Method for synchronously collecting desorption gas in coal seam coring process

Abstract

The invention discloses a method for synchronously collecting desorbed gas in a coal seam coring process, which comprises the following steps of: firstly completing the assembly and pretreatment of a coal sample collecting unit and a gas collecting unit, then assembling integrated coring equipment and conveying to a predetermined sampling position of a coal seam; gas desorbed from a coal sample is synchronously collected in the coring process, mechanical plugging and polystyrene foam dual sealing are automatically triggered after the coal sample is full, the total gas desorption amount is measured and calculated after drill retreating, and finally equipment is disassembled, the coal sample is treated, and the equipment is cleaned and reassembled for use. The method has the advantages of standard operation steps, smooth connection, no need of manual intervention of sealing and gas collection actions in the whole process, high sealing reliability, no gas dissipation, great improvement of the accuracy and efficiency of coal seam gas content measurement, complete adaptation to the conventional drilling process under the coal mine, no need of modifying the existing equipment, low operation difficulty, high safety and low cost. The coring gas collecting device is suitable for coring gas collecting operation of coal seams with different depths and different gas grades, and has extremely high field popularization and application value.

Description

Technical Field

[0001] This invention belongs to the field of coal seam gas content determination technology, and particularly relates to a method for simultaneous collection of desorbed gas during coal seam coring. Background Technology

[0002] Coal, as the cornerstone of my country's energy security, occupies an irreplaceable core position in energy supply. In 2025, my country's coal production reached 4.83 billion tons, a year-on-year increase of 1.2%. As coal mining extends to deeper areas, the gas content in coal seams increases significantly, greatly increasing the difficulty of gas disaster prevention and control. Coal seam gas content is a core indicator for predicting gas disasters and assessing the effectiveness of gas drainage; its measurement accuracy is directly related to mine safety.

[0003] Currently, the determination of coal seam gas content mainly follows the "Direct Determination Method of Coal Seam Gas Content Downhole" (AQ1066-2008), which divides the gas content into three parts: downhole desorbed gas, laboratory degassing, and lost gas. Lost gas is calculated by inverting downhole desorption data, which has inherent errors: when sampling from long-distance boreholes, the sampling time is difficult to meet the standard requirement of less than 5 minutes, leading to a sharp increase in the error of the lost gas calculation; when the downhole desorbed gas is zero, the lost gas cannot be obtained through inversion, and the measurement results are completely distorted.

[0004] While existing pressure-holding coring technology can reduce gas loss, it suffers from drawbacks such as complex operating principles, high equipment costs, high sealing failure rates, and low sampling success rates, hindering its large-scale application. Therefore, the core challenge for accurate coal seam gas content determination lies in how to collect desorbed gas from coal samples in real time during coring, thereby eliminating errors in estimating gas loss at its source. Summary of the Invention

[0005] To overcome the shortcomings of existing coal seam gas content determination technologies, such as large errors in estimating gas loss, complex operation of pressure-holding coring equipment, high cost, and poor sealing reliability, the present invention aims to provide a method for simultaneous collection of desorbed gas during coal seam coring. This method achieves real-time sealing of coal samples and full-process collection of desorbed gas during coring, thereby eliminating the error in estimating gas loss at its source and significantly improving the accuracy of coal seam gas content determination.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: The method for simultaneous collection of desorbed gas during coal seam coring is implemented using integrated equipment for coal sample coring and desorbed gas collection. This integrated equipment includes a coal sample collection unit, a gas collection unit, and an end connection unit arranged coaxially from front to back along the coring drilling direction. The rear end of the coal sample collection unit and the front end of the gas collection unit are coaxially and sealed together through matching internal and external threads. The rear end of the gas collection unit and the front end of the end connection unit are also coaxially and sealed together through matching internal and external threads. The rear end of the end connection unit is machined with an external thread interface adapted to conventional drill pipes in coal mines to achieve a rigid connection between the equipment and the drill pipe. The method includes the following steps: S1, Coal sample collection unit assembly; S2. Assembly and pretreatment of gas collection unit; S3. Overall assembly of the core sampling equipment; S4. Sampling hole construction and equipment placement; S5. Coal sample collection and desorbed gas collection are carried out simultaneously; S6. Automatic sealing and locking of the sample storage chamber; S7. Measurement of gas quantity during drilling withdrawal and desorption; S8. Disassembly of each unit of equipment and processing of coal samples; S9. Equipment cleaning and reassembly for later use.

[0007] The coal sample collection unit includes a core sampling outer cylinder, a drilling and cutting assembly, a funnel-shaped sample chute, a two-way sealing door, a platform-shaped sealing actuator, a sample storage cylinder, a piston gas guiding assembly, a lever triggering mechanism, and a high-pressure power assembly. The drilling and cutting assembly is fixed to the front end face of the core-taking outer cylinder, and the funnel-shaped sample channel is coaxially fixed to the front end inner cavity of the core-taking outer cylinder. Its inlet is directly opposite to the outlet side of the drilling and cutting assembly, and the bidirectional sealing door is hinged to the inner wall of the funnel-shaped sample channel. The platform-shaped sealing actuator is installed through the side wall of the funnel-shaped slurry channel, with its inner end facing the bidirectional sealing door. The sample storage cylinder is coaxially fixed to the inner cavity of the outer core extraction cylinder, and its front end is coaxially connected to the outlet of the funnel-shaped sample conveying channel. The piston gas guide assembly can be slidably and sealed inside the sample storage cylinder. The lever triggering mechanism is fixed to the outer wall of the rear end of the sample storage cylinder. The high-pressure power assembly is arranged in the annular cavity between the core sampling outer cylinder and the sample storage cylinder, and is respectively matched with the platform-shaped sealing execution assembly and the lever triggering mechanism. The drilling and cutting assembly includes several carbide drill teeth and cross-shaped cutting blades; the several drill teeth are uniformly welded and fixed to the front end face of the core cylinder along the circumference, and the cutting edge of each drill tooth is inclined towards the drilling direction; the cross-shaped cutting blades are fixed to the inner side of the front end face of the core cylinder and located at the feed inlet of the funnel-shaped sample channel. The cutting plane of the cutting blades is parallel to the cutting end face of the drill teeth, and is used to crush the large coal sample cut by the drill teeth into uniform particles. The funnel-shaped sample sluice channel is a square cross-section variable diameter channel, with its inner diameter gradually increasing from front to back. The front end face of the core outer cylinder of the funnel-shaped sample sluice channel is welded and fixed. The bidirectional sealing door is a rectangular metal door panel, the side of which is hinged to the inner wall of the funnel-shaped sample sluice channel through a hinge with a return torsion spring. The outer edge of the door panel is covered with a rubber sealing layer. The bidirectional sealing door remains closed in its natural state. When pushed by the coal sample, it can rotate and open towards the sample storage cylinder to form a sample passage. When pushed by the platform-shaped sealing actuator, it can rotate and close in the opposite direction, completely sealing the entire cross-section of the funnel-shaped sample sluice channel. The platform-shaped sealing actuator includes a platform-shaped hollow cylinder and a hexagonal platform-shaped nut integrally formed on the outer end of the cylinder. The outer wall of the platform-shaped hollow cylinder is machined with external threads, and the side wall of the funnel-shaped sample channel is provided with matching threaded through holes. The platform-shaped hollow cylinder is screwed into the threaded through holes through thread engagement. The platform-shaped nut at its outer end fits against the outer wall of the core-taking outer cylinder, and the inner end extends into the funnel-shaped sample channel and faces the front side of the bidirectional sealing door. The inner cavity of the platform-shaped hollow cylinder is equipped with an inflatable bladder. The side wall of the cylinder is provided with an air inlet communicating with the bladder and an injection hole communicating with the inner cavity of the cylinder. The piston-guided gas assembly includes a circular piston, an O-ring seal, a hollow wall cylinder, a gas guide tube, and a puncture hollow needle. The circular piston is coaxially disposed inside the sample storage cylinder, and its outer circumferential surface has at least two annular sealing grooves. The O-ring seal is embedded in the annular sealing grooves and is interference-fitted with the inner wall of the sample storage cylinder to form a dynamic sealing structure that can slide axially. The center of the circular piston has an axially penetrating vent hole. The hollow wall cylinder is a rigid circular tube with open ends. Its front end is coaxially welded and fixed to the rear end face of the circular piston. The vent hole of the piston is coaxially connected to the inner hole of the hollow wall cylinder. The gas guide tube is coaxially inserted into the inner hole of the hollow wall cylinder. The front end of the gas guide tube is connected to the vent hole of the piston by a threaded seal. The rear end of the gas guide tube extends out of the rear end face of the hollow wall cylinder and is coaxially welded and fixed to the puncture hollow needle. The rear end of the puncture hollow needle is a tapered puncture tip. The lever triggering mechanism includes an upper convex groove, a lower convex groove, an upper lever rod, and a lower lever rod. Both the upper and lower convex grooves are U-shaped grooves within hinged lugs, welded and fixed to the upper and lower outer walls of the sample storage cylinder's rear end, respectively. The middle part of the upper lever rod is hinged to the upper convex groove via a hinged pivot, forming a lever structure with the pivot as the fulcrum. An upper trigger plate is welded to its front end, directly above the rear end face of the hollow cylinder, and its rear end is located directly above the foam bottle switch of the high-pressure power assembly. The middle part of the lower lever rod is hinged to the lower convex groove via a hinged pivot, forming a lever structure with the pivot as the fulcrum. A lower trigger plate is welded to its front end, directly below the rear end face of the hollow cylinder, and its rear end is located directly above the high-pressure gas cylinder switch of the high-pressure power assembly. The high-pressure power assembly includes a high-pressure nitrogen cylinder, a rapid-expanding foam bottle, a high-pressure gas pipeline, a glue injection pipeline, a first fixing bolt, and a second fixing bolt. The centerlines of both the high-pressure nitrogen cylinder and the rapid-expanding foam bottle are parallel to the centerline of the outer core cylinder. The high-pressure nitrogen cylinder and the rapid-expanding foam bottle are symmetrically mounted in the annular cavity between the outer core cylinder and the sample storage cylinder, with the bottle openings facing the rear end of the sample storage cylinder. One end of the high-pressure gas pipeline is sealed to the outlet of the high-pressure nitrogen cylinder, and the other end is sealed to the inlet of the platform-shaped hollow cylinder. One end of the glue injection pipeline is connected to the rapid-expanding foam bottle. The outlet of the core-taking cylinder is sealed and connected, while the other end is sealed and connected to the injection hole of the platform-shaped hollow cylinder. Two threaded through holes are opened on the side wall of the core-taking outer cylinder. The first fixing bolt and the second fixing bolt are screwed into the corresponding threaded through holes. The inner end of the first fixing bolt extends into and is threadedly connected to the bottom of the high-pressure nitrogen cylinder, and the inner end of the second fixing bolt extends into and is threadedly connected to the bottom of the rapid foaming glue bottle, thereby achieving axial fixation of the high-pressure nitrogen cylinder and the rapid foaming glue bottle. The outer wall of the rear end of the core-taking outer cylinder is machined with external threads for sealing connection with the front internal threads of the gas collection unit.

[0008] The gas collection unit includes a gas collection cylinder, a concave gas collection channel, a puncture sealing assembly, a gas collection chamber, an extraction pipe, and a ball valve. The concave gas collection channel is coaxially welded and fixed to the front end face of the gas collection cylinder. A large-diameter countersunk hole and a small-diameter through hole are coaxially connected at its center. The large-diameter countersunk hole is located on the front side and has internal threads machined on its inner wall. The small-diameter through hole is located on the rear side and communicates with the inner cavity of the gas collection cylinder. The puncture sealing assembly includes a hollow bolt and a rubber sealing gasket. The rubber sealing gasket is embedded in the rear stepped surface of the large-diameter countersunk hole. The bolt is screwed into the internal thread of the large-diameter countersunk hole, and its rear end face is squeezed to form a static seal with a rubber sealing gasket. The center of the hollow bolt has a guide hole that fits with the piercing hollow needle. The internal cavity of the gas collection cylinder is a gas collection chamber. The gas extraction pipe is coaxially welded and fixed to the rear end face of the gas collection cylinder and communicates with the gas collection chamber. The rear end of the gas extraction pipe is sealed to the ball stop valve through a tapered pipe thread. The inner wall of the front end of the gas collection cylinder is machined with an internal thread that matches the coal sample collection unit, and the outer wall of the rear end is machined with an external thread that matches the end connection unit. The end connection unit is an integrated rigid straight connector. Its front inner wall is machined with an internal thread that matches the external thread at the rear end of the gas collection cylinder. The external thread machined on the rear outer wall is a thread commonly used in coal mine drill pipes. The inner diameter of the central through hole of the connector is not less than the inner diameter of the gas collection chamber of the gas collection cylinder, ensuring the coaxiality and fluid conductivity of the entire equipment.

[0009] The specific process of step S1 is as follows: The front end of the gas guide tube is screwed into the central vent hole of the circular piston through a thread to complete the sealing connection; two O-rings are respectively embedded in the annular sealing groove of the piston; the piston is pushed in from the rear end of the sample storage cylinder until it reaches the front end of the sample storage cylinder; the capsule is placed into the inner cavity of the platform-shaped hollow cylinder; one end of the high-pressure gas pipeline is sealed to the air inlet of the capsule, and one end of the glue injection pipeline is sealed to the glue injection hole of the platform-shaped hollow cylinder; the platform-shaped hollow cylinder is screwed into the side wall threaded through hole of the funnel-shaped sample channel through an external thread until the platform-shaped nut is in contact with the outer wall of the core extraction outer cylinder; the other end of the high-pressure gas pipeline... One end is connected to the outlet of the high-pressure nitrogen cylinder, and the other end of the glue injection pipeline is connected to the outlet of the quick-blowing glue bottle; the gas cylinder and the glue bottle are clamped into the annular cavity between the core sampling outer cylinder and the sample storage cylinder, and the first fixing bolt and the second fixing bolt are screwed into the threaded through hole of the core sampling outer cylinder respectively, and the cylinder bottom is tightened to complete the fixation; the upper lever and the lower lever are installed in the upper and lower convex grooves respectively through the hinge shaft, and the positions are adjusted so that the upper trigger plate and the lower trigger plate are facing the rear end face of the hollow wall cylinder, and the rear ends of the upper lever and the lower lever are facing the push-button switch of the glue bottle and the push-button switch of the gas cylinder respectively, thus completing the assembly of the coal sample collection unit.

[0010] The specific process of step S2 is as follows: The rubber sealing gasket is embedded in the stepped surface of the large-diameter countersunk hole in the concave gas collecting channel. The hollow bolt is screwed into the internal thread of the large-diameter countersunk hole. After tightening, the rubber sealing gasket is squeezed to complete the static seal. The volume of the gas collecting chamber is calibrated: Clean water is injected into the gas collecting chamber through the ball valve and the extraction pipe until water overflows from the small-diameter through-hole, expelling all air from the chamber. The volume of injected water is recorded as the calibrated volume of the gas collecting chamber. V 1 Pour out all the water from the gas collection chamber and dry it with compressed air; in this step S2, the volume calibration of the gas collection chamber is only performed when the equipment is used for the first time, and the volume calibrated during the first use is directly adopted for subsequent uses. V 1 Connect the right end of the extraction pipe to the downhole vacuum pump, open the ball valve, start the vacuum pump to evacuate the gas collection chamber until the vacuum level drops below 20 Pa, close the ball valve to create a stable negative pressure environment in the gas collection chamber, and complete the pretreatment of the gas collection unit.

[0011] The specific process of step S3 is as follows: screw the external thread at the rear end of the assembled coal sample collection unit into the internal thread at the front end of the gas collection unit, and tighten to complete the coaxial sealing connection; screw the external thread at the rear end of the gas collection unit into the internal thread at the front end of the end connection unit, and tighten to complete the connection, forming an integrated coring equipment; tighten and fix the external thread at the rear end of the end connection unit to the internal thread of the conventional downhole drill pipe, and complete the connection between the equipment and the drill pipe. Step S4 is as follows: Using a conventional downhole drilling rig with ordinary drill pipes, drill to the predetermined sampling position of the target coal seam, stop drilling and withdraw all ordinary drill pipes; extend the drill pipes connected to the integrated coring equipment one by one, and slowly send them into the borehole through the drilling rig until the integrated coring equipment reaches the predetermined sampling position, ready for coring operation.

[0012] The specific process of step S5 is as follows: Start the drilling rig, drive the integrated coring equipment to rotate through the drill rod, the drill teeth cut the coal seam to form a coal sample, the coal sample enters the coring equipment with the rotation, after being crushed into uniform particles by the cross-shaped blades, the sample is pushed by the funnel-shaped sample passage to rotate and open the bidirectional sealing door towards the sample storage cylinder, and the coal sample enters the sample storage cylinder; as the coal sample continues to enter, it pushes the circular piston to move backward along the inner wall of the sample storage cylinder, and simultaneously drives the hollow wall cylinder, the gas guide pipe and the piercing hollow needle to move backward. When the piston moves backward to the preset position, the conical tip of the piercing hollow needle passes through the central guide hole of the hollow bolt, punctures the rubber sealing gasket, and connects the sample storage cylinder with the negative pressure gas collection chamber. The gas desorbed by the coal sample in the sample storage cylinder during the coring process is sucked into and stored in real time by the negative pressure gas collection chamber, and there is no gas leakage throughout the process.

[0013] The specific process of step S6 is as follows: When the piston continues to move backward to the preset position at the rear end of the sample storage cylinder, the coal sample fills the sample storage cylinder. At this time, the rear end face of the hollow wall cylinder simultaneously squeezes the upper trigger plate and the lower trigger plate. Through the lever structure, the rear ends of the upper lever pressure rod and the lower lever pressure rod rotate downward simultaneously. At the same time, the press-type switch of the gas cylinder and the press-type switch of the foam bottle are opened. The high-pressure nitrogen in the high-pressure nitrogen cylinder is quickly filled into the bag through the high-pressure gas pipeline. The bag expands instantly and extends out from the platform-shaped hollow cylinder, pushing the bidirectional sealing door to rotate in the opposite direction and close, completely blocking the funnel-shaped sample passage and isolating the sample storage cylinder from the external environment of the borehole. At the same time, the foam in the rapid foam bottle is injected into the platform-shaped hollow cylinder through the glue injection pipeline, filling the gap between the bidirectional sealing door and the inner wall of the sample passage. The foam quickly solidifies, realizing the locking of the bidirectional sealing door and the secondary sealing of the sample passage, so that the sample storage cylinder and the gas collection chamber form a completely sealed cavity, and the sampling is completed.

[0014] The specific process of step S7 is as follows: After sampling is completed, stop the drilling rig, slowly withdraw all drill pipes, remove the integrated coring equipment from the borehole, and separate the equipment from the drill pipes; disconnect the end connection unit, seal the ball valve at the rear end of the gas collection unit to the air inlet of the downhole gas desorption instrument, slowly open the ball valve, measure the gas desorption amount through the desorption instrument until the desorption instrument reading does not change, indicating that the gas desorption is complete, and record the gas desorption amount measured by the desorption instrument. V 2; Calculate the volume using the gas collection chamber. V 1. Downhole ambient temperature T Atmospheric pressure P 0. Using the ideal gas law, the gas volume in the gas collecting chamber is converted to its standard condition volume and compared with the volume measured by the desorption instrument. V Adding the two together, we get the total amount of desorbed gas under standard conditions ( ). V 1 + V 2).

[0015] The specific process of step S8 is as follows: disassemble the coal sample collection unit and the gas collection unit, and disassemble each component separately: unscrew the first fixing bolt and the second fixing bolt, take out the high-pressure nitrogen cylinder and the quick-blowing foam bottle, and disconnect the high-pressure gas pipeline and the glue injection pipeline; unscrew the table-shaped hollow cylinder, remove the bag and the remaining cured foam; remove the upper lever and the lower lever, pull the piston and the gas guide tube out of the sample storage cylinder, pour out the coal sample in the sample storage cylinder, put it into the standard coal sample container and seal it for storage, and send it to the laboratory within 24 hours to determine the residual gas content of the coal sample; unscrew the hollow bolt of the gas collection unit and remove the used rubber sealing gasket; Step S9 is as follows: Clean all parts of the equipment of coal dust and residual foam, replace the rubber gasket, O-ring, and bladder, replace the high-pressure nitrogen cylinder and the rapid foam bottle, and then reassemble according to the above assembly steps for the next sampling.

[0016] Using the above technical solution, the specific functions of the three units of the integrated coal sample coring, desorption, and gas collection equipment are as follows: (I) Functions of each component in the coal sample collection unit 1. Core cylinder: The main load-bearing structure of the coal sample collection unit, providing installation and protection space for internal components, while bearing the torque and feed force during drilling and transmitting the drilling power of the drilling rig.

[0017] 2. Drilling and cutting components: Carbide drill teeth are responsible for rotating and cutting the coal seam to form a continuous coal sample; cross-shaped cutting blades are responsible for crushing large coal samples into uniform particles to avoid clogging the sample passage, ensuring that the coal sample enters the sample storage cylinder smoothly, and increasing the exposed area of ​​the coal sample to allow for the full release of desorbed gas.

[0018] 3. Funnel-shaped sample passage: It adopts a square cross-section variable diameter structure with the inner diameter gradually increasing from front to back, which can guide the crushed coal sample smoothly into the sample storage cylinder, and at the same time provide a stable installation position for the two-way sealing door and the platform-shaped sealing actuator.

[0019] 4. Two-way sealing door: The hinged structure with a reset torsion spring can be rotated to open in the direction of the sample storage cylinder when the coal sample enters, forming a sample passage; when sealed, it can be pushed by the bag to rotate in the opposite direction to close, and the outer edge is completely attached to the inner wall of the sample passage, sealing the sample passage across the entire cross section, isolating the sample storage cylinder from the external environment of the borehole, and preventing gas from escaping.

[0020] 5. Platform-shaped sealing actuator: The platform-shaped hollow cylinder provides space for the containment and conveying of the bladder and foam. It can be detached and installed by external thread, making disassembly and assembly convenient. The platform-shaped nut at the outer end is easy to tighten. The air inlet and glue injection hole on the side wall of the cylinder connect the bladder and the inner cavity of the cylinder, respectively, realizing the dual functions of inflation expansion and glue injection sealing.

[0021] 6. Sample storage cylinder: It provides a sealed storage space for coal samples, serves as the initial release chamber for coal sample desorption of gas, provides a sliding reference for the piston gas guiding assembly, and provides a fixed installation point for the lever triggering mechanism to ensure the coaxiality and action accuracy of each moving part.

[0022] 7. Piston-guided gas assembly: The circular piston moves axially along the sample storage cylinder as the coal sample accumulates, forming a dynamic seal with the inner wall of the sample storage cylinder through an O-ring to prevent gas from escaping from the rear end of the sample storage cylinder; the hollow wall cylinder is fixedly connected to the piston to provide protection for the gas guide tube, and at the same time acts as a trigger to drive the lever trigger mechanism; the gas guide tube and the piercing hollow needle are used to connect the sample storage cylinder and the gas collection chamber to realize the conduction and collection of desorbed gas.

[0023] 8. Lever triggering mechanism: Through the hinged lever structure, the axial linear movement of the hollow cylinder is converted into vertical downward pressure on the gas cylinder push-button switch. The lever amplification principle ensures reliable switch triggering, realizing automatic triggering of sealing action after the coal sample is filled, without manual intervention, and is suitable for unmanned drilling scenarios in underground mines.

[0024] 9. High-pressure power assembly: The high-pressure nitrogen cylinder provides a high-pressure power source for the expansion of the bladder, ensuring reliable closure of the two-way sealing door; the rapid-expanding foam bottle provides polyurethane rapid-expanding foam to fill the sealing gap and achieve secondary locking seal; the first fixing bolt and the second fixing bolt ensure reliable axial fixation of the gas cylinder and the foam bottle, preventing cylinder vibration and displacement during drilling and ensuring triggering accuracy.

[0025] (II) Functions of each component in the gas collection unit 1. Gas collection cylinder: The main structure of the gas collection unit, providing a sealed pressure space for the gas collection chamber, and providing installation points for the front and rear connecting threads, concave gas collection channels and gas extraction pipes, ensuring the coaxiality of each component.

[0026] 2. Concave gas collection channel: Provides installation space for the puncture sealing assembly. The coaxially arranged large-diameter countersunk hole and small-diameter through hole form a stepped guide structure, ensuring that the puncture hollow needle accurately punctures the rubber sealing gasket, while avoiding needle deviation and bending.

[0027] 3. Puncture sealing assembly: Hollow bolts are used to compress and fix the rubber sealing gasket to ensure the initial seal of the gas collection chamber. At the same time, the central guide hole provides a guide for the hollow needle. When the rubber sealing gasket is not punctured, it ensures the vacuum of the gas collection chamber. After being punctured by the hollow needle, it can rely on its own elasticity to fit tightly against the outer wall of the needle to form a dynamic seal and prevent gas from leaking from the puncture gap.

[0028] 4. Gas collection chamber: Used to store the gas desorbed from the coal sample during the entire coring process. By pre-vacuuming to create a negative pressure environment, it can actively adsorb the desorbed gas in the sample storage cylinder, achieving gas collection without leakage.

[0029] 5. Evacuation pipe and ball shut-off valve: The extraction pipe is used to connect the gas collection chamber to the external vacuum pump and desorption instrument; the ball shut-off valve is used to control the opening and closing of the gas collection chamber. It is open when vacuuming, closed to maintain pressure during sampling, and open to connect to the desorption instrument during desorption measurement. It is easy to operate and has a reliable seal.

[0030] (III) Functions of the end connection unit: The integrated rigid straight connector is mainly used to realize the rigid connection between the gas collection unit and the drilling rod, reliably transmit the torque and feed force of the drilling rig, and adapt to the conventional drilling rod in the coal mine through the thread, without the need to modify the existing drilling equipment, and has strong adaptability; it ensures the coaxiality of the equipment as a whole and prevents the equipment from wearing out during the drilling process, which may lead to sealing failure.

[0031] In summary, compared with the prior art, the overall technical effects of the present invention are as follows: (1) It achieves rapid sealing and can collect desorbed gas during the coal sample core taking process. It is safe and easy to operate, eliminates the error of lost gas quantity from the root, and achieves a qualitative leap in measurement accuracy: This invention realizes real-time, non-escape collection of coal sample desorbed gas during the entire core taking process. From the moment the coal sample enters the storage cylinder after cutting, the desorbed gas is collected by the negative pressure gas collection chamber throughout the process. There is no gas escape loss. There is no need to calculate the lost gas quantity through inversion of underground desorption data. It completely solves the industry pain point of excessive sampling time and distorted measurement results when the desorption quantity is zero. The accuracy of coal seam gas content measurement is greatly improved.

[0032] (2) Integrated linkage design, reliable sealing and convenient operation: The present invention realizes the integrated linkage of gas collection channel opening and sealing mechanism triggering through the axial movement of piston. When the coal sample is filled into the sample storage cylinder, the three main actions of gas channel connection, mechanical sealing of sample chute, and secondary sealing and locking with foam adhesive are automatically completed. No additional manual operation is required. It is fully compatible with conventional drilling technology in coal mines and greatly reduces the difficulty of underground operation and the labor intensity of personnel. The dual sealing structure of mechanical sealing and foam adhesive filling has an extremely low sealing failure rate, which can ensure the absolute sealing of sample storage cylinder and gas collection chamber and prevent gas from escaping.

[0033] (3) Modular design, low cost and strong adaptability: The present invention adopts three independent modular units for coal sample collection, gas collection and end connection. It is easy to disassemble and assemble, and simple to maintain. Consumables such as rubber gaskets, O-rings and bags can be quickly replaced and the equipment can be reused. No special drilling equipment is required. It can be directly adapted to conventional drilling rigs and drill rods in coal mines. The equipment cost is only 1 / 5 to 1 / 3 of the existing pressure-holding coring equipment, which has the conditions for large-scale promotion and application.

[0034] (4) High safety and wide applicability of coring operation: The invention completes gas collection in a closed cavity throughout the process, with no risk of gas leakage, and is suitable for sampling operations in high gas, coal and gas outburst coal seams; it can meet the coring needs of coal seams with different apertures and different sampling depths. Whether it is shallow hole rapid sampling or deep hole long distance sampling, it can achieve full collection of desorbed gas and has a wide range of applicable scenarios. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the overall structure of the integrated coal sample coring, desorption, and gas collection equipment of the present invention; Figure 2 This is a schematic diagram of the coal sample collection unit in this invention; Figure 3 This is a schematic diagram of the gas collection unit in this invention; Figure 4 This is a schematic diagram of the end connection unit in this invention; Figure 5 This is a schematic diagram of the cooperation structure between the sample storage cylinder and the piston gas guiding assembly in this invention; Figure 6 This is a schematic diagram of the integrated coring equipment after sampling is completed in this invention.

[0036] Explanation of reference numerals in the attached diagram: 1-Coal sample collection unit; 2-Gas collection unit; 3-End connection unit; 4-Drill teeth; 5-Funnel-shaped sample channel; 6-Two-way sealing door; 7-Sample storage cylinder; 8-Gas delivery tube; 9-Piercing hollow needle; 10-Circular piston; 11-O-ring seal; 12-Hollow wall cylinder; 13-Lower lever; 14-Upper groove; 15-Gas cylinder push-button switch; 16-High-pressure nitrogen cylinder; 17-First fixing bolt; 18-High-pressure gas pipeline; 19-Glue injection pipeline; 20-Bag; 21-Platform nut; 22-Upper trigger plate; 23-Rapid foaming glue bottle; 24-Cross-shaped cross blade; 25-Front end face of the core sampling outer cylinder; 2 6-External thread; 27-External thread; 28-Platform-shaped hollow cylinder; 29-Lower groove; 30-Foam bottle push-button switch; 31-Upper lever rod; 32-Second fixing bolt; 33-Lower trigger plate; 34-Inner wall of the sample channel; 35-Rubber sealing gasket; 36-Concave gas collection channel; 37-Spherical shut-off valve; 38-Gas extraction pipe; 39-Internal thread; 40-Front end face of gas collection cylinder; 41-Rear end face of gas collection cylinder; 42-Gas collection chamber; 43-Hollow bolt; 44-Small diameter through hole; 45-Large diameter countersunk hole; 46-External thread; 47-Gas collection cylinder; 48-Internal thread; 49-External thread; 50-Core extraction outer cylinder. Detailed Implementation

[0037] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0038] This embodiment provides a method for simultaneous collection of desorbed gas during coal seam coring, implemented using an integrated coal sample coring and desorbed gas collection device. The overall structure of the integrated coal sample coring and desorbed gas collection device is as follows: Figure 1 As shown, the system includes a coal sample collection unit 1, a gas collection unit 2, and an end connection unit 3, which are coaxially arranged from front to back along the core drilling direction. The outer wall of the rear end of the coal sample collection unit 1 is machined with an external thread 26, and the inner wall of the front end of the gas collection unit 2 is machined with an internal thread 39. The two are connected by coaxial tightening through a tapered tube sealing thread, and an end face sealing gasket is embedded between the mating end faces. The outer wall of the rear end of the gas collection unit 2 is machined with an external thread 46, and the inner wall of the front end of the end connection unit 3 is machined with an internal thread 48. The two are connected by a threaded seal. The outer wall of the rear end of the end connection unit 3 is machined with an external thread 49, which is an API standard thread adapted to conventional drill pipes in coal mines, and is used for rigid connection with the drill pipe.

[0039] The method includes the following steps: S1, Coal sample collection unit assembly; S2. Assembly and pretreatment of gas collection unit; S3. Overall assembly of the core sampling equipment; S4. Sampling hole construction and equipment placement; S5. Coal sample collection and desorbed gas collection are carried out simultaneously; S6. Automatic sealing and locking of the sample storage chamber; S7. Measurement of gas quantity during drilling withdrawal and desorption; S8. Disassembly of each unit of equipment and processing of coal samples; S9. Equipment cleaning and reassembly for later use.

[0040] like Figure 2 As shown, the coal sample collection unit 1 includes a core sampling outer cylinder 50, a drilling and cutting assembly, a funnel-shaped sample conveying channel 5, a two-way sealing door 6, a platform-shaped sealing execution assembly, a sample storage cylinder 7, a piston gas guiding assembly, a lever triggering mechanism, and a high-pressure power assembly.

[0041] The drilling and cutting assembly includes four carbide drill teeth 4 and cross-shaped cutting blades 24. The four drill teeth 4 are uniformly welded and fixed to the front end face 25 of the core extraction outer cylinder 50 along the circumference. The cutting edge of each drill tooth is inclined at 15° towards the drilling direction. The cross-shaped cutting blades 24 are welded and fixed to the inner side of the front end face 25 of the core extraction outer cylinder 50 and are located at the feed inlet of the funnel-shaped sample channel 5. The cutting plane of the cross-shaped cutting blades is parallel to the cutting end face of the drill teeth, and the axial distance between the two is 10mm.

[0042] The funnel-shaped sampling channel 5 is a square cross-section variable diameter channel with an inner diameter that gradually increases from front to back. The funnel-shaped sampling channel 5 is welded and fixed to the front end face 25 of the core sampling outer cylinder 50, and the rear end is coaxially welded and connected to the front end of the sample storage cylinder 7. The bidirectional sealing door 6 is a rectangular metal door panel, the side of which is hinged to the inner wall face 34 of the funnel-shaped sampling channel 5 through a hinge with a return torsion spring. The outer edge of the door panel is covered with a 2mm thick nitrile rubber sealing layer. The bidirectional sealing door 6 is naturally kept closed under the action of the return torsion spring. When pushed by the coal sample, it can rotate and open in the direction of the sample storage cylinder 7 to form a sample passage. When pushed by the bag, it can rotate and close in the opposite direction to completely block the entire cross-section of the sampling channel.

[0043] The platform-shaped sealing actuator includes a platform-shaped hollow cylinder 28 and a hexagonal platform-shaped nut 21 integrally formed on the outer end of the cylinder. The outer wall of the platform-shaped hollow cylinder 28 is machined with external threads 27. The side wall of the funnel-shaped sample channel 5 is provided with matching threaded through holes. The platform-shaped hollow cylinder 28 is screwed into the threaded through holes through thread engagement. The platform-shaped nut 21 at the outer end fits against the outer wall of the core-taking outer cylinder 50, and the inner end extends into the funnel-shaped sample channel 5, facing the front side of the bidirectional sealing door 6. The inner cavity of the platform-shaped hollow cylinder 28 is equipped with a nylon composite rubber bag 20. The side wall of the platform-shaped hollow cylinder 28 is provided with an air inlet communicating with the bag 20 and an injection hole communicating with the inner cavity of the platform-shaped hollow cylinder 28.

[0044] like Figure 5 As shown, the piston air guide assembly includes a circular piston 10, an O-ring seal 11, a hollow wall cylinder 12, an air guide tube 8, and a puncture hollow needle 9. A circular piston 10 is coaxially disposed inside the sample storage cylinder 7. Two annular sealing grooves are formed on its outer circumference. An O-ring 11 is embedded in the sealing groove and is press-fitted with the inner wall of the sample storage cylinder 7 to form a dynamic sealing structure that can slide along the axial direction. An axially penetrating vent hole is formed in the center of the circular piston 10. The hollow wall cylinder 12 is a seamless steel pipe with open ends. Its front end is coaxially welded and fixed to the rear end face of the circular piston 10. The vent hole of the piston is coaxially connected to the inner hole of the hollow wall cylinder 12 and has the same inner diameter. The air guide pipe 8 is a stainless steel air pipe that is coaxially inserted into the inner hole of the hollow wall cylinder 12. The front end of the air guide pipe 8 is sealed and connected to the vent hole of the piston by a thread. The rear end of the air guide pipe 8 extends out of the rear end face of the hollow wall cylinder 12 and is coaxially welded and fixed to the puncture hollow needle 9. The rear end of the puncture hollow needle 9 is a conical puncture tip, and two radial air outlet holes are formed on the side wall.

[0045] The lever triggering mechanism includes an upper convex groove 14, a lower convex groove 29, an upper lever pressure rod 31, and a lower lever pressure rod 13. The upper convex groove 14 and the lower convex groove 29 are both U-shaped grooves within hinged lugs, respectively welded and fixed to the upper and lower outer walls of the rear end of the sample storage cylinder 7 (as shown in the diagram, they are actually centrally symmetrically arranged). The middle part of the upper lever pressure rod 31 is hinged to the upper convex groove 14 via a hinged pivot, forming a lever structure with the pivot as the fulcrum. An upper triggering iron plate 22 is welded to its front end, directly above the rear end face of the hollow wall cylinder 12, with its rear end located at the rapid-expanding foam bottle 2. The upper lever 31 and the lower lever 13 are directly above the foam bottle push-button switch 30; the middle part of the lower lever rod 13 is hinged to the lower protrusion 29 through the hinge shaft, forming a lever structure with the shaft as the fulcrum. The lower trigger plate 33 is welded to the front end of the lower lever rod 31, which is directly below the rear end face of the hollow wall cylinder 12. Its rear end is located directly above the cylinder push-button switch 15 of the high-pressure nitrogen cylinder 16; the ratio of the power arm to the resistance arm of the upper lever rod 31 and the lower lever rod 13 is 2 to 5:1.

[0046] The high-pressure power assembly includes a high-pressure nitrogen cylinder 16, a rapid-expanding foam bottle 23, a high-pressure gas pipeline 18, a glue injection pipeline 19, and fixing bolts 17 and 32. The high-pressure nitrogen cylinder 16 and the rapid-expanding foam bottle 23 are symmetrically mounted in the annular cavity between the core sampling outer cylinder 50 and the sample storage cylinder 7, with the openings of both cylinders facing the rear end of the sample storage cylinder 7. One end of the high-pressure gas pipeline 18 is sealed to the outlet of the high-pressure nitrogen cylinder 16, and the other end is sealed to the inlet of the platform-shaped hollow cylinder 28. One end of the glue injection pipeline 19 is sealed to the outlet of the rapid-expanding foam bottle 23, and the other end is sealed to the glue injection hole of the platform-shaped hollow cylinder 28. Two threaded through holes are provided on the side wall of the core sampling outer cylinder 50. Fixing bolts 17 and 32 are screwed into these threaded through holes, with their inner ends abutting against the bottom of the gas cylinder and the glue bottle, respectively, to achieve axial fixation of the cylinders.

[0047] like Figure 3As shown, the gas collection unit 2 includes a gas collection cylinder 47, a concave gas collection channel 36, a puncture sealing assembly, a gas collection chamber 42, an extraction pipe 38, and a ball shut-off valve 37. The concave gas collection channel 36 is coaxially welded and fixed to the front end face 40 of the gas collection cylinder. A large-diameter countersunk hole 45 and a small-diameter through hole 44 are coaxially connected in the center. The large-diameter countersunk hole 45 is located on the front side and has internal threads on its inner wall. The small-diameter through hole 44 is located on the rear side and communicates with the gas collection chamber 42. The puncture sealing assembly includes a hollow bolt 43 and a rubber sealing gasket 35. The rubber sealing gasket 35 is made of fluororubber and is 3mm thick. It is embedded in the rear stepped surface of the large-diameter countersunk hole 45. The hollow bolt 43 is screwed into the internal thread of the large-diameter countersunk hole 45. Its rear end face compresses the rubber sealing gasket 35 to form a static seal. A guide through hole with clearance fit to the puncture hollow needle 9 is opened in the center of the hollow bolt 43. The guide through hole is completely coincident with the central axis of the puncture hollow needle 9, the piston vent hole, and the small-diameter through hole 44.

[0048] The internal cavity of the gas collection cylinder 47 is a gas collection chamber 42 with a calibrated volume of 1000mL and a rated pressure of 1.6MPa. The extraction pipe 38 is coaxially welded and fixed to the rear end face 41 of the gas collection cylinder and communicates with the gas collection chamber 42. The rear end of the extraction pipe 38 is sealed to the ball stop valve 37 through a tapered pipe thread. The outlet end of the ball stop valve 37 is equipped with a standard interface adapted to the downhole gas desorption instrument.

[0049] like Figure 4 As shown, the end connection unit 3 is an integrated steel straight connector. Its front end inner wall is machined with an internal thread 48, which matches the external thread 46 at the rear end of the gas collection cylinder 47. The external thread 49 machined on the rear end outer wall is the API standard thread commonly used in coal mine drill pipes. The inner diameter of the central through hole of the connector is consistent with the inner diameter of the gas collection chamber 42.

[0050] Step S1 is as follows: The front end of the gas guide tube 8 is screwed into the central vent hole of the circular piston 10 to complete the sealing connection; two O-rings 11 are respectively embedded in the annular sealing groove of the piston; the piston is pushed in from the rear end of the sample storage cylinder 7 until it reaches the front end of the sample storage cylinder 7; the bag 20 is placed into the inner cavity of the platform-shaped hollow cylinder 28; one end of the high-pressure gas pipeline 18 is sealed to the air inlet of the bag 20, and one end of the glue injection pipeline 19 is sealed to the glue injection hole of the platform-shaped hollow cylinder 28; the platform-shaped hollow cylinder 28 is screwed into the side wall threaded through hole of the funnel-shaped sample channel 5 through the external thread 27 until the platform-shaped nut 21 is in contact with the outer wall of the core extraction outer cylinder 50; the other end of the high-pressure gas pipeline 18 is connected to the outlet of the high-pressure nitrogen cylinder 16. The other end of the glue injection pipe 19 is connected to the glue outlet of the rapid foaming glue bottle 23; the gas cylinder and the glue bottle are clamped into the annular cavity between the core sampling outer cylinder 50 and the sample storage cylinder 7, and the first fixing bolt 17 and the second fixing bolt 32 are screwed into the threaded through hole of the core sampling outer cylinder 50 respectively, and the threaded connection and abut against the bottom of the high-pressure nitrogen gas cylinder 16 and the rapid foaming glue bottle 23 are fixed; the upper lever pressure rod 31 and the lower lever pressure rod 13 are installed in the upper protrusion 14 and the lower protrusion 29 respectively through the hinge shaft, and the position is adjusted so that the upper trigger iron plate 22 and the lower trigger iron plate 33 are facing the rear end face of the hollow wall cylinder 12, and the rear ends of the upper lever pressure rod 31 and the lower lever pressure rod 13 are facing the foaming glue bottle push switch 30 and the gas cylinder push switch 15 respectively, thus completing the assembly of the coal sample collection unit 1.

[0051] Step S2 is as follows: The rubber sealing gasket 35 is embedded in the stepped surface of the large-diameter countersunk hole 45 in the concave gas collecting channel 36. The hollow bolt 43 is screwed into the internal thread of the large-diameter countersunk hole 45. After tightening, the rubber sealing gasket 35 is compressed to complete the static seal. The volume of the gas collecting chamber 42 is calibrated: Clean water is injected into the gas collecting chamber 42 through the ball valve 37 and the extraction pipe 38 until water overflows from the small-diameter through hole 44, expelling all air from the gas collecting chamber 42. The volume of injected water is recorded as the calibrated volume of the gas collecting chamber 42. V 1 Pour out all the water from the air collection chamber 42 and dry it with compressed air; in this embodiment, the volume calibration of the air collection chamber is only performed when the equipment is used for the first time, and the volume calibrated during the first use is directly adopted for subsequent uses. V 1 Connect the right end of the extraction pipe 38 to the downhole vacuum pump, open the ball valve 37, start the vacuum pump to evacuate the gas collection chamber 42 until the vacuum level drops below 20 Pa, close the ball valve 37 to create a stable negative pressure environment in the gas collection chamber 42, and complete the pretreatment of the gas collection unit 2.

[0052] Step S3 is as follows: Screw the external thread 26 at the rear end of the assembled coal sample collection unit 1 into the internal thread 39 at the front end of the gas collection unit 2, and tighten to complete the coaxial sealing connection; screw the external thread 46 at the rear end of the gas collection unit 2 into the internal thread 48 at the front end of the end connection unit 3, and tighten to complete the connection, forming an integrated coring equipment; tighten and fix the external thread 49 at the rear end of the end connection unit 3 to the internal thread of the conventional downhole drill pipe, and complete the connection between the equipment and the drill pipe.

[0053] Step S4 is as follows: Using a conventional downhole drilling rig with ordinary drill pipes, drill to the predetermined sampling position of the target coal seam, stop drilling and withdraw all ordinary drill pipes; extend the drill pipes connected to the integrated coring equipment one by one, and slowly send them into the borehole through the drilling rig until the integrated coring equipment reaches the predetermined sampling position, ready for coring operation.

[0054] Step S5 is as follows: Start the drilling rig, drive the integrated coring equipment to rotate through the drill rod, the drill teeth 4 cut the coal seam to form a coal sample, the coal sample enters the coring equipment with the rotation, after being crushed into uniform particles by the cross-shaped cross blades 24, it is pushed by the funnel-shaped sample passage 5 to rotate and open the bidirectional sealing door 6 towards the sample storage cylinder 7, and the coal sample enters the sample storage cylinder 7; as the coal sample continues to enter, it pushes the circular piston 10 to move backward along the inner wall of the sample storage cylinder 7, and simultaneously drives the hollow wall cylinder 12, the gas guide pipe 8 and the piercing hollow needle 9 to move backward. When the piston 10 moves backward to the preset position, the conical tip of the piercing hollow needle 9 passes through the central guide hole of the hollow bolt 43 and punctures the rubber sealing gasket 35, so that the sample storage cylinder 7 is connected to the negative pressure gas collection chamber 42. The gas desorbed by the coal sample in the sample storage cylinder 7 during the coring process is sucked into and stored in real time by the negative pressure gas collection chamber 42, and there is no gas leakage throughout the process.

[0055] The specific process of step S6 is as follows: When the piston 10 continues to move backward to the preset position at the rear end of the sample storage cylinder 7, the coal sample fills the sample storage cylinder 7. At this time, the rear end face of the hollow wall cylinder 12 simultaneously squeezes the upper trigger plate 22 and the lower trigger plate 33. Through the lever structure, the rear ends of the upper lever pressure rod 31 and the lower lever pressure rod 13 rotate downward synchronously. At the same time, the lower trigger gas cylinder push switch 15 and the foam bottle push switch 30 are opened. High-pressure nitrogen from the high-pressure nitrogen cylinder 16 is rapidly injected into the bag 20 via the high-pressure gas pipeline 18. The bag 20 expands instantly, extending from the platform-shaped hollow cylinder 28, pushing the bidirectional sealing door 6 to rotate in the opposite direction and close, completely sealing the funnel-shaped sample passage 5 and isolating the sample storage cylinder 7 from the external environment of the borehole. Simultaneously, the expanding foam from the rapid-expanding foam bottle 23 is injected into the platform-shaped hollow cylinder 28 via the injection pipeline 19, filling the gap between the bidirectional sealing door 6 and the inner wall of the sample passage. The expanding foam quickly cures, achieving the locking of the bidirectional sealing door 6 and the secondary sealing of the sample passage, making the sample storage cylinder 7 and the gas collecting chamber 42 form a completely sealed cavity. Sampling is completed, and the state is as follows. Figure 6As shown.

[0056] Step S7 is as follows: After sampling is completed, stop the drilling rig, slowly withdraw all drill pipes, remove the integrated coring equipment from the borehole, and separate the equipment from the drill pipes; disconnect the end connection unit, seal the ball valve at the rear end of the gas collection unit to the air inlet of the downhole gas desorber, slowly open the ball valve, and measure the amount of gas desorption using the desorber until the desorber reading shows no change, indicating complete gas desorption. Record the amount of gas desorption measured by the desorber. V 2; Calculate the volume using the gas collection chamber. V 1. Downhole ambient temperature T Atmospheric pressure P 0. Using the ideal gas law, the gas volume in the gas collecting chamber is converted to its standard condition volume and compared with the volume measured by the desorption instrument. V Adding the two together, we get the total amount of desorbed gas under standard conditions ( ). V 1+ V 2).

[0057] Step S8 is as follows: Disassemble the coal sample collection unit 1 and the gas collection unit 2, and disassemble each component separately: unscrew the first fixing bolt 17 and the second fixing bolt 32, remove the high-pressure nitrogen cylinder 16 and the quick-blowing foam bottle 23, and disconnect the high-pressure gas pipeline 18 and the glue injection pipeline 19; unscrew the table-shaped hollow cylinder 28, remove the bag 20 and the remaining cured foam; remove the two levers, pull out the piston 10 and the gas guide tube 8 from the sample storage cylinder 7, pour out the coal sample in the sample storage cylinder 7, put it into the standard coal sample container, seal and store it, and send it to the laboratory within 24 hours to determine the residual gas content of the coal sample; unscrew the hollow bolt 43 of the gas collection unit 2, and remove the used rubber sealing gasket 35.

[0058] Step S9 is as follows: Clean all parts of the equipment of coal dust and residual foam, replace consumables such as rubber sealing gasket 35, O-ring 11, and bag 20, replace the high-pressure nitrogen cylinder 16 and the rapid foam bottle 23, and reassemble according to the above assembly steps for the next sampling.

[0059] The equipment and method of this embodiment achieve non-escape collection of desorbed gas from coal samples throughout the entire coring process, completely eliminating the estimation error of lost gas amount and significantly improving the accuracy of coal seam gas content determination. At the same time, the equipment is easy to operate, reliably sealed, and inexpensive, and can be directly adapted to conventional drilling equipment in coal mines, possessing extremely strong value for field promotion and application.

[0060] The above embodiments illustrate the basic principles and features of the present invention, but are merely preferred embodiments and are not limited to these embodiments. Those skilled in the art, inspired by this patent, can make many modifications and improvements without departing from the spirit and scope of the claims, all of which fall within the scope of protection of the present invention. Therefore, the scope of this patent and its protection should be determined by the appended claims.

Claims

1. A method for simultaneous collection of desorbed gas during coal seam coring, characterized in that: The process employs an integrated coal sample coring, desorption, and gas collection system. This system comprises a coal sample collection unit, a gas collection unit, and an end-connection unit arranged coaxially from front to back along the coring drilling direction. The rear end of the coal sample collection unit and the front end of the gas collection unit are coaxially and sealed together via matching internal and external threads. Similarly, the rear end of the gas collection unit and the front end of the end-connection unit are coaxially and sealed together via matching internal and external threads. The rear end of the end-connection unit is machined with an external thread interface compatible with conventional drill pipes in coal mines, enabling a rigid connection between the equipment and the drill pipe. The method includes the following steps: S1, Coal sample collection unit assembly; S2. Assembly and pretreatment of gas collection unit; S3. Overall assembly of the core sampling equipment; S4. Sampling hole construction and equipment placement; S5. Coal sample collection and desorbed gas collection are carried out simultaneously; S6. Automatic sealing and locking of the sample storage chamber; S7. Measurement of gas quantity during drilling withdrawal and desorption; S8. Disassembly of each unit of equipment and processing of coal samples; S9. Equipment cleaning and reassembly for later use.

2. The method for simultaneous collection of desorbed gas during coal seam coring according to claim 1, characterized in that: The coal sample collection unit includes a core sampling outer cylinder, a drilling and cutting assembly, a funnel-shaped sample chute, a two-way sealing door, a platform-shaped sealing actuator, a sample storage cylinder, a piston gas guiding assembly, a lever triggering mechanism, and a high-pressure power assembly. The drilling and cutting assembly is fixed to the front end face of the core-taking outer cylinder, and the funnel-shaped sample channel is coaxially fixed to the front end inner cavity of the core-taking outer cylinder. Its inlet is directly opposite to the outlet side of the drilling and cutting assembly, and the bidirectional sealing door is hinged to the inner wall of the funnel-shaped sample channel. The platform-shaped sealing actuator is installed through the side wall of the funnel-shaped slurry channel, with its inner end facing the bidirectional sealing door. The sample storage cylinder is coaxially fixed to the inner cavity of the outer core extraction cylinder, and its front end is coaxially connected to the outlet of the funnel-shaped sample conveying channel. The piston gas guide assembly can be slidably and sealed inside the sample storage cylinder. The lever triggering mechanism is fixed to the outer wall of the rear end of the sample storage cylinder. The high-pressure power assembly is arranged in the annular cavity between the core sampling outer cylinder and the sample storage cylinder, and is respectively matched with the platform-shaped sealing execution assembly and the lever triggering mechanism. The drilling and cutting assembly includes several carbide drill teeth and cross-shaped cutting blades; the several drill teeth are uniformly welded and fixed to the front end face of the core cylinder along the circumference, and the cutting edge of each drill tooth is inclined towards the drilling direction; the cross-shaped cutting blades are fixed to the inner side of the front end face of the core cylinder and located at the feed inlet of the funnel-shaped sample channel. The cutting plane of the cutting blades is parallel to the cutting end face of the drill teeth, and is used to crush the large coal sample cut by the drill teeth into uniform particles. The funnel-shaped sample sluice channel is a square cross-section variable diameter channel, with its inner diameter gradually increasing from front to back. The front end face of the core outer cylinder of the funnel-shaped sample sluice channel is welded and fixed. The bidirectional sealing door is a rectangular metal door panel, the side of which is hinged to the inner wall of the funnel-shaped sample sluice channel through a hinge with a return torsion spring. The outer edge of the door panel is covered with a rubber sealing layer. The bidirectional sealing door remains closed in its natural state. When pushed by the coal sample, it can rotate and open towards the sample storage cylinder to form a sample passage. When pushed by the platform-shaped sealing actuator, it can rotate and close in the opposite direction, completely sealing the entire cross-section of the funnel-shaped sample sluice channel. The platform-shaped sealing actuator includes a platform-shaped hollow cylinder and a hexagonal platform-shaped nut integrally formed on the outer end of the cylinder. The outer wall of the platform-shaped hollow cylinder is machined with external threads, and the side wall of the funnel-shaped sample channel is provided with matching threaded through holes. The platform-shaped hollow cylinder is screwed into the threaded through holes through thread engagement. The platform-shaped nut at its outer end fits against the outer wall of the core-taking outer cylinder, and the inner end extends into the funnel-shaped sample channel and faces the front side of the bidirectional sealing door. The inner cavity of the platform-shaped hollow cylinder is equipped with an inflatable bladder. The side wall of the cylinder is provided with an air inlet communicating with the bladder and an injection hole communicating with the inner cavity of the cylinder. The piston-guided gas assembly includes a circular piston, an O-ring seal, a hollow wall cylinder, a gas guide tube, and a puncture hollow needle. The circular piston is coaxially disposed inside the sample storage cylinder, and its outer circumferential surface has at least two annular sealing grooves. The O-ring seal is embedded in the annular sealing grooves and is interference-fitted with the inner wall of the sample storage cylinder to form a dynamic sealing structure that can slide axially. The center of the circular piston has an axially penetrating vent hole. The hollow wall cylinder is a rigid circular tube with open ends. Its front end is coaxially welded and fixed to the rear end face of the circular piston. The vent hole of the piston is coaxially connected to the inner hole of the hollow wall cylinder. The gas guide tube is coaxially inserted into the inner hole of the hollow wall cylinder. The front end of the gas guide tube is connected to the vent hole of the piston by a threaded seal. The rear end of the gas guide tube extends out of the rear end face of the hollow wall cylinder and is coaxially welded and fixed to the puncture hollow needle. The rear end of the puncture hollow needle is a tapered puncture tip. The lever triggering mechanism includes an upper convex groove, a lower convex groove, an upper lever rod, and a lower lever rod. Both the upper and lower convex grooves are U-shaped grooves within hinged lugs, welded and fixed to the upper and lower outer walls of the sample storage cylinder's rear end, respectively. The middle part of the upper lever rod is hinged to the upper convex groove via a hinged pivot, forming a lever structure with the pivot as the fulcrum. An upper trigger plate is welded to its front end, directly above the rear end face of the hollow cylinder, and its rear end is located directly above the foam bottle switch of the high-pressure power assembly. The middle part of the lower lever rod is hinged to the lower convex groove via a hinged pivot, forming a lever structure with the pivot as the fulcrum. A lower trigger plate is welded to its front end, directly below the rear end face of the hollow cylinder, and its rear end is located directly above the high-pressure gas cylinder switch of the high-pressure power assembly. The high-pressure power assembly includes a high-pressure nitrogen cylinder, a rapid-expanding foam bottle, a high-pressure gas pipeline, a glue injection pipeline, a first fixing bolt, and a second fixing bolt. The centerlines of both the high-pressure nitrogen cylinder and the rapid-expanding foam bottle are parallel to the centerline of the outer core cylinder. The high-pressure nitrogen cylinder and the rapid-expanding foam bottle are symmetrically mounted in the annular cavity between the outer core cylinder and the sample storage cylinder, with the bottle openings facing the rear end of the sample storage cylinder. One end of the high-pressure gas pipeline is sealed to the outlet of the high-pressure nitrogen cylinder, and the other end is sealed to the inlet of the platform-shaped hollow cylinder. One end of the glue injection pipeline is connected to the rapid-expanding foam bottle. The outlet of the core-taking cylinder is sealed and connected, while the other end is sealed and connected to the injection hole of the platform-shaped hollow cylinder. Two threaded through holes are opened on the side wall of the core-taking outer cylinder. The first fixing bolt and the second fixing bolt are screwed into the corresponding threaded through holes. The inner end of the first fixing bolt extends into and is threadedly connected to the bottom of the high-pressure nitrogen cylinder, and the inner end of the second fixing bolt extends into and is threadedly connected to the bottom of the rapid foaming glue bottle, thereby achieving axial fixation of the high-pressure nitrogen cylinder and the rapid foaming glue bottle. The outer wall of the rear end of the core-taking outer cylinder is machined with external threads for sealing connection with the front internal threads of the gas collection unit.

3. The method for simultaneous collection of desorbed gas during coal seam coring according to claim 2, characterized in that: The gas collection unit includes a gas collection cylinder, a concave gas collection channel, a puncture sealing assembly, a gas collection chamber, an extraction pipe, and a ball valve. The concave gas collection channel is coaxially welded and fixed to the front end face of the gas collection cylinder. A large-diameter countersunk hole and a small-diameter through hole are coaxially connected at its center. The large-diameter countersunk hole is located on the front side and has internal threads machined on its inner wall. The small-diameter through hole is located on the rear side and communicates with the inner cavity of the gas collection cylinder. The puncture sealing assembly includes a hollow bolt and a rubber sealing gasket. The rubber sealing gasket is embedded in the rear stepped surface of the large-diameter countersunk hole. The bolt is screwed into the internal thread of the large-diameter countersunk hole, and its rear end face is squeezed to form a static seal with a rubber sealing gasket. The center of the hollow bolt has a guide hole that fits with the piercing hollow needle. The internal cavity of the gas collection cylinder is a gas collection chamber. The gas extraction pipe is coaxially welded and fixed to the rear end face of the gas collection cylinder and communicates with the gas collection chamber. The rear end of the gas extraction pipe is sealed to the ball stop valve through a tapered pipe thread. The inner wall of the front end of the gas collection cylinder is machined with an internal thread that matches the coal sample collection unit, and the outer wall of the rear end is machined with an external thread that matches the end connection unit. The end connection unit is an integrated rigid straight connector. Its front inner wall is machined with an internal thread that matches the external thread at the rear end of the gas collection cylinder. The external thread machined on the rear outer wall is a thread commonly used in coal mine drill pipes. The inner diameter of the central through hole of the connector is not less than the inner diameter of the gas collection chamber of the gas collection cylinder, ensuring the coaxiality and fluid conductivity of the entire equipment.

4. The method for simultaneous collection of desorbed gas during coal seam coring according to claim 3, characterized in that: The specific process of step S1 is as follows: The front end of the gas guide tube is screwed into the central vent hole of the circular piston through a thread to complete the sealing connection; two O-rings are respectively embedded in the annular sealing groove of the piston; the piston is pushed in from the rear end of the sample storage cylinder until it reaches the front end of the sample storage cylinder; the capsule is placed into the inner cavity of the platform-shaped hollow cylinder; one end of the high-pressure gas pipeline is sealed to the air inlet of the capsule, and one end of the glue injection pipeline is sealed to the glue injection hole of the platform-shaped hollow cylinder; the platform-shaped hollow cylinder is screwed into the side wall threaded through hole of the funnel-shaped sample channel through an external thread until the platform-shaped nut is in contact with the outer wall of the core extraction outer cylinder; the other end of the high-pressure gas pipeline... One end is connected to the outlet of the high-pressure nitrogen cylinder, and the other end of the glue injection pipeline is connected to the outlet of the quick-blowing glue bottle; the gas cylinder and the glue bottle are clamped into the annular cavity between the core sampling outer cylinder and the sample storage cylinder, and the first fixing bolt and the second fixing bolt are screwed into the threaded through hole of the core sampling outer cylinder respectively, and the cylinder bottom is tightened to complete the fixation; the upper lever and the lower lever are installed in the upper and lower convex grooves respectively through the hinge shaft, and the positions are adjusted so that the upper trigger plate and the lower trigger plate are facing the rear end face of the hollow wall cylinder, and the rear ends of the upper lever and the lower lever are facing the push-button switch of the glue bottle and the push-button switch of the gas cylinder respectively, thus completing the assembly of the coal sample collection unit.

5. The method for simultaneous collection of desorbed gas during coal seam coring according to claim 4, characterized in that: The specific process of step S2 is as follows: The rubber sealing gasket is embedded in the stepped surface of the large-diameter countersunk hole in the concave gas collecting channel. The hollow bolt is screwed into the internal thread of the large-diameter countersunk hole. After tightening, the rubber sealing gasket is squeezed to complete the static seal. The volume of the gas collecting chamber is calibrated: Clean water is injected into the gas collecting chamber through the ball valve and the extraction pipe until water overflows from the small-diameter through-hole, expelling all air from the chamber. The volume of injected water is recorded as the calibrated volume of the gas collecting chamber. V 1 Pour out all the water from the gas collection chamber and dry it with compressed air; in this step S2, the volume calibration of the gas collection chamber is only performed when the equipment is used for the first time, and the volume calibrated during the first use is directly adopted for subsequent uses. V 1 Connect the right end of the extraction pipe to the downhole vacuum pump, open the ball valve, start the vacuum pump to evacuate the gas collection chamber until the vacuum level drops below 20 Pa, close the ball valve to create a stable negative pressure environment in the gas collection chamber, and complete the pretreatment of the gas collection unit.

6. The method for simultaneous collection of desorbed gas during coal seam coring according to claim 5, characterized in that: The specific process of step S3 is as follows: screw the external thread at the rear end of the assembled coal sample collection unit into the internal thread at the front end of the gas collection unit, and tighten to complete the coaxial sealing connection; screw the external thread at the rear end of the gas collection unit into the internal thread at the front end of the end connection unit, and tighten to complete the connection, forming an integrated coring equipment; tighten and fix the external thread at the rear end of the end connection unit to the internal thread of the conventional downhole drill pipe, and complete the connection between the equipment and the drill pipe. Step S4 is as follows: Using a conventional downhole drilling rig with ordinary drill pipes, drill to the predetermined sampling position of the target coal seam, stop drilling and withdraw all ordinary drill pipes; extend the drill pipes connected to the integrated coring equipment one by one, and slowly send them into the borehole through the drilling rig until the integrated coring equipment reaches the predetermined sampling position, ready for coring operation.

7. The method for simultaneous collection of desorbed gas during coal seam coring according to claim 6, characterized in that: The specific process of step S5 is as follows: Start the drilling rig, drive the integrated coring equipment to rotate through the drill rod, the drill teeth cut the coal seam to form a coal sample, the coal sample enters the coring equipment with the rotation, after being crushed into uniform particles by the cross-shaped blades, the sample is pushed by the funnel-shaped sample passage to rotate and open the bidirectional sealing door towards the sample storage cylinder, and the coal sample enters the sample storage cylinder; as the coal sample continues to enter, it pushes the circular piston to move backward along the inner wall of the sample storage cylinder, and simultaneously drives the hollow wall cylinder, the gas guide pipe and the piercing hollow needle to move backward. When the piston moves backward to the preset position, the conical tip of the piercing hollow needle passes through the central guide hole of the hollow bolt, punctures the rubber sealing gasket, and connects the sample storage cylinder with the negative pressure gas collection chamber. The gas desorbed by the coal sample in the sample storage cylinder during the coring process is sucked into and stored in real time by the negative pressure gas collection chamber, and there is no gas leakage throughout the process.

8. The method for simultaneous collection of desorbed gas during coal seam coring according to claim 7, characterized in that: The specific process of step S6 is as follows: When the piston continues to move backward to the preset position at the rear end of the sample storage cylinder, the coal sample fills the sample storage cylinder. At this time, the rear end face of the hollow wall cylinder simultaneously squeezes the upper trigger plate and the lower trigger plate. Through the lever structure, the rear ends of the upper lever pressure rod and the lower lever pressure rod rotate downward simultaneously. At the same time, the press-type switch of the gas cylinder and the press-type switch of the foam bottle are opened. The high-pressure nitrogen in the high-pressure nitrogen cylinder is quickly filled into the bag through the high-pressure gas pipeline. The bag expands instantly and extends out from the platform-shaped hollow cylinder, pushing the bidirectional sealing door to rotate in the opposite direction and close, completely blocking the funnel-shaped sample passage and isolating the sample storage cylinder from the external environment of the borehole. At the same time, the foam in the rapid foam bottle is injected into the platform-shaped hollow cylinder through the glue injection pipeline, filling the gap between the bidirectional sealing door and the inner wall of the sample passage. The foam quickly solidifies, realizing the locking of the bidirectional sealing door and the secondary sealing of the sample passage, so that the sample storage cylinder and the gas collection chamber form a completely sealed cavity, and the sampling is completed.

9. The method for simultaneous collection of desorbed gas during coal seam coring according to claim 8, characterized in that: The specific process of step S7 is as follows: After sampling is completed, stop the drilling rig, slowly withdraw all drill pipes, remove the integrated coring equipment from the borehole, and separate the equipment from the drill pipes; disconnect the end connection unit, seal the ball valve at the rear end of the gas collection unit to the air inlet of the downhole gas desorption instrument, slowly open the ball valve, measure the gas desorption amount through the desorption instrument until the desorption instrument reading does not change, indicating that the gas desorption is complete, and record the gas desorption amount measured by the desorption instrument. V 2; Calculate the volume using the gas collection chamber. V 1. Downhole ambient temperature T Atmospheric pressure P 0. Using the ideal gas law, the gas volume in the gas collecting chamber is converted to its standard condition volume and compared with the volume measured by the desorption instrument. V Adding the two together, we get the total amount of desorbed gas under standard conditions ( ). V 1 +V 2).

10. The method for simultaneous collection of desorbed gas during coal seam coring according to claim 9, characterized in that: The specific process of step S8 is as follows: disassemble the coal sample collection unit and the gas collection unit, and disassemble each component separately: unscrew the first fixing bolt and the second fixing bolt, take out the high-pressure nitrogen cylinder and the quick-blowing foam bottle, and disconnect the high-pressure gas pipeline and the glue injection pipeline; unscrew the table-shaped hollow cylinder, remove the bag and the remaining cured foam; remove the upper lever and the lower lever, pull the piston and the gas guide tube out of the sample storage cylinder, pour out the coal sample in the sample storage cylinder, put it into the standard coal sample container and seal it for storage, and send it to the laboratory within 24 hours to determine the residual gas content of the coal sample; unscrew the hollow bolt of the gas collection unit and remove the used rubber sealing gasket; Step S9 is as follows: Clean all parts of the equipment of coal dust and residual foam, replace the rubber gasket, O-ring, and bladder, replace the high-pressure nitrogen cylinder and the rapid foam bottle, and then reassemble according to the above assembly steps for the next sampling.

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