Hydraulic boosting nipple capable of keeping well fluid circulation

Abstract

A hydraulic boosting nipple capable of keeping well fluid circulation belongs to the field of petroleum drilling tools and comprises a hydraulic cylinder sleeve, a connecting sleeve, a piston, a central shaft sleeve, a pushing and supporting sleeve, a spring and a fixing ring, the hydraulic cylinder sleeve is connected with the connecting sleeve, the fixing ring is embedded in the upper portion of the hydraulic cylinder sleeve, the central shaft sleeve is coaxially connected to the lower end of the fixing ring, and the upper portion of an internal well fluid channel is a large-aperture area. The lower portion of the hydraulic cylinder sleeve is a small-hole-diameter area with the hole diameter suddenly reduced, a piston and a push-support sleeve are sleeved outside the hydraulic cylinder sleeve, the piston is embedded in the hydraulic cylinder sleeve to seal an annular space between the hydraulic cylinder sleeve and the central shaft sleeve and divides the annular space into a liquid injection space and a liquid drainage space, and a liquid injection hole is formed in the central shaft sleeve in the liquid injection space. A liquid drainage hole is formed in the hydraulic cylinder sleeve in the liquid drainage space, a spring is embedded between the pushing and supporting sleeve and the connecting sleeve, the hydraulic boosting short section utilizes local high-pressure mud to drive a piston to transmit axial acting force to the pushing and supporting sleeve, communication of a well liquid channel is always kept while assistance is provided for an underground drilling tool, the accident risk can be reduced, and production safety is guaranteed.

Description

Technical Field

[0001] The utility model relates to the field of oil drilling tools, in particular to a hydraulic booster nipple capable of maintaining well fluid circulation. Background Art

[0002] During oilfield drilling, maintaining downhole mud circulation through wellhead pump pressure control is an essential technical step in the drilling production process. Using circulating mud to clean the well bottom, stabilize the wellbore, stabilize well pressure, and protect the environment not only ensures the safety and efficiency of drilling operations, but also contributes to environmental protection and the efficient use of resources. With the continuous advancement of technology, the mud pressure pumped from the wellhead is often used as an additional auxiliary power source for downhole operations in oilfield production to ensure operational effectiveness and improve production efficiency. Patent publication number CN104514507B discloses a "hydraulic-assisted salvage tool" that utilizes well fluid pressure to assist in salvaging the inner barrel of a drill-free plugging tool. The disclosed technical solution of this "hydraulic-assisted salvage tool" is to provide additional lifting force to the central tube by dropping a ball into the inner lumen of the central tube, thereby blocking the inner lumen of the central tube, thereby blocking the mud circulation channel of the drill tool. This assists in salvaging the inner barrel of the drill-free plugging tool. As is well known, the drill tool mud circulation channel is not only a component of the downhole mud circulation channel, but also a safe channel for implementing downhole pressure control. During the operation, if a kick or blowout occurs, the wellhead must be immediately sealed and the mud must be pumped into the downhole through the drill tool mud circulation channel to perform well pressure control to prevent major oilfield production accidents. Therefore, although the "hydraulic assisted salvage tool" technical solution disclosed in the prior art can achieve the purpose of assisting downhole salvage operations, since the drill tool mud circulation channel must be completely sealed during the salvage process, it is impossible to deal with the kick or blowout in a timely manner, which is very likely to cause a production accident. There are obvious risk protection defects and safety hazards in production, and it cannot meet the requirements of oilfield production. Therefore, it is necessary to research and develop a new downhole hydraulic assisted tool that can ensure the unobstructed flow of the drill tool mud circulation channel while utilizing the well fluid pressure to provide additional operating power for the downhole operation tool, thereby solving the problems of the prior art. Utility Model Content

[0003] The purpose of the utility model is to provide a hydraulic booster nipple that can maintain well fluid circulation, provide axial thrust to the drilling tool while ensuring downhole mud flow circulation, reduce accident risks, and ensure production safety.

[0004] A hydraulic booster sub for maintaining well fluid circulation, comprising: a cylinder sleeve, a connecting sleeve, a piston, a central shaft sleeve, a push sleeve, a spring and a fixed ring; the cylinder sleeve and the connecting sleeve are both circular cylinders, which are connected to each other from top to bottom to form a sub main body, and mechanical connection structures are respectively provided at the upper end of the cylinder sleeve and the lower end of the connecting sleeve to connect the sub main body to the drilling tool; the fixed ring is axially limited and sealed and embedded in the upper part of the inner cavity of the cylinder sleeve, and the central shaft sleeve has an axially penetrating well fluid channel, which is coaxially arranged in the inner cavity of the sub main body, and the sealing fit is The cam is fixedly connected to the lower end of the fixing ring, the upper part of the internal well fluid channel is a large aperture area, and the lower part is a small aperture area with a sudden reduction in aperture. The circulating well fluid at the sudden reduction position of aperture between the large aperture area and the small aperture area will restrict the flow and generate an increase in local fluid pressure. The piston and the push sleeve are sequentially mounted on the outside of the center sleeve from top to bottom; the axial limit of the piston is set in the liquid cylinder sleeve, and has a push stroke distance H2 for up and down movement relative to the center sleeve, and the inner and outer sides are respectively connected to the center sleeve and the liquid The cylinder sleeves form a sealing match, which not only seals the annular space between the liquid cylinder sleeve and the center sleeve, but also separates the annular space into an injection space and a drainage space that are independently sealed from each other. In the injection space, the center sleeve is provided with an injection hole that passes through the side wall of the large-aperture area to conduct the well fluid pressure from the inside of the center sleeve to the injection space. In the drainage space, the liquid cylinder sleeve is provided with a drainage hole that passes through the side wall to balance the well fluid pressure between the drainage space and the outside of the liquid cylinder sleeve. The upper end of the push sleeve is connected to The liquid cylinder sleeve corresponds to the sealing fit, and the lower end extends beyond the end of the connecting sleeve. The connecting sleeve limits the upward stroke of the push sleeve. An annular spring device groove is provided between the push sleeve body and the connecting sleeve. The spring is fitted and embedded in the spring device groove and supported between the liquid cylinder sleeve and the push sleeve, applying an elastic force to the push sleeve relative to the liquid cylinder sleeve, pushing and limiting the static spatial state of the push sleeve. In the static spatial state, the push sleeve has a reverse stroke distance H1 for upward movement relative to the connecting sleeve.

[0005] The hydraulic booster nipple capable of maintaining well fluid circulation is preferably provided with an annular strain space between the lower end face of the piston and the upper end face of the push sleeve, a strain ring is embedded in the strain space, the strain ring is made of a metal material with a specific yield strength, and the radial width △r is smaller than the radial width △R of the strain space, and a radial adaptive filling space is reserved in the strain space for the strain ring when it is subjected to axial compression deformation.

[0006] The hydraulic booster nipple capable of maintaining well fluid circulation is preferably provided with a spring pad in the spring device groove, and the spring pad is arranged at the bottom of the spring device groove, so that one end of the piston is supported on the spring pad, and an elastic force is applied to the push sleeve through the spring pad, thereby enhancing the stability and reliability of the application of the elastic force.

[0007] The hydraulic booster nipple capable of maintaining well fluid circulation is preferably provided with a flow limiting plug installed on a diameter reduction shoulder formed by a sudden reduction in the aperture between the large-aperture area and the small-aperture area inside the center sleeve, wherein the flow limiting plug has a center shaft hole connected up and down, the aperture of the center shaft hole is smaller than the aperture of the small-aperture area in the well fluid channel of the center sleeve, and the flow limiting plug is connected to the center sleeve in a detachable and replaceable manner to further preset and adjust the aperture of the small-aperture area at the position where the aperture suddenly reduces in the well fluid channel of the center sleeve, and control and set the circulating well fluid at the position where the aperture suddenly reduces between the large-aperture area and the small-aperture area to limit the flow and increase the local fluid pressure, thereby regulating the pushing force applied by the well fluid flow to the push sleeve, thereby meeting the process requirements for controlling and increasing the force to the downhole tool during drilling production.

[0008] The cam is connected to the upper end of the hydraulic cylinder sleeve by a screw thread, and the lower end of the hydraulic cylinder sleeve is fixed by a fixing ring set in the hydraulic cylinder sleeve. The upper end is provided with a mechanical connection structure for connecting with the drilling tool. The guide sleeve and the guide shoe are connected to the lower end of the connecting sleeve in sequence. An internal bevel thread is provided on the inner circumference of the guide sleeve. The overshot is a circular cylinder with a cut-off groove opened at the lower end. The lower part has radial elastic deformation ability. The cut-off groove is evenly distributed along the cross-sectional circumference of the overshot, and an external bevel thread is provided on the outer circumference. The external bevel thread is connected to the upper opening of the guide sleeve. The inner bevel thread structures correspond to each other, and inverted teeth are provided on the inner circumferential surface. The overshot tube is installed inside the guide sleeve through the mutual cooperation of the outer bevel thread and the inner bevel thread. An anti-rotation mechanism is provided between the overshot tube and the guide sleeve to limit the circumference of the overshot tube relative to the guide sleeve. Under the elastic force of the spring, the upper end surface of the overshot tube corresponds to the lower end surface of the push sleeve to form an elastic contact fit, and is pushed by the push sleeve to produce a downward movement stroke relative to the guide sleeve. At the same time, due to the interaction between the spiral conical surfaces corresponding to each other on the inner bevel thread and the outer bevel thread, the lower part of the overshot tube undergoes initial elastic diameter shrinkage deformation, and the inner hole diameter is reduced.

[0009] The slip salvage device using a hydraulic booster sub is preferably equipped with a sleeve milling head in the guide sleeve. The sleeve milling head is arranged at the lower part of the salvage tube and is kept limited relative to the circumference of the guide sleeve. The fish head of the fish introduced into the well through the guide shoe is cleaned and trimmed in advance before entering the salvage tube, thereby improving the coordination between the fish and the salvage tube and enhancing the salvage effect.

[0010] The beneficial effects of the present invention are to provide a hydraulic booster sub that can maintain well fluid circulation and a slip fisher using the hydraulic booster sub. The hydraulic booster sub adopts a structural form in which the aperture of the well fluid channel in the central shaft sleeve is suddenly reduced, so that the pressure of the local mud well fluid at the position where the aperture is suddenly reduced is increased due to the restricted flow effect. Under the premise of not affecting the smooth connection of the well fluid channel and ensuring the normal circulation of the mud well fluid, the local high-pressure mud well fluid is used to transmit the well fluid pressure to the injection space, and the hydraulically driven piston transmits the axial force to the push sleeve, which provides additional pushing force to the downhole drilling tool connected to the lower end of the hydraulic booster sub through the push sleeve. force, improving the process performance of downhole drilling production tools. At the same time, during the production operation, it can always keep the well fluid channel unobstructed and start the mud well fluid circulation at any time, ensuring timely safety protection and disposal of possible well kicks or blowouts, reducing accident risks, ensuring production safety, and reducing economic losses; further, a strain ring is set between the piston and the push sleeve, and the plastic deformation of the strain ring is used to alleviate the damage to the overshot tube caused by the strong impact force generated by the large-scale and large-gradient increase in the wellhead pump pressure, thereby ensuring the safety, stability and reliability of the function realization in production applications and achieving the purpose of the utility model. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a structural diagram of the hydraulic booster sub that can maintain well fluid circulation.

[0012] Figure 2 for Figure 1 Sectional view along line AA.

[0013] Figure 3 This is the basic structural diagram of the slip salvage device using a hydraulic booster sub.

[0014] Figure 4 for Figure 3 Cross-sectional view along the midline BB.

[0015] Figure 5 This is a structural diagram of the slip salvage device using a hydraulic booster sub in salvage status.

[0016] Figure 6 This is a structural diagram of the boosted state of the slip salvage device using a hydraulic booster sub.

[0017] Among them: 1 is the cylinder sleeve, 2 is the connecting sleeve, 3 is the piston, 4 is the center sleeve, 5 is the push sleeve, 6 is the spring, 7 is the spring washer, 8 is the fixing ring, 9 is the strain ring, 10 is the flow limiting plug, 11 is the upper joint, 12 is the guide sleeve, 13 is the guide shoe, 14 is the overshot, 15 is the sleeve milling head, 16 is the injection hole, 17 is the drainage hole, 18 is the injection space, 19 is the drainage space, 20 is the fish dropped in the well, and 21 is the anti-rotation pin. DETAILED DESCRIPTION

[0018] Further, in conjunction with the specific embodiments and the accompanying drawings Figures 1 to 6 , give a detailed description of the technical solution for which protection is requested in this utility model.

[0019] A slip salvage device using a hydraulic booster sub, such as Figures 3 to 6 As shown, it consists of a cylinder sleeve 1, a connecting sleeve 2, a piston 3, a central sleeve 4, a push sleeve 5, a spring 6, a spring washer 7, a fixing ring 8, a strain ring 9, a flow limiter 10, an upper joint 11, a guide sleeve 12, a guide shoe 13, an overshot tube 14 and a sleeve milling head 15, wherein: Figure 1 and Figure 2 As shown, the cylinder sleeve 1, the connecting sleeve 2, the piston 3, the central sleeve 4, the push sleeve 5, the spring 6, the spring pad 7, the fixing ring 8, the strain ring 9 and the flow limiting plug 10 constitute a hydraulic booster nipple capable of maintaining well fluid circulation.

[0020] The upper joint 11, the liquid cylinder sleeve 1, the connecting sleeve 2, the guide sleeve 12 and the guide shoe 13 are sequentially connected by threaded fittings in sequence. The upper end of the upper joint 11 is provided with a connecting internal thread for accessing the drill rod of the drilling tool, and an internal bevel thread is provided on the inner circumferential surface of the guide sleeve 12; the upper and lower ends of the fixing ring 8 are respectively limited by the upper joint 11 and the liquid cylinder sleeve 1, and are sealed and fixedly embedded in the upper inner cavity of the liquid cylinder sleeve 1. The central shaft sleeve 4 is coaxially arranged, sealed and fixedly connected to the lower end of the fixing ring 8, and has an axially through-well fluid channel inside, and the upper part of the well fluid channel is a large-diameter area The lower part is a small-aperture area with an aperture smaller than that of the large-aperture area, and the lower end extends into the guide sleeve 12. A flow limiting plug 10 is installed on the diameter reduction shoulder between the large-aperture area and the small-aperture area. The flow limiting plug 10 is used to preset and further control and adjust the flow limiting aperture of the small-aperture area in the central sleeve 4 to the well fluid channel. The piston 3, the strain ring 9 and the push sleeve 5 are sequentially mounted on the outside of the central sleeve 4 from top to bottom; the piston 3 is axially limited and embedded in the liquid cylinder sleeve 1, and the inner and outer sides respectively form a sealing fit with the central sleeve 4 and the liquid cylinder sleeve 1, so that the liquid cylinder sleeve 1 and the annular space between the center sleeve 4 is divided into an injection space 18 and a drainage space 19 that are independently sealed from each other. Two injection holes 16 are provided on the center sleeve 4 through the side walls to connect the injection space 18 with the large-aperture area in the well fluid channel of the center sleeve 4. Two drainage holes 17 are provided on the cylinder sleeve 1 through the side walls to connect the drainage space 19 with the outside of the cylinder sleeve 1. The piston 3 has an axial movement stroke relative to the center sleeve 4 in the cylinder sleeve 1; the upper end of the push sleeve 5 is sealed with the cylinder sleeve 1, and the lower end is sealed with the center sleeve 4. It should extend into the guide sleeve 12, and the sleeve body of the push sleeve 5 and the connecting sleeve 2 surround an annular spring device groove, in which the spring 6 and the spring washer 7 are embedded. The spring washer 7 is arranged at the bottom of the spring device groove. The spring 6 is supported between the cylinder sleeve 1 and the spring washer 7, and applies an elastic force to the push sleeve 5 relative to the cylinder sleeve 1; the strain ring 9 is made of a lead alloy material with a low yield strength, and is arranged in the annular strain space between the lower end surface of the piston 3 and the upper end surface of the push sleeve 5, and the radial width △r is smaller than the radial width △R of the strain space;The cylinder body of the overshot tube 14 is provided with 6 cut-off grooves with lower openings, and the cut-off grooves are arranged axially along the overshot tube 14 and evenly distributed on the cross-sectional circumference. An external bevel thread is provided on the outer circumferential surface of the overshot tube 14, and the external bevel thread corresponds to the internal bevel thread structure provided on the guide sleeve 12. An inverted tooth is provided on the inner circumferential surface. The overshot tube 14 is installed inside the guide sleeve 12 by the mutual cooperation of the external bevel thread and the internal bevel thread, and the upper end surface is connected to the lower end of the push sleeve 5 that is extended into the guide sleeve 12 by the action of the spring 6. The milling head 15 is disposed at the lower portion of the overshot tube 14 and is threadedly mounted within the guide sleeve 12. Milling teeth are provided on the annular surface of the lower end, and an anti-rotation pin 21 is provided on the upper end. Anti-rotation grooves are provided on the guide sleeve 12 and the overshot tube 14, respectively, and overlap with each other and correspond to the anti-rotation pin 21. The anti-rotation pin 21 is fitted into the two overlapping anti-rotation grooves provided on the guide sleeve 12 and the overshot tube 14, thereby circumferentially limiting the overshot tube 14 and the milling head 15 relative to the guide sleeve 12 and restricting rotation.

[0021] The operation method of using the slip salvage device using the hydraulic booster sub described in this embodiment to salvage fish dropped in a well is as follows:

[0022] Step 1. Before the oilfield salvage operation, first assemble the slip salvage device using the hydraulic booster sub at the surface wellhead so that it is as shown in the figure. Figure 3 The basic structural state shown is then achieved by threading the upper connector 11 to the drill pipe of the drilling tool and deploying it downhole. During deployment, mud is pumped through the wellhead to maintain normal well fluid circulation.

[0023] Step 2. When the slip salvage device using a hydraulic booster sub is lowered to the salvage position, the drill pipe of the drilling tool is rotated to guide the downhole fish 20 into the guide shoe 13, and the head of the downhole fish 20 is cleaned and necessary milling and shaping is performed by the sleeve milling head 15, while the drilling tool drill pipe is continued to be lowered. Since the diameter of the head of the downhole fish 20 is larger than the inner hole diameter of the overshot tube 14 in the initial state, the downhole fish 20 will push the overshot tube 14 and the push sleeve 5 to overcome the elastic force of the spring 6 and move upward along the central shaft sleeve 4. During the movement, the overshot tube 14 is gradually reduced by the radial constraint of the guide sleeve 12, and the elastic diameter of the lower part gradually recovers. When the inner When the hole diameter is expanded to correspond to the head of the downhole fish 20, the downhole fish 20 can enter the inner hole of the overshot tube 14, and the drilling tool drill pipe is continuously sent down to make the downhole fish 20 fully enter the overshot tube 14. Then, the drilling tool drill pipe is lifted, and the friction between the downhole fish 20 and the overshot tube 14 will initially pull the overshot tube 14 downward relative to the guide sleeve 12. During the downward process, it is constrained by the radial limit of the guide sleeve 12, and the overshot tube 14 will gradually tighten the downhole fish 20 and pull the downhole fish 20 to rise with the drilling tool drill pipe. In this process, the slip salvage device using a hydraulic booster short section presents the following Figure 5 The state of the salvaged structure shown;

[0024] Step 3. When the fish head structure of the fish 20 being salvaged is complex and cannot form an ideal hoop fit with the overshot tube 14, or the weight of the fish 20 is too heavy to ensure a direct salvage effect, increase the pumping pressure of the wellhead mud to 10-14 MPa, and maintain the pumping pressure after reaching the power-assisted process setting value. By means of the high mud and well fluid pressure pumped from the wellhead, increase the clamping force of the overshot tube 14 on the hoop of the fish 20. At the same time, lift the drill pipe of the drilling tool while maintaining the high-pressure mud and well fluid circulation state until the fish 20 is salvaged out of the well and the salvage operation is completed. In this process, the slip salvage device using a hydraulic booster short section presents the following Figure 6 The force-enhancing structural state shown.

[0025] The working principle of the assisting function of the Cava salvage device using a hydraulic booster short section in the process of salvaging fish in the well is as follows: in step 1, when the Cava salvage device using a hydraulic booster short section is sent down the well, the well fluid circulation in a normal state is always maintained in the well. At this time, the circulating well fluid at the position where the aperture suddenly decreases between the large aperture area and the small aperture area in the well fluid channel inside the central shaft sleeve 4 will be restricted to produce an increase in local fluid flow pressure, and the increase in local fluid flow pressure increases with the increase in the flow restriction degree of the small aperture area and the increase in the pumping pressure of the mud and well fluid at the wellhead. This locally increased fluid flow pressure can be conducted into the fluid injection space 18 through the fluid injection hole 16 provided on the central shaft sleeve 4, pushing the piston 3 in the cylinder sleeve 1 along the central axis The sleeve 4 moves downward until it forms an elastic contact fit with the strain ring 9. Since the local pressure increase at the position where the aperture of the well fluid channel suddenly shrinks under normal well fluid circulation conditions is small and the yield strength of the strain ring 9 is insufficient to cause the strain ring 9 to produce axial plastic deformation, it maintains a rigid state and is supported between the piston 3 and the push sleeve 5 and transmits the piston 3 to the push sleeve 5. The push sleeve 5 pushes the overshot tube 14 to produce a slight displacement downward relative to the guide sleeve 12. Through the interaction between the inner bevel thread on the guide sleeve 12 and the outer bevel thread on the overshot tube 14, the lower part of the overshot tube 14 undergoes elastic diameter contraction deformation after displacement and generates an elastic force between the guide sleeve 12. The elastic force and the driving force of the piston 3 are axially balanced. Figure 3 As shown, the rigid combination of the piston 3, the strain ring 9, the overshot tube 14 and the guide sleeve 12 can form a stable static equilibrium structural state; during the salvage operation in step 2, when the downhole fish 20 interacts with the overshot tube 14 in the salvage position, the downhole fish 20 can simultaneously overcome the elastic force of the spring 6 and the driving force of the circulating well fluid in the injection space 18, as shown in FIG. Figure 5As shown, the overshot tube 14 is pushed to move upward relative to the guide sleeve 12 and finally enter the overshot tube 14 to capture the fish 20 in the well. In the process of boosting and assisting in step 3, the wellhead pumping mud is converted into a pressurized well fluid circulation by increasing the pumping pressure. Since the wellhead pump pressure usually needs to be raised to 15-20 MPa in a relatively short time during the conversion process, not only the pressure increase is large, but also the pressure change gradient is large, so that the local liquid flow pressure at the position where the aperture suddenly decreases in the well fluid channel is rapidly and substantially increased. This sudden increase in liquid flow pressure is transmitted to the injection space 18 and strongly impacts the piston 3, which will inevitably cause the piston 3 to pressurize the strain ring 9's driving force suddenly increases and instantaneously exceeds the yield strength of the strain ring 9, and the strain ring 9 is thereby plastically deformed, the axial height is compressed and reduced, and the radial width is adaptively increased, effectively alleviating the impact of the piston 3, and preventing the impact of the piston 3 from being directly transmitted to the overshot tube 14 during the process of increasing the wellhead mud pumping pressure, causing the overshot tube 14 to be plastically deformed or broken and damaged, thereby making it impossible to complete the salvage operation. As the pumping pressure enters the holding stage of the power-assisted process set pressure, the strain ring 9 after plastic deformation also completely fills the strain space accommodating the strain ring 9. At this time, the liquid flow pressure in the injection space 18 has tended to be gentle and stable, as shown in FIG. Figure 6 As shown, the plastically deformed strain ring 9 can transmit the gentle and stable force of the piston 3 to the push sleeve 5, and apply additional driving force to the overshot tube 14 through the push sleeve 5, so as to help increase the force of the hoop to clamp the fish 20 downhole, improve the salvage effect, and enhance the stability and reliability of the salvage operation.

[0026] At the same time, during the process of salvaging a fish 20 dropped downhole using the slip salvage device using a hydraulic booster nipple as described in this embodiment, since the fluid flow passage on the central axis of the upper joint 11, the central shaft sleeve 4, the salvage tube 14 and the sleeve milling head 15 that are interconnected always remains unobstructed and connected, once a well kick or blowout occurs, safe disposal can be carried out at any time, thereby avoiding major production safety accidents, reducing risks and hidden dangers, minimizing economic losses, and ensuring production safety.

Claims

1. A hydraulic booster sub capable of maintaining well fluid circulation, characterized in that: include: A liquid cylinder sleeve (1), a connecting sleeve (2), a piston (3), a central shaft sleeve (4), a push sleeve (5), a spring (6) and a fixed ring (8); the liquid cylinder sleeve (1) and the connecting sleeve (2) are both circular cylinders, which are connected to each other at the top and bottom to form a short section body, and a mechanical connection structure is respectively provided at the upper end of the liquid cylinder sleeve (1) and the lower end of the connecting sleeve (2); the fixed ring (8) is axially limited and sealed and is embedded in the upper part of the inner cavity of the liquid cylinder sleeve (1); the central shaft sleeve (4) has an axially penetrating well fluid channel and is coaxially arranged in the inner cavity of the short section body , the sealing fit is fixedly connected to the lower end of the fixing ring (8), the upper part of the internal well fluid channel is a large aperture area, and the lower part is a small aperture area with a sudden decrease in aperture, and the piston (3) and the push sleeve (5) are sequentially mounted on the outside of the central sleeve (4) from top to bottom; the piston (3) is axially limited and embedded in the liquid cylinder sleeve (1), and has a motion stroke relative to the central sleeve (4), and the inner and outer sides respectively form a sealing fit with the central sleeve (4) and the liquid cylinder sleeve (1), and the liquid cylinder sleeve (1) and the central sleeve (4) are sealed and sealed. The annular space between the shaft sleeves (4) is also divided into an injection space (18) and a drainage space (19) that are independently sealed from each other. In the injection space (18), the central shaft sleeve (4) is provided with an injection hole (16) that passes through the side wall of the large-aperture area. In the drainage space (19), the liquid cylinder sleeve (1) is provided with a drainage hole (17) that passes through the side wall. The upper end of the push sleeve (5) is sealed in correspondence with the liquid cylinder sleeve (1), and the lower end extends to the outside of the end of the connecting sleeve (2). 2) limiting the upward travel of the push sleeve (5), a spring device groove in an annular shape is provided between the push sleeve (5) sleeve body and the connecting sleeve (2), the spring (6) is cooperatively embedded in the spring device groove and supported between the liquid cylinder sleeve (1) and the push sleeve (5), applying an elastic force to the push sleeve (5) relative to the liquid cylinder sleeve (1), pushing and limiting the static spatial state of the push sleeve (5), and in the static spatial state, the push sleeve (5) has a reverse travel distance H1 of upward movement relative to the connecting sleeve (2).

2. A hydraulic booster sub capable of maintaining well fluid circulation according to claim 1, characterized in that: A strain space in the shape of an annulus is provided between the lower end surface of the piston (3) and the upper end surface of the push sleeve (5), and a strain ring (9) is embedded in the strain space. The radial width △r of the strain ring (9) is smaller than the radial width △R of the strain space, and a radial adaptive filling space is reserved in the strain space for the strain ring (9) when it is deformed by axial compression.

3. A hydraulic booster sub capable of maintaining well fluid circulation as claimed in claim 2, characterized in that: The strain ring (9) is made of lead alloy material.

4. A hydraulic booster sub capable of maintaining well fluid circulation according to any one of claims 1 to 3, characterized in that: A spring pad (7) is provided in the spring device groove, and the spring pad (7) is provided at the bottom of the spring device groove, so that one end of the piston (3) is supported on the spring pad (7), and an elastic force is applied to the push sleeve (5) through the spring pad (7).

5. A hydraulic booster sub capable of maintaining well fluid circulation as claimed in claim 4, characterized in that: Inside the center sleeve (4), a flow limiting plug (10) is installed on a diameter reduction shoulder formed by a sudden reduction in the aperture between the large aperture area and the small aperture area. The flow limiting plug (10) has a central axis hole that is connected up and down. The aperture of the central axis hole is smaller than the aperture of the small aperture area in the well fluid channel of the center sleeve (4). The flow limiting plug (10) is connected to the center sleeve (4) in a detachable and replaceable manner.

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