A core pre-cut high-recovery coring tool and method

Abstract

This invention pertains to the field of ultra-deep well coring in oil and gas drilling operations, specifically relating to a high-yield coring tool and method for pre-cutting cores. The tool includes an outer cylinder and an inner cylinder. From top to bottom, a resettable steel ball seat, a first spring, and a guide clamp are sequentially arranged within the inner cylinder. One end of the resettable steel ball seat is connected to one end of the first spring, and the other end of the first spring is connected to a step on the inner wall of the inner cylinder. Above the resettable steel ball seat, the inner cylinder has a through hole. Below the guide clamp, the inner cylinder is connected to a cutting structure. The inner wall of the outer cylinder is connected to the outer wall of the inner cylinder, and a flow channel is provided between the outer wall of the inner cylinder and the inner wall of the outer cylinder. The upper end of the flow channel communicates with the through hole, and the lower end of the flow channel communicates with the cutting structure. This invention, by incorporating a cutting structure, enables pre-cutting of the core during coring, which not only improves the integrity of the core but also shortens the operation time and reduces coring costs.

Description

Technical Field

[0001] This invention belongs to the field of ultra-deep well coring in oil and gas drilling operations, specifically relating to a high-yield coring tool and method for pre-cutting cores. Background Technology

[0002] Core sampling is a crucial piece of geological exploration equipment, primarily used to extract columnar samples from geological media such as soil and rock cores. The extracted core samples provide information on subsurface structure, mineral distribution, and hydrogeological data, offering scientific support for engineering projects, mineral development, and environmental monitoring. In practice, however, the core sampling process is often less efficient than expected, typically involving multiple stages such as drilling, core extraction, and hoisting.

[0003] Chinese patent CN204311998U discloses a hydraulically pressurized coring tool, including a safety joint, a hydraulic pressurization device, an outer cylinder assembly, an inner cylinder assembly, and a core claw assembly. The safety joint is a hollow, cone-shaped structure with a wider top and narrower bottom. The middle part of the safety joint is threaded to the outer cylinder assembly, and the lower part is threaded to the hydraulic pressurization device. The inner cylinder assembly is suspended below the hydraulic pressurization device via a suspension device, and the core claw assembly is located below the inner cylinder assembly. The hydraulic pressurization device, inner cylinder assembly, and core claw assembly are located inside the outer cylinder assembly. This coring tool has the following problems during the coring process: poor core integrity; long operation time, affecting the overall progress and increasing coring costs.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] To address the technical problems existing in the prior art, this invention provides a high-yield core pre-cutting tool and method. By setting a cutting structure, this invention can pre-cut the core during core extraction, which not only improves the integrity of the core but also shortens the operation time and reduces the core extraction cost.

[0006] This invention includes the following technical solutions:

[0007] The present invention provides a high-yield core pre-cutting tool, comprising an outer cylinder and an inner cylinder. From top to bottom, a resettable steel ball seat, a first spring, and a guide clamp are sequentially arranged inside the inner cylinder. The resettable steel ball seat is connected to one end of the first spring, and the other end of the first spring is connected to a step provided on the inner wall of the inner cylinder. Above the resettable steel ball seat, the inner cylinder has a through hole. Below the guide clamp, the inner cylinder is connected to a cutting structure.

[0008] The inner wall of the outer cylinder is connected to the outer wall of the inner cylinder. A flow channel is provided between the outer wall of the inner cylinder and the inner wall of the outer cylinder. The upper end of the flow channel is connected to the through hole, and the lower end of the flow channel is connected to the cutting structure.

[0009] Furthermore, the cutting structure includes a limiting annular cavity, a second spring, a moving part, a cutting part, and a limiting part; the outer cylinder is fixedly connected to the limiting annular cavity, and the moving part is movably connected within the inner annular cavity of the limiting annular cavity. One end of the moving part facing the inner annular cavity of the inner cylinder is connected to the cutting part, and the other end is connected to the limiting part; the second spring is provided between the limiting annular cavity and the limiting part along the axial direction of the limiting annular cavity.

[0010] Furthermore, the inner diameter of the limiting ring cylinder is adapted to the outer diameter of the moving part.

[0011] Furthermore, both ends of the second spring are connected to sealing rings.

[0012] Furthermore, multiple second springs are provided, and the multiple second springs are arranged circumferentially along the outer side of the moving part.

[0013] Furthermore, the cutting portion is made of diamond.

[0014] Furthermore, multiple cutting structures are provided, and the multiple cutting structures are evenly connected around the inner cylinder.

[0015] Furthermore, the inner wall of the inner cylinder is provided with an annular groove, the circumferential wall of the resettable steel ball seat and the first spring is embedded in the annular groove, and the lower end of the first spring is connected to the step formed by the annular groove.

[0016] Furthermore, the inner cylinder includes a first inner cylinder and a second inner cylinder, which are connected by threads. The resettable steel ball seat and the first spring are connected to the first inner cylinder, and the guide clamp and the cutting structure are connected to the second inner cylinder.

[0017] Furthermore, the guide clamp is provided with a tapered hole, the diameter of the upper end of the tapered hole is larger than the diameter of the lower end, and a notch communicating with the tapered hole is opened on the wall of the guide clamp, with the two ends of the notch extending towards the upper end and the lower end of the guide clamp, respectively.

[0018] This embodiment provides a high-yield core pre-cutting method, based on the aforementioned core extraction tool, and the core extraction method includes the following steps:

[0019] Lower the coring tool into the well and fit the guide clamp onto the core;

[0020] Insert steel balls into the inner cylinder;

[0021] Drilling fluid is injected into the inner cylinder, which drives the steel ball to squeeze and reset the steel ball seat and the first spring;

[0022] Continue injecting drilling fluid, which drives the cutting structure to cut the core through the through-holes and flow channels;

[0023] Stop injecting drilling fluid, use the core extraction tool to break off the core sample, and complete the core sampling.

[0024] By adopting the above technical solution, the present invention has the following advantages:

[0025] 1. By setting up a cutting structure, the present invention can pre-cut the rock core during core sampling, which not only improves the integrity of the core sampling, but also shortens the operation time and reduces the core sampling cost.

[0026] 2. The cutting structure of the present invention is simple and easy to manufacture.

[0027] 3. The core-taking tool of this invention uses injected drilling fluid to pressurize and control the cutting structure to cut the core, forming a groove in the core. This concentrates the stress in the core, reduces the tensile load on the core, thereby reducing the difficulty of core taking, effectively improving the overall safety of the system, and improving the efficiency and quality of core taking operations.

[0028] 4. The cutting part of the cutting structure of the present invention is made of diamond, which effectively ensures the completion of core cutting.

[0029] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention can be realized and obtained by means of the structures pointed out in the description and the drawings. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the structure of a high-yield core pre-cutting tool according to an embodiment of the present invention;

[0032] Figure 2 This is a schematic diagram of the cutting structure in an embodiment of the present invention. Figure 1 ;

[0033] Figure 3 This is a schematic diagram of the cutting structure in an embodiment of the present invention. Figure 2 ;

[0034] Figure 4 This is a schematic diagram of the guide clamp structure in an embodiment of the present invention;

[0035] Figure 5 This is the usage state of a high-yield core pre-cutting coring tool according to an embodiment of the present invention. Figure 1 ;

[0036] Figure 6 This is the usage state of a high-yield core pre-cutting coring tool according to an embodiment of the present invention. Figure 2 ;

[0037] Figure 7 This is the usage state of a high-yield core pre-cutting coring tool according to an embodiment of the present invention. Figure 3 ;

[0038] In the figure, 10-outer cylinder, 101-protrusion, 20-inner cylinder, 21-first inner cylinder, 22-second inner cylinder, 201-through hole, 202-annular groove, 30-resettable steel ball seat, 40-first spring, 50-guide clamp, 501-notch, 502-protruding tooth, 60-cutting structure, 61-limiting ring cylinder, 62-second spring, 63-moving part, 64-cutting part, 65-limiting part, 66-sealing ring, 70-flow channel, 80-steel ball. Detailed Implementation

[0039] The following description provides many different embodiments or examples for implementing various features of the invention. The elements and arrangements described in the specific examples below are only for concise expression of the invention and are merely examples, not intended to limit the invention.

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] This embodiment provides a high-yield core pre-cutting tool, such as... Figure 1As shown, the device includes an outer cylinder 10 and an inner cylinder 20. From top to bottom, a resettable steel ball seat 30, a first spring 40, and a guide clamp 50 are sequentially arranged inside the inner cylinder 20. The resettable steel ball seat 30 is connected to one end of the first spring 40, and the other end of the first spring 40 is connected to a step provided on the inner wall of the inner cylinder 20. Above the resettable steel ball seat 30, the inner cylinder 20 has a through hole 201. Below the guide clamp 50, the inner cylinder 20 is connected to a cutting structure 60.

[0042] The inner wall of the outer cylinder 10 is connected to the outer wall of the inner cylinder 20. A flow channel 70 is provided between the outer wall of the inner cylinder 20 and the inner wall of the outer cylinder 10. The upper end of the flow channel 70 is connected to the through hole 201, and the lower end of the flow channel 70 is connected to the cutting structure 60.

[0043] Drilling fluid can enter the flow channel 70 through the through hole 201, and the drilling fluid entering the flow channel 70 drives the cutting structure 60 to cut the rock core.

[0044] The connection between the outer wall of the inner cylinder 20 and the outer wall of the outer cylinder 10 can be direct or indirect. In the direct connection structure, the flow channel 70 can be formed on the outer wall of the inner cylinder 20, on the inner wall of the outer cylinder 10, or simultaneously on both. Furthermore, the connection between the outer wall of the inner cylinder 20 and the inner wall of the outer cylinder 10 can be integrally formed.

[0045] The outer wall of the inner cylinder 20 and the inner wall of the outer cylinder 10 can be indirectly connected by a connecting structure. For example, a connecting ring can be provided between the outer wall of the inner cylinder 20 and the inner wall of the outer cylinder 10 to connect the inner cylinder 20 and the outer wall. The connecting ring is preferably located above the through hole 201. With this structure, a flow channel 70 is naturally formed between the outer wall of the inner cylinder 20 and the inner wall of the outer cylinder 10. It should be noted that this indirect connection method is only an example and does not imply a limitation on the present invention.

[0046] At the same time, such as Figure 1 As shown, a boss 101 is provided on the inner wall of the outer cylinder 10, and the lower end of the outer cylinder 20 is connected to the boss 101. This connection method can also be understood as the outer wall of the inner cylinder 20 and the inner wall of the outer cylinder 10 being indirectly connected.

[0047] The present invention does not limit the size of the flow channel 70, nor does it limit the number of flow channels 70. The present invention also does not limit the size of the through hole 201, nor does it limit the number of through holes 201.

[0048] For structures where flow channels 70 are formed on the outer wall of the inner cylinder 20 and / or on the inner wall of the outer cylinder 10, the number of cutting structures 60 is preferably equal to the number of flow channels 70, and the number of flow channels 70 is preferably equal to the number of through holes 201. The number of through holes 201 and flow channels 70 is preferably determined based on the number of cutting structures 60; this avoids setting up useless through holes 201 and flow channels 70.

[0049] In some embodiments, multiple cutting structures 60 are provided, and the multiple cutting structures 60 are evenly connected around the inner cylinder 20; it should be understood that multiple evenly arranged cutting structures 60 are connected in the circumferential direction of the inner cylinder 20. The provision of multiple cutting structures 60 corresponds to the provision of multiple flow channels 70 and multiple through holes 201. This structure with multiple cutting structures 60 allows the multiple cutting structures 60 to cut multiple discontinuous grooves in the core, which is more conducive to core sampling; at the same time, the evenly arranged cutting structures 60 can ensure that the multiple discontinuous grooves are uniform, ensuring the uniformity of core stress and improving the integrity and uniformity of core sampling.

[0050] It should be noted that a structure with only one cutting structure 60 should also be within the scope of protection of this invention. Similarly, a structure with multiple cutting structures 60 that are not evenly distributed should also be within the scope of protection of this invention.

[0051] like Figure 1 As shown, a boss 101 is provided on the outer cylinder 10, and the lower end of the outer cylinder 10 is connected to the boss 101. The cutting structure 60 is also connected to the boss 101. Of course, the connection structure and position shown in the figure are only schematic and do not represent a limitation of the present invention. The cutting structure 60 can also be connected to other positions, but the cutting structure 60 needs to be located below the guide clamp 50.

[0052] In some embodiments, such as Figure 2 As shown, the cutting structure 60 includes a limiting annular cylinder 61, a second spring 62, a moving part 63, a cutting part 64, and a limiting part 65. The outer cylinder 10 is fixedly connected to the limiting annular cylinder 61, and the moving part 63 is movably connected within the inner annular cavity of the limiting annular cylinder 61. The limiting annular cylinder 61 can guide and limit the moving part 63. One end of the moving part 63 facing the inner annular cavity of the inner cylinder 20 is connected to the cutting part 64, and the other end is connected to the limiting part 65. In the axial direction of the limiting annular cylinder 61, the second spring 62 is provided between the limiting annular cylinder 61 and the limiting part 65. Drilling fluid drives the limiting part 65 to move towards the inner annular cavity of the inner cylinder 20 to compress the second spring 62. After the drilling fluid injection stops, the second spring 62 can help the limiting part 65 return to its initial position.

[0053] The second spring 62 is provided between the limiting ring cylinder 61 and the limiting part 65 in several ways: (1) the two ends of the second spring 62 are movably connected to the limiting ring cylinder 61 and the limiting part 65 respectively; (2) one end of the second spring 62 is fixedly connected to the limiting part 65 and the other end is movably connected to the limiting ring cylinder 61; (3) one end of the second spring 62 is movably connected to the limiting part 65 and the other end is fixedly connected to the limiting ring cylinder 61; (4) the two ends of the second spring 62 are fixedly connected to the limiting part 65 and the limiting ring cylinder 61 respectively.

[0054] The cutting structure 60 is connected to the inner cylinder 20 by threads, and specifically, the outer surface of the limiting ring hollow cylinder 61 is provided with threads. Figure 1 In this design, the cutting structure 60 is located precisely at the boss 101. The cutting structure 60 is threadedly connected to both the inner cylinder 20 and the outer cylinder 10; that is, both the inner cylinder 20 and the outer cylinder 10 have partially threaded holes. This threaded connection facilitates the replacement of the cutting structure 60. However, the location of the threaded connection is not limited to the position shown in the diagram. In this structure, to improve the sealing of the inner cylinder 20, the end of the inner cylinder 20 can also be integrally formed with the boss 101.

[0055] Of course, the cutting structure 60 can also be fixedly connected to the inner cylinder 20 by other connection methods, such as welding; for example, the limiting ring hollow cylinder 61 is integrally formed with the inner cylinder 20.

[0056] like Figure 3 As shown, since the cutting structure 60 is driven by drilling fluid, if the sealing is not good enough, the drilling fluid may flow in the direction of the arrow shown in the figure, resulting in a small driving force on the limiting part 65 and a poor cutting effect; moreover, in the case of the limiting ring cylinder 61 being connected by threads, it will impact the connection and cause the connection to fail.

[0057] Therefore, to improve this problem, in some embodiments, the inner diameter of the limiting annulus 61 is adapted to the outer diameter of the moving part 63. This prevents drilling fluid from entering the annulus. Figure 3 The arrow-shaped flow not only improves the cutting effect but also reduces the impact on the threaded connection, thus extending its service life.

[0058] To further improve this problem, in some embodiments, both ends of the second spring 62 are connected to sealing rings 66. It should be noted that this arrangement of the sealing rings 66 is not merely a further improvement on the premise that the inner diameter of the limiting ring cylinder 61 matches the outer diameter of the moving part 63; when there is no structure where the inner diameter of the limiting ring cylinder 61 matches the outer diameter of the moving part 63, simply setting the sealing ring 66 can also improve the cutting effect, reduce the impact on the threaded connection, and increase service life. Preferably, the sealing ring 66 is an O-ring. O-rings have good sealing performance and deformation space, which further improves their sealing performance after deformation.

[0059] The structure in which sealing rings 66 are connected to both ends of the second spring 62 includes a variety of connection methods: (1) both ends of the sealing ring 66 are movably connected to the limiting ring cylinder 61 and the limiting part 65; (2) one sealing ring 66 is fixedly connected to the limiting part 65, and the other sealing ring 66 is movably connected to the limiting ring cylinder 61; (3) one sealing ring 66 is movably connected to the limiting part 65, and the other sealing ring 66 is fixedly connected to the limiting ring cylinder 61; (4) the two sealing rings 66 are fixedly connected to the limiting part 65 and the limiting ring cylinder 61 respectively.

[0060] Of course, the way in which one end of the second spring 62 is connected to the sealing ring 66 should also be within the scope of protection of this invention, as only two sealing rings 66 provide a better sealing effect. Specifically, the sealing ring 66 is connected to the end of the second spring 62 near the limiting ring cylinder 61, or the sealing ring 66 is movably connected to the end of the second spring 62 near the limiting part 65. The connection method with only one sealing ring 66 is similar to the connection method with two sealing rings 66, and will not be described in detail here.

[0061] Since the second spring 62 mainly functions to help the limiting part 65 and the moving part 63 reset, the specific number of the second spring 62 is not limited in this invention. In some embodiments, multiple second springs 62 are provided, and multiple second springs (62) are arranged circumferentially around the outside of the moving part (63); preferably, multiple second springs (62) are evenly arranged around the outside of the moving part 63; multiple second springs (62) can provide greater restoring force, so that the limiting part 65 and the moving part 63 can be quickly reset; the evenly arranged multiple second springs (62) provide uniform restoring force, avoiding the displacement of the moving part 63.

[0062] In some embodiments, the cutting portion 64 is made of diamond. Using diamond provides better cutting results. Of course, the cutting portion 64 can also be made of cemented carbide.

[0063] Since the first spring 40 and the resettable steel ball seat 30 mainly support the inserted steel ball 80, it is necessary to ensure that after the steel ball 80 is inserted into the coring tool in this embodiment, the steel ball 80 blocks the vertical channel of the coring tool and also blocks the through hole 201. After the drilling fluid is injected, it is necessary to ensure that the through hole 201 is not blocked by the steel ball 80. Therefore, after the drilling fluid is injected, the steel ball 80 is driven to compress the first spring 40 and move downward, so that the drilling fluid enters the through hole 201. Therefore, the inner cylinder 20 only needs to be provided with a step to support the first spring 40 to ensure that the above functions are achieved. The first spring 40 can be placed directly on the step or fixedly connected to the step.

[0064] Of course, in order to improve the stability of the first spring 40 and the returnable steel ball seat 30, in some embodiments, such as Figure 1 As shown, the inner wall of the inner cylinder 20 is provided with an annular groove 202. The circumferential walls of the resettable steel ball seat 30 and the first spring 40 are embedded in the annular groove 202. The lower end of the first spring 40 is connected to the step formed by the annular groove 202.

[0065] The lower end of the resettable steel ball seat 30 is connected to the first spring 40. Similarly, the connection between the resettable steel ball seat 30 and the first spring 40 includes a fixed connection and a movable connection. Of course, the fixed connection has better stability.

[0066] The resettable steel ball seat 30 should be understood as a structure that is reset by the first spring 40. The present invention does not limit the specific shape of the resettable steel ball seat 30. The resettable steel ball seat 30 itself can be made of a material that can be deformed and reset, so that the resettable steel ball seat 30 and the first spring 40 together achieve the extension and contraction function. The resettable steel ball seat 30 can also be made of a material that does not have the ability to deform.

[0067] Meanwhile, the resettable steel ball seat 30 and the first spring 40 also need to allow drilling fluid to pass through, ensuring that the drilling fluid can pass through during the drilling process. The first spring 40 itself is set along the axial direction of the inner cylinder 20, so the drilling fluid can pass through; while the resettable steel ball seat 30 needs to be provided with a channel for the drilling fluid to pass through, in order to ensure that the drilling fluid can pass through during the drilling process.

[0068] like Figure 1 As shown, the upper end of the annular groove 202 is an inclined step, and an inclined surface that cooperates with the inclined step is provided on the outer wall surface of the resettable steel ball seat 30 to limit the resettable steel ball seat 30.

[0069] like Figure 1As shown, a portion of the upper end of the resettable steel ball seat 30 extends beyond the annular groove 202. Of course, structures where the upper end of the resettable steel ball seat 30 does not extend beyond the annular groove 202 should also be within the protection scope of this invention.

[0070] In some embodiments, such as Figure 1 As shown, the inner cylinder 20 includes a first inner cylinder 21 and a second inner cylinder 22, which are connected by threads. The resettable steel ball seat 30 and the first spring 40 are connected to the first inner cylinder 21, and the guide clamp 50 and the cutting structure 60 are connected to the second inner cylinder 22. This divides the inner cylinder 20 into two parts, thus securing the guide clamp 50 and the cutting structure 60.

[0071] like Figure 1 The first inner cylinder 21 is provided with a male connector at its lower end and the second inner cylinder is provided with a female connector at its upper end. The male connector is provided with a thread on its outer surface and the female connector is provided with a thread on its inner surface.

[0072] In some embodiments, such as Figure 4 As shown, the guide clamp 50 is provided with a tapered hole, the diameter of the upper end of the tapered hole being larger than the diameter of the lower end. A notch 501 communicating with the tapered hole is formed on the wall surface of the guide clamp 50, with both ends of the notch 501 extending towards the upper and lower ends of the guide clamp 50, respectively. This structure facilitates the installation of the guide clamp on the rock core for coring.

[0073] The notch 501 ensures that the guide clamp 50 has a telescopic function during coring. In this embodiment, when the coring tool is lowered into the well, the lower end of the guide clamp 50 is opened by the core, and the core enters the guide clamp 50; then the lower end of the guide clamp 50 naturally contracts to clamp the core. At the same time, the tapered hole is also for the purpose of facilitating the clamping of the core.

[0074] Therefore, in order to ensure the expansion and contraction function of the notch 501, the guide clamp 50 is positioned such that the notch 501 is not fixedly connected to the inner cylinder 20, and there needs to be a certain gap between it and the inner wall surface of the inner cylinder 20. After the guide clamp 50 is connected to the inner cylinder 20, its tapered hole is preferably coaxial with the inner cylinder 20.

[0075] The shape of the outer surface of the guide clamp 50 is not limited in this invention.

[0076] In some embodiments, such as Figure 4 The guide clamp 50 has protruding teeth 502 on its inner wall. By providing protruding teeth 502, the friction with the rock core is increased, which has the advantage of improving the core sampling efficiency. Preferably, the guide clamp 50 has multiple sets of protruding teeth 502 on its inner wall, and each set of protruding teeth 502 is arranged linearly from the upper end to the lower end of the guide clamp 50.

[0077] By setting the cutting structure 60, the present invention can pre-cut the rock core to release stress before core cutting, which can alleviate the problems of excessive core cutting force in ultra-deep dense or highly plastic formations, causing rock core claw deformation and weak rock core gripping, thereby improving the core recovery rate and reducing drilling costs.

[0078] When using the coring tool of this invention, steel balls need to be inserted, and a hydraulic system is used to inject drilling fluid to pressurize and control the cutting structure to cut the rock core, forming a groove in the rock core. This concentrates the stress in the rock core, reduces the tensile load on the rock core, thereby reducing the difficulty of coring, effectively improving the overall safety of the system, and improving the efficiency and quality of coring operations.

[0079] This embodiment also provides a high-yield core pre-cutting method, implemented using the core extraction tool of this embodiment. The core extraction method includes the following steps:

[0080] like Figure 5 As shown, the coring tool is lowered into the well, and the guide clamp 50 is fitted onto the core.

[0081] Steel balls 80 are inserted into the inner cylinder 20; after the steel balls are inserted, they block the through hole 201 and the vertical channel.

[0082] Drilling fluid is injected into the inner cylinder 20, driving the steel ball 80 to squeeze the resettable steel ball seat 30 and the first spring 40; the pressure of the drilling fluid pushes the steel ball 80 and the resettable steel ball seat 30 downward to compress the first spring 40, causing the through hole 201 to leak out, and the drilling fluid enters the flow channel 70 through the through hole 201.

[0083] like Figure 6 As shown, drilling fluid continues to be injected, and the drilling fluid drives the cutting structure 60 to cut the core through the through hole 201 and the flow channel 70; the hydraulic pressure pushes the cutting part 64 of the cutting structure 60 to move towards the core, so that the cutting part 64 cuts the core, thereby reducing the tensile force required to break the core.

[0084] like Figure 7 As shown, stop injecting drilling fluid, use the core extraction tool to break off the core, and complete the core sampling.

[0085] Existing coring tools often encounter problems during coring. If the core sample is too large or has high strength, insufficient core gripper strength can lead to core slippage. In highly abrasive formations, the core gripper wears significantly, resulting in weak gripping force and easy core slippage. This embodiment addresses this by using a cutting structure to cut the core, ensuring its integrity during the core fracturing process. Furthermore, cutting the core reduces the difficulty of the fracturing process, ensuring core integrity, reducing coring time, and lowering costs.

[0086] In some embodiments, the coring tool is rotated while the driving cutting structure 60 cuts the core, creating a groove around the core, which facilitates core extraction. Simultaneously rotating the coring tool during cutting, the cutting section 64 circumferentially cuts the core, creating a groove (i.e., a stress groove), thereby reducing the tensile force required to break the core. This has the advantages of reducing the difficulty of core extraction and improving the integrity of the core sample.

[0087] It should be noted that if the core is cut directly by hydraulically driving the cutting unit 64, a larger hydraulic pressure is required, and the cutting difficulty is also greater. Therefore, rotating the core-taking tool at the same time during the cutting process has the advantage of reducing the cutting difficulty.

[0088] When core-taking is performed by rotating the core-taking tool during cutting, it is preferable that the cutting tool has only one cutting structure 60, which has the advantage of reducing the cost of the cutting tool.

[0089] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0090] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows for communication; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of multiple components or the interaction between multiple components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0091] 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.

[0092] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A core pre-slit high yield coring tool characterized by, The device includes an outer cylinder (10) and an inner cylinder (20). From top to bottom, a resettable steel ball seat (30), a first spring (40), and a guide clamp (50) are sequentially arranged inside the inner cylinder (20). The resettable steel ball seat (30) is connected to one end of the first spring (40), and the other end of the first spring (40) is connected to a step provided on the inner wall of the inner cylinder (20). Above the resettable steel ball seat (30), the inner cylinder (20) has a through hole (201). Below the guide clamp (50), the inner cylinder (20) is connected to a cutting structure (60). The inner wall of the outer cylinder (10) is connected to the outer wall of the inner cylinder (20). A flow channel (70) is provided between the outer wall of the inner cylinder (20) and the inner wall of the outer cylinder (10). The upper end of the flow channel (70) is connected to the through hole (201), and the lower end of the flow channel (70) is connected to the cutting structure (60).

2. A core pre-shearing high recovery coring tool according to claim 1, characterized in that, The cutting structure (60) includes a limiting annular cavity (61), a second spring (62), a moving part (63), a cutting part (64), and a limiting part (65); the outer cylinder (10) is fixedly connected to the limiting annular cavity (61), and the moving part (63) is movably connected to the inner annular cavity of the limiting annular cavity (61). One end of the moving part (63) facing the inner annular cavity of the inner cylinder (20) is connected to the cutting part (64), and the other end is connected to the limiting part (65); the second spring (62) is provided between the limiting annular cavity (61) and the limiting part (65) in the axial direction of the limiting annular cavity (61).

3. A core pre-shearing high recovery coring tool according to claim 2, wherein, The inner diameter of the limiting ring cylinder (61) is adapted to the outer diameter of the moving part (63).

4. The core pre-cutting high-yield coring tool according to claim 2, characterized in that, Both ends of the second spring (62) are connected to sealing rings (66).

5. A high-yield core pre-cutting tool according to claim 2, characterized in that, Multiple second springs (62) are provided, and the multiple second springs (62) are arranged circumferentially along the outer side of the moving part (63).

6. A high-yield core pre-cutting tool according to claim 2, characterized in that, The cutting part (64) is made of diamond.

7. A high-yield core pre-cutting tool according to any one of claims 1-6, characterized in that, Multiple cutting structures (60) are provided, and the multiple cutting structures (60) are evenly connected around the inner cylinder (20).

8. The high-yield core pre-cutting tool according to claim 1, characterized in that, The inner wall of the inner cylinder (20) is provided with an annular groove (202), and the circumferential walls of the resettable steel ball seat (30) and the first spring (40) are embedded in the annular groove (202). The lower end of the first spring (40) is connected to the step formed by the annular groove (202).

9. A high-yield core pre-cutting tool according to claim 1 or 8, characterized in that, The inner cylinder (20) includes a first inner cylinder (21) and a second inner cylinder (22), which are connected by threads. The resettable steel ball seat (30) and the first spring (40) are connected to the first inner cylinder (21), and the guide clamp (50) and the cutting structure (60) are connected to the second inner cylinder (22).

10. A high-yield core pre-cutting tool according to claim 1, characterized in that, The guide clamp (50) is provided with a tapered hole, the diameter of the upper end of the tapered hole is larger than the diameter of the lower end, and a notch (501) communicating with the tapered hole is opened on the wall surface of the guide clamp (50), the two ends of the notch (501) extending to the upper end and the lower end of the guide clamp (50) respectively.

11. A method for high-yield core extraction by pre-cutting core samples, characterized in that, Based on the core extraction tool as described in claims 1-10, the core extraction method includes the following steps: The core sampling tool is lowered into the well, and the guide clamp (50) is fitted onto the core. Steel balls (80) are inserted into the inner cylinder (20); Drilling fluid is injected into the inner cylinder 20, driving the steel ball (80) to squeeze the resettable steel ball seat (30) and the first spring (40); Continue injecting drilling fluid, which drives the cutting structure (60) to cut the core through the through hole (201) and flow channel (70); Stop injecting drilling fluid, use the core extraction tool to break off the core sample, and complete the core sampling.

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