Deep coal mine pressure and gas maintaining coring device and rapid fidelity testing method

Abstract

The invention relates to a deep coal mine pressure-maintaining gas-maintaining coring device and a rapid fidelity testing method. The deep coal mine pressure-maintaining gas-maintaining coring device comprises an outer pipe, a center rod with the lower end connected with a core barrel, the core barrel arranged in the outer pipe, a rock sample crushing mechanism arranged in the core barrel, a flap valve arranged in the lower end of the outer pipe and a coring drill bit connected with the lower end of the outer pipe. The method comprises the steps that a coal sample is obtained through the deep coal mine pressure-maintaining and gas-maintaining coring device, after coring is completed, the coring device is integrally taken out of a drill hole, a transmission shaft is connected with a power driving device, and the power driving device drives a tool bit in a core barrel to rotate, so that the coal sample is crushed; a gas collecting pipe is connected to the gas collecting butt joint and connected with a gas content measuring device, and the gas content is measured through the gas content measuring device. According to the method, pressure-maintaining coring can be achieved, gas content measurement is facilitated, gas leakage is avoided in the whole coal sample transfer testing process, the gas content measurement precision is high, dependence on empirical formulas is avoided, estimation errors do not exist, and the gas content measurement result is accurate.

Description

Technical Field

[0001] This invention relates to the field of gas content determination technology, and in particular to a pressure-maintaining and gas-preserving coring device for deep coal mines and a rapid and accurate testing method. Background Technology

[0002] Accurate determination of gas content is crucial for coal mine gas disaster prevention and control and coalbed methane resource development. Direct sampling (obtaining samples directly from the coal seam) is widely used in gas measurement in major coal mines due to its simplicity and ease of operation. The direct method is further divided into open sampling and closed sampling. Open sampling obtains samples directly at the borehole opening, but it cannot prevent gas loss during the transfer of the sample from the bottom of the borehole to the closed desorption tank; this loss is called gas loss. Gas loss can usually be estimated using empirical formulas, but the accuracy depends on the degree of matching between the formula parameters and the actual coal mine conditions, resulting in unavoidable estimation errors. Closed sampling, on the other hand, obtains samples from the bottom of the borehole and stores the coal sample in a sealed container during transfer, effectively preventing gas loss during the transfer process and thus improving the accuracy of gas content determination.

[0003] Among existing methods for determining methane content is pressure-controlled coring (a type of closed sampling method). This method allows for bottom-hole sampling, in-situ storage and transfer of samples under pressure conditions, reducing the escape of methane from the sample into open spaces. Furthermore, because storage occurs under pressure, it effectively prevents the conversion of large amounts of adsorbed methane into free methane due to drastic changes in environmental pressure, thus contributing to the stability of the methane storage state of the coal sample. However, existing pressure-controlled coring technology is complex and time-consuming (requiring significant time to transfer samples from underground to a surface laboratory for testing), hindering its widespread adoption in mining areas.

[0004] Other methods for determining gas content involve obtaining coal samples through orifice sampling, recording the sampling time, then crushing the coal sample in a sealed container to collect the gas and obtain the gas desorption amount. Gas loss is calculated using empirical algorithms combined with the sampling time, and finally, the total gas content is obtained by adding the gas loss to the gas desorption amount. However, this method uses orifice sampling, which involves significant gas escape during the transfer to the sealed container (especially in deep-hole sampling), and the estimation based on empirical formulas has certain estimation errors, failing to meet the requirements for accurate gas content determination in coal mine development.

[0005] However, rapid measurement methods for gas content underground involve significant gas leakage during coal sample transfer, and the reliance on empirical formulas to estimate gas loss leads to estimation errors in gas content determination, failing to meet the requirements for high-quality development of coal mines. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a pressure-maintaining and gas-preserving coring device for deep coal mines and a rapid, high-fidelity testing method.

[0007] This invention is achieved through the following technical solution:

[0008] The deep coal mine pressure-maintaining and gas-maintaining coring device provided in this application includes an outer pipe with a gas-collecting docking joint on its wall, a central rod connected to the core tube at its lower end, a core tube installed inside the outer pipe, a rock sample crushing mechanism installed inside the core tube, a flap valve installed inside the lower end of the outer pipe, and a coring drill bit connected to the lower end of the outer pipe.

[0009] Optionally, the flap valve includes a valve seat, a valve cover, and a resilient element. The valve seat is installed inside the outer tube, and one side of the valve cover is rotatably connected to the upper end of the valve seat. The resilient element acts on the valve seat and the valve cover. Under the action of the resilient element, the valve cover tends to close with the valve seat.

[0010] Optionally, the rock sample crushing mechanism includes a drive shaft, a cutter bar, and a cutter head. The upper end of the cutter bar is connected to the drive shaft, the lower end of the cutter bar extends into the core tube, and the lower end of the cutter bar is connected to the cutter head.

[0011] Optionally, a central rod guide tube is coaxially mounted on the upper end of the outer tube, and the central rod is installed inside the central rod guide tube and slides with it.

[0012] Optionally, the lower end of the center rod is connected to the tool holder, the tool shank is installed in the tool shank hole in the center of the tool holder and is clearance-fitted with it, the tool head is located below the tool holder, and the upper end of the core tube is connected to the tool holder.

[0013] Optionally, the tool holder has a first outer step, the drive shaft has a second outer step, and the tool holder is restricted between the first and second outer steps to achieve axial positioning of the tool holder.

[0014] Optionally, the center rod is connected to the tool holder via a connecting sleeve, and the drive shaft is located inside the connecting sleeve.

[0015] Optionally, the cutter head includes three layers of blades.

[0016] The method for accurate and rapid determination of gas content in deep coal mines provided in this application uses the aforementioned deep coal mine pressure-maintaining and gas-preserving coring device. The method includes the following steps:

[0017] In the initial state, the flap valve is open; coal samples are obtained through the deep coal mine pressure-maintaining and gas-preserving core sampler, and the coal samples are stored in the core tube inside the core sampler;

[0018] After core sampling is completed, the core tube is lifted upwards. Once the core tube is lifted to a certain height, the flap valve closes.

[0019] The core extractor is removed from the borehole as a whole, the connecting sleeve is removed, and the drive shaft is connected to the power drive device. The power drive device drives the cutter head inside the core tube to rotate, thereby achieving coal sample crushing.

[0020] Connect the gas collection pipe to the gas collection docking joint, and then connect the gas collection pipe to the gas content measuring device to measure the gas content.

[0021] Specifically, when crushing coal samples, the coring device is inverted with the coring drill bit positioned above.

[0022] Compared with the prior art, this application has at least the following beneficial effects:

[0023] 1. The deep coal mine pressure-maintaining and gas-maintaining coring device of this application can not only maintain pressure for coring, but also facilitate the measurement of gas content. It combines the advantages of accurate gas content determination of the pressure-maintaining coring method with the advantages of convenient operation and rapid results of the rapid gas content determination method.

[0024] 2. In this phase, a lightweight pressure-holding core extractor is used to obtain samples from the bottom of the borehole and transfer them to the borehole opening under pressure, with no gas leakage throughout the process. This application uses the pressure-holding core extractor as a crushing chamber, which is connected to a power source to drive the crushing mechanism that has been integrated inside the core extractor to crush the sample. Then, through the gas collection docking joint set on the side wall, gas can be collected quickly.

[0025] 3. Using this application, there is no gas leakage in the entire process of coal sample transfer and testing, the gas content determination is highly accurate, it does not rely on empirical formulas, there is no estimation error, and the gas content determination results are accurate;

[0026] 4. This application reduces equipment redundancy by directly integrating the crushing device into the pressure chamber, eliminating the need to transfer the sample to a ground laboratory, shortening the sample transfer time, and greatly reducing the gas content measurement time. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the deep coal mine pressure-maintaining and gas-preserving coring device in the initial state of the embodiment;

[0029] Figure 2 This is a schematic diagram of the core sampling device for maintaining pressure and gas in deep coal mines after core sampling is completed in the embodiment.

[0030] Figure 3 This is a perspective view of the rock sample crushing mechanism in the embodiment;

[0031] Figure 4 This is a cross-sectional view of the rock sample crushing mechanism installed in the cutter holder in the embodiment. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0033] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other. It should also be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments; similar or identical parts between embodiments can be referred to interchangeably.

[0034] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used to facilitate the description of this invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0035] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, a direct connection, or an indirect connection through an intermediate medium; or they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0036] This embodiment proposes a precise and rapid method for determining gas content in deep coal mines based on pressure-preserving coring, taking into account both the advantages of pressure-preserving coring in maintaining stable gas content and the advantages of rapid gas content determination at multiple underground locations.

[0037] like Figure 1 , Figure 2 As shown, the preferred embodiment of the present invention discloses a deep coal mine pressure-maintaining and gas-preserving coring device, which includes an outer tube 1, a central rod 2, a core tube 3, a rock sample crushing mechanism 4, a flap valve, and a coring drill bit 6.

[0038] The lower end of the outer tube 1 is connected to the core drill bit 6. The core tube 3 is installed inside the outer tube 1. The upper end of the core tube 3 is connected to the center rod 2. The flap valve is installed inside the outer tube 1 and located at the lower part of the outer tube 1. The rock sample crushing mechanism 4 is installed inside the core tube 3.

[0039] The flap valve includes a valve seat 51, a valve cover 52, and an elastic element 53. The valve seat 51 is fixed inside the outer tube 1. One side of the valve cover 52 is rotatably connected to the upper end of the valve seat 51. The elastic element 53 acts on the valve seat 51 and the valve cover 52. Under the action of the elastic element 53, the valve cover 52 tends to close with the valve seat 51.

[0040] like Figure 3 As shown, the rock sample crushing mechanism 4 includes a drive shaft 41, a cutter bar 42, and a cutter head. The upper end of the cutter bar 42 is connected to the drive shaft 41, and the lower end of the cutter bar 42 extends into the core tube 3. The lower end of the cutter bar 42 is connected to the cutter head. Optionally, the upper end of the cutter bar 42 is threadedly connected to the drive shaft 41.

[0041] In some embodiments, the cutter head is designed with three layers. Specifically, the cutter head includes a primary blade 43, a secondary blade 44, and a tertiary blade 45 arranged from top to bottom, with the primary blade 43 and the secondary blade 44 arranged at an angle. The bottom tertiary blade 45 acts as a sweeping blade, which can be used to move the coal dust accumulated at the bottom; the middle secondary blade 44 is mainly for secondary crushing to increase crushing efficiency; and the top primary blade 43 is for primary crushing, mainly for cutting columnar coal samples.

[0042] In some embodiments, the primary blade 43 and the secondary blade 44 are arranged at a 90-degree angle.

[0043] In some embodiments, there is an angle θ between the third-stage blade 45 and the second-stage blade 44.

[0044] In some embodiments, a central rod guide tube 7 is coaxially mounted on the upper end of the outer tube 1, and the central rod 2 is installed inside the central rod guide tube 7 and slides therewith. The central rod guide tube 7 is used to guide the axial movement of the central rod 2.

[0045] In some embodiments, the lower end of the central rod 2 is connected to the tool holder 8, the tool bar 42 is installed in the tool bar hole in the center of the tool holder 8 and is clearance-fitted with it, the tool head is located below the tool holder 8, and the upper end of the core tube 3 is threadedly connected to the tool holder 8.

[0046] In some embodiments, such as Figure 4 As shown, the tool holder 42 has a first outer step 46, the transmission shaft 41 has a second outer step 47, and the tool holder 8 is restricted between the first outer step 46 and the second outer step 47. Under the action of the first outer step 46 and the second outer step 47, the axial positioning of the tool holder 42 is achieved, the axial displacement of the tool holder 42 is restricted, and the rotational degree of freedom of the tool holder 42 is retained.

[0047] In some embodiments, the center rod 2 is threadedly connected to the tool holder 8 via a connecting sleeve 11. Optionally, the upper end of the connecting sleeve 11 is connected to the lower end of the center rod 2 via a pin 12, the lower end of the connecting sleeve 11 is sleeved on the tool holder 8, and the drive shaft 41 is located inside the connecting sleeve 11.

[0048] The drive shaft 41 is used to connect to the power drive device, which drives the rock sample crushing mechanism 4 to rotate. It is worth noting that the power drive device can be an electric motor, a pneumatic motor, or other unit capable of providing rotational power.

[0049] In some embodiments, pin 12 is an R2-d46 pin.

[0050] The middle section of the outer pipe 1 serves as the gas collection section. The pipe wall of the middle section of the outer pipe 1 has an opening for installing a gas collection docking joint 9 and a plug 10. The plug 10 is located above the gas collection docking joint 9 and can be used as a backup safety pressure relief device.

[0051] Optionally, plug 10 is a G1-8 plug.

[0052] In some embodiments, the equipment has an overall length of 1m and a lightweight design, which is conducive to use in mines.

[0053] This embodiment also provides a method for accurate and rapid determination of gas content in deep coal mines, which uses the aforementioned deep coal mine pressure-maintaining and gas-preserving coring device, and specifically includes the following steps:

[0054] S1, the core extractor connects to the drill pipe; as shown... Figure 1 As shown, in the initial state, the core tube 3 is located inside the valve seat 51. Under the obstruction of the core tube 3, the valve cover 52 is opened. The drilling rig outputs axial power and rotational torque to drive the deep coal mine pressure-maintaining and gas-maintaining core sampler to drill and obtain coal samples. The coal samples are stored in the core tube 3 inside the core sampler.

[0055] S2, as Figure 2 As shown, after the core sampling is completed, the core tube 3 is lifted upwards. When the core tube 3 is lifted to a certain height, the valve cover 52 flips over to close with the valve seat 51.

[0056] S3. Remove the core sampler entirely from the borehole and place it on a flat underground surface. Remove the connecting sleeve 11 and connect the drive shaft 41 to the power drive device. The power drive device drives the internal cutter head to rotate, thereby achieving rapid crushing of the coal sample.

[0057] S4. Connect the gas collection pipe to the gas collection docking joint 9. Connect the gas collection pipe to the gas content measuring device.

[0058] Optionally, the gas content measuring device includes a methane flow meter that can read the methane flow rate and cumulative flow in real time.

[0059] S5. Observe the changes in the gas content measuring device until the cumulative measurement value no longer changes significantly within 5 minutes. The obtained gas content is the total gas content of the coal sample.

[0060] Optionally, the specific process of S3 is as follows: the coring device is inverted, with the coring drill bit 6 positioned above, thus ensuring that the coal sample inside the chamber can be concentrated at the drill bit position. Then, the power drive device is activated to drive the transmission shaft 41 to rotate, completing the coal sample crushing.

[0061] In some embodiments, a power drive device with a crushing speed of up to 20,000 RPM is selected, and the coal sample circulation at the crushing point can be achieved by the rotational motion of the blades, that is, heavy coal particles gather at the drill bit, while small coal particles are suspended and move upward.

[0062] This application employs a pressure-holding coring method, effectively preventing gas escape during sample transfer from the bottom of the borehole to the borehole opening, and avoiding estimations based on empirical formulas. Therefore, its accuracy is better than traditional gas content determination methods. Furthermore, since this method allows for sample crushing and gas measurement on a leveled surface within the underground tunnel, eliminating the need to transfer samples to a surface laboratory, it significantly reduces sample transfer time and improves efficiency.

[0063] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A pressure-maintaining and gas-preserving coring device for deep coal mines, characterized in that, include: The outer pipe (1) is provided with a gas collection docking joint (9) on the pipe wall; The lower end of the central rod (2) is connected to the core tube (3); Core tube (3) installed inside outer tube (1); Rock sample crushing mechanism (4) installed inside core tube (3); The flap valve installed inside the lower end of the outer pipe (1), and The core drill bit (6) is connected to the lower end of the outer tube (1).

2. The deep coal mine pressure-maintaining and gas-preserving coring device according to claim 1, characterized in that, The flap valve includes a valve seat (51), a valve cover (52), and an elastic element (53). The valve seat (51) is installed inside the outer tube (1). One side of the valve cover (52) is rotatably connected to the upper end of the valve seat (51). The elastic element (53) acts on the valve seat (51) and the valve cover (52). Under the action of the elastic element (53), the valve cover (52) tends to close with the valve seat (51).

3. The deep coal mine pressure-maintaining and gas-preserving coring device according to claim 1, characterized in that, The rock sample crushing mechanism (4) includes a drive shaft (41), a cutter bar (42) and a cutter head. The upper end of the cutter bar (42) is connected to the drive shaft (41), the lower end of the cutter bar (42) extends into the core tube (3), and the lower end of the cutter bar (42) is connected to the cutter head.

4. The deep coal mine pressure-maintaining and gas-preserving coring device according to claim 1, characterized in that, The upper end of the outer tube (1) is coaxially fitted with a central rod guide tube (7), and the central rod (2) is installed inside the central rod guide tube (7) and slides with it.

5. The deep coal mine pressure-maintaining and gas-preserving coring device according to claim 1 or 4, characterized in that, The lower end of the center rod (2) is connected to the tool holder (8), the tool rod (42) is installed in the tool rod hole in the center of the tool holder (8) and is clearance-fitted with it, the tool head is located below the tool holder (8), and the upper end of the core tube (3) is connected to the tool holder (8).

6. The deep coal mine pressure-maintaining and gas-preserving coring device according to claim 5, characterized in that, The tool holder (42) has a first outer step (46), the transmission shaft (41) has a second outer step (47), and the tool holder (8) is restricted between the first outer step (46) and the second outer step (47) to achieve axial positioning of the tool holder (42).

7. The deep coal mine pressure-maintaining and gas-preserving coring device according to claim 5, characterized in that, The center rod (2) is connected to the tool holder (8) through the connecting sleeve (11), and the drive shaft (41) is located inside the connecting sleeve (11).

8. The deep coal mine pressure-maintaining and gas-preserving coring device according to claim 3, characterized in that, The blade head consists of three layers of blades.

9. A method for accurate and rapid determination of gas content in deep coal mines, characterized in that, The deep coal mine pressure-maintaining and gas-preserving coring device as described in any one of claims 1-8 includes the following steps: In the initial state, the flap valve is open; coal samples are obtained through the deep coal mine pressure-maintaining and gas-maintaining core sampler, and the coal samples are stored in the core tube (3) inside the core sampler; After the core is taken, the core tube (3) is lifted upwards. When the core tube (3) is lifted to a certain height, the flap valve is closed. Remove the core extractor from the borehole, remove the connecting sleeve (11), connect the drive shaft (41) to the power drive device, and drive the cutter head inside the core tube (3) to rotate, thereby achieving coal sample crushing. Connect the gas collection pipe to the gas collection docking joint (9), and connect the gas collection pipe to the gas content measuring device to measure the gas content.

10. The method for accurate and rapid determination of gas content in deep coal mines according to claim 9, characterized in that, When crushing coal samples, the core extractor is inverted and the core drill bit (6) is positioned on top.

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