A wireline coring or core barrel tool
By designing a core retrieval tool with a drill bit lifting mechanism, the problems of easy core loss and poor drill bit passability were solved, achieving efficient core extraction and protection and improving the core retrieval rate.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NUCLEAR IND CORPS 216
- Filing Date
- 2023-09-25
- Publication Date
- 2026-05-26
AI Technical Summary
In existing technologies, core samples are prone to falling off during core drilling and the drill bit has poor throughput, resulting in low core recovery rates. Conventional drill bits are also prone to damaging and wearing out the core samples during core retrieval.
The core retrieval tool adopts a lifting-type design. Through the cooperation of the internal and external assemblies of the drill bit, the sliding block is extended or retracted by the snap ring assembly and elastic element to form a drill bit structure with a variable inner diameter. This enhances the core entry capability and protects incomplete and fragmented core pieces from falling off at the end of the core retrieval process.
It improved core recovery rate, reduced core wear and drill string jamming in complex well sections, enhanced drill string passability, and protected the integrity of the core.
Smart Images
Figure CN117231152B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of drilling engineering technology, specifically to a core retrieval or coring tool for lifting drill bits. Background Technology
[0002] Core drilling is a drilling method and process aimed at obtaining core samples of geological formations, and it is an important component of drilling engineering. In drilling fields such as solid mineral exploration, oil and gas exploration, geothermal development, and scientific drilling, core drilling is a crucial method for acquiring geological information. Obtaining core samples significantly improves the accuracy of stratigraphic evaluation and related geological information collection, providing original stratigraphic data for direct investigation of mineral lithofacies, resource distribution, and reservoir evaluation, which is of great significance for resource exploration and development and geological scientific research.
[0003] Core drilling is more difficult and complex than conventional full drilling. It is significantly affected by tools, and the integrity of the formation and the complexity of the wellbore conditions all influence the success of core sampling. During drilling, due to formation or drill string issues, core samples often fail to be retrieved from the well after core drilling is completed; in other words, the core is detached from the drill string. To avoid significant loss of formation data, core retrieval is typically performed. However, once the core is detached from the drill string, the core column, lacking radial space constraint, often breaks into multiple sections or accumulates at the bottom of the hole. Using conventional drill string for core retrieval in this situation would damage and wear down a large portion of the core, leading to substantial data loss.
[0004] After the core is extracted from the core retrieval tool, it will accumulate at the bottom of the hole in the form of multiple core columns and fragments. When retrieving the core with conventional tools, it can only be successfully entered when the core column is coaxial with the inner annulus of the drill bit. However, this situation is extremely rare. Only when the drill bit repeatedly grinds the core columns or fragments in different states to the inner diameter size of the drill bit can the core enter the core retrieval tool. In this process, a large amount of core will inevitably be worn away. Summary of the Invention
[0005] The purpose of this invention is to provide a core retrieval or core sampling tool for drilling, so as to solve the problems existing in the prior art, improve the drill bit passability, and at the same time avoid the loss of incomplete drill bit and fragmented rock core, thereby improving the core retrieval rate or rock core recovery rate.
[0006] To achieve the above objectives, the present invention provides the following solution:
[0007] This invention provides a core retrieval or coring tool, comprising an outer drill string assembly, an inner drill string assembly, and a centralizer. The inner drill string assembly is suspended within the central channel of the outer drill string assembly via the centralizer. The lower end of the inner drill string assembly is a retaining spring assembly, and the lower end of the outer drill string assembly comprises a drill bit and multiple sliding blocks. One end of each sliding block extends into one end of the drill bit and is suspended by an elastic element. One end of the retaining spring assembly passes through the drill bit and extends between the sliding blocks, with the outer wall of the retaining spring assembly engaging with the inner wall of each sliding block via an inclined surface. Drilling fluid is introduced into the inner drill string assembly, causing it to move downward relative to the outer drill string assembly. The downward movement of the retaining spring assembly pushes the sliding blocks outward away from the drill bit's centerline. When the inner drill string assembly resets, the elastic element causes the sliding blocks to reset towards the drill bit's centerline.
[0008] Preferably, the outer assembly of the drill bit includes the sliding block, and an upper connector, a bearing cavity, a suspension seat, an outer tube, an outer tube stabilizer, and the drill bit connected in sequence by threads. One end of the upper connector is used for the introduction of drilling fluid, and the upper connector is connected to one end of the inner assembly of the drill bit. The other end of the upper connector extends into the bearing cavity and there is a first annular gap between it and the end of the inner assembly of the drill bit. There is a second annular gap between the outer assembly of the drill bit and the inner assembly of the drill bit, which is connected to the first annular gap. Multiple bearings are provided between the inner wall of the bearing cavity and the outer wall of the inner assembly of the drill bit.
[0009] Preferably, one side of the sliding tire block is provided with an inner conical surface, a contact protrusion, and a limiting groove. The contact protrusion is located between the inner conical surface and the limiting groove. The inner conical surface is used to engage with the outer conical surface of the snap ring assembly. When the snap ring assembly moves down to its position, it can abut against the contact protrusion. A limiting ring is provided in the limiting groove, and the limiting ring can be embedded in the limiting groove of each sliding tire block and radially limit the sliding tire block.
[0010] Preferably, the limiting ring has a notch.
[0011] Preferably, the drill bit has a plurality of sliding grooves circumferentially provided at one end away from the outer tube stabilizer. The side of the sliding block opposite to the inner conical surface is embedded in the sliding groove and can slide radially along the drill bit under the drive of the snap ring assembly. The elastic element is a first spring, and the two ends of the first spring abut against the sliding groove and the side of the sliding block opposite to the inner conical surface, respectively.
[0012] Preferably, the drill bit assembly includes a mandrel, and a suspension shaft, an inner tube connector, a core tube, a core tube connector, and a retaining ring assembly connected in sequence by threads. Both ends of the mandrel are mounted in the bearing cavity via bearings. One end of the suspension shaft is suspended from the inner stepped surface of one end of the mandrel by a second spring. The other end of the suspension shaft extends into the core tube, and the outer wall of the suspension shaft is threadedly connected to the inner wall of the core tube. Both the mandrel and the suspension shaft are hollow inside, and one end of the mandrel communicates with the upper connector and the mandrel also communicates with the suspension shaft. The end of the suspension shaft extending out of the mandrel is provided with a flow-blocking hole, which can be closed by ball dropping. The outer wall of the suspension shaft is also provided with a liquid outlet hole, which is located outside the mandrel, and the liquid outlet hole can communicate with the suspension shaft and the second annular gap.
[0013] Preferably, the drill bit assembly further includes a suspension sleeve, which is supported by a bearing and sits on the inner cavity step of the suspension seat, and one end of the mandrel abuts against the inner cavity step of the suspension sleeve.
[0014] Preferably, the core retainer assembly includes an upper core retainer seat, a lower core retainer seat, and two core retainers. The two core retainers are located in the upper core retainer seat and the lower core retainer seat, respectively. One end of the upper core retainer seat is short-connected to the core tube by a threaded connection, and the other end of the upper core retainer seat is threaded to one end of the lower core retainer seat. The outer wall of the lower core retainer seat is used to contact the inner conical surface.
[0015] Preferably, a bearing is provided between the outer wall of the lower core retainer and the inner cavity stepped surface of the drill bit.
[0016] The present invention achieves the following technical effects compared to the prior art:
[0017] The present invention provides a core retrieval or coring tool with an internal drill string assembly suspended in the central channel of the external drill string assembly via a centralizer. During actual operation, the bearings between the internal and external drill string assemblies allow the external assembly to rotate while the internal assembly remains stationary, forming a single-acting, double-tube coring tool. The lower end of the internal drill string assembly is a retaining spring assembly, and the lower end of the external drill string assembly contains the drill bit and multiple sliding blocks. One end of each sliding block extends into one end of the drill bit and is suspended by an elastic element. One end of the retaining spring assembly passes through the drill bit and extends between the sliding blocks, with the outer wall of the retaining spring assembly engaging with the inner wall of the sliding blocks via an inclined surface. Drilling fluid is introduced into the internal drill string assembly, and under pressure, the drill string... Compared to the outer assembly of the drill string, the inner assembly moves downwards, and the snap ring assembly moves downwards, pushing the sliding block outwards away from the drill bit centerline. This causes the sliding block to extend outwards, increasing the drill bit's outer diameter to the wellbore size and its inner diameter to exceed the normal core diameter. The lip thickness decreases, creating a thin-walled drill bit structure compared to conventional core drilling bits. This is more conducive to core entry and solves the problem of damage to disordered cores at the bottom of the hole caused by small inner diameter drill bits and thick-walled drill bit structures during core retrieval. When drilling fluid is stopped, the inner assembly resets, and the elastic element drives the sliding block back towards the drill bit centerline, minimizing the outer diameter of the sliding block. This reduces the risk of the drill string getting stuck in complex well sections during core retrieval or core drilling, improving drill string throughput. Simultaneously, the semi-enclosed state created by the variable inner diameter of the drill bit protects against the loss of incomplete and fragmented cores at the drill bit location, improving the core retrieval rate or core recovery rate. Attached Figure Description
[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0019] Figure 1 This is a cross-sectional view of the core retrieval or core extraction tool in the present invention in its initial state.
[0020] Figure 2 This is a cross-sectional view of the core retrieval or core extraction tool used in this invention during core retrieval / drilling.
[0021] Figure 3 This is a cross-sectional view of the suspension shaft in this invention;
[0022] Figure 4 This is a schematic diagram of the drill bit structure in this invention;
[0023] Figure 5 yes Figure 4 Cross-sectional view of the drill bit;
[0024] Figure 6 This is a schematic diagram of the structure of the lower core retainer in this invention;
[0025] Figure 7 yes Figure 6 AA section view;
[0026] Figure 8 This is a schematic diagram of the sliding block structure in this invention;
[0027] Figure 9 yes Figure 8 Cross-sectional view of the sliding block in the middle;
[0028] Figure 10 This is a schematic diagram of the limiting ring in this invention;
[0029] In the diagram: 1-Upper connector, 2-Bearing cavity, 3-First bearing, 4-Mandrel, 5-Second bearing, 6-Suspension shaft, 61-Liquid outlet, 62-Blocking hole, 7-Second spring, 8-Suspension sleeve, 9-Third bearing, 10-Suspension seat, 11-Inner tube connector, 12-Outer tube, 13-Core tube, 14-Outer tube stabilizer, 15-Core tube short connector, 16-Upper core snap ring seat, 17-Drill bit, 171-Sliding groove, 18-Core tube stabilizer ring, 19-Lower core snap ring seat, 191-Outer conical surface, 20-First spring, 21-Sliding block, 211-Inner conical surface, 212-Contact protrusion, 213-Limiting groove, 22-Core snap ring, 23-Limiting ring. Detailed Implementation
[0030] 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, and 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.
[0031] The purpose of this invention is to provide a core retrieval or coring tool for drilling, in order to solve the technical problems of easy core loss during well dredging and poor drill string passability.
[0032] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0033] like Figures 1-10As shown, this embodiment provides a core retrieval or coring tool, including an outer drill string assembly, an inner drill string assembly, and a centralizer. The centralizer is a core tube centralizer ring 18. The inner drill string assembly is suspended in the central channel of the outer drill string assembly via the centralizer. During actual operation, in conjunction with the bearing between the inner and outer drill string assemblies, the outer drill string assembly rotates while the inner drill string assembly remains stationary, forming a single-acting double-tube coring tool. The lower end of the inner drill string assembly is a retaining spring assembly, and the lower end of the outer drill string assembly is a drill bit 17 and multiple sliding blocks 21. One end of each sliding block 21 extends into one end of the drill bit 17 and is suspended by an elastic element. One end of the retaining spring assembly passes through the drill bit 17 and extends between the sliding blocks 21. The outer wall of the retaining spring assembly and the inner wall of the sliding blocks 21 are engaged by an inclined surface, moving towards the inner drill string assembly. Drilling fluid is introduced into the drill string. Under pressure, the internal assembly moves downward relative to the external assembly. The snap ring assembly moves downward and pushes the sliding block 21 outward away from the centerline of the drill bit 17, causing the sliding block 21 to extend outward. The outer diameter of the drill bit 17 increases to the wellbore size, and the inner diameter increases beyond the normal core diameter. The lip thickness decreases, forming a thin-walled drill bit structure compared to conventional core drilling bits. This is more conducive to core entry and solves the problem of the small inner diameter of the drill bit 17 and the damage to the disordered core at the bottom of the hole caused by the thick-walled drill bit structure during core retrieval. When the drilling fluid is stopped, the internal assembly of the drill string returns to its original position. The elastic element drives the sliding block 21 to return to its original position closer to the centerline of the drill bit 17, thereby minimizing the outer diameter of the sliding block 21. This reduces the obstruction of the drill string in complex well sections during core retrieval or core drilling and improves the drill string's throughput. Meanwhile, the semi-enclosed state formed by the variable inner diameter of drill bit 17 can protect the incomplete and fragmented rock cores at drill bit 17 from falling off, thereby improving the core retrieval rate or core recovery rate.
[0034] Specifically, the outer assembly of the drill string includes a sliding block 21, and an upper connector 1, a bearing cavity 2, a suspension seat 10, an outer tube 12, an outer tube stabilizer 14, and a drill bit 17 connected in sequence by threads. One end of the upper connector 1 is used for the introduction of drilling fluid, which can play a role in lubrication, cleaning, and providing driving force. Multiple bearings are provided between the inner wall of the bearing cavity 2 and the outer wall of the inner assembly of the drill string. The upper connector 1 is connected to one end of the inner assembly of the drill string, and the other end of the upper connector 1 extends into the bearing cavity 2 and there is a first annular gap between it and the end of the inner assembly of the drill string. That is, most of the drilling fluid enters the inner assembly of the drill string through the inner cavity of the upper connector 1, and a small part of the drilling fluid enters the first annular gap to lubricate the bearings in the bearing cavity 2. There is a second annular gap between the outer assembly of the drill string and the inner assembly of the drill string, which connects to the first annular gap, so that after the drilling fluid lubricates the bearings in the bearing cavity 2, it continues to lubricate the bearings behind it.
[0035] One side of the sliding block 21 is provided with an inner conical surface 211, a contact protrusion 212 and a limiting groove 213. The contact protrusion 212 is located between the inner conical surface 211 and the limiting groove 213. The inner conical surface 211 is used to cooperate with the outer conical surface 191 of the snap ring assembly. When the snap ring assembly moves down to the position, it can abut against the contact protrusion 212. The limiting groove 213 is provided with a limiting ring 23, and the limiting ring 23 can be embedded in the limiting groove 213 of each sliding block 21 and radially limit the sliding block 21. When the sliding block 21 is reset, the inner bottom surface of the limiting groove 213 contacts the limiting ring 23 and is limited. At this time, the inner diameter of the sliding block 21 is the minimum value.
[0036] The limiting ring 23 has a notch to facilitate assembly. Since the limiting ring 23 has a certain elasticity and its outer diameter is larger than the inner diameter of the drill bit 17, the outer diameter of the limiting ring 23 needs to be compressed to the inner diameter of the drill bit 17 during installation. After being inserted into the limiting groove 213 on the inner wall of the drill bit 17, the outer diameter increases in a free state to match the limiting groove 213.
[0037] The drill bit 17 has multiple sliding grooves 171 circumferentially arranged at one end away from the outer tube stabilizer 14. The side of the sliding block 21 opposite to the inner conical surface 211 is embedded in the sliding groove 171 and can slide radially along the drill bit 17 under the drive of the snap ring assembly to adjust the inner and outer diameters of the sliding block 21. In turn, the inner and outer diameter changes can be controlled according to the actual operation process to meet the usage requirements. The elastic element is a first spring 20. The two ends of the first spring 20 abut against the sliding groove 171 and the side of the sliding block 21 opposite to the inner conical surface 211, respectively. When the pressure difference decreases or disappears, the first spring 20 pushes the sliding block 21 to reset.
[0038] The drill string assembly includes a mandrel 4, and a suspension shaft 6, an inner tube connector 11, a core tube 13, a core tube short connector 15, and a retaining ring assembly, all connected in sequence by threads. Both ends of the mandrel 4 are mounted in bearing cavities 2 via bearings, specifically a first bearing 3 and a second bearing 5. One end of the suspension shaft 6 is suspended from the inner stepped surface of one end of the mandrel 4 by a second spring 7. The other end of the suspension shaft 6 extends into the core tube 13, and its outer wall is threaded to the inner wall of the core tube 13. Both the mandrel 4 and the suspension shaft 6 are hollow internally, and one end of the mandrel 4 is connected to the upper connector 1. Shaft 4 is also connected to suspension shaft 6. One end of suspension shaft 6 that extends out of mandrel 4 is provided with flow-blocking hole 62. When coring begins in fractured or mudstone formations, flow-blocking hole 62 can be sealed by dropping a ball. Suspension shaft 6 is also provided with fluid outlet hole 61 on its outer wall. Fluid outlet hole 61 is located outside mandrel 4 and can connect suspension shaft 6 and the second annulus. Under the action of flow-blocking hole 62, most of the drilling fluid flows to the second annulus through the fluid outlet hole and eventually flows to drill bit 17 and bottom of hole. A very small amount of drilling fluid flows from flow-blocking hole 62 into core tube 13 to clean and lubricate its inner wall before flowing to drill bit 17 and bottom of hole.
[0039] The drill string assembly also includes a suspension sleeve 8, which is supported by a bearing and sits on the inner cavity step of the suspension seat 10. One end of the spindle 4 abuts against the inner cavity step of the suspension sleeve 8. A bearing, namely the third bearing 9, is provided between the suspension sleeve 8 and the suspension seat 10.
[0040] The core retainer assembly includes an upper core retainer seat 16, a lower core retainer seat 19, and two core retainers 22. The two core retainers 22 are located in the upper core retainer seat 16 and the lower core retainer seat 19, respectively. One end of the upper core retainer seat 16 is threadedly connected to the core tube short circuit 15, and the other end of the upper core retainer seat 16 is threadedly connected to one end of the lower core retainer seat 19. The outer wall of the lower core retainer seat 19 is used to contact the inner conical surface 211 so as to realize the outward extension of the sliding block 21 through the inclined surface engagement.
[0041] A bearing is provided between the outer wall of the lower core retainer 19 and the inner cavity stepped surface of the drill bit 17.
[0042] The specific functionality of this embodiment is implemented as follows:
[0043] When drilling fluid is not circulated or is circulated at a low rate during drilling and hoisting, the drill string assembly and drill bit 17, etc. Figure 1 As shown, the suspension shaft 6, inner tube joint 11, core tube 13, core tube short connector 15, upper core retainer 16, and lower core retainer 19 are in the upper position under the elastic support of the second spring 7. The inner conical surface 211 of the sliding block 21 is the same as the inner diameter of the drill bit 17. At this time, the outer diameter of the drill bit 17 is at its minimum value, which reduces the jamming of the drill string in complex well sections and improves the passability of the drill string during core retrieval or core drilling.
[0044] During the drilling process or during the small-volume circulation before drilling, the drilling fluid flows in through the central channel of the upper connector 1. A small amount of drilling fluid lubricates the first bearing 3 and the second bearing 5 through the first annular gap formed by the mandrel 4 and the bearing cavity 2. It continues to flow into the second annular gap between the suspension sleeve 8 and the suspension seat 10 through the water hole at the lower end of the bearing cavity 2, lubricates the third bearing 9, and then flows into the second annular gap behind it and finally flows to the drill bit 17 and the bottom of the hole. Most of the drilling fluid flows into the central channel of the suspension shaft 6 through the central channel of the mandrel 4. Under the action of the flow-blocking hole 62, most of the drilling fluid flows from the outlet hole 61 to the second annular gap behind it and finally flows to the drill bit 17 and the bottom of the hole. A very small amount of drilling fluid flows into the core tube 13 from the flow-blocking hole 62 to clean and lubricate its inner wall before flowing to the drill bit 17 and the bottom of the hole. When coring begins in fractured formations or soft mudstone formations, the flow-blocking hole 62 can be closed by dropping a ball to prevent the drilling fluid from entering the interior of the core tube 13.
[0045] When core retrieval or core drilling is performed, the drilling fluid discharge rate is increased. At this time, the drilling fluid forms a pressure difference on the upper end face of the suspension shaft 6, pushing the second spring 7 downward. As a result, the suspension shaft 6, inner pipe joint 11, core tube 13, core tube short connector 15, upper core retainer 16, and lower core retainer 19 move downward as a whole. At this time, the lower outer conical surface 191 of the lower core retainer 19 moves downward and acts on the upper inner conical surface 211 of the sliding block 21, causing the sliding block 21 to compress the first spring 20 and slide radially outward along the sliding groove 171 at the lower end of the drill bit 17 until the suspension shaft 6 moves to the lower position. When this position is reached, the lower end face of the lower core retainer 19 maintains a certain distance from the inner step surface of the sliding block 21, and the outer circumferential surface of the lower core retainer 19 contacts the contact protrusion 212, forming radial support and limiting for the sliding block 21. This ensures that the outer circumferential diameter of all sliding blocks 21 mounted on the drill bit 17 remains unchanged, that is, the outer diameter of the drill bit 17 is fixed. Figure 2 As shown.
[0046] After core retrieval or core drilling is completed, the flow rate is reduced or circulation is stopped. At this time, the pressure difference of the drilling fluid on the upper end face of the suspension shaft 6 decreases or disappears. The entire assembly consisting of the suspension shaft 6, inner pipe joint 11, core pipe 13, core pipe short connector 15, upper core retaining spring seat 16, and lower core retaining spring seat 19 moves upward to the upper position under the elastic support of the second spring 7. Figure 1 As shown, after the lower core retainer 19 separates from the contact protrusion, the radial limiting of the sliding block 21 is released. Under the elastic support of the first spring 20, the sliding block 21 slides radially inward along the sliding groove 171 at the lower end of the drill bit 17 until the inner wall of the limiting groove 213 contacts the outer wall of the limiting ring 23, at which point it is radially limited. At this time, the inner diameter of the drill bit 17 and the inner wall of the sliding block 21 are the same, which is the minimum value. After the sliding block 21 contracts radially inward, the inner diameter of the drill bit 17 becomes smaller, forming a semi-closed state, as shown. Figure 1 As shown, this can protect fragmented rock cores from falling off, thereby increasing the core retrieval rate or core recovery rate.
[0047] In this embodiment, to reduce core wear during core insertion, the inner diameters of the core tube 13 and the drill bit 17 are increased, widening the threshold size for core columns or blocks to enter the drill bit 17, thus effectively reducing core wear. Simultaneously, a diamond variable-diameter drill bit with mud pressure differential control is used. During drilling, the sliding block 21 of the drill bit 17 retracts, reducing the outer diameter of the drill string, thereby ensuring the drill string's passability in complex well conditions. During core retrieval, mud circulation and discharge control cause the sliding block 21 of the drill bit 17 to extend outwards, increasing the outer diameter of the drill bit 17 to the wellbore size and the inner diameter to exceed the normal core diameter. The lip thickness is reduced, forming a thin-walled drill bit structure compared to conventional core retrieval drill bits, which is more conducive to core entry.
[0048] This specification uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be construed as a limitation of the present invention.
Claims
1. A core-retrieval or core-extraction tool for drilling, characterized in that: The system includes an outer drill string assembly, an inner drill string assembly, and a centralizer. The inner drill string assembly is suspended within the central channel of the outer drill string assembly via the centralizer. The lower end of the inner drill string assembly is a retaining spring assembly. The lower end of the outer drill string assembly consists of a drill bit and multiple sliding blocks. One end of each sliding block extends into one end of the drill bit and is suspended by an elastic element. One end of the retaining spring assembly passes through the drill bit and extends between the sliding blocks. The outer wall of the retaining spring assembly engages with the inner wall of each sliding block via a bevel. Drilling fluid is introduced into the inner drill string assembly, causing it to move downward relative to the outer drill string assembly. The downward movement of the retaining spring assembly pushes the sliding blocks outward away from the drill bit's centerline. When the inner drill string assembly resets, the elastic element causes the sliding blocks to reset towards the drill bit's centerline. The sliding tire block has an inner conical surface, a contact protrusion, and a limiting groove on one side. The contact protrusion is located between the inner conical surface and the limiting groove. The inner conical surface is used to engage with the outer conical surface of the snap ring assembly. When the snap ring assembly moves down to its position, it can abut against the contact protrusion. The limiting groove is provided with a limiting ring, and the limiting ring can be embedded in the limiting groove of each sliding tire block and radially limit the sliding tire block. The sliding block has a limiting protrusion at one end away from the inner conical surface, and the limiting protrusion is positioned toward the center line of the drill bit.
2. The core retrieval or core extraction tool according to claim 1, characterized in that: The outer assembly of the drill bit includes the sliding block, and an upper connector, a bearing cavity, a suspension seat, an outer tube, an outer tube stabilizer, and the drill bit, which are connected in sequence by threads. One end of the upper connector is used for the introduction of drilling fluid, and the upper connector is connected to one end of the inner assembly of the drill bit. The other end of the upper connector extends into the bearing cavity and there is a first annular gap between it and the end of the inner assembly of the drill bit. There is a second annular gap between the outer assembly of the drill bit and the inner assembly of the drill bit, which is connected to the first annular gap. Multiple bearings are provided between the inner wall of the bearing cavity and the outer wall of the inner assembly of the drill bit.
3. The core retrieval or core extraction tool according to claim 1, characterized in that: The limiting ring has a notch.
4. The core-retrieval or core-extraction tool according to claim 2, characterized in that: The drill bit has multiple sliding grooves circumferentially arranged at one end away from the outer tube stabilizer. The side of the sliding block opposite to the inner conical surface is embedded in the sliding groove and can slide radially along the drill bit under the drive of the snap ring assembly. The elastic element is a first spring, and the two ends of the first spring abut against the sliding groove and the side of the sliding block opposite to the inner conical surface, respectively.
5. The core retrieval or core extraction tool according to claim 2, characterized in that: The drill string assembly includes a mandrel, and a suspension shaft, an inner tube connector, a core tube, a core tube connector, and a retaining ring assembly connected in sequence by threads. Both ends of the mandrel are mounted in the bearing cavity via bearings. One end of the suspension shaft is suspended from the inner stepped surface of one end of the mandrel by a second spring. The other end of the suspension shaft extends into the core tube, and the outer wall of the suspension shaft is threadedly connected to the inner wall of the core tube. Both the mandrel and the suspension shaft are hollow inside, and one end of the mandrel is connected to the upper connector. The mandrel is also connected to the suspension shaft. The end of the suspension shaft extending out of the mandrel is provided with a flow-blocking hole, which can be closed by ball dropping. The outer wall of the suspension shaft is also provided with a liquid outlet hole, which is located outside the mandrel and can connect the suspension shaft and the second annular gap.
6. The core retrieval or core extraction tool according to claim 5, characterized in that: The drill bit assembly also includes a suspension sleeve, which is supported by a bearing and sits on the inner cavity step of the suspension seat, and one end of the mandrel abuts against the inner cavity step of the suspension sleeve.
7. The core retrieval or coring tool according to claim 5, characterized in that: The core retainer assembly includes an upper core retainer seat, a lower core retainer seat, and two core retainers. The two core retainers are located in the upper core retainer seat and the lower core retainer seat, respectively. One end of the upper core retainer seat is short-connected to the core tube by a threaded connection, and the other end of the upper core retainer seat is threaded to one end of the lower core retainer seat. The outer wall of the lower core retainer seat is used to contact the inner conical surface.
8. The core retrieval or coring tool according to claim 7, characterized in that: A bearing is provided between the outer wall of the lower core retainer and the inner stepped surface of the drill bit.