A water-resistant micro-reverse circulation guided coring device

Abstract

This invention relates to a water-reverse circulation guided coring device. The invention includes a drill bit and a retaining ring seat, with the retaining ring seat nested within the drill bit. A through-flow water groove is provided on the outer wall of the retaining ring seat. One end of the drill bit is provided with a drill bit body and a working layer of the drill bit body. The drill bit body and the working layer of the drill bit body are provided with direct water jets and side water jets communicating with the water grooves. Direct water jet grooves and side water jet grooves are also provided within the drill bit body and the working layer of the drill bit body. This invention integrates other cooperating structures of the wireline coring tool, enabling them to be effectively combined. While avoiding direct erosion of the rock core by drilling fluid, it can guide the fractured formation smoothly into the inner tube and shorten the core retrieval distance during coring, thereby improving the core recovery rate.

Description

Technical Field

[0001] This invention relates to coring tools for geological drilling, mainly targeting loose and easily eroded strata in structurally fractured zones. It belongs to the field of geological engineering technology and is a water-tight micro-reverse circulation guided coring device. Background Technology

[0002] In wireline core drilling, loose and fractured strata are easily eroded and abraded by drilling fluid during drilling, leading to a decrease in core recovery rate and affecting geological prospecting results. Complex strata with insufficient recovery rates and the phenomena observed during drilling share several common characteristics:

[0003] First, most of these formations are clastic, powdery, muddy, or structurally fractured zones, characterized by loose structure and weak cementation. Second, the core sample is easily eroded by drilling fluid at the bottom of the drill bit during drilling. Third, the fractured core sample easily becomes clogged at the bottom of the retaining ring and the inner step of the drill bit, significantly extending the time required for mechanical breaking of the borehole wall and core, thus exacerbating core fragmentation and prolonging the repeated wear of the core by the drill bit, making it more susceptible to erosion. Fourth, these formations require drilling fluids with relatively high viscosity and high solids content for wall protection, which can easily lead to increased pump pressure, induced leakage, false circulation, and reduced drilling speed during drilling. Therefore, insufficient core recovery rate usually causes a vicious cycle of drilling quality and borehole stability problems.

[0004] To address this issue, industry professionals have developed numerous technical methods in an attempt to solve it, including the "308 drilling tool," bottom-jet drilling bits, and jet reverse circulation drilling tools. However, none of these methods have proven effective in practice, especially for wireline core drilling, which has resulted in their widespread adoption in drilling operations. Summary of the Invention

[0005] To address the aforementioned technical problems in the background art, this invention provides a water-tight micro-reverse circulation guided coring device, which integrates other cooperating structures of the wireline coring drill bit for effective combination. This avoids direct erosion of the rock core by drilling fluid, while guiding the fractured strata smoothly into the inner tube and shortening the core-retrieval distance during coring, thereby improving the core recovery rate.

[0006] The technical solution of this invention is as follows: This invention is a water-resistant micro-reverse circulation guided coring device, which is characterized in that: the device includes a drill bit and a snap ring seat, the snap ring seat is nested in the drill bit, a through water groove is provided on the outer wall of the snap ring seat, one end of the drill bit is provided with a drill bit body and a drill bit body working layer, the drill bit body and the drill bit body working layer are provided with a direct water injection port and a side water injection port communicating with the water groove, and the drill bit body and the drill bit body working layer are also provided with a direct water injection groove and a side water injection groove, so as to achieve the ability to carry clean rock cuttings at the bottom of the drill bit and cool the drill bit during drilling, while avoiding direct erosion of loose formations, and at the same time, enabling part of the drilling fluid flowing out of the direct water injection port to flow in reverse circulation from the outside to the inside through the direct water injection groove and the side water injection groove.

[0007] Preferably, there are multiple water tanks, evenly distributed on the outer wall of the snap ring seat.

[0008] Preferably, there are 6 water tanks, which provide a water passage between the snap ring seat and the inner wall of the drill bit steel body.

[0009] Preferably, there are multiple direct water jets and side water jets, evenly distributed on the drill bit matrix and the working layer of the drill bit matrix.

[0010] Preferably, there are 6 side spray nozzles and 4 direct spray nozzles.

[0011] Preferably, the end of the drill bit body that connects to the circlip seat is provided with a water-proof and core-guided step, and the inner side of the end of the circlip seat that connects to the drill bit body is provided with a wedge angle that extends into the water-proof and core-guided step.

[0012] Preferably, the cross-section of the water-blocking and core guide step is triangular with a rounded top, which can block the drilling fluid flowing in the annular space between the inner wall of the drill bit and the outer wall of the snap ring seat.

[0013] Preferably, the wedge angle is a cutting edge with an outer chamfer of ∠30° and an inner chamfer of 15°, and the bottom cross-section is rounded. The wedge angle can extend into the water inlet of the drill bit's water-stop and the core guide step, satisfying the condition of wedge insertion into the bottom of the water-stop and core guide step without obstructing water flow.

[0014] Preferably, the inner wall of the snap ring seat has a tapered structure with a minimum inner diameter of φ24.0mm at the bottom end, so as to achieve the purpose of snap ring retraction within a short distance.

[0015] This invention provides a water-tight micro-reverse circulation directional drill bit and circlip seat assembly structure for improving core recovery rate in fractured and loose formations. It is primarily applicable to the water-passing structure described in wireline coring drilling, a technique commonly used in geological core drilling. The structure includes a drill bit water-passing structure combining a direct water inlet and a side water inlet, and a direct water inlet channel and a side water inlet channel. A water-tight and core-guided step is formed, where the inner wall of the drill bit's triangular cross-section is higher than the water inlet. A water-tight assembly structure is provided, where the bottom edge of the circlip seat is wedged into the water-tight and core-guided step. A micro-circulation structure is also provided, where the drilling fluid, after passing through the circlip seat's backflow groove and the edge, creates a negative pressure zone at the annular gap between the water-tight and core-guided step and the edge, drawing some of the drilling fluid flowing through the direct water inlet and across the bottom lip of the drill bit into the inner tube.

[0016] This invention addresses the working conditions of wireline coring drilling with medium-to-high viscosity drilling fluids containing 5%–7% solids. It increases the drill bit's outer diameter, combining side-jet and direct-jet nozzles, side-jet and direct-jet channels, and water-blocking and core-guided steps with the snap ring seat wedge and snap ring seat water channel to create a micro-reverse circulation water-passing structure at the drill bit body. This prevents drilling fluid from directly eroding the core, avoids blockage between the snap ring seat and the drill bit's internal steps, and guides the core smoothly into the core tube, thereby improving the core recovery rate.

[0017] This invention features a coordinated design of the core-taking tool structure at the bottom of the drill bit. Through this structural design, the high-speed flow of drilling fluid is fully utilized, adding an auxiliary core-taking function to traditional wireline core drilling. By leveraging the negative pressure zone and the water-blocking and core-guided flow effects generated by the high-speed flow of drilling fluid through the drill bit's internal steps, side nozzles, true nozzles, and the gap between the snap ring and the drill bit's outer casing, a portion of the drilling fluid flowing out through the direct nozzle re-enters the core through the direct and side nozzles on the drill bit's bottom lip. This creates a localized reverse circulation within the drill bit, allowing the drilling fluid to play a role in assisting in core-propulsion.

[0018] This invention also increases the outer diameter of the drill bit, providing a larger annular space for drilling fluids with high viscosity and high solids content. The snap ring seat is thickened, and a water groove is designed within the snap ring seat to concentrate the water flow cross-section and velocity as much as possible. A wedge angle at the bottom of the snap ring seat ensures proper engagement with the water-blocking and core guide steps, as well as its flow-guiding effect, optimizing the snap ring's retraction and extension space and improving the efficiency of clamping the rock core. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the drill bit structure of the present invention;

[0020] Figure 2 yes Figure 1 Side view;

[0021] Figure 3 yes Figure 2 A sectional view;

[0022] Figure 4 This is a schematic diagram of the structure of the snap ring holder of the present invention;

[0023] Figure 5 yes Figure 4 Side view;

[0024] Figure 6 yes Figure 5 A sectional view.

[0025] The symbols in the attached image are explained as follows:

[0026] 1. Direct water jet trough; 2. Side water jet trough; 3. Water-blocking and core guide step; 4. Side water jet nozzle; 5. Drill bit matrix working layer; 6. Drill bit matrix; 7. Direct water jet nozzle; 8. Core; 9. Water jet trough; 10. Wedge angle. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to specific embodiments:

[0028] See Figure 1 —6. The structure of a specific embodiment of the present invention includes a drill bit and a snap ring seat. The snap ring seat is inserted into the drill bit. The outer wall of the snap ring seat is slightly concave inward to form a through water groove 9. One end of the drill bit is provided with a drill bit body 6 and a drill bit body working layer 5. The drill bit body 6 and the drill bit body working layer 5 are provided with a direct water jet 7 and a side water jet 4 that communicate with the water groove 9. The drill bit body 6 and the drill bit body working layer 5 are also provided with a direct water jet groove 1 and a side water jet groove 2.

[0029] The drill bit body 6 has a water-proof and core guide step 3 at one end connected to the circlip seat. A wedge angle 10 is provided on the inner side of the end where the circlip seat connects to the drill bit body 6, extending into the water-proof and core guide step 3. After the drilling fluid flows through the water tank 9, it can only flow out from the side nozzle 4 and the direct nozzle 7, protecting the core 8 from direct erosion by the drilling fluid. The water-proof and core guide step 3 has a triangular cross-section with a rounded apex. The wedge angle 10 is a cutting edge with an outer chamfer of ∠30° and an inner chamfer of 15°, and a rounded bottom cross-section.

[0030] In this embodiment, the snap ring seat has a conical structure inside, with a minimum inner diameter of φ24.0mm at the bottom end, to achieve the purpose of snap ring retraction within a short distance. Six water grooves 9 are arranged on the outside of the snap ring seat, increasing the wall thickness to 5.5mm. The drill bit water inlet consists of six side water inlets 4 with a diameter of φ4.0mm, four direct water inlets 7 with a diameter of φ2.0mm, and direct water inlets 1 and side water inlets 2 with corresponding diameters.

[0031] When the invention is in operation, the drilling fluid can only flow out from the side spray nozzle 4 and the direct spray nozzle 7 after passing through the water tank 9. By utilizing the negative pressure zone generated by the high-speed flow of the drilling fluid through the water-isolation and core guide steps 3, the side spray nozzle 4, the direct spray nozzle 7, and the gap between the snap ring seat and the inner wall of the drill bit, and the guiding effect of the water-isolation and core guide steps 3, part of the drilling fluid that has flowed out through the direct spray nozzle 7 is recirculated into the core 8 through the direct spray groove 1 and the side spray groove 2 on the bottom lip of the drill bit, thereby forming a local reverse circulation inside the drill bit, so that the drilling fluid plays a certain role in assisting to push the core.

[0032] The above are merely specific embodiments disclosed in this invention, but the scope of protection disclosed in this invention is not limited thereto. The scope of protection disclosed in this invention should be determined by the scope of the claims.

Claims

1. A water-resistant micro-reverse circulation guided coring device, characterized in that: The device includes a drill bit and a circlip seat, with the circlip seat nested within the drill bit. A through water channel is provided on the outer wall of the circlip seat. One end of the drill bit is provided with a drill bit body and a working layer of the drill bit body. The drill bit body and the working layer of the drill bit body are provided with a direct water jet nozzle and a side water jet nozzle that communicate with the water channel. The drill bit body and the working layer of the drill bit body are also provided with a direct water jet channel and a side water jet channel. The end of the drill bit body connected to the circlip seat is provided with a water-blocking and core guiding step. The inner side of the end of the circlip seat connected to the drill bit body is provided with a wedge angle that extends into the water-blocking and core guiding step.

2. The water-resistant micro-reverse circulation guided coring device according to claim 1, characterized in that: There are multiple water tanks, which are evenly distributed on the outer wall of the snap ring seat.

3. The water-jacketed micro-reverse circulation guided coring device according to claim 2, characterized in that: There are 6 water tanks.

4. The water-jacketed micro-reverse circulation guided coring device according to claim 1, characterized in that: There are multiple direct water jets and side water jets, which are evenly distributed on the drill bit body and the working layer of the drill bit body.

5. The water-repellent micro-reverse circulation guided coring device according to claim 4, characterized in that: There are 6 side spray nozzles and 4 direct spray nozzles.

6. The water-repellent micro-reverse circulation guided coring device according to any one of claims 1 to 5, characterized in that: The cross-section of the water-blocking and core guide steps is triangular with a rounded top.

7. The water-jacketed micro-reverse circulation guided coring device according to claim 6, characterized in that: The wedge angle is a blade-shaped shape with an outer chamfer of ∠30° and an inner chamfer of 15°, and the bottom cross-section is arc-shaped.

8. The water-repellent micro-reverse circulation guided coring device according to claim 7, characterized in that: The inner wall of the snap ring seat has a tapered structure, with a minimum inner diameter of φ24.0mm at the bottom.

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