A device and method for collecting coal bed methane in a drilling fluid

Abstract

This invention discloses a device and method for collecting coalbed methane from drilling fluid, belonging to the field of coalbed methane exploration and development technology. The device includes a drilling fluid collection component, a flow-conducting metering component, and a coalbed methane collection component. The method achieves leak-free, complete extraction, accurate quantification, and pure sampling of coalbed methane from drilling fluid through pre-testing for air tightness and pressure resistance, quantitative collection of drilling fluid at the wellhead, heating and stirring for degassing, vacuum gas collection with clean water replacement, sealed bottle replacement for testing, and equipment cleaning and recovery. This invention solves the problems of traditional gas logging methods, which can only perform qualitative analysis, not quantitative analysis, and cannot obtain qualified gas samples. It has advantages such as reliable air tightness, complete degassing, accurate metering, simple on-site operation, and high sample fidelity. It can be directly used for the analysis of coalbed methane components, isotopes, mercury content, etc., and is suitable for rapid evaluation of gas content and geological reserve estimation in coalbed methane drilling sites.

Description

Technical Field

[0001] This invention belongs to the field of coalbed methane exploration and development technology, specifically relating to a device and method for collecting coalbed methane from drilling fluid. Background Technology

[0002] Coalbed methane (CBM) is an unconventional natural gas that coexists with coal resources. It is a clean energy source and is listed as a strategic mineral resource in my country. my country boasts abundant CBM reserves, ranking third in the world, with predicted reserves exceeding 70 trillion cubic meters. It is a crucial component of my country's natural gas supply system. With the global tightening of fossil fuel supply and the continuous growth of domestic natural gas demand, the scale of CBM development and utilization is constantly expanding, playing an irreplaceable role in ensuring national energy security.

[0003] my country's coalbed methane resources are characterized by complex occurrence conditions, high extraction difficulty, and relatively high geological risks. Therefore, increasing exploration and development efforts must be based on accurate geological surveys and resource assessments. Determining the gas-bearing characteristics and geological conditions of coal seams is crucial for reducing exploration and development risks and improving the reliability of reserve submissions. Accurately and quantitatively evaluating the gas content of encountered coal seams during drilling has become a core technical requirement for coalbed methane exploration and evaluation.

[0004] Currently, the evaluation of formation gas content in China mainly employs two technical methods: gas logging and core sampling. For a large number of coalbed methane wells that do not require core sampling, only gas logging can be used to qualitatively determine gas content. This makes it impossible to conduct quantitative evaluations of gas content or perform chemical analyses of coalbed methane genesis, composition, and isotopes. This severely affects the accuracy of resource potential evaluation and leads to insufficient measured gas content data when submitting geological reserves.

[0005] Gas logging technology involves deploying a degasser at the wellhead drilling fluid return point and connecting it to a gas chromatograph to continuously collect hydrocarbon and non-hydrocarbon gases from the drilling fluid. Chromatographic analysis yields the components and relative concentrations, which are then used to identify gas-bearing features in the formation. However, this technology has significant limitations: the chromatograph can only detect the relative percentage of hydrocarbon components and cannot determine the absolute content of coalbed methane per unit volume of drilling fluid. Furthermore, it cannot collect qualified gas samples suitable for quantitative laboratory testing and genetic analysis, making it difficult to meet the requirements for precise evaluation and reserve verification of coalbed methane resources.

[0006] Therefore, it is urgent to efficiently, quantitatively, and in a sealed manner collect coalbed methane samples from the circulating drilling fluid at the wellhead without core drilling. This would solve the technical problem that existing gas logging can only perform qualitative analysis, not quantitative analysis, and cannot sample and test the samples, thus providing reliable technical support for quantitative evaluation of coalbed methane content, reserve calculation, and reservoir analysis. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a device and method for collecting coalbed methane in drilling fluid, achieving leak-free sealing, complete desorption, no air mixing, accurate quantification, safe operation, and convenient testing of coalbed methane in drilling fluid. This solves the technical problems of traditional gas logging, which can only perform qualitative evaluation, cannot obtain qualified gas samples for testing, and cannot perform quantitative measurement.

[0008] To achieve the above objectives, the present invention provides a device for collecting coalbed methane in drilling fluid, comprising a drilling fluid collection component, a flow metering component, and a coalbed methane collection component; The drilling fluid collection assembly includes a drilling fluid inlet pipe, a drilling fluid storage container, and an exhaust pipe; the drilling fluid inlet pipe is located at the bottom of the drilling fluid storage container, and the exhaust pipe is located at the top of the drilling fluid storage container. The flow guiding and metering assembly includes a flow guiding pipe and a metering container; the inlet of the flow guiding pipe is located near the bottom of the drilling fluid storage container, a flow guiding valve is installed on the flow guiding pipe, and the height of the outlet of the flow guiding pipe is the same as the top height of the coalbed methane collection assembly; a metering container is located directly below the outlet of the flow guiding pipe, which is used to receive the extruded drilling fluid and simultaneously achieve indirect quantitative metering of the pressure balance inside the tank and the volume of coalbed methane. The coalbed methane collection component is sealed and connected to the exhaust pipe. After the drilling fluid in the drilling fluid collection component releases coalbed methane, it enters the coalbed methane collection component through the exhaust pipe to collect the released coalbed methane.

[0009] Preferably, the drilling fluid inlet pipe is equipped with an inlet valve, and the vent pipe is equipped with an vent valve.

[0010] Preferably, the coalbed methane collection assembly includes a gas sampling bottle, a connecting pipe, and a cap; the connecting pipe is located at the bottom of the gas sampling bottle, and the connecting pipe is detachably connected to the exhaust pipe, and a drain valve is provided on the connecting pipe; the top of the gas sampling bottle is provided with a bottle mouth, and a cap is installed on the bottle mouth; the connecting pipe and the exhaust pipe are detachably connected.

[0011] Preferably, the gas sampling bottle is equipped with graduations.

[0012] Preferably, the coalbed methane collection device in the drilling fluid further includes a coalbed methane separation component, which is a heater, a stirrer, or a combination of a heater and a stirrer; the heater is located at the bottom of the drilling fluid storage container, or at the bottom and the side wall; the stirrer is located inside the drilling fluid storage container.

[0013] Preferably, the heater is a constant temperature heater, and the drilling fluid storage container includes a tank body and a top cover. The top cover is installed on the top of the tank body and is detachably installed on the tank body. A sealing gasket is installed at the contact position between the top cover and the tank body. An airtightness test pressure gauge is installed on the top cover, and an exhaust pipe is located in the middle of the top cover.

[0014] Preferably, a guide pipe fixing clamp is provided on the side wall of the drilling fluid storage container, and the guide pipe fixing clamp is connected to the middle or upper part of the guide pipe; a metering container fixing clamp is provided on the guide pipe, and the metering container is installed on the metering container fixing clamp; the metering container is a measuring cylinder.

[0015] This invention also provides a method for collecting coalbed methane from drilling fluid, comprising the following steps: S1. Air tightness test of the device: Before operation, close the exhaust valve and the liquid inlet valve, open the guide valve, and inject air into the tank through the drilling fluid inlet pipe to pressurize it. After pressurization, close the liquid inlet valve and use the air tightness test pressure gauge to test the air tightness of the tank. If there is no obvious pressure drop after the pressure stabilizes, it means that the device is sealed and qualified.

[0016] S2. Pretreatment of gas sampling bottle: Close the drain valve; open the bottle cap and fill the gas sampling bottle with clean water through the bottle opening to expel the air inside the gas sampling bottle; tighten the bottle cap to create an air-free sealed environment inside the sampling bottle.

[0017] S3. Drilling fluid quantitative filling: Open the inlet valve and the vent valve; close the guide valve; pour drilling fluid into the tank through the drilling fluid inlet pipe until it is full and all internal air is expelled; after filling, close the vent valve, then open the guide valve and continue to add drilling fluid through the drilling fluid inlet pipe. When drilling fluid flows out of the outlet of the guide pipe, close the inlet valve and the guide valve to complete the drilling fluid filling.

[0018] S4. Gas collection assembly connection: Connect the connecting pipe of the pretreated gas sampling bottle to the exhaust pipe to ensure a reliable seal.

[0019] S5. Degassing: Keep the exhaust valve and drain valve closed, and open the guide valve; select the degassing method according to the site conditions: only turn on the heater for constant temperature heating; only turn on the agitator for stirring; turn on the heater and agitator for combined degassing; during the degassing process, the pressure inside the tank increases, causing the drilling fluid to flow into the metering container along the guide pipe. Degassing is completed when the drilling fluid stops flowing out of the outlet of the guide pipe. Read and record the volume of drilling fluid collected in the metering container.

[0020] S6. Gas Collection and Volume Measurement: Open the exhaust valve and drain valve. The precipitated coalbed methane enters the gas sampling bottle through the exhaust pipe. At the same time, the clean water in the gas sampling bottle flows into the tank along the exhaust pipe. When there is no clean water in the gas sampling bottle, close the exhaust valve and drain valve. Then remove the gas sampling bottle and replace it with a gas sampling bottle filled with clean water to collect coalbed methane again until the water level in the gas sampling bottle no longer drops, thus completing the gas collection.

[0021] S7. Sampling and Testing and Device Recovery: After collection, close the drain valve of the connecting pipe and remove the gas sampling bottle; puncture the bottle cap to extract gas, seal it, and send it to the laboratory for component, isotope, mercury, and other tests; turn off the heater and stirrer in sequence, drain the drilling fluid from the tank and pipeline, rinse the device with clean water, and complete the recovery.

[0022] In step "S5, Degassing", the heating temperature is set to be consistent with the formation temperature of the coal seam encountered during drilling, so that the coalbed methane in the drilling fluid can be fully and stably released.

[0023] In step "S6, Gas Collection and Volume Measurement", the height of the end of the guide tube is consistent with the height of the gas sampling bottle opening, forming an equal-height balanced guide structure to ensure stable pressure inside the tank.

[0024] The beneficial effects of this invention are as follows: The drilling fluid coalbed methane collection device provided by this invention, through a sealed combination structure of drilling fluid collection component, flow guiding and metering component and coalbed methane collection component, achieves leak-free sealed collection of coalbed methane in drilling fluid, full degassing and release, accurate quantitative measurement and pure sampling. It effectively solves the technical defects of traditional gas logging that can only make qualitative judgments, cannot make quantitative evaluations, and is difficult to obtain qualified gas samples for testing. It provides reliable technical support for rapid evaluation of coal seam gas content and estimation of geological reserves in coalbed methane exploration sites. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0026] Figure 1 This is a structural diagram of the present invention.

[0027] Figure 2 This is a state diagram for the use of the present invention.

[0028] In the diagram: Drilling fluid collection assembly 1, drilling fluid inlet pipe 11, drilling fluid storage container 12, tank body 121, top cover 122, airtightness test pressure gauge 123, guide pipe fixing clamp 124, support frame 125, power interface 126, power control panel 127, handle 128, exhaust pipe 13, exhaust valve 131, flow metering assembly 2, flow pipe 21, flow valve 211, metering container 22, coalbed methane collection assembly 3, gas sampling bottle 31, bottle mouth 311, connecting pipe 32, drain valve 321, bottle cap 33, coalbed methane separation assembly 4, heater 41, stirrer 42, motor 421, stirring impeller 422. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the embodiments of this invention will be described in further detail below with reference to the accompanying drawings. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0030] like Figure 1 As shown, the coalbed methane collection device in drilling fluid includes a drilling fluid collection component 1, a flow guiding and metering component 2, and a coalbed methane collection component 3. The components are connected by pipelines, valves and sealing structures to form a closed collection system, ensuring that there is no leakage of coalbed methane during the drilling fluid collection and degassing process, avoiding loss of coalbed methane, and providing a basis for quantitative collection.

[0031] The drilling fluid collection assembly 1 is used to quantitatively fill and maintain a seal of drilling fluid. It includes a drilling fluid inlet pipe 11, a drilling fluid storage container 12, and an exhaust pipe 13. The drilling fluid storage container 12 consists of a tank body 121 and a top cover 122. The top cover 122 is removable, and a sealing gasket is installed at the connection between the top cover 122 and the tank body 121 to ensure overall sealing. The removable sealed tank body facilitates cleaning and maintenance and is suitable for field disassembly and assembly. The sealing gasket prevents air and fluid leakage, improving airtightness and reliability. The drilling fluid inlet pipe 11 is located at the lower part of the tank body 121, and an inlet valve 111 is installed on the drilling fluid inlet pipe 11 to control the entry of drilling fluid. Low-level inlet allows for rapid purging of air from the tank, and valve control facilitates quantitative filling and prevents overflow. An exhaust pipe 13 is installed in the middle of the top cover 122, and an airtightness testing pressure gauge 123 is installed on the top. The airtightness testing pressure gauge 123 is used to test the airtightness of the device before operation; the top pressure gauge can screen for sealing defects in advance to prevent air leakage during the degassing stage, which would lead to data distortion and ensure the accuracy of data collection. An exhaust valve 131 is installed on the exhaust pipe 13, and the exhaust pipe 13 is sealed and connected to the coalbed methane collection component 3. The sealed connection between the exhaust pipe 13 and the coalbed methane collection component 3 ensures that the coalbed methane is discharged in one direction without air mixing in, thus ensuring the purity of the gas sample. The flow guiding and metering component 2 includes a flow guiding pipe 21 and a metering container 22. The inlet of the flow guiding pipe 21 is located near the bottom of the drilling fluid storage container 12 to facilitate the discharge of pressurized drilling fluid from the drilling fluid storage container 12. A flow guiding valve 211 is installed on the flow guiding pipe 21. The height of the outlet of the flow guiding pipe 21 is the same as the height of the top of the coalbed methane collection component 3, and the equal height structure balances the pressure of the drilling fluid storage container 12. The metering container 22 is located directly below the outlet of the flow guiding pipe 21, and the metering container 22 realizes the indirect and accurate conversion of coalbed methane volume.

[0032] During use, the coalbed methane collection assembly 3 is not installed on the exhaust pipe 13. Clean water is added to the coalbed methane collection assembly 3 to purge the air inside. The exhaust valve 131 and the guide valve 211 are opened, and drilling fluid is injected into the tank 121 through the drilling fluid inlet pipe 11, causing the air inside the tank 121 to be discharged along the exhaust pipe 13. After the tank 121 is filled with drilling fluid, the exhaust valve 131 is closed to prevent the coalbed methane in the drilling fluid from being released to the outside through the exhaust pipe 13, which would reduce the amount of coalbed methane collected by the coalbed methane collection assembly 3 and affect the accuracy of the detection. Then, drilling fluid is continuously injected into the drilling fluid collection assembly 3. When drilling fluid flows out of the outlet of the guide pipe 21, close the inlet valve 111 and the guide valve 211. At this time, install the coalbed methane collection assembly 3 on the exhaust pipe 13, open the exhaust valve 131 and the guide valve 211, so that the coalbed methane in the tank 121 is released and gathers towards the exhaust pipe and enters the coalbed methane collection assembly 3 along the exhaust pipe. The gradually collected coalbed methane gathers at the top of the coalbed methane collection assembly 3 and discharges the clean water inside it into the tank 121 along the exhaust pipe. The drilling fluid in the tank 121 is pressurized and gradually flows from the outlet of the guide pipe 21 into the metering container 22.

[0033] The coalbed methane separation assembly 4 is used to fully desorb and release coalbed methane from the drilling fluid. It includes a heater 41 and a stirrer 42: the heater 41 is a constant-temperature heater, located at the bottom of the tank 121, and can maintain a constant temperature according to the formation temperature. The stirrer 42 is installed inside the tank 121 and is driven by a motor to stir the drilling fluid and accelerate gas release.

[0034] In other embodiments, heater 41 is located at the bottom and side wall of tank 121.

[0035] The coalbed methane separation component 4 can be either a heater 41 or a stirrer 42.

[0036] The coalbed methane separation component 4 can achieve three degassing modes: degassing by heating alone, degassing by stirring alone, and degassing by a combination of heating and stirring. These multi-mode degassing methods flexibly adapt to field conditions, ensuring stable degassing performance under different drilling fluids and coal seam conditions.

[0037] The coalbed methane collection assembly 3 is used to collect air-free pure coalbed methane. It includes a gas sampling bottle 31, a connecting tube 32, and a cap 33. The gas sampling bottle 31 has volume graduations for collection and measurement. The connecting tube 32 is located at the bottom of the gas sampling bottle 31 and has a drain valve 321. The connecting tube 32 is detachably connected to the exhaust pipe 13. The top of the gas sampling bottle 31 has a bottle opening 311, and the cap 33 is installed on the bottle opening 311. The cap 33 is a sealed structure. Before use, the drain valve 321 is closed, and the cap 33 is opened. The air inside the gas sampling bottle 31 is completely expelled by filling it with clean water, and then the cap 33 is installed on the bottle opening. The graduated gas sampling bottle allows for direct measurement, and the detachable connection facilitates quick replacement of the gas sampling bottle 31 for sampling. The sealed cap ensures long-term accurate gas collection after puncture, meeting the high-precision testing requirements of the laboratory.

[0038] A guide pipe fixing clamp 124 is provided on the side wall of the drilling fluid storage container 12. The guide pipe fixing clamp 124 is connected to the middle or upper part of the guide pipe 21. The guide pipe fixing clamp 124 secures the guide pipe 21 to the drilling fluid storage container 12 to prevent the guide pipe 21 from shaking. A metering container fixing clamp 212 is provided on the guide pipe 21 to fix the metering container 22. The metering container 22 is a measuring cylinder used to receive the drilling fluid discharged from the guide pipe 21 and realize the volume conversion.

[0039] A support frame 125 is provided at the bottom of the drilling fluid storage container 12. The agitator 42 includes a motor 421 and an agitator impeller 422. The motor 421 is mounted on the support frame 125. The shaft of the motor 421 extends through the bottom of the drilling fluid storage container 12 and into the interior of the drilling fluid storage container 12. The contact point between the shaft of the motor 421 and the drilling fluid storage container 12 is sealed with a sealed bearing, which can effectively prevent the drilling fluid from leaking into the container and the entry of external air, ensuring the overall sealing of the device. The agitator impeller 422 is arranged inside the drilling fluid storage container 12 and is fixedly mounted on the top of the shaft of the motor 421. It can rotate synchronously with the shaft to agitate the drilling fluid inside the container.

[0040] A power interface 126 is provided on the support frame 125. The power interface 126 is electrically connected to the motor 421 and the heater 41. The power interface 126 can be connected to an external power source or to a battery. A power control panel 127 and two handles 128 are provided on the tank body 121. The speed of the motor 421 and the heating temperature of the heater 41 are set through the power control panel 127. The two handles 128 are distributed on both sides of the tank body 121, which facilitates the handling of this device.

[0041] A method for extracting coalbed methane from drilling fluid, comprising the following steps: S1. Air tightness test of the device: Before operation, close the exhaust valve 131 and the diversion valve 211, open the liquid inlet valve 111, and inject air into the tank 121 through the drilling fluid inlet pipe 11 to pressurize it. The air pressure in the tank 121 is 1 MPa when pressurization is completed. After pressurization, close the liquid inlet valve 111 and use the air tightness test pressure gauge 123 to test the air tightness of the tank 121. Observe for 30 minutes. If there is no obvious pressure drop after the pressure stabilizes, it means that the device is sealed and qualified.

[0042] S2. Pretreatment of gas sampling bottle: Close the drain valve 321; open the bottle cap 33 and fill the gas sampling bottle 31 with clean water through the bottle opening 311 to expel the air inside the gas sampling bottle 31; tighten the bottle cap 33 to create an air-free sealed environment inside the sampling bottle.

[0043] S3. Drilling fluid quantitative filling: Open the inlet valve 111 and the vent valve 131; close the guide valve 211; pour the drilling fluid into the tank 121 from the drilling fluid inlet pipe 11 until it is full and the internal air is completely expelled; after filling, close the vent valve 111, then open the guide valve 211 and continue to add drilling fluid from the drilling fluid inlet pipe 11. When the drilling fluid flows out of the outlet of the guide pipe 21, close the inlet valve 111 and the guide valve 211 to complete the drilling fluid filling.

[0044] S4. Gas collection assembly docking: Connect the connecting pipe 32 of the pretreated gas sampling bottle 31 to the exhaust pipe 13 to ensure a reliable seal.

[0045] S5. Degassing: Keep the exhaust valve 131 and the drain valve 321 closed, and open the guide valve 211; select the degassing method according to the site conditions: only turn on the heater 41 for constant temperature heating; only turn on the agitator 42 for stirring; turn on the heater 41 and the agitator 42 for combined degassing; during the degassing process, the pressure inside the tank 121 increases, causing the drilling fluid to flow into the metering container 22 along the guide pipe 21. Degassing is completed when the drilling fluid no longer flows out of the outlet of the guide pipe 21. Read and record the volume of drilling fluid collected in the metering container 22; multi-mode degassing adapts to the site conditions, the tank pressurization degassing efficiency is high, and the volume of drilling fluid discharged directly corresponds to the volume of coalbed methane, achieving accurate quantitative measurement.

[0046] S6. Gas Collection and Volume Measurement: Open the exhaust valve 131 and the drain valve 321. The released coalbed methane enters the gas sampling bottle 31 through the exhaust pipe 13, pushing the water in the bottle downwards. At the same time, the pressure inside the tank 121 increases, pushing the drilling fluid into the guide pipe 21 and into the metering container 22. Since the end of the guide pipe 21 is at the same height as the bottle opening 311, the pressure inside the tank remains stable, with no risk of overpressure. When there is no water in the gas sampling bottle 31, close the exhaust valve 131 and the drain valve 321, then remove the gas sampling bottle 31. Replace it with a gas sampling bottle 31 filled with water and collect coalbed methane again until the water level in the gas sampling bottle 31 stops dropping, completing the gas collection. The equal-height balance structure avoids overpressure inside the tank. The water-displacement gas collection method simultaneously completes gas sample collection and volume measurement. Continuous sampling from multiple bottles ensures complete coalbed methane collection, and the data can be cross-verified.

[0047] Ultimately, an equal relationship is established: the volume of coalbed methane entering the gas sampling bottle is equal to the volume of water discharged from the sampling bottle; the volume of coalbed methane released is equal to the volume of drilling fluid received by the metering container 22; the two sets of data are mutually verified to achieve accurate measurement.

[0048] S7. Sampling and Device Recovery: After collection, close the drain valve 321 of the connecting pipe 32 and remove the gas sampling bottle 31; puncture the bottle cap 33 to extract gas, seal it, and send it to the laboratory for component, isotope, mercury, and other tests; turn off the heater and stirrer in sequence, drain the drilling fluid from the tank 121 and pipeline, rinse the device with clean water, and complete the recovery.

[0049] In step "S5, Degassing", the heating temperature is set to match the formation temperature of the coal seam encountered during drilling, ensuring the full and stable release of coalbed methane from the drilling fluid. In practical applications, when drilling into shallow coal seams, the formation temperature is 25-40℃, corresponding to a heating temperature of 25-40℃; when drilling into medium-sized coal seams, the formation temperature is 40-60℃, corresponding to a heating temperature of 40-60℃; and when drilling into deep coal seams, the formation temperature is 60-100℃, corresponding to a heating temperature of 60-100℃.

[0050] In step "S6, Gas Collection and Volume Measurement", the height of the end of the guide tube 21 is consistent with the height of the mouth 311 of the gas sampling bottle 31, forming an equal-height balanced guide structure to ensure stable pressure inside the tank.

Claims

1. A device for collecting coalbed methane from drilling fluid, characterized in that, It includes a drilling fluid collection assembly (1), a flow metering assembly (2), and a coalbed methane collection assembly (3). The drilling fluid collection assembly (1) includes a drilling fluid inlet pipe (11), a drilling fluid storage container (12), and an exhaust pipe (13); the drilling fluid inlet pipe (11) is located at the lower part of the drilling fluid storage container (12), and the exhaust pipe (13) is located at the top of the drilling fluid storage container (12); The flow guiding and metering assembly (2) includes a flow guiding pipe (21) and a metering container (22); the inlet of the flow guiding pipe (21) is located near the bottom of the drilling fluid storage container (12), and a flow guiding valve (211) is installed on the flow guiding pipe (21). The height of the outlet of the flow guiding pipe (21) is the same as the height of the top of the coalbed methane collection assembly (3); a metering container (22) is installed directly below the outlet of the flow guiding pipe (21) for receiving and metering the discharged drilling fluid. The coalbed methane collection assembly (3) is sealed and connected to the exhaust pipe (13).

2. The coalbed methane collection device in drilling fluid according to claim 1, characterized in that, The drilling fluid inlet pipe (11) is equipped with an inlet valve (111), and the vent pipe (13) is equipped with an vent valve (131).

3. The coalbed methane collection device in drilling fluid according to claim 1, characterized in that, The coalbed methane collection assembly (3) includes a gas sampling bottle (31), a connecting pipe (32), and a cap (33); the connecting pipe (32) is located at the bottom of the gas sampling bottle (31), and the connecting pipe (32) is detachably connected to the exhaust pipe (13), and a drain valve (321) is provided on the connecting pipe (32); the top of the gas sampling bottle (31) is provided with a bottle mouth (311), and a cap (33) is installed on the bottle mouth (311); the connecting pipe (32) and the exhaust pipe (13) are detachably connected.

4. The coalbed methane collection device in drilling fluid according to claim 3, characterized in that, The gas sampling bottle (31) is equipped with a scale.

5. The coalbed methane collection device in drilling fluid according to claim 1, characterized in that, The coalbed methane collection device in drilling fluid also includes a coalbed methane separation component (4), which includes a heater (41) and a stirrer (42). The heater (41) is located at the bottom or side wall of the drilling fluid storage container (12), and the stirrer (42) is located inside the drilling fluid storage container (12).

6. The coalbed methane collection device in drilling fluid according to claim 1, characterized in that, The drilling fluid storage container (12) includes a tank body (121) and a top cover (122). The top cover (122) is installed on the top of the tank body (121). The top cover (122) is installed on the tank body (121) in a detachable manner. A sealing gasket is installed at the contact position between the top cover (122) and the tank body (121). An airtightness test pressure gauge (123) is installed on the top cover (122). An exhaust pipe (13) is installed at the middle position of the top cover (122).

7. The device for collecting coalbed methane in drilling fluid according to claim 1, characterized in that, A guide pipe fixing clamp (124) is provided on the side wall of the drilling fluid storage container (12), and the guide pipe fixing clamp (124) is connected to the middle or upper part of the guide pipe (21); a metering container fixing clamp (212) is provided on the guide pipe (21), and the metering container (22) is installed on the metering container fixing clamp (212); the metering container (22) is a measuring cylinder.

8. A method for collecting coalbed methane from drilling fluid, characterized in that, Includes the following steps: S1. Air tightness test of the device: Before operation, close the exhaust valve (131) and the diversion valve (211), open the liquid inlet valve (111), and inject air into the tank (121) through the drilling fluid inlet pipe (11) to pressurize it. After pressurization, close the liquid inlet valve (111) and use the air tightness test pressure gauge (123) to test the air tightness of the tank (121). If there is no obvious pressure drop after the pressure stabilizes, it means that the device is sealed and qualified. S2. Pretreatment of gas sampling bottle: Close the drain valve (321); open the bottle cap (33), fill the gas sampling bottle (31) with clean water through the bottle mouth (311) to expel the air inside the gas sampling bottle (31); close the bottle cap (33) tightly to form an airless sealed environment inside the sampling bottle; S3. Drilling fluid quantitative filling: Open the inlet valve (111), the vent valve (131), and the guide valve (211); pour the drilling fluid into the tank (121) from the inlet pipe (11) until it is full and the internal air is completely expelled; after the tank (121) is full, close the vent valve (131), keep the guide valve (211) open, and continue to inject drilling fluid from the drilling fluid inlet pipe (11). When the drilling fluid flows out of the outlet of the guide pipe (21), close the inlet valve (111) and the guide valve (211). S4. Gas collection assembly docking: Connect the connecting pipe (32) of the pretreated gas sampling bottle (31) to the exhaust pipe (13) to ensure a reliable seal; S5, Degassing: Keep the exhaust valve (131) and the drain valve (321) closed, and open the guide valve (211); select the degassing method according to the on-site working conditions: only turn on the heater (41) for constant temperature heating; only turn on the agitator (42) for stirring; turn on the heater (41) and the agitator (42) for combined degassing at the same time; during the degassing process, the pressure inside the tank (121) increases, causing the drilling fluid to flow into the metering container (22) along the guide pipe (21). After the drilling fluid stops flowing out of the outlet of the guide pipe (21), the degassing is completed. Read and record the volume value of the drilling fluid collected in the metering container (22); S6. Gas collection and volume measurement: Open the exhaust valve (131) and the drain valve (321). The coalbed methane that is released enters the gas sampling bottle (31) through the exhaust pipe (13). At the same time, the clean water in the gas sampling bottle (31) flows into the tank (121) along the exhaust pipe (13). When there is no clean water in the gas sampling bottle (31), close the exhaust valve (131) and the drain valve (321). Then remove the gas sampling bottle (31) and replace it with a gas sampling bottle (31) filled with clean water to collect coalbed methane again until the water level in the gas sampling bottle (31) no longer drops and the gas collection is completed. S7. Sampling and Device Recovery: After collection, close the drain valve (321) of the connecting pipe (32) and remove the gas sampling bottle (31); puncture the bottle cap (33) to obtain gas, seal it and send it to the laboratory for component, isotope, mercury and other tests; turn off the heater (41) and stirrer (42) in sequence, drain the drilling fluid in the tank (121) and pipeline, rinse the device with clean water and complete the recovery.

9. The method according to claim 8, characterized in that, In step "S5, Degassing", the heating temperature is set to be consistent with the formation temperature of the coal seam encountered during drilling, so that the coalbed methane in the drilling fluid can be fully and stably released.

10. The method according to claim 8, characterized in that, In step "S6, Gas Collection and Volume Measurement", the end height of the guide tube (21) is consistent with the height of the mouth (311) of the gas sampling bottle (31), forming an equal-height balanced guide structure to ensure stable pressure inside the tank.

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