Self-locking core cutting mechanism for taking large-diameter core

Abstract

The utility model relates to the technical field of downhole tools, in particular to a self-locking core cutting mechanism for taking a large-diameter core. The self-locking core cutting mechanism for taking the large-diameter core comprises a coring drill bit, an outer cylinder, an inner cylinder and a core catcher, the outer cylinder is sleeved with the coring drill bit, the inner cylinder is arranged in the outer cylinder, the core catcher is arranged in the inner cylinder, the left end of the core catcher is embedded into the inner cylinder, and the right end of the core catcher protrudes out of the inner cylinder. According to the self-locking core cutting mechanism for taking the large-diameter core, the core catcher is matched with the inner wall of the coring drill bit to carry out coring work, so that the inner cylinder can be thinner, the radial coring space is saved, and the core with a larger diameter can be obtained; the distance between the core catcher and the inner cylinder is shortened, so that no gap exists when the core enters the cylinder, and the core can enter the inner cylinder to complete coring work; the drilling fluid is subjected to annular flow-back through the through holes formed in the inner wall of the coring drill bit, and the purposes of circulating the drilling fluid, cooling the drill bit and improving the coring work efficiency are achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of downhole tools, in particular to a self-locking core cutting mechanism for taking large-diameter cores. Background Art

[0002] During the exploration and development of underground resources such as oil and natural gas, coring is used to understand the lithology, oil, gas, and water content of the formation, providing accurate geological data for subsequent drilling and production operations. The coring tool is connected to the drill pipe and drill collar and lowered to the bottom of the well. The hollow drill bit cuts the formation into a columnar shape, which then enters the inner barrel. A specific action then separates the core and brings it to the surface. Self-locking coring for lifting the drill bit is the most important and commonly used method for coring in drilling. Existing self-locking coring methods primarily consist of a clamp seat, a clamp seat connector, and a core claw. The clamp seat is located within the drill bit cavity, and a certain clearance must be maintained between its lower end and the drill bit shoulder to ensure unimpeded mud flow. During the coring process, the drilled core overcomes the elastic friction of the core claw, pushing it open and entering the inner barrel. The lower end of the clamp seat connector acts as an axial limiter for the core claw. During the core cutting process, the core claws remain stationary due to static friction between them and the core, while the drill string is lifted, and the clamp seat moves upward with the drill string. At this point, the core claws descend along the conical surface of the clamp seat, generating a radial clamping force that locks the core. When the upward force reaches the core's ultimate breaking force, the core is severed. Existing technologies suffer from the radial space occupied by the clamp seat within the drill bit cavity, limiting the core diameter. This limits the device's applicability and makes it unsuitable for large-diameter coring operations. Summary of the Invention

[0003] (1) Technical issues to be resolved

[0004] The utility model provides a self-locking core cutting mechanism for taking large-diameter cores, so as to overcome the problem in the prior art of the risk of backlash when used in inclined wells and the limitation of the core diameter due to the small inner cavity of the drill bit during the coring operation.

[0005] (2) Technical solution

[0006] To achieve the above-mentioned purpose, the utility model provides a self-locking core cutting mechanism for taking large-diameter cores, comprising: a coring drill bit, an outer cylinder, an inner cylinder and a core claw;

[0007] The core drill bit is arranged at the right end of the outer cylinder, the core drill bit is threadedly connected to the outer cylinder, and an inner cylinder is arranged in the outer cylinder;

[0008] The inner cylinder is a hollow cylindrical structure, and a shoulder is provided on the outer wall of the right end of the inner cylinder;

[0009] The core claw is a hollow conical structure with a notch on one side and the cone apex of the core claw is located at the right end;

[0010] The righting structure of the left end of the core claw is embedded in the inner wall of the inner cylinder, and the outer conical surface of the right end of the core claw is in close contact with the inner wall of the core drill bit;

[0011] The inner wall of the core drill bit is evenly provided with a plurality of through holes. The core drill bit is a hollow cylindrical structure, and the inner wall of the core drill bit is provided with a tapered surface.

[0012] Preferably, it also includes a drill crown, which is arranged at the right end of the core drill bit, and a plurality of through holes are arranged on the top of the drill crown.

[0013] Preferably, a straightening skirt is provided at the right end of the core claw, and the taper of the outer wall of the core claw matches the taper of the conical surface of the inner wall of the core drill bit.

[0014] Preferably, the outer wall of the core claw is provided with a plurality of rectangular grooves.

[0015] Preferably, a shoulder is provided on the inner wall of the right end of the inner cylinder, and the core claw is provided on the right side of the shoulder.

[0016] Preferably, the inner wall of the centralizing skirt provided at the right end of the core claw is evenly provided with a plurality of rectangular convex grooves, and the surfaces of the rectangular convex grooves are welded with tungsten carbide powder.

[0017] Preferably, a plurality of rectangular grooves are evenly distributed on the inner wall of the outer cylinder, and the plurality of rectangular grooves, a plurality of through holes provided on the inner wall of the core drill bit and a plurality of through holes provided on the top of the drill bit crown constitute a drainage channel.

[0018] (3) Beneficial effects

[0019] The utility model provides a self-locking core cutting mechanism for taking large-diameter cores, which can realize the core cutting work by cooperating with the core claw and the inner wall of the core drill bit, and the core cutting force is borne by the core drill bit, which solves the problem of the inner barrel being broken due to excessive core cutting force, so that the inner barrel can be thinner, saving radial space for coring, and cores with larger diameter can be obtained; by shortening the distance between the core claw and the inner barrel, there is no gap when the core is taken into the barrel, which is conducive to the core entering the inner barrel to complete the coring work; the drilling fluid is annularly returned through the through hole provided on the inner wall of the core drill bit, thereby achieving the purpose of realizing drilling fluid circulation, cooling the drill bit, and improving the efficiency of coring work. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of the structure of a self-locking core cutting mechanism for taking large-diameter cores is shown in the utility model;

[0021] Figure 2 A schematic diagram of the front view of a self-locking core cutting mechanism for taking large-diameter cores according to the present invention is shown;

[0022] Figure 3The utility model shows a structural schematic diagram of a coring drill bit with a self-locking core cutting mechanism for taking large-diameter cores.

[0023] Among them: 1: core drill bit; 2: outer tube; 3: inner tube; 4: core claw; 5: drill bit crown. DETAILED DESCRIPTION

[0024] The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0025] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by “up”, “down”, “left”, “right”, “inside”, “outside”, “top”, “bottom”, etc. are all based on the directions or positional relationships shown in the accompanying drawings. The purpose is only to facilitate the description of the present invention and simplify the description. It does not indicate or imply that the referred parts must have a specific direction, be constructed and operated in a specific direction. Therefore, it cannot be understood as a limitation on the present invention.

[0026] like Figure 1-3 As shown, the utility model provides a self-locking core cutting mechanism for taking large-diameter cores, comprising: a coring drill bit 1, an outer cylinder 2, an inner cylinder 3 and a core claw 4;

[0027] The core drill bit 1 is arranged at the right end of the outer cylinder 2. The core drill bit 1 is threadedly connected to the outer cylinder 2 to ensure a firm connection with the outer cylinder 2. The outer cylinder 2 is provided with an inner cylinder 3, and the inner cylinder 3 is provided with a core claw 4. The left end of the core claw 4 has a straightening structure embedded in the inner wall of the inner cylinder 3, and the right end of the core claw 4 is in close contact with the inner wall of the core drill bit 1. The inner wall of the core drill bit 1 is evenly provided with a plurality of through holes. These through holes are used to discharge rock chips during drilling to ensure the cleanliness of the inside of the drill bit. The inner wall of the core drill bit 1 is provided with an annular groove;

[0028] The coring drill bit 1 is made of high-quality steel and has high strength and wear resistance. A drill crown 5 is provided at the right end of the coring drill bit 1. Several through holes are provided at the top of the drill crown 5. These through holes are used to discharge rock cuttings and cool the drill crown 5 during drilling. The several through holes provided at the top of the drill crown 5 ensure the cleanliness and cooling of the drill crown 5. The drill crown 5 can efficiently crush rocks, improve drilling speed and coring efficiency. The coring drill bit 1 is provided at the right end of the outer cylinder 2. The coring drill bit 1 is threadedly connected to the outer cylinder 2 for easy installation and disassembly. The left end of the coring drill bit 1 is a hollow cylindrical structure, and the inner wall of the coring drill bit 1 is provided with a tapered surface.

[0029] The inner cylinder 3 is a hollow cylindrical structure. The inner wall of the right end of the inner cylinder 3 is provided with an inwardly extending shoulder. The core claw 4 is provided on the right side of the shoulder. The shoulder plays the role of clamping the core claw 4 and limiting the axial movement of the core claw 4. The core claw 4 can slide along the inner cylinder 3 until it hits the shoulder. The shoulder ensures that the core claw 4 is accurately positioned in the axial direction.

[0030] The core claw 4 is a hollow conical structure, and a plurality of rectangular grooves are provided on the outer wall of the core claw 4, which improves the guiding and supporting capabilities of the core claw 4. A straightening skirt is provided on the right end of the core claw 4, and a notch is provided on one side of the core claw 4. The taper of the outer wall of the core claw 4 matches the taper of the tapered surface of the inner wall of the core drill bit 1, so that the core claw 4 can be tightened under the cooperation of the tapered inner wall of the core drill bit 1. As the core claw 4 slides to the left, it will gradually tighten to complete the coring work.

[0031] The inner wall of the straightening skirt provided at the right end of the core claw 4 is evenly provided with a number of rectangular grooves. The rectangular grooves are rectangular protrusions processed on the surface of the core claw 4. The surfaces of the rectangular grooves are welded with tungsten carbide powder. The rectangular grooves are used to increase the friction between the core claw 4 and the rock, thereby improving its guiding and supporting capabilities. The surface of the rectangular grooves is welded with tungsten carbide powder. Tungsten carbide is a material with high hardness and good wear resistance. Welding tungsten carbide powder on the surface of the rectangular grooves can significantly improve the service life of the straightening skirt and the friction between the core claw 4 and the core.

[0032] The inner wall of the outer cylinder 2 is evenly distributed with a number of rectangular grooves. These rectangular grooves and the through holes provided at the top of the drill crown 5 together constitute a drainage channel. The drainage channel is used to ensure the smooth discharge of fluid during the drilling process, thereby improving the drilling efficiency and the quality of the rock sample. During the drilling process, it is very important to discharge the rock cuttings and coolant in a timely manner. This not only keeps the drill bit clean, but also effectively cools the drill bit and prolongs its service life.

[0033] The following is a detailed introduction to the actual working scenario of the self-locking core cutting mechanism for taking large diameter cores.

[0034] In actual work, before coring begins, the core claw 4 is located on the conical surface of the inner wall of the coring drill bit 1, waiting for the start of the coring operation. When coring starts, the coring drill bit 1 starts to rotate and drill downward, and the core claw 4 also moves downward under the drive of the drill bit. As the drilling goes deeper, the core is gradually formed and moves upward into the inner cylinder 3 under the action of the rotation and downward pressure of the drill bit. The core moves upward in a columnar shape, and it smoothly enters the inner cylinder 3 after the core claw 4 is stretched. As the core continues to rise, the core claw 4 is also driven upward. When the outer surface conical shoulder of the core claw 4 contacts the shoulder at the lower end of the inner cylinder 3, the upper end of the core claw 4 The lifting action will stop. At this time, the core needs to overcome the elastic friction of the core claws 4 to continue to enter the inner tube 3. In this process, the core claws 4 play a good guiding and fixing role, ensuring that the core can smoothly enter the inner tube 3. When the coring operation is completed, the drill tool needs to be lifted. At this time, the coring drill bit 1 rises accordingly, and the core claws 4 tightly hold the core surface, relying on friction to keep the core stationary. Next, the core claws 4 start to descend along the conical surface of the inner wall of the coring drill bit 1. In this process, the force of the drill tool lifting will gradually increase. When this force exceeds the tensile limit of the core, the core will be broken, thereby completing the core cutting operation.

[0035] It can be understood that the above-mentioned embodiments mentioned in the present invention can be combined with each other to form combined embodiments without violating the principle logic. Due to space limitations, the present invention will not elaborate on them.

[0036] Those skilled in the art will understand that in the above-mentioned method of the specific implementation method, the writing order of each step does not mean a strict execution order and does not constitute any limitation on the implementation process. The specific execution order of each step should be determined by its function and possible internal logic.

[0037] The utility model provides a self-locking core cutting mechanism for taking large-diameter cores. The core claws 4 cooperate with the inner wall of the coring drill bit 1 to perform the coring work. The core cutting force is borne by the coring drill bit 1, which solves the problem of the inner cylinder 3 being broken due to excessive core cutting force. The inner cylinder 3 can be thinner, saving radial space for coring, and a core with a larger diameter can be obtained. By shortening the distance between the core claws 4 and the inner cylinder 3, there is no gap when the core is fed into the cylinder, which is beneficial for the core to enter the inner cylinder 3 to complete the coring work. The drilling fluid is returned to the annulus through the through hole provided on the inner wall of the coring drill bit 1, thereby achieving the purpose of circulating the drilling fluid, cooling the drill bit, and improving the efficiency of the coring work.

[0038] While various embodiments of the present invention have been described above, the above descriptions are illustrative and non-exhaustive, and are not intended to be limiting of the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is selected to best explain the principles of the embodiments, their practical applications, or technological improvements in the marketplace, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A self-locking core cutting mechanism for taking large diameter cores, characterized in that: include: A core drill bit (1), an outer cylinder (2), an inner cylinder (3), and a core claw (4); The core drill bit (1) is arranged at the right end of the outer cylinder (2), the core drill bit (1) is threadedly connected to the outer cylinder (2), and an inner cylinder (3) is arranged in the outer cylinder (2); The inner cylinder (3) is a hollow cylindrical structure, and a shoulder is provided on the outer wall of the right end of the inner cylinder (3); The core claw (4) is a hollow conical structure, a notch is provided on one side of the core claw (4), and the conical apex of the core claw (4) is located at the right end; The left end of the core claw (4) is partially embedded in the inner wall of the inner cylinder (3), and the outer conical surface of the right end of the core claw (4) is in close contact with the inner wall of the core drill bit (1); The inner wall of the core drill bit (1) is evenly provided with a plurality of through holes. The core drill bit (1) is a hollow cylindrical structure, and the inner wall of the core drill bit (1) is provided with a tapered surface.

2. The self-locking core cutting mechanism for taking large diameter cores according to claim 1, characterized in that: It also includes a drill crown (5), which is arranged at the right end of the core drill bit (1), and a plurality of through holes are provided at the top of the drill crown (5).

3. The self-locking core cutting mechanism for taking large diameter cores according to claim 1, characterized in that: The right end of the core claw (4) is provided with a straightening skirt, and the taper of the outer wall of the core claw (4) matches the taper of the inner wall conical surface of the core drill bit (1).

4. The self-locking core cutting mechanism for taking large diameter cores according to claim 1, characterized in that: The outer wall of the core claw (4) is provided with a plurality of rectangular grooves.

5. The self-locking core cutting mechanism for taking large diameter cores according to claim 1, characterized in that: A shoulder is provided on the inner wall of the right end of the inner cylinder (3), and a core claw (4) is provided on the right side of the shoulder.

6. The self-locking core cutting mechanism for taking large diameter cores according to claim 3, characterized in that: The inner wall of the right-end of the core claw (4) is provided with a plurality of rectangular convex grooves, and the surface of the rectangular convex grooves is welded with tungsten carbide powder.

7. The self-locking core cutting mechanism for taking large diameter cores according to claim 2, characterized in that: The inner wall of the outer cylinder (2) is evenly distributed with a plurality of rectangular grooves, and the plurality of rectangular grooves, the plurality of through holes provided on the inner wall of the core drill bit (1), and the plurality of through holes provided on the top of the drill bit crown (5) form a drainage channel.

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