Hydraulic self-triggering type pressure maintaining coring tool

Abstract

The utility model relates to the technical field of well drilling coring, and discloses a hydraulic self-triggering type pressure-maintaining coring tool which comprises a shell, a piston pipe, a cylinder barrel, a coring barrel and a pressure-maintaining controller are coaxially arranged in the shell, one end of the piston pipe is fixedly connected with the rear end of the shell, a piston is fixedly arranged at the other end of the piston pipe, the piston is arranged in the cylinder barrel in a sliding mode, and the coring barrel is connected with the pressure-maintaining controller. The rear end of the cylinder barrel is in sliding fit with the piston tube, the front end of the cylinder barrel is rotatably connected with one end of the coring barrel, and the other end of the coring barrel is matched with the pressure maintaining controller; an inner cavity of the piston pipe, an inner cavity of the piston and a rodless cavity are sequentially communicated, a penetrating flow channel is formed in the front end of the cylinder barrel, a pressurizing hole is machined in the piston pipe, the two ends of the pressurizing hole are communicated with the inner cavity of the piston pipe and a rod cavity respectively, a ball seat is machined in the piston, and a sealing ball is thrown into the ball seat to block the inner cavity of the piston. According to the hydraulic self-triggering type pressure maintaining coring tool, the front end of the coring barrel can be closed when coring is completed, and the in-situ environment is guaranteed when a rock core is taken out.

Description

Technical Field

[0001] This utility model relates to the field of drilling coring technology, specifically a hydraulic self-triggering pressure-holding coring tool. Background Technology

[0002] Core drilling is one of the most direct methods in deep resource exploration. Its basic principle is to drill cores from deep reservoir environments, conduct loading tests and analyses, and estimate energy reserves and rock mechanical parameters. In shallow resource exploration, conventional core drilling techniques generally meet engineering application requirements. However, with increasing excavation depth, formation pressure and temperature rise significantly, and geological conditions become more complex, posing significant challenges to conventional core drilling techniques. In deep geological environments, the temperature and pressure of the in-situ environment are released during core drilling, causing the oil, gas, and water components in the sample to escape, and minerals to transform. When the core is recovered to the laboratory, it is often difficult to maintain its original state, leading to a decrease in the accuracy of experimental and analytical results, and making it impossible to accurately assess the energy reserves in the in-situ environment through testing. Furthermore, under these complex conditions, core samples may undergo physical and chemical changes due to sudden changes in pressure and temperature, leading to crack propagation and other problems, which in turn affect subsequent mechanical analysis and formation geological parameter assessment. How to obtain authentic and effective core samples from deep reservoirs without damaging their original properties has become a core issue that urgently needs to be addressed in the field of deep resource exploration.

[0003] To maintain in-situ pressure on rock samples during deep coring and maximize the preservation of in-situ rock characteristics, existing technologies employ various pressure-holding controllers, such as ball valves and flap valves. During coring, the coring cylinder passes through the controller to allow its tip to approach the rock strata and collect the core. After coring, the cylinder tip retracts to the rear of the controller, and the valve core or valve plate closes to maintain pressure and preserve the core's integrity. As can be seen from this process, axial displacement occurs between the coring cylinder and the pressure control device during pressure-holding coring operations. Therefore, the design of pressure-holding coring tools must incorporate control measures for this axial displacement. Utility Model Content

[0004] The purpose of this utility model is to provide a hydraulic self-triggering pressure-holding coring tool. After coring is completed, the tool can be pressurized by throwing a ball, and the hydraulic pressure can drive the coring cylinder to move axially, so that the pressure-holding controller can seal the front end of the coring cylinder, thereby completing the pressure-holding and high-fidelity coring process.

[0005] The objective of this utility model is achieved through the following technical solution:

[0006] A hydraulically self-triggered pressure-holding coring tool includes a housing. A coring drill bit is fixedly connected to the front end of the housing. A coring cylinder is coaxially arranged inside the housing, located at the rear end of the coring drill bit. A piston tube, a cylinder, and a pressure-holding controller are also coaxially arranged inside the housing. One end of the piston tube is fixedly connected to the rear end of the housing, and a piston is fixedly arranged at the other end of the piston tube. The piston is slidably disposed inside the cylinder, which is slidably adapted to the housing. The rear end of the cylinder is slidably adapted to the piston tube. One end of the coring cylinder is closed, and the front end of the cylinder is rotatably connected to the closed end of the coring cylinder. The other end of the coring cylinder is adapted to the pressure-holding controller. The piston divides the cylinder interior into a rod chamber and a rodless chamber. The piston has a hollow structure, and the inner cavity of the piston tube, the inner cavity of the piston, and the rodless chamber are sequentially connected. A through flow channel is provided at the front end of the cylinder, and one end of the through flow channel is connected to the rodless chamber. The outer wall of the core tube and the inner wall of the shell form an annular cavity, and the other end of the through flow channel is connected to the annular cavity. A pressure hole is machined on the piston tube near the piston, and the two ends of the pressure hole are connected to the inner cavity of the piston tube and the rod chamber, respectively. A ball seat is machined inside the piston, and a sealing ball is also included. The sealing ball can be inserted into the ball seat through the inner cavity of the piston tube, and the sealing ball can be used to seal the inner cavity of the piston.

[0007] Furthermore, a first snap-fit ​​connector is fixedly provided at the rear end of the housing, and a second snap-fit ​​connector is fixedly provided at the rear end of the cylinder. When the first snap-fit ​​connector and the second snap-fit ​​connector are brought close together, the first snap-fit ​​connector can be connected to the second snap-fit ​​connector.

[0008] Specifically, the first clamping connector has several clamping claws evenly distributed around its circumference at the end near the cylinder, and the second clamping connector has a truncated cone at the end near the first clamping connector, the truncated cone being adapted to the clamping claws.

[0009] Specifically, there are several through channels, and these through channels are evenly distributed around the circumference.

[0010] Specifically, the through channel is inclined, with one end of the through channel away from the core tube positioned near the cylinder axis, and the other end of the through channel positioned away from the cylinder axis.

[0011] Specifically, a check sleeve is fixedly installed inside the core tube, and several ratchet teeth are evenly distributed around the inner circumference of the check sleeve. The ratchet teeth are configured to allow the core and the check sleeve to move only in the direction of moving closer to each other.

[0012] The beneficial effects of this utility model are:

[0013] A hydraulically self-triggering pressure-holding coring tool includes a housing, a coring drill bit fixedly connected to the front end of the housing, a piston tube, a cylinder, a coring cylinder, and a pressure-holding controller coaxially arranged inside the housing, one end of the piston tube being fixedly connected to the rear end of the housing, and a piston being fixedly mounted at the other end of the piston tube. The piston is slidably mounted inside the cylinder, one end of the cylinder being slidably adapted to the piston tube, and the other end of the cylinder being rotatably connected to one end of the coring cylinder. The other end of the coring cylinder is adapted to the pressure-holding controller. During coring, drilling fluid flows from the inner cavity of the piston tube and piston into the rodless cavity of the cylinder. Under hydraulic pressure, it pushes the cylinder and coring tube towards the coring bit and maintains a forward-moving trend. As the coring bit drills forward, the core can smoothly enter the coring tube through the center hole of the coring bit. A ball seat is installed inside the piston, and a pressure hole is opened on the piston tube. The two ends of the pressure hole are connected to the inner cavity of the piston tube and the rod cavity of the cylinder, respectively. After coring is completed and the root of the core is cut off, a sealing ball is inserted into the inner cavity of the piston tube. Under the action of drilling fluid, the sealing ball can be pressed tightly on the ball seat to seal the inner cavity of the piston. At this time, drilling fluid flows into the rod cavity of the cylinder through the pressure hole, driving the cylinder, coring tube, and the core inside the coring tube to move towards the rear end of the tool until the front end of the coring tube moves to the position of the pressure holding controller. The valve core or valve of the pressure holding controller is closed, which can seal the front end of the coring tube and keep the environment inside the coring tube the actual environment of the deep rock formation. Therefore, this hydraulically self-triggered pressure-holding coring tool can achieve pressure-holding and high-fidelity coring of deep rock formations, which is beneficial for maintaining the in-situ environmental state of deep rock cores and avoiding the impact of changes in the external environment on the core properties during the process of retrieving the core from the wellhead. This helps improve the accuracy of experimental and analytical results of the core samples. Furthermore, this hydraulically self-triggered pressure-holding coring tool has a compact overall structure with small axial and radial dimensions. When connected to flexible drill pipe, it is suitable for applications requiring confined spaces, ultra-short radii of curvature, and multi-directional coring. The axial position switching of the coring cylinder can be achieved simply by dropping a ball, making the operation extremely convenient. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the external structure of a hydraulic self-triggering pressure-holding coring tool according to the present invention;

[0015] Figure 2 This is a schematic diagram of the internal structure of a hydraulic self-triggering pressure-holding coring tool according to the present invention;

[0016] Figure 3 This is a cross-sectional structural diagram of a hydraulic self-triggering pressure-holding coring tool of the present invention during the coring stage;

[0017] Figure 4 This is a cross-sectional view of the hydraulic self-triggering pressure-holding coring tool of this utility model after coring is completed;

[0018] Figure 5 This is a schematic diagram of the structure of the first snap-fit ​​connector in this utility model;

[0019] Figure 6 This is a schematic diagram of the structure of the second snap-fit ​​connector in this utility model;

[0020] Figure 7 This is a schematic diagram of the clamping sleeve in this utility model;

[0021] In the diagram, 1-shell, 2-core drill bit, 3-pressure holding controller, 4-piston tube, 5-cylinder, 6-core tube, 7-piston, 8-rod chamber, 9-rodless chamber, 10-through flow channel, 11-pressure hole, 12-check valve sleeve, 13-ratchet, 14-first clamping connector, 15-second clamping connector, 16-cone, 17-clamping claw, 18-sealing ball. Detailed Implementation

[0022] The technical solution of this utility model is described in further detail below with reference to the accompanying drawings, but the scope of protection of this utility model is not limited to the following description.

[0023] like Figures 1 to 7 As shown, a hydraulically self-triggered pressure-holding coring tool includes a housing 1. A coring drill bit 2 is fixedly connected to the front end of the housing 1. A coring cylinder 6 is coaxially arranged inside the housing 1, located at the rear end of the coring drill bit 2. The coring drill bit 2 can rotate freely relative to the coring cylinder 6. The coring drill bit 2 is a ring-shaped drill bit used in conventional coring techniques. During use, the rear end of the housing 1 is connected to the drill rod. The drill rod drives the housing 1 and the coring drill bit 2 to rotate and provides drilling pressure. When the coring drill bit 2 drills forward, the rock core can enter the coring cylinder 6 from the center hole of the coring drill bit 2. After drilling a set distance, the drill rod is pulled outward, and the rock core can be pulled along by the coring cylinder 6 until the root of the rock core is cut off, thus completing the conventional coring operation.

[0024] To achieve pressure-maintaining and accurate coring, a pressure-maintaining controller 3 is coaxially installed inside the housing 1. The pressure-maintaining controller 3 can be any type of pressure-maintaining controller, such as a ball valve or a flap valve, which are available in the prior art. The rear end of the coring cylinder 6 is a closed end, and the front end of the coring cylinder 6 is adapted to the pressure-maintaining controller 3. During coring operations, the front end of the coring cylinder 6 passes through the pressure-maintaining controller 3 and extends to the rear side of the center hole of the coring drill bit 2 to receive and collect the rock core. After coring is completed, the front end of the coring cylinder 6 retracts into the pressure-maintaining controller 3, and the valve core or valve cover of the pressure-maintaining controller 3 is closed. Thus, the front end of the coring cylinder 6 can be sealed through the pressure-maintaining controller 3. In addition, the rear end of the coring cylinder 6 is designed as a closed end, which can form a closed environment inside the coring cylinder 6 when the pressure-maintaining controller 3 is closed, thereby achieving pressure maintenance and accurate measurement of the environment around the rock core inside the coring cylinder 6.

[0025] To achieve the switching action of the 6-axis position of the core-taking cylinder, such as Figures 2 to 4 As shown, a piston tube 4 and a cylinder 5 are coaxially arranged inside the housing 1. One end of the piston tube 4 is fixedly connected to the rear end of the housing 1, and a piston 7 is fixedly arranged at the other end of the piston tube 4. The piston 7 is slidably arranged inside the cylinder 5. The cylinder 5 is slidably adapted to the housing 1. The rear end of the cylinder 5 is slidably adapted to the piston tube 4. The front end of the cylinder 5 is rotatably connected to one end of the core-taking cylinder 6. The piston 7 divides the cylinder interior into a rod chamber 8 and a rodless chamber 9. The piston 7 has a hollow structure. The inner cavity of the piston tube 4, the inner cavity of the piston 7, and the rodless chamber 9 are connected in sequence. A through flow channel 10 is opened at the front end of the cylinder 5. One end of the through flow channel 10 is connected to the rodless chamber 9. The outer wall of the core tube 6 and the inner wall of the shell 1 form an annular cavity. The other end of the through flow channel 10 is connected to the annular cavity. A pressure hole 11 is machined on the piston tube 4 near the piston 7. The two ends of the pressure hole 11 are connected to the inner cavity of the piston tube 4 and the rod chamber 8, respectively. A ball seat is machined inside the piston 7. It also includes a sealing ball 18. The sealing ball 18 can be inserted into the ball seat through the inner cavity of the piston tube 4. The sealing ball 18 can be used to seal the inner cavity of the piston 7.

[0026] During the core sampling stage, before the sealing ball 18 is inserted, the drilling fluid can flow into the rodless chamber 9 through the inner cavity of the piston tube 4 and the inner cavity of the piston 7, applying hydraulic pressure to the cylinder 5 in the direction of the core drill bit 2, thereby providing an axial force to the core tube 6 in the direction of the tool tip, so as to prevent the core tube 6 from retracting under the reaction force of the rock core during the core sampling process, thus ensuring that the core can be successfully sampled from the core tube 6; since the through flow channel 10 is provided, part of the drilling fluid in the rodless chamber 9 will flow out to the tip of the tool through the through flow channel 10 and the annular cavity, so as to cool and lubricate the core drill bit 2 and carry rock cuttings during the drilling process. It should be understood that the through-channel 10 has a small diameter and will not affect the pressure built up by the drilling fluid in the rodless chamber 9. When the flow rate and pressure of the drilling fluid injected into the tool are large enough, it can ensure that the core tube 6 can successfully extract the core. It should also be understood that although some drilling fluid may enter the rod chamber 8 through the pressure hole 11 when the drilling fluid is injected, the end of the cylinder 5 near the rodless chamber has a larger contact area with the drilling fluid. When the drilling fluid pressure is the same at both ends of the cylinder 5, the hydraulic pressure at the front end of the cylinder 5 is greater, which will also maintain the tendency to push the cylinder 5 forward, thereby ensuring that the core tube 6 can be successfully extracted.

[0027] After core sampling and cutting off the core root, a sealing ball 18 is inserted from the outside through the inner cavity of the piston tube 4. Under the push of the drilling fluid, the sealing ball 18 is pressed into the ball seat to seal the inner cavity of the piston 7. At this time, the drilling fluid flows into the rod chamber 8 through the pressure hole 11. Since no drilling fluid enters the rodless chamber 9 and the through flow channel 10 can depressurize the rodless chamber 9, when the drilling fluid flows into the rod chamber 8, it can drive the cylinder 5, the core tube 6 and the core in the core tube 6 to move together towards the rear end of the tool until the front end of the core tube 6 moves to the position of the pressure holding controller 3. At this time, the pressure holding controller 3 seals the front end of the core tube 6 to complete the pressure holding process. Because this action is performed in a deep rock environment, after sealing the core tube 6, the true deep in-situ environment state is preserved inside the core tube 6.

[0028] After the pressure holding process is completed, the cylinder 5, core barrel 6 and core can be kept in a retracted state towards the tool by maintaining the injection pressure of the drilling fluid. Then, the drill pipe and the drill string as a whole can be taken out of the well to complete the deep rock formation pressure holding and core taking process.

[0029] As can be seen from the above process, this hydraulic self-triggering pressure-holding coring tool can achieve pressure-holding and high-fidelity coring of deep rock formations. This is beneficial for maintaining the in-situ environmental state of deep rock cores and avoiding the impact of environmental changes on core performance during the process of retrieving the core from deep locations to the wellhead. This also helps improve the accuracy of experimental and analytical results of core samples. Furthermore, in this hydraulic self-triggering pressure-holding coring tool, the piston tube 4, cylinder 5, and core tube 6 are all located within the housing 1, resulting in a compact overall structure with small axial and radial dimensions. When connected to flexible drill pipes, it is suitable for applications requiring confined spaces, ultra-short radii of curvature, and multi-directional coring. The axial position switching of the core tube 6 can be achieved simply by dropping a ball, making the operation extremely convenient.

[0030] It should be understood that the pressure holding controller 3 shown in the attached figure is only a structural illustration. It can be selected from various structural forms such as existing ball valves and flap valves. For example, in a specific implementation, the pressure holding controller 3 can be selected from the pressure holding controller disclosed in Chinese Patent A Pressure Holding Control Device and Fidelity Controller Based on Magnetic Field Action (Application No.: 202110349469.6), which includes a magnetic valve seat, a valve cover and a triggering magnetic element. One end of the magnetic valve seat is movably connected to one end of the valve cover, and the triggering magnetic element and the magnetic valve seat can provide a magnetic force to attract the valve cover. During assembly, the magnetic valve seat is rotatably mounted inside the housing 1. The front end of the core barrel 6 slides and seals against the end of the magnetic valve seat away from the core drill bit 2 (similar to the assembly structure of the piston rod and cylinder end in a hydraulic cylinder). The valve cover is located at the end of the magnetic valve seat near the core drill bit 2. During core extraction, the front end of the core barrel 6 extends outside the magnetic valve seat, and the inner side of the valve cover abuts against the outer wall of the core barrel 6 to limit and maintain the valve cover in the open state. After core extraction is completed, the front end of the core barrel 6 retracts into the magnetic valve seat, and the valve cover closes under the action of magnetic force to seal the front end of the core barrel 6. Several medium holes are also provided on the magnetic valve seat. These medium holes are evenly distributed around the circumference and located close to the inner wall of the housing 1 so that the drilling fluid flowing into the annular cavity through the through-flow channel 10 can flow out through these medium holes and act on the core drill bit 2. The pressure-holding control device based on magnetic field action is not limited by the direction of core drilling, and can ensure the reliability of valve cover closure when drilling and coring in all directions, which is beneficial for application in multi-directional coring environments.

[0031] In specific implementation, a check sleeve 12 is fixedly installed inside the core-taking cylinder 6, such as... Figure 7 As shown, the inner circumference of the check sleeve 12 is evenly distributed with several ratchet bars 13. The ratchet bars 13 are arranged along the axial direction of the core barrel 6. Each ratchet tooth on the ratchet bar 13 is wedge-shaped, and the tip of the ratchet tooth faces the direction of the core drill bit 2. Thus, the ratchet bars 13 make the core and the check sleeve 12 move only in the direction of moving closer to each other. During core drilling, the core can be inserted from the check sleeve 12 into the core barrel 6. During the subsequent core cutting, core barrel 6 retraction and removal of the entire tool from the well, the check sleeve 12 limits the core, and the core will not fall out of the core barrel 6.

[0032] In specific implementation, there are several through channels 10, which are evenly distributed around the circumference. The drilling fluid discharged through each through channel 10 is also sprayed out circumferentially, making the sprayed drilling fluid evenly distributed, which is beneficial for the drilling fluid to play its role in cooling, lubrication, and carrying cuttings. Furthermore, the through channels 10 are set at an angle, with one end of the through channel 10 away from the core barrel 6 located near the axis of the cylinder 5, and the other end of the through channel 10 located away from the axis of the cylinder 5. On the one hand, the outlet end of the through channel 10 is close to the inner wall of the shell 1, which is conducive to the drilling fluid being sprayed out circumferentially along the inner wall of the shell 1. On the other hand, the angled setting of the through channel 10 ensures ease of processing while increasing the length of the through channel 10 in a limited space, which in turn helps the injected drilling fluid to build up pressure in the rodless chamber 9.

[0033] Furthermore, such as Figure 2 As shown, a first clamping connector 14 is fixedly installed at the rear end of the housing, and a second clamping connector 15 is fixedly installed at the rear end of the cylinder. During the pressure holding process, the rear end of the cylinder 5 drives the second clamping connector 15 to move close to the first clamping connector 14. When the first clamping connector 14 and the second clamping connector 15 come together, the first clamping connector 14 can be connected to the second clamping connector 15. Thus, when the entire tool is taken out later, it is not necessary to maintain the drilling fluid injection pressure. The cylinder 5 and the core barrel 6 can be directly retracted to the rear end of the tool through the connection between the first clamping connector 14 and the second clamping connector 15.

[0034] The first snap-fit ​​connector 14 and the second snap-fit ​​connector 15 can be selected from various active connection or passive snap-fit ​​structures. In this embodiment, for example... Figure 5 , Figure 6 As shown, the first clamping connector 14 is generally annular, and is fixedly inserted into the rear end of the housing 1 and fixedly sleeved on the rear end of the piston tube 4. Several clamping claws 17 are evenly distributed around the circumference of the end of the first clamping connector 14 near the cylinder 5. The second clamping connector 15 is generally annular, and is sleeved on the piston tube 4. A truncated cone 16 is machined at the end of the second clamping connector 15 near the first clamping connector 14, and the truncated cone 16 is adapted to the clamping claws 17. The pawl 17 has a certain degree of elasticity, and its end is provided with a hook head that bends towards the center of the first pawl 14. The large-diameter end of the cone 16 forms a limiting shoulder. As the second pawl 15 approaches the first pawl 14, the outer side of the small-diameter end of the cone 16 first contacts the hook head end of each pawl 17. As it continues to approach, the conical surface of the cone 16 pushes each pawl 17 to open outward until the cone 16 is located inside each pawl 17. At this time, each pawl 17 springs back to its original position, and each hook head hooks the limiting shoulder of the cone 16. At this time, the connection between the first pawl 14 and the second pawl 15 can be completed.

[0035] The above description is merely a preferred embodiment of this utility model. It should be understood that this utility model is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the concept described herein through the above teachings or related technologies or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of this utility model should be protected within the scope of the appended claims.

Claims

1. A hydraulically self-triggered pressure-holding coring tool, comprising a housing, a coring drill bit fixedly connected to the front end of the housing, and a coring cylinder coaxially disposed within the housing, the coring cylinder being located at the rear end of the coring drill bit, characterized in that, The housing also includes a piston tube, a cylinder, and a pressure holding controller coaxially arranged inside. One end of the piston tube is fixedly connected to the rear end of the housing, and a piston is fixedly mounted on the other end of the piston tube. The piston is slidably mounted inside the cylinder, and the cylinder is slidably adapted to the housing. The rear end of the cylinder is slidably adapted to the piston tube. One end of the core-taking tube is closed, and the front end of the cylinder is rotatably connected to the closed end of the core-taking tube. The other end of the core-taking tube is adapted to the pressure holding controller. The piston divides the inside of the cylinder into a rod chamber and a rodless chamber. The piston has a hollow structure. The inner cavity of the piston tube, the inner cavity of the piston, and the rodless chamber are connected in sequence. A through flow channel is opened at the front end of the cylinder. One end of the through flow channel is connected to the rodless chamber. The outer wall of the core tube and the inner wall of the shell form an annular cavity. The other end of the through flow channel is connected to the annular cavity. A pressure hole is machined on the piston tube near the piston. The two ends of the pressure hole are connected to the inner cavity of the piston tube and the rod cavity, respectively. A ball seat is machined inside the piston, and a sealing ball is also included. The sealing ball can be inserted into the ball seat through the inner cavity of the piston tube. The sealing ball can be used to seal the inner cavity of the piston.

2. The hydraulic self-triggering pressure-holding coring tool according to claim 1, characterized in that, A first snap-fit ​​connector is fixedly provided at the rear end of the housing, and a second snap-fit ​​connector is fixedly provided at the rear end of the cylinder. When the first snap-fit ​​connector and the second snap-fit ​​connector are brought close together, the first snap-fit ​​connector can be connected to the second snap-fit ​​connector.

3. The hydraulic self-triggering pressure-holding coring tool according to claim 2, characterized in that, The first clamping connector has several clamping claws evenly distributed around its circumference at one end near the cylinder barrel, and the second clamping connector has a truncated cone machined at one end near the first clamping connector, the truncated cone being adapted to the clamping claws.

4. The hydraulic self-triggering pressure-holding coring tool according to claim 1, characterized in that, There are several through channels, and these through channels are evenly distributed around the circumference.

5. A hydraulically self-triggered pressure-holding coring tool according to claim 4, characterized in that, The through-flow channel is inclined, with one end of the through-flow channel away from the core tube positioned near the cylinder axis, and the other end of the through-flow channel positioned away from the cylinder axis.

6. A hydraulically self-triggered pressure-holding coring tool according to claim 1, characterized in that, A check sleeve is fixedly installed inside the core tube. Several ratchet teeth are evenly distributed around the inner circumference of the check sleeve. The ratchet teeth are configured to allow the core and the check sleeve to move only in the direction of moving closer to each other.

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