As a preferred embodiment of the continuous vibration unlocking device provided by the present invention, the upper end of the secondary cylinder liner is threadedly sleeved on the lower end of the primary cylinder liner, the inner wall of the secondary cylinder liner is recessed with a second limiting step, and a first fixing sleeve is sleeved on the primary piston rod. The upper end of the first fixing sleeve contacts the lower end face of the primary cylinder liner, and the lower end of the first fixing sleeve contacts the second limiting step.

[0020] The upper end of the third-stage cylinder liner is threaded onto the lower end of the second-stage cylinder liner. The inner wall of the third-stage cylinder liner is recessed with a third limiting step. A second fixing sleeve is fitted onto the second-stage piston rod. The upper end of the second fixing sleeve contacts the lower end face of the second-stage cylinder liner, and the lower end of the second fixing sleeve contacts the third limiting step.

[0021] As a preferred embodiment of the continuous vibration unlocking device provided by the present invention, the first-stage piston rod includes a first sleeve portion and a first rod body connected together. The first sleeve portion is threaded onto the main hammer rod and a first sealing element is sandwiched between it and the inner wall of the first-stage cylinder liner. The first fixing sleeve is sleeved onto the first rod body and a second sealing element is sandwiched between it and the first rod body. A third sealing element is sandwiched between the outer wall of the first fixing sleeve and the inner wall of the second-stage cylinder liner.

[0022] The secondary piston rod includes a second sleeve portion and a second rod body connected together. The second sleeve portion is threaded onto the lower end of the first rod body and a fourth sealing element is sandwiched between the second sleeve portion and the first rod body. A fifth sealing element is sandwiched between the outer wall of the second sleeve portion and the inner wall of the secondary cylinder liner. The second fixing sleeve is sleeved on the second rod body and a sixth sealing element is sandwiched between the second rod body and the second fixing sleeve. A seventh sealing element is sandwiched between the outer wall of the second fixing sleeve and the inner wall of the tertiary cylinder liner.

[0023] The third-stage piston rod is threaded onto the second rod body, and an eighth sealing element is sandwiched between the third-stage piston rod and the second rod body. A ninth sealing element is sandwiched between the outer wall of the third-stage piston rod and the inner wall of the third-stage cylinder liner.

[0024] As a preferred embodiment of the continuous vibration unlocking device provided by the present invention, the mounting sleeve includes a stator sleeve and a connecting sleeve arranged from top to bottom. The end of the stator sleeve away from the connecting sleeve is connected to the cylinder assembly, and the end of the connecting sleeve away from the stator sleeve is connected to the unlocking component. The upper disc valve and the lower disc valve are both disposed in the connecting sleeve. A rotor is rotatably disposed in the stator sleeve. The lower end of the rotor is connected to a universal joint, and the lower end of the universal joint is connected to the upper disc valve.

[0025] The beneficial effects of this invention are:

[0026] This invention provides a continuous shock release device, comprising a pulse shock unit and a differential pressure unit. The pulse shock unit includes a hammer base, a cylinder assembly, and a piston assembly. The hammer base has a first chamber through which flowing liquid can pass. The cylinder assembly is a cylindrical structure open at both ends and connected to the hammer base. One end of the piston assembly is movably inserted into the first chamber, and the other end is movably inserted into the inner cavity of the cylinder assembly, meaning the piston assembly can move relative to the cavity wall of the first chamber and the inner cavity wall of the cylinder assembly. The differential pressure unit includes a mounting sleeve, a release element, an upper valve, and a lower valve. The mounting sleeve is open at both ends, with one end connected to the end of the cylinder assembly away from the hammer base, and the inner cavity of the mounting sleeve communicating with the inner cavity of the cylinder assembly. The other end of the mounting sleeve is connected to the release element, which is configured to connect with the fish to be retrieved. The release element has a second chamber vertically extending through it, and the second chamber communicating with the inner cavity of the mounting sleeve. The upper valve is rotatably mounted within the mounting sleeve, while the lower valve is fixedly mounted within the mounting sleeve; that is, the upper and lower valves are positioned opposite each other, and the upper valve can rotate relative to the lower valve. The lower valve has a main hole and a secondary hole vertically connected along its upper edge, with the diameter of the main hole being larger than that of the secondary hole. When retrieving a fallen fish, the continuous vibration release device is first installed on the entire retrieval drill string. The entire retrieval drill string is then lowered into the well, and the release device is connected to the fallen fish below. Subsequently, the retrieval drill string is raised to create a certain tensile stress between the drill string and the fallen fish. Then, flowing fluid is pumped into the entire retrieval drill string. Continuous flowing fluid can be introduced into the continuous vibration release device through its first chamber. Simultaneously, the upper valve rotates relative to the lower valve. When the pumped flowing fluid reaches a certain discharge rate, the continuous vibration release device begins to vibrate. Specifically, the upper valve has a first state and a second state during rotation. When the upper valve rotates to the first state, it covers the main hole and avoids the secondary hole, so that the mounting sleeve is under high pressure. Under high pressure, the piston assembly hammers the bottom wall of the first chamber, that is, the piston assembly moves upward and hammers the hammer seat. The hammer seat vibrates under the impact force. This vibration is transmitted to the release component below through the cylinder assembly and the mounting sleeve, thus causing vibration of the fish and its stuck position. When the upper valve rotates to the second state, it covers the secondary hole and avoids the main hole, so that the mounting sleeve is under normal pressure. Under normal pressure, the piston assembly moves in the opposite direction and resets, that is, the piston assembly moves away from the bottom wall of the first chamber under normal pressure. Because the upper valve rotates continuously relative to the lower valve, the piston assembly moves repeatedly under continuous high-pressure-low-pressure conditions, hammering the hammer seat at a high frequency. This transmits high-frequency, pulsed shock waves to the fish through the release component, thus causing the fish to release. This continuous shock release device can continuously shock the fish that has fallen into the water, and the shock wave is directly transmitted to the fish. It has a high frequency and a large shock force, which effectively improves the success rate of releasing the fish and has a high safety factor. Attached Figure Description

[0027] Figure 1This is a cross-sectional view of the continuous shock card releaser provided in a specific embodiment of the present invention;

[0028] Figure 2 This is a cross-sectional view of the pulse shock unit provided in a specific embodiment of the present invention;

[0029] Figure 3 This is a cross-sectional view of the differential pressure unit provided in a specific embodiment of the present invention;

[0030] Figure 4 This is a cross-sectional view of the upper half of the pulse shock unit provided in a specific embodiment of the present invention;

[0031] Figure 5 yes Figure 4 A partial view in the middle;

[0032] Figure 6 This is a cross-sectional view of the lower half of the pulse shock unit provided in a specific embodiment of the present invention;

[0033] Figure 7 yes Figure 6 A magnified view of a section at point A in the middle;

[0034] Figure 8 yes Figure 6 A magnified view of a section at point B in the middle;

[0035] Figure 9 yes Figure 6 A magnified view of a section at point C;

[0036] Figure 10 This is a schematic diagram of the structure of the three-stage piston rod provided in a specific embodiment of the present invention;

[0037] Figure 11 This is a schematic diagram of the upper half of the flow-blocking differential pressure unit provided in a specific embodiment of the present invention;

[0038] Figure 12 yes Figure 11 Cross-sectional view in the DD direction;

[0039] Figure 13 This is a schematic diagram of the lower half of the flow-blocking differential pressure unit provided in a specific embodiment of the present invention;

[0040] Figure 14 yes Figure 13 Cross-sectional view along the EE direction;

[0041] Figure 15 yes Figure 13 A cross-sectional view along the FF direction.

[0042] In the picture:

[0043] 1. Pulse shock unit; 2. Differential pressure unit;

[0044] 11. Hammer base; 12. Cylinder assembly; 13. Piston assembly; 15. Ball bearing; 16. First retaining sleeve; 17. Second retaining sleeve;

[0045] 111. First chamber; 112. Drainage chamber;

[0046] 121. Primary cylinder liner; 122. Secondary cylinder liner; 123. Tertiary cylinder liner; 124. Breather hole;

[0047] 1211, First limiting step; 1221, Second limiting step; 1231, Third limiting step;

[0048] 131. Main hammer rod; 132. First-stage piston rod; 133. Second-stage piston rod; 134. Third-stage piston rod; 135. Flow orifice;

[0049] 1321. First set of components; 1322. First rod; 1331. Second set of components; 1332. Second rod;

[0050] 141. Limiting sleeve; 142. Upper stop ring; 143. Elastic element; 144. Lower stop ring;

[0051] 181. First seal; 182. Second seal; 183. Third seal; 184. Fourth seal; 185. Fifth seal; 186. Sixth seal; 187. Seventh seal; 188. Eighth seal; 189. Ninth seal;

[0052] 21. Installation sleeve; 22. Unlocking device; 23. Upper disc valve; 24. Lower disc valve; 25. Rotor; 26. Flow divider seat; 27. Universal joint;

[0053] 211. Stator sleeve; 212. Connecting sleeve; 2121. Adapter sleeve; 2122. Connecting sleeve;

[0054] 221. Second chamber; 231. Connecting part; 232. Valve body;

[0055] 241. Main hole; 242. Secondary hole; 243. First diameter; 244. Second diameter. Detailed Implementation

[0056] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0057] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0058] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0059] In the description of this embodiment, the terms "upper," "lower," "left," and "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0060] like Figures 1 to 3 As shown, this embodiment provides a continuous shock unlocking device, including a pulse shock unit 1 and a differential pressure unit 2. The pulse shock unit 1 is installed above the differential pressure unit 2, and the differential pressure unit 2 can provide a differential pressure power source for the pulse shock unit 1.

[0061] See Figure 1 and Figure 2 The pulse impact unit 1 includes a hammer base 11, a cylinder assembly 12, and a piston assembly 13. (See also...) Figure 4 The hammer base 11 is provided with a first chamber 111, into which a flowing liquid can pass. The cylinder assembly 12 is a cylindrical structure with open ends and is connected to the hammer base 11. One end of the piston assembly 13 is movably inserted into the first chamber 111, and the other end is movably inserted into the inner cavity of the cylinder assembly 12, that is, the piston assembly 13 can move relative to the cavity wall of the first chamber 111 and the inner cavity wall of the cylinder assembly 12.

[0062] See Figure 1 and Figure 3 The differential pressure unit 2 includes a mounting sleeve 21, a release element 22, an upper valve 23, and a lower valve 24. The mounting sleeve 21 is open at both ends, with one end connected to the end of the cylinder assembly 12 away from the hammer seat 11. The inner cavity of the mounting sleeve 21 communicates with the inner cavity of the cylinder assembly 12. The other end of the mounting sleeve 21 is connected to the release element 22, which is configured to connect with the fish to be retrieved. A second chamber 221 is vertically provided along the upper edge of the release element 22, and the second chamber 221 communicates with the inner cavity of the mounting sleeve 21. In this embodiment, a retractable retrieval tool is connected to the lower end of the release element 22. The retractable retrieval tool is used to connect the fish. Retractable retrieval tools come in various types, such as snap-fit ​​short sections, retractable retrieval tubes, retractable retrieval spears, female cones, and male cones.

[0063] See Figure 3 The upper disc valve 23 is rotatably mounted within the mounting sleeve 21, while the lower disc valve 24 is fixedly mounted within the mounting sleeve 21. That is, the upper disc valve 23 and the lower disc valve 24 are positioned opposite each other, and the upper disc valve 23 can rotate relative to the lower disc valve 24. (See also...) Figure 13 and Figure 15 The lower valve 24 has a main hole 241 and a secondary hole 242 vertically connected along its upper edge. The diameter of the main hole 241 is larger than the diameter of the secondary hole 242.

[0064] When retrieving a fallen fish, the continuous shock release device is first installed on the entire retrieval drill string. The entire retrieval drill string is then lowered into the well, and the retractable retrieval tool below the release device 22 catches the fallen fish. Next, the retrieval drill string is lifted to create tensile stress between it and the fallen fish. Then, flowing fluid is pumped into the entire retrieval drill string. The continuous shock release device allows continuous flowing fluid to pass through the first chamber 111. Simultaneously, the upper valve 23 rotates relative to the lower valve 24. When the pumped fluid reaches a certain discharge rate, the continuous shock release device begins to vibrate. Specifically, the upper valve 23 has a first state and a second state during rotation. When the upper valve 23 rotates to the first state, it covers the main hole 241 and avoids the secondary hole 242, causing the mounting sleeve 21 to be under high pressure. Under this high pressure, the piston assembly 13 hammers the bottom wall of the first chamber 111. That is, the piston assembly 13 moves upward and strikes the hammer seat 11. The hammer seat 11 vibrates under the impact force. This vibration is transmitted to the release component 22 below through the cylinder assembly 12 and the mounting sleeve 21, thereby causing vibration of the fish and the stuck position. When the upper valve 23 rotates to the second state, the upper valve 23 covers the secondary hole 242 and avoids the main hole 241, so that the mounting sleeve 21 is under normal pressure. The piston assembly 13 moves in the opposite direction and resets under normal pressure, that is, the piston assembly 13 moves away from the bottom wall of the first chamber 111 under normal pressure.

[0065] Because the upper valve 23 rotates continuously relative to the lower valve 24, the piston assembly 13 moves repeatedly under constant high and low pressure, striking the hammer seat 11 at a high frequency. This transmits the high-frequency, pulsed shock wave to the fish via the release element 22, thus releasing the fish from its stuck position. This continuous shock release device can continuously shock the fish and transmit the shock wave directly to it. Its high frequency and strong shock force effectively improve the success rate of releasing the fish, while also ensuring a high safety factor.

[0066] In this embodiment, the retrieval drilling tools can be combined in several ways. For example, combination one, from bottom to top, consists of a retractable retrieval tool (such as the aforementioned retractable retrieval spear, retractable retrieval tube, etc.) + safety joint + continuous shock release device + drill pipe; combination two, from bottom to top, consists of a retractable retrieval tool + safety joint + continuous shock release device + hydraulic impactor + drill collars (3-6 pieces) + hydraulic accelerator + weighted drill pipe (10 pieces) + drill pipe; combination three, from bottom to top, consists of a retractable retrieval tool + safety joint + continuous shock release device + drilling shock device + weighted drill pipe (10 pieces) + drill pipe. Only three combinations of retrieval drilling tools are listed here. In actual retrieval, a suitable combination can be selected based on the specific type and gravity of the fish, and is not limited to the combinations listed in this embodiment.

[0067] In the prior art, the force applied when lifting the retrieval tool is relatively large, which leads to overload lifting. In this embodiment, the force applied when lifting the retrieval tool is relatively small. The fish can be released by continuous vibration (180 to 300 vibrations per minute), and the fish can be lifted up smoothly after being released.

[0068] See Figure 1 , Figure 2 as well as Figure 3 This continuous shock release device has a through-channel inside for pumping in flowing liquid. See also Figure 4 The upper end of the hammer base 11 is provided with a flow guiding chamber 112, which communicates with the first chamber 111. The lower end of the flow guiding chamber 112 and the first chamber 111 form a stepped hole structure, allowing the piston assembly 13 to hammer against the stepped surface of the stepped hole structure. The upper end of the hammer base 11 can be connected to other components, and its flow guiding chamber 112 can introduce pumped flowing fluid. In this embodiment, a mud pump is used to pump drilling fluid into the entire through-channel of the continuous impact release device.

[0069] See Figure 13 and Figure 15In this embodiment, two main holes 241 and two secondary holes 242 are provided on the lower disc valve 24. The two main holes 241 are spaced apart along the first diameter 243 of the lower disc valve 24, and the two secondary holes 242 are spaced apart along the second diameter 244 of the lower disc valve 24, with the first diameter 243 perpendicular to the second diameter 244. That is, the main holes 241 and the secondary holes 242 are arranged at a 90-degree interval. Furthermore, the distance between the center of the main hole 241 and the center of the lower disc valve 24 is equal to the distance between the center of the secondary hole 242 and the center of the lower disc valve 24, that is, the two main holes 241 and the two secondary holes 242 are distributed on the same circumference.

[0070] See Figure 13 and Figure 14 The upper disc valve 23 includes a connecting part 231 and a valve body 232. The connecting part 231 is used to connect to the power component that drives the upper disc valve 23 to rotate, and the valve body 232 is used to cover the main hole 241 and the secondary hole 242. The cross-section of the valve body 232 is rectangular. When it covers the two main holes 241 along the first diameter 243 direction, it can just avoid the two secondary holes 242. At this time, the second chamber 221 is connected to the mounting sleeve 21 through the two secondary holes 242. The liquid flow rate through the lower disc valve 24 decreases instantaneously per unit time, causing the liquid in the mounting sleeve 21 and the space at the lower end of the piston assembly 13 to be in a high-pressure state. Under the action of the high-pressure liquid, the piston assembly 13 hammers the hammer seat 11 upward. When it covers the two secondary holes 242 along the second direction, it can just avoid the two main holes 241. At this time, the second chamber 221 is connected to the mounting sleeve 21 through two main holes 241. The liquid flow rate through the lower plate valve 24 increases instantaneously per unit time, causing the liquid in the mounting sleeve 21 and the space at the lower end of the piston assembly 13 to return to normal pressure. The piston assembly 13 moves in the opposite direction to return to its original position.

[0071] See Figure 2 In this embodiment, an elastic element 143 is provided inside the cylinder assembly 12. When the piston assembly 13 strikes the bottom wall of the first chamber 111 of the hammer seat 11, it can compress the elastic element 143. When the upper valve 23 rotates to the second state, that is, when the lower end of the piston assembly 13 is under normal pressure, the piston assembly 13 can move away from the second chamber 221 under the elastic force of the elastic element 143 to return to its original position. By providing the elastic element 143, the piston assembly 13 can automatically return to its original position under normal pressure, thereby realizing the repeated movement of the piston assembly 13, which can perform pulsed, high-frequency hammering on the hammer seat 11.

[0072] The upper end of the cylinder assembly 12 is threaded onto the hammer seat 11. The piston assembly 13 is fitted with a limiting sleeve 141, an upper stop ring 142, an elastic element 143, and a lower stop ring 144 from top to bottom. The limiting sleeve 141 can abut against the bottom surface of the hammer seat 11. The inner wall of the cylinder assembly 12 is provided with a first limiting step 1211. The side of the lower stop ring 144 facing away from the elastic element 143 can abut against the first limiting step 1211.

[0073] join Figure 2 , Figure 4 as well as Figure 6 Optionally, in this embodiment, the cylinder assembly 12 includes a first-stage cylinder liner 121, a second-stage cylinder liner 122, and a third-stage cylinder liner 123 connected sequentially from top to bottom. The piston assembly 13 includes a main hammer rod 131, a first-stage piston rod 132, a second-stage piston rod 133, and a third-stage piston rod 134 connected sequentially from top to bottom. The main hammer rod 131, the first-stage piston rod 132, the second-stage piston rod 133, and the third-stage piston rod 134 are all vertically connected with cavities. One end of the main hammer rod 131 is movably inserted into the first chamber 111, and the other end is movably inserted into the first-stage cylinder liner 121. One end of the first-stage piston rod 132 is movably inserted into the first-stage cylinder liner 121, and the other end is movably inserted into the second-stage cylinder liner 122. One end of the second-stage piston rod 133 is movably inserted into the second-stage cylinder liner 122, and the other end is movably inserted into the third-stage cylinder liner 123. The third-stage piston rod 134 is movably inserted into the third-stage cylinder liner 123. The main hammer rod 131, first-stage piston rod 132, second-stage piston rod 133, and third-stage piston rod 134 move synchronously under the pressure of high-pressure liquid, enabling the main hammer rod 131 to strike the hammer seat 11. By designing the cylinder assembly 12 and piston assembly 13 as separate units, manufacturing, transportation, and installation are more convenient. Of course, in other embodiments, the number of cylinder liners and piston rods can be appropriately increased or decreased; no specific limitation is made here regarding the number of cylinder liners and piston rods.

[0074] In this embodiment, the upper end of the first-stage cylinder liner 121 is threaded onto the lower end of the hammer seat 11, which makes installation convenient and quick, and the connection strength is high and not easy to loosen.

[0075] In this embodiment, see Figure 4 and Figure 5The upper end of the first-stage piston rod 132 is threaded onto the bottom end of the main hammer rod 131. The limiting sleeve 141, upper stop ring 142, elastic element 143, and lower stop ring 144 are all fitted onto the main hammer rod 131. The top surface of the first-stage piston rod 132 is used to push the lower stop ring 144 to move, thereby compressing the elastic element 143. The first limiting step 1211 is provided on the first-stage cylinder liner 121. The top surface of the first-stage piston rod 132 and the outer wall of the main hammer rod 131 form an annular stepped structure. When it moves upward to abut against the lower stop ring 144, it can push the lower stop ring 144 upward, and the elastic element 143 is then compressed under the push of the lower stop ring 144. When the upper valve 23 rotates to the second state, the thrust on the entire piston assembly 13 disappears, and the elastic element 143 releases its elastic potential energy to drive the lower stop ring 144 to move downward until the lower stop ring 144 abuts against the first limiting step 1211. Optionally, the elastic element 143 is a disc spring assembly, which has excellent strength and stiffness and a long service life.

[0076] Optionally, see Figure 5 A ball bearing 15 is provided between the main hammer rod 131 and the inner wall of the limiting sleeve 141. When the main hammer rod 131 moves within the first-stage cylinder liner 121, the ball bearing 15 rolls between itself and the main hammer rod 131, and between itself and the inner wall of the limiting sleeve 141. This supports the axial movement of the main hammer rod 131 and prevents it from deviating during movement. It also reduces the frictional resistance of the main hammer rod 131 during movement.

[0077] Furthermore, a limiting groove is recessed on the outer wall of the main hammer rod 131, and the ball bearing 15 is rotatably disposed within the limiting groove and can roll into contact with the inner wall of the limiting sleeve 141. By providing the limiting groove, the ball bearing 15 can be limited, ensuring that it always moves with the main hammer rod 131. Optionally, the limiting groove can be an annular groove, with the ball bearing 15 arranged circumferentially along the annular groove, and multiple rows arranged therein.

[0078] See Figure 6 and Figure 7 The upper end of the secondary cylinder liner 122 is threaded onto the lower end of the primary cylinder liner 121, facilitating connection and providing strong stability. A second limiting step 1221 is recessed into the inner wall of the secondary cylinder liner 122. A first fixing sleeve 16 is fitted onto the primary piston rod 132. The upper end of the first fixing sleeve 16 contacts the lower end face of the primary cylinder liner 121, and the lower end of the first fixing sleeve 16 contacts the second limiting step 1221. That is, the first fixing sleeve 16 is confined between the lower end face of the primary cylinder liner 121 and the step surface of the second limiting step 1221, preventing relative slippage. The first fixing sleeve 16, fitted onto the primary piston rod 132, provides support and guidance for the vertical movement of the primary piston rod 132, preventing it from tilting during movement.

[0079] Similarly, see Figure 6 and Figure 8 The upper end of the third-stage cylinder liner 123 is threaded onto the lower end of the second-stage cylinder liner 122. A third limiting step 1231 is recessed into the inner wall of the third-stage cylinder liner 123. A second fixing sleeve 17 is fitted onto the second-stage piston rod 133. The upper end of the second fixing sleeve 17 contacts the lower end face of the second-stage cylinder liner 122, and the lower end of the second fixing sleeve 17 contacts the third limiting step 1231. That is, the second fixing sleeve 17 is confined between the lower end face of the second-stage cylinder liner 122 and the step surface of the third limiting step 1231, preventing relative slippage of the second fixing sleeve 17. The second fixing sleeve 17, fitted onto the second-stage piston rod 133, provides support and guidance for the vertical movement of the second-stage piston rod 133, preventing it from tilting during movement.

[0080] See Figure 6 and Figure 7 The first-stage piston rod 132 includes a first sleeve portion 1321 and a first rod body 1322 connected together. The first sleeve portion 1321 is threaded onto the main hammer rod 131, and a first sealing element 181 is sandwiched between it and the inner wall of the first-stage cylinder liner 121 to ensure a sealed sliding contact between the first sleeve portion 1321 and the inner wall of the first-stage cylinder liner 121. A first fixing sleeve 16 is sleeved onto the first rod body 1322, and a second sealing element 182 is sandwiched between it and the first rod body 1322 to ensure a sealed sliding contact between the first rod body 1322 and the inner wall of the first fixing sleeve 16. A third sealing element 183 is sandwiched between the outer wall of the first fixing sleeve 16 and the inner wall of the second-stage cylinder liner 122 to ensure a tight seal between them.

[0081] Optionally, the first seal 181 and the second seal 182 are both YO-rings, and the third seal 183 is an O-ring.

[0082] See Figure 6 and Figure 8 The secondary piston rod 133 includes a second sleeve portion 1331 and a second rod body 1332 connected together. The second sleeve portion 1331 is threaded onto the lower end of the first rod body 1322, and a fourth sealing element 184 is sandwiched between the second sleeve portion 1331 and the first rod body 1322 to ensure the sealing of the connection position between the secondary piston rod 133 and the primary piston rod 132. A fifth sealing element 185 is sandwiched between the outer wall of the second sleeve portion 1331 and the inner wall of the secondary cylinder liner 122 to ensure a sealed sliding contact between the second sleeve portion 1331 and the inner wall of the secondary cylinder liner 122. See also Figure 6 and Figure 9The second fixing sleeve 17 is fitted onto the second rod 1332, and a sixth sealing element 186 is sandwiched between the second rod 1332 and the second fixing sleeve 17 to ensure a sealed sliding contact between the second rod 1332 and the inner wall of the second fixing sleeve 17. A seventh sealing element 187 is sandwiched between the outer wall of the second fixing sleeve 17 and the inner wall of the third-stage cylinder liner 123 to ensure the sealing between the outer wall of the second fixing sleeve 17 and the inner wall of the third-stage cylinder liner 123.

[0083] Optionally, the fourth seal 184 is an O-ring, the fifth seal 185 is a YO-ring, the sixth seal 186 is a YO-ring, and the seventh seal 187 is an O-ring.

[0084] See Figure 6 and Figure 10 The third-stage piston rod 134 is threaded onto the second rod body 1332, and an eighth seal 188 is sandwiched between them to ensure a tight seal between the second-stage piston rod 133 and the third-stage piston rod 134. A ninth seal 189 is sandwiched between the outer wall of the third-stage piston rod 134 and the inner wall of the third-stage cylinder liner 123 to ensure a sealed sliding contact between them.

[0085] Optionally, the eighth seal 188 is an O-ring, and the ninth seal 189 is a YO-ring.

[0086] See Figure 6 and Figure 8 Both the first-stage piston rod 132 and the second-stage piston rod 133 are provided with flow holes 135 to provide liquid passages for the operation of the first-stage piston rod 132 and the second-stage piston rod 133. (See also...) Figure 6 , Figure 7 as well as Figure 9 Breathing holes 124 are provided on both sides of the secondary cylinder liner 122 and the tertiary cylinder liner 123 to ensure that the secondary piston rod 133 and the tertiary piston rod 134 can move normally.

[0087] See Figure 11 and Figure 13The mounting sleeve 21 includes a stator sleeve 211 and a connecting sleeve 212 arranged from top to bottom. The end of the stator sleeve 211 away from the connecting sleeve 212 is connected to the cylinder assembly 12, and the end of the connecting sleeve 212 away from the stator sleeve 211 is connected to the release element 22. The upper disc valve 23 and the lower disc valve 24 are both located within the connecting sleeve 212. A rotor 25 is rotatably mounted inside the stator sleeve 211, and the rotor 25 can rotate relative to the stator sleeve 211 to drive the upper disc valve 23 to rotate relative to the lower disc valve 24. In this embodiment, the stator sleeve 211 and the rotor 25 form a screw drill tool structure. A screw drill tool structure is a volumetric downhole power drill tool that uses drilling fluid as power to convert liquid pressure energy into mechanical energy. When the drilling fluid pumped by the mud pump flows through the motor, a certain pressure difference is formed at the motor's inlet and outlet, driving the rotor 25 to perform eccentric planetary motion around the stator sleeve 211. Figure 12 As shown.

[0088] See Figure 11 and Figure 13 The lower end of the rotor 25 is connected to a universal joint 27, and the lower end of the universal joint 27 is connected to the upper disc valve 23. That is, the rotor 25 is connected to the connection part 231 of the upper disc valve 23 through the universal joint 27 to drive the upper disc valve 23 to perform a centered rotational movement within the connecting sleeve 212, preventing the upper disc valve 23 from being eccentric during rotation. Further, a flow divider seat 26 is provided between the rotor 25 and the universal joint 27. The flow divider seat 26 is provided with a flow divider hole, and a cavity is provided vertically inside the rotor 25. The inner cavity of the connecting sleeve 212 can communicate with the cavity of the rotor 25 through the flow divider hole to ensure that the drilling fluid can push the piston assembly 13 upward. Optionally, the rotor 25 and the flow divider seat 26, as well as the flow divider seat 26 and the universal joint 27, are all threaded connections.

[0089] See Figure 13 The connecting sleeve 212 includes a connected adapter sleeve 2121 and a connecting sleeve 2122. The end of the adapter sleeve 2121 away from the connecting sleeve 2122 is threadedly connected to the stator sleeve 211, and the end of the connecting sleeve 2122 away from the adapter sleeve 2121 is threadedly connected to the release element 22. Both the upper disc valve 23 and the lower disc valve 24 are located inside the connecting sleeve 2122. The lower inner wall of the stator sleeve 211 has internal threads, and the upper inner wall of the connecting sleeve 2122 also has internal threads. Both the upper and lower ends of the adapter sleeve 2121 have external threads, thus allowing the stator sleeve 211 and the connecting sleeve 2122 to be connected via the adapter sleeve 2121. Furthermore, designing the connecting sleeve 212 as a separate unit makes manufacturing, transportation, and installation more convenient.

[0090] The general procedure for retrieving fallen fish using the continuous vibration unlocker provided in this embodiment is as follows:

[0091] S1. Well Condition Understanding: Collect well history data, understand basic information such as well site, roads, and casing dimensions, and ensure that the fish cavity is not blocked by sand and the annulus is not buried by sand. If there are sand blockages or sand burials, the appropriate size tools must be used to clean them first.

[0092] S2. Selecting a retrieval tool: Based on the situation of the fish (type and weight, etc.), select a suitable retractable retrieval tool (the retractable retrieval tool must have internal and external circulation channels);

[0093] S3. Determine the fishing string: Based on the fish loss situation and well characteristics, formulate a reasonable fishing drill string combination and construction design. The combination of fishing drill string has been described in detail above and will not be repeated here.

[0094] S4. Determine construction personnel, construction units, and construction dates: Coordinate with various construction units, construction equipment, and construction personnel to select a reasonable time for on-site construction;

[0095] S5. On-site construction: All equipment and personnel shall arrive at the construction site within the specified time in accordance with the construction design;

[0096] S6. Inspect the retrieval drilling tools: Accurately measure and record the length of each drill pipe; inspect the snap-fit ​​type of the retrieval drilling tools, check for any mechanical damage, and provide the basic dimensions and structural diagram of the retrieval drilling tool assembly;

[0097] S7. Drilling: Drill the fishing tool according to the construction design. When the retractable fishing tool is 1 to 2 meters away from the top of the fish, turn on the mud pump at a small displacement to flush the top of the fish until it is thoroughly cleaned. Then, lower the pressure by 10 to 30 kN and lift the fishing tool. After confirming that the fish has been caught, lift the fishing tool by 200 to 400 kN (excluding the weight of the tool itself) to make the retractable fishing tool tightly engage with the fish. Then, rotate the fishing tool clockwise 5 to 6 times and lock the turntable.

[0098] S8. Vibration Release: Start the mud pump and slowly increase the pump flow rate (the tool starts working when the flow rate reaches 10L / s or more). When you observe obvious fluctuations in the riser pressure gauge, weight indicator, or drilling rig wire rope, it indicates that the tool has started working. Continue working at this flow rate and pressure until the fish is released. If the tool still cannot release the fish after prolonged vibration at this flow rate and pressure, you can change the pump flow rate to change the vibration frequency of the tool.

[0099] Inside the continuous shock release device, the upper valve 23 rotates relative to the lower valve 24. Each rotation of the upper valve 23 generates one high-pressure and one normal-pressure cycle, thus providing a differential pressure power source for the pulse shock unit 1. When the upper valve 23 rotates to the first state, it covers the main hole 241 and avoids the secondary hole 242, so that the mounting sleeve 21 is under high pressure. Under high pressure, the piston assembly 13 hammers the bottom wall of the first chamber 111, that is, hammers the hammer seat 11. In this embodiment, under hydraulic pressure, the piston assembly 13 can quickly impact the hammer seat 11 with an impact force of 400KN, thereby directly transmitting the shock wave to the release component 22 - the retractable retrieval tool - the fish, while compressing the elastic element 143 to store energy. When the upper valve 23 rotates to the second state, it covers the secondary hole 242 and avoids the main hole 241, so that the mounting sleeve 21 is under normal pressure. The elastic element 143 releases the stored elastic potential energy, causing the piston assembly 13 to move in the opposite direction and reset, i.e., away from the bottom wall of the first chamber 111. Since the upper valve 23 rotates continuously, the above action is repeated cyclically, 180 to 300 times per minute, forming a pulsed, high-frequency shock wave that is transmitted to the fallen fish, achieving efficient retrieval.

[0100] S9. Pulling out the drill bit: If the weight indicator or wire rope is found to be obviously loose during the operation of the tool, it means that the fish may have been unstuck. Raise the retrieval drill bit 2 meters, lower the retrieval drill bit again to try to retrieve the fish. If the suspended weight does not increase significantly, it means that the fish has been unstuck (or the retrieval tool and the fish are stuck together). Retrieve all the retrieval drill bit according to the construction design.

[0101] S10. Construction completed, awaiting the next step.

[0102] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A continuous vibration card unlocking device, characterized in that, include: The pulse shock unit (1) includes a hammer seat (11), a cylinder assembly (12) and a piston assembly (13). The hammer seat (11) is provided with a first chamber (111) in which flowing liquid can be introduced. The cylinder assembly (12) is a cylindrical structure with open ends and is connected to the hammer seat (11). One end of the piston assembly (13) is movably inserted into the first chamber (111) and the other end is movably inserted into the inner cavity of the cylinder assembly (12). The differential pressure unit (2) includes an installation sleeve (21), a release element (22), an upper plate valve (23), and a lower plate valve (24). The installation sleeve (21) is open at both ends. One end is connected to the end of the cylinder assembly (12) away from the hammer seat (11), and the other end is connected to the release element (22). The release element (22) is configured to connect with the fish. The release element (22) has a second chamber (221) vertically through it. The upper plate valve (23) is rotatably disposed in the installation sleeve (21). The lower plate valve (24) is fixedly disposed in the installation sleeve (21). The lower plate valve (24) has a main hole (241) and a secondary hole (242) vertically through it. The diameter of the main hole (241) is larger than the diameter of the secondary hole (242). The upper valve (23) has a first state and a second state. When the upper valve (23) is rotated to the first state, the upper valve (23) covers the main hole (241) and avoids the secondary hole (242) so that the mounting sleeve (21) is under high pressure and the piston assembly (13) hammers the bottom wall of the first chamber (111) under high pressure. When the upper valve (23) is rotated to the second state, the upper valve (23) covers the secondary hole (242) and avoids the main hole (241) so that the mounting sleeve (21) is under normal pressure and the piston assembly (13) moves in the opposite direction and resets under normal pressure. The mounting sleeve (21) includes a stator sleeve (211) and a connecting sleeve (212) arranged from top to bottom. The end of the stator sleeve (211) away from the connecting sleeve (212) is connected to the cylinder assembly (12), and the end of the connecting sleeve (212) away from the stator sleeve (211) is connected to the unlocking component (22). The upper disc valve (23) and the lower disc valve (24) are both disposed in the connecting sleeve (212). A rotor (25) is rotatably disposed in the stator sleeve (211). The lower end of the rotor (25) is connected to a universal joint (27), and the lower end of the universal joint (27) is connected to the upper disc valve (23). Two main holes (241) and two secondary holes (242) are provided on the lower plate valve (24). The two main holes (241) are spaced apart along the first diameter (243) of the lower plate valve (24), and the two secondary holes (242) are spaced apart along the second diameter (244) of the lower plate valve (24). The first diameter (243) is perpendicular to the second diameter (244). The upper plate valve (23) includes a valve body (232) for covering the main holes (241) and the secondary holes (242). The cross-section of the valve body (232) is rectangular. The cylinder assembly (12) is provided with an elastic element (143). When the piston assembly (13) hammers the bottom wall of the first chamber (111), it can compress the elastic element (143). When the upper plate valve (23) rotates to the second state, the piston assembly (13) can move away from the second chamber (221) under the elastic force of the elastic element (143).

2. The continuous vibration card releaser according to claim 1, characterized in that, The upper end of the cylinder assembly (12) is threaded onto the hammer seat (11). The piston assembly (13) is provided with a limiting sleeve (141), an upper stop ring (142), the elastic element (143), and a lower stop ring (144) from top to bottom. The limiting sleeve (141) can abut against the bottom surface of the hammer seat (11). The inner wall of the cylinder assembly (12) is provided with a first limiting step (1211). The side of the lower stop ring (144) facing away from the elastic element (143) can abut against the first limiting step (1211).

3. The continuous vibration card releaser according to claim 2, characterized in that, It also includes a ball bearing (15), and the outer wall of the piston assembly (13) is recessed with a limiting groove. The ball bearing (15) is disposed in the limiting groove and can roll and cooperate with the inner wall of the limiting sleeve (141).

4. The continuous vibration card releaser according to claim 2, characterized in that, The cylinder assembly (12) includes a first-stage cylinder liner (121), a second-stage cylinder liner (122), and a third-stage cylinder liner (123) connected sequentially from top to bottom. The piston assembly (13) includes a main hammer rod (131), a first-stage piston rod (132), a second-stage piston rod (133), and a third-stage piston rod (134) connected sequentially from top to bottom. One end of the main hammer rod (131) is movably inserted into the first chamber (111), and the other end is movably inserted into the first-stage cylinder liner (121). One end of the first-stage piston rod (132) is movably inserted into the first-stage cylinder liner (121), and the other end is movably inserted into the second-stage cylinder liner (122). One end of the second-stage piston rod (133) is movably inserted into the second-stage cylinder liner (122), and the other end is movably inserted into the third-stage cylinder liner (123). The third-stage piston rod (134) is movably inserted into the third-stage cylinder liner (123).

5. The continuous vibration card releaser according to claim 4, characterized in that, The upper end of the first-stage piston rod (132) is threaded onto the bottom end of the main hammer rod (131). The limiting sleeve (141), the upper stop ring (142), the elastic element (143), and the lower stop ring (144) are all sleeved on the main hammer rod (131). The top surface of the first-stage piston rod (132) is used to push the lower stop ring (144) to move, so as to compress the elastic element (143).

6. The continuous vibration card releaser according to claim 4, characterized in that, The upper end of the secondary cylinder liner (122) is threaded onto the lower end of the primary cylinder liner (121). The inner wall of the secondary cylinder liner (122) is recessed with a second limiting step (1221). A first fixing sleeve (16) is fitted onto the primary piston rod (132). The upper end of the first fixing sleeve (16) contacts the lower end face of the primary cylinder liner (121), and the lower end of the first fixing sleeve (16) contacts the second limiting step (1221). The upper end of the third-stage cylinder liner (123) is threaded onto the lower end of the second-stage cylinder liner (122). The inner wall of the third-stage cylinder liner (123) is recessed with a third limiting step (1231). A second fixing sleeve (17) is fitted onto the second-stage piston rod (133). The upper end of the second fixing sleeve (17) contacts the lower end face of the second-stage cylinder liner (122), and the lower end of the second fixing sleeve (17) contacts the third limiting step (1231).

7. The continuous vibration card releaser according to claim 6, characterized in that, The first-stage piston rod (132) includes a first sleeve portion (1321) and a first rod body (1322) connected together. The first sleeve portion (1321) is threaded onto the main hammer rod (131) and a first sealing element (181) is sandwiched between it and the inner wall of the first-stage cylinder liner (121). The first fixing sleeve (16) is sleeved onto the first rod body (1322) and a second sealing element (182) is sandwiched between it and the first rod body (1322). A third sealing element (183) is sandwiched between the outer wall of the first fixing sleeve (16) and the inner wall of the second-stage cylinder liner (122). The secondary piston rod (133) includes a second sleeve portion (1331) and a second rod body (1332) connected together. The second sleeve portion (1331) is threaded onto the lower end of the first rod body (1322) and a fourth sealing element (184) is sandwiched between the second sleeve portion (1322) and the first rod body (1322). A fifth sealing element (185) is sandwiched between the outer wall of the second sleeve portion (1331) and the inner wall of the secondary cylinder liner (122). The second fixing sleeve (17) is sleeved on the second rod body (1332) and a sixth sealing element (186) is sandwiched between the second rod body (1332). A seventh sealing element (187) is sandwiched between the outer wall of the second fixing sleeve (17) and the inner wall of the tertiary cylinder liner (123). The third-stage piston rod (134) is threaded onto the second rod body (1332), and an eighth seal (188) is sandwiched between the third-stage piston rod (1332) and the second rod body (1332). A ninth seal (189) is sandwiched between the outer wall of the third-stage piston rod (134) and the inner wall of the third-stage cylinder liner (123).

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