Device and method for measuring coal seam gas content by sampling while drilling at fixed point

Abstract

The invention relates to the technical field of coal mine safety, and discloses a while-drilling fixed-point sampling and measuring device and method for coal seam gas content. The device comprises a drill bit (1), a double-wall drill rod (2), a sampling device (3), a measuring device (4) and a tail braid (5). The drill bit (1) is provided with an inclined hole (11), and the drill rod (2) regulates and controls an air flow path through a vent hole (24) and a gap groove (26); the sampling device (3) switches filter screens (351 and 352) through a sealing cover (34) to realize graded collection of coal samples; and the measuring device (4) converts the gas content by using the displacement of the magnetic sealing assembly (42). The method comprises the steps of compressed air path switching, coal sample collection, desorption determination and multi-point repeated operation. According to the invention, the problems of low sampling purity, large time error and difficult particle size screening in the prior art are solved, and the precision and efficiency of gas content measurement are obviously improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of coal mine safety, and relates to a device and method for measuring the gas content in coal seams at fixed points while drilling. Background Art

[0002] With the continuous increase of coal mining depth, the in-situ stress increases, and the gas content and gas pressure in coal seams also increase accordingly. The threat of gas disasters becomes more serious. In order to achieve safe and efficient coal mining, it is necessary to effectively prevent and control gas. Gas content is of great significance in predicting gas outburst risk.

[0003] The existing technologies for measuring gas content in coal seams mainly rely on the airtight coring method and the orifice sampling method. The airtight coring method requires long-time sampling and is difficult to meet the rapid detection needs underground; the orifice sampling method has large measurement errors due to the easy contamination of coal samples and the inability to determine the peeling time. In addition, neither method can achieve multi-point continuous sampling in the borehole, and the screening efficiency of coal sample particle size is low, further affecting data accuracy. With the increase of coal mining depth, the risk of gas disasters intensifies. There is an urgent need for a technology that can sample at fixed points in real time during drilling and quickly measure the gas content to improve the reliability and timeliness of coal mine safety monitoring. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a device and method for measuring the gas content in coal seams at fixed points while drilling to avoid the above technical problems.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A device for measuring the gas content in coal seams at fixed points while drilling, comprising:

[0007] A hollow sampling drill bit: The drill bit is provided with an inclined hole for slag discharge and air pressure guiding;

[0008] A double-wall drill pipe: including an outer drill pipe and an inner drill pipe; A positioning step is provided in the middle section of the inner drill pipe for fixing the sampling device; The inner drill pipe is axially distributed with ventilation holes for balancing the internal and external air pressures;

[0009] A sampling device: including a fixing block, a spring, a sampling mechanism, a sampling chamber, and a linear mechanism; The fixing block is fixed on the positioning step; The spring includes a spring 1 with both ends connecting the fixing block and the sampling mechanism, and a spring 2 installed inside the sampling mechanism; The sampling mechanism is nested at the front end of the inner drill pipe and aligned with the inclined hole;

[0010] Measuring device: It includes a measurement chamber, a magnetic seal assembly, a support frame, ball bearings, a coal sample desorption chamber, and an atmospheric communication chamber; the measurement chamber is fixed at the rear end of the drill bit and covers the ventilation hole; the magnetic seal assembly is installed in the measurement chamber to isolate the coal sample desorption chamber from the atmospheric communication chamber; the support frame is fixed to the inner wall of the measurement chamber, and the ball bearings are evenly distributed to reduce the movement resistance of the magnetic seal assembly; the coal sample desorption chamber is connected to the inner pipe of the drill pipe through a gap groove; the atmospheric communication chamber is connected to the central channel of the drill pipe through the ventilation hole;

[0011] Tail braid: It includes an inner pipe and an outer pipe of the tail braid, and is connected to the end of the drill pipe to balance the internal and external pressures.

[0012] Optionally, a gap groove is provided at the end of the annular gap between the inner pipe and the outer pipe of the drill pipe, serving as a flow channel for the desorbed gas of the coal sample.

[0013] Optionally, a sealing groove is provided at the connection end of the inner pipe of the drill pipe near the drill bit for installing a sealing ring to maintain airtightness.

[0014] Optionally, the sampling device further includes a cover, a pin, and a rotating mechanism; the cover covers the entrance of the sampling chamber, and the switching of the filter screen is controlled by the cooperation of the sliding groove of the rotating mechanism and the pin; a 1-mm aperture filter screen and a 3-mm aperture filter screen are provided in the sampling chamber for the classification and screening of coal samples.

[0015] Optionally, the sliding groove of the rotating mechanism is a periodic swinging structure, and is linked with the linear motion of the linear mechanism through the pin to drive the cover to rotate 90° to realize the switching between the 1-mm filter screen and the 3-mm filter screen.

[0016] Optionally, the radial surface of the annular magnet of the magnetic seal assembly is serrated, the magnetic fluid is filled between the inner and outer circles of the magnet, and the steel balls are evenly distributed in the grooves of the support frame.

[0017] Optionally, the elastic forces of the spring 1 and the spring 2 respectively satisfy the following formulas:

[0018] F1 = 0.7·P·S1 and F2 = 0.7·P·S2

[0019] Wherein, P is the pressure in the central channel of the drill pipe, S1 is the surface area in contact with the pressure of the coal sample collection chamber, and S2 is the surface area in contact with the pressure of the linear mechanism.

[0020] A method for on-site sampling and determination of coal seam gas content based on the above device includes the following steps:

[0021] Preparation before sampling: Input compressed air through the annular gap of the drill pipe to cool the drill bit and discharge slag. After drilling to the target depth, verify whether the displacement change of the magnetic seal assembly is less than 1%;

[0022] Sampling stage: Switch the compressed air to the central channel of the drill pipe, push the linear mechanism forward, drive the cover to rotate through the cooperation of the pin and the chute to cover the 1mm filter screen, open the coal sample collection channel, and the coal sample enters the sampling cavity through the inclined hole;

[0023] Post-sampling treatment: Close the compressed air in the central channel, and springs 1 and 2 reset the sampling device. The cover is switched to the 3mm filter screen to prevent coal sample leakage;

[0024] Measurement stage: The coal sample in the desorption cavity releases gas, forms a pressure difference with the atmosphere communication chamber, drives the displacement of the magnetic seal assembly, records the displacement through the displacement sensor, and calculates the gas content according to the formula Q = K·S·ΔL, where S is the annular cross-sectional area of the desorption cavity, ΔL is the displacement, and K is the conversion coefficient;

[0025] Multi-point measurement: Repeat the above steps to achieve continuous measurement of gas content at different depths in the same borehole.

[0026] Optionally, the displacement of the pressure difference-driven magnetic seal assembly reduces the friction error through the ball, and the displacement measurement accuracy is controlled within ±0.5mm.

[0027] Optionally, the 1mm filter screen is used to intercept coal chips with a particle size greater than 1mm, and the 3mm filter screen is used to prevent the coal sample from retreating. The double-stage screening ensures the purity of the sample.

[0028] The beneficial effects of the present invention are as follows:

[0029] High-precision sampling: Through the double-wall drill pipe and compressed air path switching technology, fixed-point collection of coal samples at the target depth is achieved, avoiding orifice contamination; the double-filter design of 1mm and 3mm effectively screens the particle size of coal samples, improving the purity of the sample.

[0030] Real-time measurement: The magnetic seal assembly combined with the pressure difference drive mechanism can immediately start the desorption measurement after sampling, eliminating the error of uncontrollable coal sample exposure time in the traditional method and ensuring the timeliness of data.

[0031] Structure optimization: The serrated magnet and ball design enhance the sealing performance and motion stability, reducing friction loss; the spring mechanical formula accurately matches the pressure conditions to ensure the reliability of the device operation.

[0032] Efficient multi-point detection: Through repeated operations, continuous sampling and measurement at different depths in the same borehole are achieved, greatly improving the efficiency of gas content distribution analysis and providing comprehensive data support for gas disaster early warning.

[0033] Process compatibility: The device has a compact structure and can be directly integrated into conventional drilling equipment without additional complex modification, suitable for various underground coal mine environments.

[0034] In summary, this solution realizes the collection of coal samples by changing the path of the compressed air flow to control the action of the sampling device, and measures the displacement by constructing a pressure difference to push the magnetic seal balance device, and then converts the gas content. It solves the problems of low purity of coal sample determination and sampling during the long borehole process, inability to measure the time from coal sample peeling from the coal seam to the start of determination, and difficulty in particle size screening.

[0035] Other advantages, objectives, and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the following specification. Brief Description of the Drawings

[0036] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be described in detail preferably in conjunction with the accompanying drawings, where:

[0037] Figure 1 is a schematic diagram of the overall device of the present invention;

[0038] Figure 2 is a schematic diagram of the drill bit structure;

[0039] Figure 3 is a schematic diagram of the drill pipe structure;

[0040] Figure 4 is a schematic diagram of the sampling device;

[0041] Figure 5 is a schematic diagram of the measuring device;

[0042] Figure 6 is a schematic diagram of the tail whip;

[0043] Figure 7 is a sectional view of the sampling chamber;

[0044] Figure 8 is a schematic diagram of the rotating mechanism;

[0045] Reference numerals: 1 drill bit, 2 drill pipe, 3 sampling device, 4 measuring device, 5 tail whip, 11 inclined hole, 21 drill pipe outer tube, 22 drill pipe inner tube, 23 positioning step, 24 ventilation hole, 25 sealing groove, 26 clearance groove, 31 fixing block, 32 spring, 33 sampling mechanism, 34 cover, 35 sampling chamber, 36 linear mechanism, 37 pin, 38 rotating mechanism, 41 measuring chamber, 42 magnetic seal assembly, 43 support frame, 44 ball, 45 coal sample desorption chamber, 46 atmosphere communication chamber, 51 tail whip inner tube, 52 tail whip outer tube, 351 sampling chamber 1mm aperture filter screen, 352 sampling chamber 3mm aperture filter screen, 381 sliding groove. Detailed Description of the Embodiment

[0046] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand the other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the drawings provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0047] Among them, the drawings are only for illustrative purposes, showing only schematic diagrams, not physical diagrams, and should not be construed as a limitation on the present invention; in order to better illustrate the embodiments of the present invention, some components in the drawings will be omitted, enlarged or reduced, which does not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0048] In the drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only for illustrative purposes and should not be construed as a limitation on the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0049] Please refer to Figures 1 to 8 , this embodiment discloses a device for measuring the in-situ sampling of coal seam gas content while drilling, including a hollow sampling bit 1, a double-walled drill pipe 2, a sampling device 3, a measuring device 4, and a tail braid 5. The action of the sampling device 3 is controlled by switching the path of the compressed air flow to collect coal samples, and the movement of the magnetic seal assembly 42 is driven based on the air pressure difference to measure the displacement, and finally the gas content is converted.

[0050] (I) Detailed description of the device structure

[0051] 1. Double-walled drill pipe 2

[0052] The inner pipe 22 of the drill pipe is provided with the following functional structures:

[0053] Sealing groove 25: a circumferential groove inside the inner pipe 22 of the drill pipe near the connection end of the bit 1, used to install a sealing ring to ensure the airtightness between the inner pipe 22 of the drill pipe and the sampling device 3 and prevent the leakage of compressed air.

[0054] Positioning step 23: An annular protrusion provided on the inner wall of the middle section of the drill rod inner tube 22, used to fix the fixing block 31 of the sampling device 3, limit its axial displacement, and ensure that the sampling cavity 35 is aligned with the inclined hole 11 of the drill bit 1.

[0055] The vent holes 24 are multiple through holes distributed along the axial direction of the drill pipe inner tube 22, located behind the positioning step 23, connecting the central channel of the drill pipe with the atmosphere communication chamber 46, balancing the internal and external air pressures, and preventing the coal sample desorption chamber 45 from pressure fluctuations.

[0056] Gap groove 26 : located at the end of the annular gap between the drill pipe inner tube 22 and the drill pipe outer tube 21 , serving as a flow channel for coal sample desorption gas, directing the gas to the coal sample desorption chamber 45 .

[0057] 2. Hollow sampling drill bit 1

[0058] An inclined hole 11 is provided at the front end of the drill bit 1 for slag discharge and compressed air guidance.

[0059] 3. Sampling device 3

[0060] Fixed block 31: fixed on the positioning step 23, serving as a mounting base for the spring 32 and the sampling mechanism 33.

[0061] Spring 32:

[0062] The two ends of the spring 1 are respectively connected to the fixing block 31 and the sampling mechanism 33, and are used to reset the sampling mechanism 33;

[0063] The spring 2 is installed inside the sampling mechanism 33 to assist the motion control of the linear mechanism 36 .

[0064] The sampling mechanism 33 is nested in the front end of the drill rod inner tube 22 and aligned with the inclined hole 11 , and pushes the coal sample into the sampling cavity 35 through the linear mechanism 36 .

[0065] Cover 34: covers the entrance of the sampling chamber 35, and is linked with the pin 37 through the rotating mechanism 38 to control the switching of the 1 mm pore size filter 351 and the 3 mm pore size filter 352.

[0066] Linear mechanism 36 and pin 37: The linear mechanism 36 slides axially along the drill rod inner tube 22, and the pin 37 passes through the slide groove 381 of the linear mechanism 36 and the rotary mechanism 38, converting the linear motion into rotary motion to drive the cover 34 to open and close.

[0067] Rotating mechanism 38: installed outside the sampling cavity 35, the slide groove 381 cooperates with the pin 37 to control the rotation angle of the cover 34 through periodic swing.

[0068] The sampling chamber 35 is a hollow cylindrical structure, and the filter screen 351 with a pore size of 1 mm and the filter screen 352 with a pore size of 3 mm are evenly distributed on the wall surface to achieve graded screening of coal samples.

[0069] 4. Measuring device 4

[0070] Measuring chamber 41: Fixed to the rear end of the drill bit 1 by threads, covering the ventilation hole 24, and used to accommodate the magnetic seal assembly 42 and the coal sample desorption chamber 45.

[0071] Magnetic seal assembly 42: Comprising an annular magnet, magnetic fluid and steel balls 44, installed in the measuring chamber 41, isolating the coal sample desorption chamber 45 from the atmospheric communication chamber 46 through magnetic seal effect, and only allowing displacement driven by pressure difference.

[0072] Support frame 43 and ball bearings 44: The support frame 43 is fixed to the inner wall of the measuring chamber 41, and the ball bearings 44 are evenly distributed in the grooves to reduce the movement friction of the magnetic seal assembly 42.

[0073] Coal sample desorption chamber 45: Communicates with the inner pipe 22 of the drill pipe through the gap groove 26, temporarily stores the coal sample and promotes the desorption of gas.

[0074] Atmospheric communication chamber 46: Communicates with the central channel of the drill pipe through the ventilation hole 24 to keep it consistent with the external atmospheric pressure.

[0075] 5. Tail braid 5

[0076] Comprising an inner pipe 51 and an outer pipe 52 of the tail braid, connected to the end of the drill pipe 2 to balance the internal and external pressures.

[0077] (II) Spring elastic force calculation formula

[0078] Elastic force of spring 1: F1 = 0.7·P·S1, where P is the pressure in the central channel of the drill pipe and S1 is the surface area of contact between the coal sample collection chamber and the pressure.

[0079] Elastic force of spring 2: F2 = 0.7·P·S2, where S2 is the surface area of contact between the linear mechanism 36 and the pressure.

[0080] (III) Gas desorption amount measurement method

[0081] Volume change: ΔV = S·ΔL, where S is the annular cross-sectional area of the coal sample desorption chamber 45 and ΔL is the displacement of the magnetic seal assembly 42.

[0082] Gas content: Q = K·ΔV, where K is the conversion coefficient between the gas desorption amount and the content model.

[0083] (IV) Operation process

[0084] A. Preparation before sampling

[0085] Pressurized air enters from the annular gap of the drill pipe 2, cools the drill bit 1 through the inclined hole 11 and discharges slag; after reaching the target depth, verify whether the displacement change of the magnetic seal assembly 42 is less than 1%.

[0086] B. Sampling stage

[0087] Switch the compressed air to the central channel of the drill pipe, push the linear mechanism 36 forward, and the pin 37 cooperates with the chute 381 to drive the cover 34 to rotate and cover the 1 mm filter screen 351, and the coal sample enters the sampling chamber 35 through the inclined hole 11.

[0088] C. Post-sampling processing

[0089] Close the compressed air in the central channel, and the springs 1 and 2 reset the sampling device 3. The cover 34 is switched to the 3 mm filter screen 352 to prevent the coal sample from leaking.

[0090] D. Measurement stage

[0091] The coal sample in the coal sample desorption chamber 45 releases gas, forms a pressure difference with the atmosphere communication chamber 46, drives the displacement of the magnetic seal assembly 42, and the displacement amount is recorded by the sensor and the gas content is calculated.

[0092] E. Multi-point measurement

[0093] Repeat the above steps to achieve continuous measurement of the gas content at different depths in the borehole.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the present technical solution, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A device for measuring the in-situ gas content of coal seams by sampling at fixed points during drilling, characterized in that, Comprising: Hollow sampling drill bit (1): The drill bit (1) is provided with an inclined hole (11) for slag discharge and air pressure guiding; Double-wall drill pipe (2): Comprising an outer drill pipe (21) and an inner drill pipe (22); A positioning step (23) is provided in the middle section of the inner drill pipe (22) for fixing the sampling device (3); The inner drill pipe (22) is axially distributed with ventilation holes (24) for balancing the internal and external air pressures; Sampling device (3): Comprising a fixing block (31), a spring (32), a sampling mechanism (33), a sampling chamber (35), and a linear mechanism (36); The fixing block (31) is fixed on the positioning step (23); The spring (32) includes a spring 1 with both ends connecting the fixing block (31) and the sampling mechanism (33), and a spring 2 installed inside the sampling mechanism (33); The sampling mechanism (33) is nested at the front end of the inner drill pipe (22) and aligned with the inclined hole (11); Measuring device (4): Comprising a measuring chamber (41), a magnetic sealing component (42), a support frame (43), a ball (44), a coal sample desorption chamber (45), and an atmospheric communication chamber (46); The measuring chamber (41) is fixed at the rear end of the drill bit (1) and covers the ventilation hole (24); The magnetic sealing component (42) is installed in the measuring chamber (41) for isolating the coal sample desorption chamber (45) from the atmospheric communication chamber (46); The support frame (43) is fixed on the inner wall of the measuring chamber (41), and the balls (44) are evenly distributed to reduce the movement resistance of the magnetic sealing component (42); The coal sample desorption chamber (45) is communicated with the inner drill pipe (22) through a gap groove (26); The atmospheric communication chamber (46) is communicated with the central channel of the drill pipe through the ventilation hole (24); Tail braid (5): Comprising an inner tail braid pipe (51) and an outer tail braid pipe (52), connected to the end of the drill pipe (2) to balance the internal and external pressures.

2. The device according to claim 1, characterized in that: A gap groove (26) is provided at the end of the annular gap between the inner drill pipe (22) and the outer drill pipe (21), serving as a flow channel for the desorbed gas of the coal sample.

3. The device according to claim 1, characterized in that: A sealing groove (25) is provided at the connection end of the inner drill pipe (22) close to the drill bit (1) for installing a sealing ring to maintain airtightness.

4. The device according to claim 1, characterized in that: The sampling device (3) further comprises a cover (34), a pin (37), and a rotating mechanism (38); The cover (34) covers the entrance of the sampling chamber (35), and the filter screen is controlled to switch through the cooperation of the sliding groove (381) of the rotating mechanism (38) and the pin (37); A 1mm aperture filter screen (351) and a 3mm aperture filter screen (352) are provided in the sampling chamber (35) for grading and screening of the coal sample.

5. The device according to claim 4, wherein The sliding groove (381) of the rotating mechanism (38) is a periodic swinging structure, and is linked with the linear motion of the linear mechanism (36) through the pin (37) to drive the cover (34) to rotate 90° to realize the switching between the 1mm filter screen (351) and the 3mm filter screen (352).

6. The device according to claim 1, characterized in that The radial surface of the annular magnet of the magnetic sealing component (42) is serrated, magnetic fluid is filled between the inner and outer circles of the magnet, and steel balls are evenly distributed in the grooves of the support frame (43).

7. The device according to claim 1, characterized in that, The elastic forces of the spring 1 and the spring 2 respectively satisfy the following formulas: F1 = 0.7·P·S1 and F2 = 0.7·P·S2 Wherein, P is the pressure in the central channel of the drill pipe, S1 is the surface area of the coal sample collection chamber in contact with the pressure, and S2 is the surface area of the linear mechanism (36) in contact with the pressure.

8. A method for measuring the in-situ sampling of coal seam gas content during drilling based on the device according to claim 5, characterized in that It includes the following steps: Preparation before sampling: Input compressed air through the annular gap of the drill pipe (2) to cool the drill bit (1) and discharge slag. After drilling to the target depth, verify whether the displacement change of the magnetic seal assembly (42) is less than 1%; Sampling stage: Switch the compressed air to the central channel of the drill pipe, push the linear mechanism (36) forward, drive the cover (34) to rotate and cover the 1 mm filter screen (351) through the cooperation of the pin (37) and the sliding groove (381), open the coal sample collection channel, and the coal sample enters the sampling chamber (35) through the inclined hole (11); Post-sampling treatment: Close the compressed air in the central channel, the springs 1 and 2 reset the sampling device (3), and the cover (34) switches to the 3 mm filter screen (352) to prevent the coal sample from leaking back; Measurement stage: The coal sample in the coal sample desorption chamber (45) releases gas, forms a pressure difference with the atmosphere communication chamber (46), drives the displacement of the magnetic seal assembly (42), records the displacement amount through the displacement sensor, and calculates the gas content according to the formula Q = K·S·ΔL, where S is the annular cross-sectional area of the desorption chamber, ΔL is the displacement amount, and K is the conversion coefficient; Multi-point measurement: Repeat the above steps to continuously measure the gas content at different depths in the same borehole.

9. The method according to claim 8, wherein The displacement amount of the pressure difference-driven magnetic seal assembly (42) reduces the friction error through the ball (44), and the measurement accuracy of the displacement amount is controlled within ±0.5 mm.

10. The method according to claim 8, wherein The 1 mm filter screen (351) is used to intercept coal chips with a particle size greater than 1 mm, and the 3 mm filter screen (352) is used to prevent the coal sample from retreating, and the double-stage screening ensures the sample purity.

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