A kind of equalizing device for preventing hole collapse in the flow field inside extraction borehole

Abstract

The utility model discloses a kind of extraction borehole internal flow field anti-caving hole balanced adjusting device, by being equipped with different aperture mesh on the multiple section screen pipe, mesh diameter gradually increases from borehole orifice to hole bottom, so that extraction negative pressure is more evenly distributed in the length direction of extraction borehole, so that the gas of extraction borehole hole bottom easily flows into extraction system, so as to change extraction borehole internal flow field, effectively avoid the uneven problem of extraction long borehole extraction effect, eliminate extraction long borehole extraction blank zone, so as to improve the gas extraction of extraction long borehole hole bottom;Anti-caving hole gas permeation device is arranged outside screen pipe, can effectively inhibit coal and rock mass caving.In the support of hole wall simultaneously allow gas to pass freely.

Description

Technical Field

[0001] This utility model belongs to the field of coal mine gas disaster prevention and control technology, specifically relating to a flow field anti-collapse hole equalization adjustment device inside a drainage borehole. Background Technology

[0002] Methane gas is an associated gas in the coal formation process. In the mining of coal resources, methane gas control is a necessary means to ensure production safety. The main component of methane gas is methane, which is flammable and explosive. Directly releasing it into the atmosphere will cause the greenhouse effect. High-methane mines must carry out methane gas extraction. At the same time, methane gas is also a clean energy source with high calorific value. Extracting and utilizing it through drilling is one of the effective measures for methane gas control in my country's coal mines, which achieves both the purpose of methane gas control and the utilization of clean energy.

[0003] With the development of drilling technology, high-power drilling and extraction equipment have been applied. In recent years, directional drilling rigs have been widely used, increasing borehole length from 80-100m to 200-300m, thus enabling large-area pre-extraction of the coal seam and significantly improving gas extraction efficiency. Simultaneously, high-power extraction pumps have also been put into use. Horizontal long boreholes, cross-holes, and dense boreholes have been promoted and applied, significantly improving borehole length, borehole opening negative pressure, and borehole density. However, the gas extraction effect has not met expectations. With increased borehole length, gas extraction near the borehole opening is better, while extraction near the bottom is poorer, resulting in zoning of extraction effectiveness and forming a "blank zone" at the bottom of the borehole. Even after long borehole extraction, despite meeting the gas pre-extraction rate standards, instances of exceeding efficiency limits and even gas dynamic phenomena frequently occur.

[0004] In addition, the drainage boreholes are prone to collapse, and the coal dust from the collapse will block the screen holes of the screen pipe, which will also affect the efficiency of gas drainage operations, and the drainage consumes a lot of energy. Utility Model Content

[0005] The purpose of this invention is to provide a flow field anti-collapse hole equalization adjustment device inside the gas extraction borehole to overcome the technical problems of poor extraction effect and low efficiency of existing gas extraction devices.

[0006] To solve the above problems, the present invention adopts the following technical solution: A flow field anti-collapse hole equalization adjustment device inside a extraction borehole includes an extraction pipe and a screen pipe connected to one end of the extraction pipe. The screen pipe includes multiple sections of screen pipe connected in sequence, and each section of screen pipe has a screen hole. The sieve apertures gradually increase in size from the sieve section connected to the extraction pipe; The screen tube is equipped with an anti-collapse venting mechanism on its exterior. A conical guide frame is provided at one end of the screen tube away from the extraction tube, and the conical guide frame is connected to the anti-collapse hole ventilation mechanism.

[0007] Furthermore, the anti-collapse hole ventilation mechanism includes a cylindrical frame and multiple positioning rings. The multiple positioning rings are fitted onto the screen tube, and the multiple positioning rings and the cylindrical frame are connected by multiple spokes. The conical guide frame is installed at the end of the cylindrical frame.

[0008] Furthermore, both the cylindrical frame and the conical guide frame are wrapped with wire mesh.

[0009] Furthermore, the plurality of positioning rings and the screen tube are fixed together by set screws.

[0010] Furthermore, a support rod is provided between adjacent spokes.

[0011] Furthermore, the extraction pipe and the screen pipe are connected by a reducing pipe joint.

[0012] Furthermore, the outer diameter of the extraction tube is larger than the outer diameter of the screen tube.

[0013] Furthermore, the screen tube is made of double-resistant U-PVC pipe.

[0014] Furthermore, the lengths of the sieve tubes in each section are the same, and the number of sieve holes on the sieve tubes is the same.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects: This invention provides a flow field anti-collapse hole equalization adjustment device inside a drainage borehole. By opening screen holes of different diameters on multiple sections of screen pipe, with the screen hole diameter gradually increasing from the borehole opening to the bottom, the drainage negative pressure is more evenly distributed along the length of the drainage borehole. This allows the gas at the bottom of the drainage borehole to easily flow into the drainage system, thereby changing the flow field inside the drainage borehole. This effectively avoids the problem of uneven drainage effect in long drainage boreholes, eliminates the drainage blank zone in long drainage boreholes, and thus improves the gas drainage effect at the bottom of long drainage boreholes.

[0016] This invention effectively suppresses coal and rock mass collapse by installing an anti-collapse venting device on the outside of the screen tube. It supports the borehole wall while allowing gas to pass freely.

[0017] Preferably, the anti-collapse hole ventilation device uses a top screw to press the outer circumference of the screen tube, fixing the positioning ring to the screen tube. This, in turn, ensures that the cylindrical frame and wire mesh are coaxially fixed to the screen tube. The wire mesh outside the cylindrical frame supports the extraction borehole, preventing coal dust from falling and clogging the screen holes, while also providing good ventilation. Furthermore, the cylindrical frame ensures that the screen tube maintains near-coaxiality with the centerline of the extraction pipe within the extraction borehole, guaranteeing the reliability of the threaded connections between screen tubes and between the screen tube and the extraction pipe. In the event of a large collapse hole, which could damage the cylindrical frame, the triangular structure formed by the two spokes and one support rod provides greater stability. Therefore, the triangular prism frame structure formed by the three support rods further supports the external forces causing the collapse hole, ensuring good permeability of the screen holes and extending the normal operation of gas extraction.

[0018] Preferably, the conical guide frame serves to guide the screen pipe and the anti-collapse ventilation device into the extraction borehole. During the gas extraction process, the conical guide frame and the external wire mesh prevent coal dust from clogging the inner port of the screen pipe and the adjacent screen holes. Attached Figure Description

[0019] Figure 1 This is a front view of the structure of a flow field anti-collapse hole equalization adjustment device for extraction boreholes according to the present invention. Figure 2 This is a structural diagram of a flow field anti-collapse hole equalization adjustment device for extraction boreholes according to the present invention. Figure 3 This is a structural diagram of the first sieve tube; Figure 4 This is a structural diagram of the second sieve tube; Figure 5 This is a structural diagram of the third sieve tube.

[0020] The components include: 1. extraction borehole; 2. screen pipe; 3. screen hole; 4. extraction pipe; 5. reducing pipe joint; 6. sealing section; 7. cylindrical frame; 8. positioning ring; 9. top screw; 10. spoke rod; 11. support rod; 12. conical guide frame; and 13. wire mesh. Detailed Implementation

[0021] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. 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 should fall within the protection scope of the present invention.

[0022] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this utility model are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the utility model described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0023] This utility model provides a device for adjusting the flow field inside a extraction borehole to prevent collapse and balance the borehole flow. Figure 1 As shown, it includes a screen tube 2 and a extraction tube 4. One end of the screen tube 2 is connected to the extraction tube 4, and a screen hole 3 is opened on the screen tube 2. Optionally, the screen tube 2 adopts a segmented structure, including multiple segments of screen tubes connected in sequence. Starting from the screen tube connected to the extraction tube 4, the aperture of the screen holes 3 on the screen tube gradually increases. Preferably, the length, outer diameter and number of sieve holes of each section of the sieve tube are the same, the sieve holes 3 on the same sieve tube have the same diameter, and an anti-collapse venting mechanism is installed on the outside of the sieve tube 2.

[0024] In one optional embodiment, a flow field anti-collapse hole equalization adjustment device is provided inside the extraction borehole, including an extraction pipe 4 that extends coaxially into the extraction borehole 1. The annular cavity between the outer circle of the extraction pipe 4 and the inner wall of the borehole opening of the extraction borehole 1 forms a sealing section 6 after the grouting and sealing solidifies. A screen pipe 2 is coaxially connected to the inner end of the extraction pipe 4. From the bottom of the hole to the opening, the diameter of the screen holes 3 opened on each screen pipe gradually decreases. An anti-collapse hole ventilation device is installed on the outside of the screen pipe 2. The extraction pipe 4 is connected to the outermost screen pipe 2 through a reducing pipe joint 5, and the outer diameter of the extraction pipe 4 is larger than the outer diameter of the screen pipe 2. There are three sieve tubes 2, each sieve tube 2 is 1.5-2m long. The connection between two adjacent sieve tubes 2 is a coaxial thread connection. The diameter of the sieve hole 3 on the outermost sieve tube 2 is 4mm, the diameter of the sieve hole 3 on the middle sieve tube 2 is 7mm, and the diameter of the sieve hole 3 on the innermost sieve tube 2 is 10mm. The arrangement density of the sieve hole 3 is 24 holes / m. Screen tube 2 is made of double-resistant U-PVC pipe. The outer diameter of screen tube 2 is 32-50 mm, the wall thickness is 2.9 mm, and the nominal pressure is 2.0 MPa. The anti-collapse hole ventilation device includes a cylindrical frame 7 and several positioning rings 8 fitted on the screen tube 2. Each positioning ring 8 is threaded with a set screw 9. The inner end of the set screw 9 is pressed against the outer circle of the screen tube 2. Each positioning ring 8 has three spokes 10 evenly arranged along the circumferential direction on its outer circle. Each spoke 10 is arranged radially along the positioning ring 8. The center line of the cylindrical frame 7 coincides with the center line of the screen tube 2. The outer diameter of the cylindrical frame 7 is slightly smaller than the diameter of the extraction borehole 1. The outer ends of all spokes 10 are fixedly connected to the inner wall of the cylindrical frame 7.

[0025] like Figure 2 As shown, a support rod 11 is provided between the outer ends of any two adjacent spokes 10; a conical guide frame 12 is provided at the inner end of the cylindrical frame 7, located on the inner side of the inner end of the screen tube 2. The conical guide frame 12 is located at the end of the screen tube 2 away from the extraction tube 4. Both the conical guide frame 12 and the cylindrical frame 7 are wrapped with wire mesh 13.

[0026] The cylindrical frame 7 has three sections along its length. The length of each cylindrical frame 7 corresponds to the length of a screen tube 2. Adjacent cylindrical frame sections 7 and the innermost cylindrical frame 7 and the conical guide frame 12 are all bound together by wire mesh 13.

[0027] In a preferred embodiment of this utility model, a flow field anti-collapse hole equalization adjustment device for extraction boreholes is provided, which is mainly installed in the pre-constructed extraction borehole 1.

[0028] The device includes a extraction pipe 4 that penetrates the borehole opening. An annular gap exists between the outer wall of the extraction pipe 4 and the inner wall of the extraction borehole 1 in the borehole area. During construction, a special sealing slurry is injected into this annular gap, which solidifies to form a hard, dense sealing section 6. The function of the sealing section 6 is to seal the borehole opening, preventing external air infiltration and leakage, ensuring that the negative pressure from extraction effectively acts on the depth of the borehole. The end of the extraction pipe 4 (located within the sealing section 6) is connected to the first (outermost) screen pipe 2 via a reducing pipe joint 5. The reducing pipe joint 5 is used to adapt extraction pipes 4 and screen pipes 2 with different diameters, ensuring the airtightness and mechanical strength of the connection.

[0029] In this embodiment, as Figure 3 , Figure 4 and Figure 5As shown, there are three screen tubes 2, connected coaxially and threaded sequentially, extending from the outside to the inside (i.e., from the reducer 5 towards the bottom of the hole). Each screen tube 2 is made of double-resistant U-PVC pipe with an outer diameter of 40 mm and a wall thickness of 2.9 mm. All three screen tubes are 1.8 meters long. The core feature of the screen tubes is the large number of screen holes 3 drilled into their walls. The diameter of the screen holes 3 varies along the borehole axis: the screen holes 3 on the outermost screen tube 2 connected to the reducer 5 have a diameter of 4 mm; the screen holes 3 on the middle screen tube 2 have a diameter of 7 mm; and the screen holes 3 on the innermost screen tube 2 (closest to the bottom of the hole) have a diameter of 10 mm. All screen holes 3 are arranged at a density of 24 per meter, evenly distributed on the circumference of the tube wall. This gradient design of "larger inside and smaller outside" screen hole diameter is key to balancing the axial flow resistance and negative pressure distribution of the borehole.

[0030] The anti-collapse ventilation device is integrally fitted onto the outside of the three screen tubes 2. Its function is to support the borehole wall, prevent coal dust from clogging the screen holes, and keep the screen tubes 2 centered in the borehole. It includes a positioning ring 8, spokes 10, support rods 11, a cylindrical frame 7, and wire mesh 13. Multiple positioning rings 8 are fitted around the screen tube 2 like collars and can slide along the screen tube 2 to a preset position. Each positioning ring 8 has a threaded hole and is equipped with a set screw 9. By tightening the set screw 9, its end is pressed tightly against the outer wall of the screen tube 2, thereby firmly locking the positioning ring 8 onto the screen tube 2.

[0031] Each positioning ring 8 has three radially evenly distributed spokes 10 welded or fastened to its outer periphery. The outer ends of all spokes 10 are fixed together to the inner wall of the cylindrical frame 7. To further enhance the stability of the radial support structure, a strut 11 is also welded diagonally between the outer ends of any two adjacent spokes 10. In this way, the two spokes 10 and the strut 11 form a triangular truss, which greatly improves the overall resistance to lateral compression.

[0032] The cylindrical frame 7 is welded from steel bars or lightweight steel sections, and its outer diameter is slightly smaller than that of the borehole 1 to ensure smooth lowering and provide adequate support to the borehole wall. The entire cylindrical frame 7 is divided into three sections along the axial direction, each section matching the length of a screen pipe 2. The outside of the cylindrical frame 7 is tightly wrapped with a layer of wire mesh 13. The mesh size of the wire mesh 13 is much smaller than that of the screen holes 3, which can effectively block large pieces of coal and rock from collapsing while minimizing resistance to gas flow.

[0033] A conical guide frame 12, made of welded steel bars, is fixedly connected to the front end of the anti-collapse hole ventilation device, and is also wrapped with wire mesh 13. The conical guide frame 12 plays a guiding role when the well is lowered, and can prevent the collapse of the bottom of the hole from directly blocking the port of the innermost screen pipe 2 and the nearby screen holes 3 during extraction.

[0034] Each cylindrical frame 7 and its corresponding screen pipe section are fixed together by multiple support units with positioning rings 8. After the ends of two adjacent cylindrical frame sections 7 are joined, they are tightly bound together with multiple strands of iron wire. Similarly, the innermost cylindrical frame 7 is also fixed to the large end of the conical guide frame 12 by binding with iron wire. This connection method is simple and reliable, and facilitates downhole construction.

[0035] The preferred embodiments of this utility model have been described in detail above; however, this utility model is not limited thereto. Within the scope of the technical concept of this utility model, various simple modifications can be made to the technical solution of this utility model, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed by this utility model and are all within the protection scope of this utility model.

Claims

1. A device for balancing and adjusting the flow field inside a extraction borehole to prevent collapse, characterized in that, It includes a sampling pipe (4) and a screen pipe (2) connected to one end of the sampling pipe (4). The screen pipe includes multiple sections of screen pipe connected in sequence, and each section of the screen pipe has a screen hole (3). The sieve holes (3) gradually increase in size from the sieve section connected to the extraction pipe (4); The screen tube (2) is equipped with an anti-collapse hole ventilation mechanism on its exterior; A conical guide frame (12) is provided at one end of the screen tube (2) away from the extraction tube (4), and the conical guide frame (12) is connected to the anti-collapse hole ventilation mechanism.

2. The flow field anti-collapse hole equalization adjustment device inside the extraction borehole according to claim 1, characterized in that, The anti-collapse hole ventilation mechanism includes a cylindrical frame (7) and multiple positioning rings (8). The multiple positioning rings (8) are fitted on the screen tube (2). The multiple positioning rings (8) and the cylindrical frame (7) are connected by multiple spokes (10). The conical guide frame (12) is installed at the end of the cylindrical frame (7).

3. The flow field anti-collapse hole equalization adjustment device inside the extraction borehole according to claim 2, characterized in that, Both the cylindrical frame (7) and the conical guide frame (12) are wrapped with wire mesh (13).

4. The flow field anti-collapse hole equalization adjustment device inside the extraction borehole according to claim 2, characterized in that, The multiple positioning rings (8) and the screen tube (2) are fixed together by set screws (9).

5. The flow field anti-collapse hole equalization adjustment device inside the extraction borehole according to claim 2, characterized in that, A strut (11) is provided between adjacent spokes (10).

6. The flow field anti-collapse hole equalization adjustment device inside the extraction borehole according to claim 1, characterized in that, The extraction pipe (4) and the screen pipe (2) are connected by a reducing pipe joint (5).

7. The flow field anti-collapse hole equalization adjustment device inside the extraction borehole according to claim 1, characterized in that, The outer diameter of the extraction tube (4) is larger than the outer diameter of the screen tube (2).

8. The flow field anti-collapse hole equalization adjustment device inside the extraction borehole according to claim 1, characterized in that, The screen tube (2) is made of double-resistant U-PVC pipe.

9. A flow field anti-collapse hole equalization adjustment device for extraction boreholes according to claim 1, characterized in that, The lengths of the sieve tubes in each section are the same, and the number of sieve holes (3) on the sieve tubes is the same.

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