Coal seam CO2 phase change displacement coupling microbial degradation anti-reflection process method
By combining CO2 phase change displacement and microbial degradation, the problem of efficient extraction of coalbed methane in soft, low-permeability coal seams has been solved. This method achieves both coal seam permeability enhancement and environmental protection, realizes CO2 sequestration and conversion, improves the application of technology, and realizes efficient extraction of coalbed methane and CO2 sequestration and conversion. It also has a negative carbon effect and is environmentally friendly.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-28
- Publication Date
- 2026-04-03
AI Technical Summary
The challenge of efficiently extracting coalbed methane from soft, low-permeability coal seams is that existing permeability enhancement methods are ineffective and can easily lead to formation damage and environmental pollution.
A permeability enhancement process combining CO2 phase change displacement and microbial degradation is adopted. Liquid CO2 and biodegradation liquid are injected into the coal seam under high pressure to form fractures and promote microbial activity, thereby enhancing coal seam permeability and methane desorption.
It achieves CO2 sequestration and conversion, increases coalbed methane production, reduces dependence on fossil fuels, has a negative carbon effect, and is environmentally friendly.
Smart Images
Figure CN121781888A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of coal seam gas extraction technology, specifically to a method for a coal seam CO2 phase change displacement coupled with microbial degradation and permeability enhancement process. Background Technology
[0002] Achieving efficient gas extraction in high-gas, soft, and low-permeability coal seams presents certain challenges. Soft, low-permeability coal seams have weak inter-particle bonding, making them prone to collapse or pulverization during drilling or permeability enhancement operations. The low porosity and fracture development of these seams result in poor gas flow, making it difficult for traditional hydraulic fracturing techniques to form an effective fracture network in low-permeability coal seams, thus limiting the permeability enhancement effect.
[0003] Coalbed methane (CBM) is a methane gas produced during coal mining. As a clean energy source, its extraction and utilization are of great significance to energy security and environmental protection. However, CBM extraction is challenging, especially in soft, low-permeability coal seams where gas is difficult to effectively dissipate and flow, resulting in low recovery rates. Currently, existing physicochemical permeability enhancement methods (such as hydraulic fracturing, pre-splitting blasting, and acidic chemical reagents) can increase CBM production to some extent, but their effectiveness is poor in soft, low-permeability coal seams, easily leading to formation damage and environmental pollution. Summary of the Invention
[0004] The purpose of this invention is to provide a coal seam CO2 phase change displacement coupled with microbial degradation and permeability enhancement process, which solves the problem of efficient extraction of coalbed methane in soft and low-permeability coal seams in the prior art.
[0005] To achieve the above objectives, the present invention provides the following technical solution: a coal seam CO2 phase change displacement coupled with microbial degradation and permeability enhancement device, comprising a drainage pipe disposed within a coal seam borehole and connected at its outer end to a gas extraction system via a pipeline, and a gas online detection module installed on the pipeline connecting the outer end of the drainage pipe; the liquid CO2 storage tank is filled with liquid carbon dioxide; the biodegradation storage tank is filled with biodegradation liquid; the two input ends of the three-way valve are respectively connected to the outlets of the liquid CO2 storage tank and the biodegradation storage tank via pipelines; the input end of the high-pressure pump is connected to the output end of the three-way valve via a pipeline; the injection pipe is disposed within a coal seam borehole near the drainage pipe, and the outer end of the injection pipe is connected to the output end of the high-pressure pump via a pipeline; a pressure relief valve and a liquid flow detection module are installed on the pipeline between the outer end of the injection pipe and the output end of the high-pressure pump; a pressure detection module and a temperature detection module are installed on the pipeline between the input end of the high-pressure pump and the output end of the three-way valve.
[0006] Preferably, the injection tube includes an outer tube and a screen tube concentrically sleeved within the inner cavity of the outer tube. An annular sealing plate connects the outer peripheral wall of the screen tube near its outer end to the inner peripheral wall of the outer end of the outer tube. The outer tube should possess high pressure resistance, low-temperature resistance, corrosion resistance, and mechanical stability; the outer tube is made of 316L stainless steel. The screen tube should meet the requirements of high strength, corrosion resistance, and wear resistance. Simultaneously, its pore structure should be rationally designed to ensure uniform distribution of CO2 and biodegradable liquid, avoiding excessively high or low flow rates during injection. The screen tube is made of a composite material of polymer and metal.
[0007] Preferably, the liquid CO2 storage tank is equipped with an emergency valve. The liquid CO2 storage tank is made of stainless steel or special carbon steel, capable of withstanding low temperatures and high pressures (10 MPa). The inner wall is required to have strong corrosion resistance to prevent corrosion of the tank body due to long-term CO2 storage. For low-temperature environments, it is specifically necessary to maintain the temperature at -20°C to keep it liquid. Therefore, the liquid CO2 storage tank is equipped with an external insulation layer to reduce heat conduction.
[0008] Preferably, the biodegradable liquid in the biodegradable storage tank includes at least one of active microorganisms and biological enzymes. The tank requires a strictly sterile anaerobic environment to prevent contaminants from entering and affecting the activity of microorganisms, and also to avoid excessive oxygen or other gases from entering and causing the biological system to fail. The biodegradable storage tank is equipped with a gas replacement mechanism to maintain a suitable anaerobic environment to promote the stable growth and activity of microorganisms.
[0009] Preferably, it also includes an injection control system for adjusting the injection volume and pressure of CO2 and for adjusting the injection flow rate of biodegradable fluid.
[0010] Preferably, the high-pressure pump is a plunger-type high-pressure pump, and its drive motor is an explosion-proof motor. High pressure (10 MPa) is generated through reciprocating motion, and liquid CO2 and biodegradable liquid are transported to the coal seam under high pressure via pipeline.
[0011] Preferably, when liquid CO2 is injected into the coal seam, a fracture range with a radius of approximately 20m is formed around it. Therefore, the injection pipe and the extraction pipe are arranged parallel to each other, and the distance between the injection pipe and the extraction pipe is no more than 20m.
[0012] A method for enhancing the permeability of coal seams by coupling CO2 phase change displacement with microbial degradation includes the following steps: S1. Inspect the entire anti-reflection device system; The process includes inspecting the liquid CO2 storage tank to ensure sufficient liquid CO2 and stable storage pressure and temperature; inspecting the biodegradation storage tank to ensure good microbial activity and sufficient biodegradation liquid content; testing the high-pressure pump to ensure it operates normally and can maintain high pressure conditions during injection; and testing the pressure relief valve to ensure the safety protection equipment is in working order and to prevent accidents caused by excessive pressure.
[0013] S2. Drilling operations are carried out according to the location of the target coal seam; The drilling operation is used to construct the extraction holes for the extraction tube and the injection holes for the injection tube.
[0014] S3. Inject liquid CO2 into the coal seam injection hole; Adjust the three-way valve to connect the liquid CO2 storage tank to the high-pressure pump, and control the flow rate of liquid CO2 injected into the coal seam based on the monitoring data of the pressure detection module and the liquid flow detection module; This step lasts for 7 to 10 days.
[0015] S4. Inject biodegradable liquid into the coal seam injection hole; Adjust the three-way valve to connect the biodegradable liquid storage tank to the high-pressure pump, and control the flow rate of the biodegradable liquid injected into the coal seam based on the monitoring data of the pressure detection module and the liquid flow detection module.
[0016] S5. Verify the permeability enhancement effect of the coal seam; The gas extraction effect after coal seam permeability enhancement is verified based on the gas flow rate and gas concentration monitored by the gas online detection module.
[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. The present invention relates to a coal seam CO2 phase change displacement coupled with microbial degradation permeability enhancement process, in which liquid CO2 is injected into the coal seam borehole, thereby displacing coalbed methane and simultaneously achieving CO2 sequestration and conversion. This reduces CO2 while increasing the potential for CH4 resource utilization, exhibiting a significant negative carbon effect. By increasing coalbed methane production through biodegradation, the dependence on fossil fuel energy is further reduced, accelerating the achievement of carbon neutrality goals. Moreover, the biological materials used are ecological and environmentally friendly, posing no harm to humans or the environment.
[0018] 2. The method of CO2 phase change displacement coupled with microbial degradation and permeability enhancement in coal seams involved in this invention can not only be used for coal seam gas control and coalbed methane production enhancement, but also realize CO2 sequestration and conversion, with broad application prospects. Attached Figure Description
[0019] Figure 1This is a schematic diagram of the overall structure of the coal seam CO2 phase change displacement coupled with microbial degradation and permeability enhancement device in this invention; Figure 2 This is a schematic diagram of the cross-sectional structure of the injection tube in this invention.
[0020] 1-Liquid CO2 storage tank; 2-Biological degradation storage tank; 3-Three-way valve; 4-High-pressure pump; 5-Pressure detection module; 6-Temperature detection module; 7-Pressure relief valve; 8-Liquid flow detection module; 9-Injection tube; 9.1-Outer tube; 9.2-Sieve tube; 10 - Extract flower tubes; 11-Online gas detection module; 12-Emergency valve. Detailed Implementation
[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0022] Please see Figure 1-2 The present invention provides a technical solution, a coal seam CO2 phase change displacement coupled microbial degradation and permeability enhancement device, including a gas extraction pipe 10 installed in a coal seam borehole and connected to a gas extraction system by a pipeline at its outer end, and a gas online detection module 11 installed on the pipeline connecting the outer end of the gas extraction pipe 10.
[0023] Liquid CO2 storage tank 1 is filled with liquid carbon dioxide. It is typically made of stainless steel or special carbon steel, capable of withstanding low temperatures and high pressures (10 MPa). The inner wall requires strong corrosion resistance to prevent corrosion from long-term CO2 storage. For low-temperature environments, it needs to be maintained at -20°C to keep it liquid; therefore, the outer layer of liquid CO2 storage tank 1 usually requires a vacuum insulation layer to reduce heat conduction. An emergency valve 12 is installed on liquid CO2 storage tank 1. This valve is made of high-pressure and low-temperature resistant stainless steel to adapt to the low-temperature and high-pressure environment of liquid CO2 storage. It automatically releases excess CO2 when the pressure inside liquid CO2 storage tank 1 becomes too high to prevent rupture or explosion. The valve is set with a fixed opening pressure point. When the pressure in liquid CO2 storage tank 1 reaches the critical value, the valve automatically opens to release the pressure. This pressure value is usually slightly higher than the working pressure of liquid CO2 storage tank 1, but within the maximum allowable pressure range of the tank.
[0024] The biodegradable liquid storage tank 2 is filled with a biodegradable liquid; the biodegradable liquid in the biodegradable liquid storage tank 2 includes at least one of active microorganisms and biological enzymes. The biodegradable liquid storage tank 2 requires a strictly sterile anaerobic environment to prevent contaminants from entering and affecting microbial activity, and also to avoid excessive oxygen or other gases entering and causing the biological system to fail. Therefore, the biodegradable liquid storage tank 2 is equipped with a gas replacement mechanism to maintain a suitable anaerobic environment to promote the stable growth and activity of microorganisms.
[0025] The two input ends of the three-way valve 3 are connected to the outlets of the liquid CO2 storage tank 1 and the biodegradable liquid storage tank 2 respectively through pipelines; the three-way valve 3 is used to control the injection and discharge of liquids (liquid CO2 and biodegradable liquid) to ensure smooth flow of fluid between pipelines or storage tanks.
[0026] The input end of high-pressure pump 4 is connected to the output end of three-way valve 3 via a pipeline. High-pressure pump 4 is a plunger-type high-pressure pump, and its drive motor is an explosion-proof motor, ensuring that its power and torque can meet the operating requirements of high-pressure pump 4 while also achieving explosion-proof operation underground. High-pressure pump 4 generates high pressure (10 MPa) through reciprocating motion, and transports liquid CO2 and biodegradable liquid to the coal seam under high pressure via pipeline.
[0027] The injection pipe 9 is located in the coal seam borehole near the extraction pipe 10. The outer end of the injection pipe 9 is connected to the output end of the high-pressure pump 4 via a pipeline. The injection pipe 9 includes an outer pipe 9.1 and a screen pipe 9.2 concentrically fitted inside the outer pipe 9.1. An annular sealing plate connects the outer peripheral wall of the screen pipe 9.2 near its outer end to the inner peripheral wall of the outer end of the outer pipe 9.1. Since the outer pipe 9.1 should have high pressure resistance, low temperature resistance, corrosion resistance, and mechanical stability, it is made of 316L stainless steel. For the screen pipe 9.2, it should meet the requirements of high strength, corrosion resistance, and wear resistance. At the same time, the pore structure should be reasonably designed to ensure the uniform distribution of CO2 and biodegradable liquid and avoid excessive or insufficient flow rates during injection. Therefore, the screen pipe 9.2 is made of a composite material of polymer and metal.
[0028] A pressure relief valve 7 and a liquid flow detection module 8 are installed on the pipeline between the outer end of the injection pipe 9 and the output end of the high-pressure pump 4. A pressure detection module 5 and a temperature detection module 6 are installed on the pipeline between the input end of the high-pressure pump 4 and the output end of the three-way valve 3. The pressure relief valve 7 protects the equipment and system from excessive pressure, automatically releasing fluid exceeding the set pressure when a certain pressure threshold is reached. The pressure detection module 5 is a pressure gauge used to measure and display pressure changes within the system in real time, ensuring that the injected liquid CO2 and biodegradable liquid are within the set pressure range. The temperature detection module 6 is a temperature gauge used to measure and monitor the temperature to ensure the CO2 gas phase change effect and prevent excessively high or low temperatures from adversely affecting the process. These modules are used to adjust parameters such as the CO2 injection volume and pressure to ensure the smooth progress of the CO2 phase change displacement process.
[0029] It also includes an injection control system for regulating the injection volume and pressure of CO2, as well as the injection flow rate of the biodegradable fluid. Specifically, by precisely controlling the CO2 injection, the system ensures the generation of fractures during the phase change process and optimizes methane desorption and flow. When injecting biodegradable fluid into coal seams, the injection control system can precisely control the flow rate and injection depth of the biofluid, ensuring the effectiveness of the biodegradation process and preventing excessive damage to the coal seam.
[0030] When liquid CO2 is injected into the coal seam, a fracture range with a radius of about 20m is formed around it. The injection pipe 9 and the extraction pipe 10 are set parallel to each other, and the distance between the injection pipe 9 and the extraction pipe 10 is no more than 20m.
[0031] A method for enhancing the permeability of coal seams by coupling CO2 phase change displacement with microbial degradation includes the following steps: S1. Inspect the entire anti-reflection device system; The process includes inspecting liquid CO2 storage tank 1 to ensure sufficient liquid CO2 and stable storage pressure and temperature; inspecting biological degradation storage tank 2 to ensure good microbial activity and sufficient biodegradation liquid; testing high-pressure pump 4 to ensure it operates normally and can maintain high pressure conditions during the injection process; and testing pressure relief valve 7 to ensure the safety protection equipment is in working condition and to prevent accidents caused by excessive pressure. S2. Drilling operations are carried out according to the location of the target coal seam; Among them, drilling operations are used to construct extraction holes for extraction pipe 10 and injection holes for injection pipe 9. S3. Inject liquid CO2 into the coal seam injection hole; Adjusting the three-way valve 3 connects the liquid CO2 storage tank 1 to the high-pressure pump 4. The flow rate of liquid CO2 injected into the coal seam is controlled based on monitoring data from the pressure detection module 5 and the liquid flow detection module 8. After entering the coal seam, the liquid CO2 undergoes a phase change due to the coal seam temperature. During this process, its volume expands hundreds of times, generating a driving force that forms micro-fractures with a radius of approximately 20m in the coal seam, expanding the pore network of the coal body and increasing the permeability of the coal seam. Simultaneously, because CO2 has a stronger adsorption capacity than CH4, CO2 molecules adsorb onto the organic matter in the coal, replacing CH4 molecules, thereby accelerating the desorption process of CH4. This causes the methane originally adsorbed in the coal seam to desorb and enter the fractures and pores, completing one stage of CO2 displacement of CH4.
[0032] During the liquid CO2 injection process, the phase change effect of CO2 completely evaporates after 7-10 days. Therefore, this step should continue for 7-10 days before proceeding to the next step. If the system pressure becomes too high during the injection process, emergency valve 12 will automatically release some CO2 to prevent system damage or accidents.
[0033] S4. Inject biodegradable liquid into the coal seam injection hole; Adjust the three-way valve 3 to connect the biodegradation storage tank 2 to the high-pressure pump 4. Control the flow rate of the biodegradation liquid injected into the coal seam based on monitoring data from the pressure detection module 5 and the liquid flow detection module 8. After injection, microorganisms begin to grow and metabolize in the coal seam, accelerating the decomposition of large molecules in the complex organic matter of the coal into smaller molecules, thus performing a secondary displacement of methane. During the injection process, the pressure detection module 5 and the temperature detection module 6 are used to monitor the injection conditions. After injection is complete, close all valves and wait for the CO2 gas and biodegradation liquid to gradually take effect, a process that takes approximately 1-2 months. The CO2 (intermediate product) produced by microbial metabolism can displace methane gas from the coal seam pores for a second time. Simultaneously, the CO2 gas adsorbed in the coal seam can also serve as an intermediate product of anaerobic fermentation by microorganisms, being converted into methane or short-chain organic matter. Ultimately, this leads to the sustained development of the coal seam pore network and a significant improvement in the coal seam's seepage characteristics.
[0034] S5. Verify the permeability enhancement effect of the coal seam; The gas flow rate and gas concentration monitored by the online gas detection module 11 were used to verify the gas extraction effect after the coal seam permeability enhancement.
[0035] It should be noted that in this article, relational terms such as first and second are only used to refer to... Distinguishing one entity or operation from another does not necessarily require or imply any such actual relationship or order between those entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.
[0036] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A coal seam CO2 phase change displacement coupled with microbial degradation and permeability enhancement device, comprising a gas extraction pipe (10) disposed within a coal seam borehole and connected at its outer end to a gas extraction system via a pipeline, and a gas online detection module (11) installed on the pipeline connecting the outer end of the gas extraction pipe (10), characterized in that, Also includes: A liquid CO2 storage tank (1) is filled with liquid carbon dioxide; A biodegradable liquid storage tank (2) is filled with biodegradable liquid; Three-way valve (3), the two input ends of the three-way valve (3) are respectively connected to the outlet of the liquid CO2 storage tank (1) and the biological decomposition storage tank (2) through pipelines; High pressure pump (4), the input end of the high pressure pump (4) is connected to the output end of the three-way valve (3) through a pipeline; The injection pipe (9) is located in the coal seam borehole near the extraction pipe (10), and the outer end of the injection pipe (9) is connected to the output end of the high-pressure pump (4) through a pipeline. A pressure relief valve (7) and a liquid flow detection module (8) are installed in the pipeline between the outer end of the injection pipe (9) and the output end of the high-pressure pump (4). A pressure detection module (5) and a temperature detection module (6) are installed in the pipeline between the input end of the high-pressure pump (4) and the output end of the three-way valve (3).
2. The coal seam CO2 phase change displacement coupled with microbial degradation and permeability enhancement device according to claim 1, characterized in that: The injection tube (9) includes an outer tube (9.1) and a sieve tube (9.2) concentrically sleeved in the inner cavity of the outer tube (9.1). An annular sealing plate is connected between the outer peripheral wall of the sieve tube (9.2) near its outer end and the inner peripheral wall of the outer end of the outer tube (9.1).
3. The coal seam CO2 phase change displacement coupled with microbial degradation and permeability enhancement device according to claim 1, characterized in that: An emergency valve (12) is installed on the liquid CO2 storage tank (1), and an insulation layer is provided on the outside of the liquid CO2 storage tank (1).
4. The coal seam CO2 phase change displacement coupled with microbial degradation and permeability enhancement device according to claim 1, characterized in that: The biodegradation liquid in the biodegradation storage tank (2) includes at least one of active microorganisms and biological enzymes, and the biodegradation storage tank (2) is equipped with a gas replacement mechanism.
5. The coal seam CO2 phase change displacement coupled with microbial degradation and permeability enhancement device according to claim 1, characterized in that: It also includes a pressure control system for adjusting the injection volume and pressure of CO2, as well as for adjusting the injection flow rate of biodegradable fluid.
6. The coal seam CO2 phase change displacement coupled with microbial degradation and permeability enhancement device according to claim 1, characterized in that: The high-pressure pump (4) is a plunger-type high-pressure pump, and its drive motor is an explosion-proof motor.
7. The coal seam CO2 phase change displacement coupled with microbial degradation and permeability enhancement device according to claim 1, characterized in that: The injection pipe (9) and the extraction pipe (10) are arranged parallel to each other, and the distance between the injection pipe (9) and the extraction pipe (10) is no more than 20m.
8. The coal seam CO2 phase change displacement coupled with microbial degradation and permeability enhancement device according to claim 2, characterized in that: The outer tube (9.1) is a 316L stainless steel tube, and the screen tube (9.2) is a composite material of polymer and metal.
9. A method for a coal seam CO2 phase change displacement coupled with microbial degradation and permeability enhancement process, characterized in that: The coal seam CO2 phase change displacement coupled with microbial degradation and permeability enhancement process method, using the coal seam CO2 phase change displacement coupled with microbial degradation and permeability enhancement device as described in any one of claims 1-8, includes the following steps: S1. Inspect the entire anti-reflection device system; The process includes: inspecting the liquid CO2 storage tank (1) to ensure sufficient liquid CO2 and stable storage pressure and temperature; inspecting the biodegradation storage tank (2) to ensure good microbial activity and sufficient biodegradation liquid; testing the high-pressure pump (4) to ensure normal operation and ability to maintain high pressure during injection; and testing the pressure relief valve (7) to ensure the safety protection equipment is in working condition and to prevent accidents caused by excessive pressure. S2. Drilling operations are carried out according to the location of the target coal seam; Among them, the drilling operation is used to construct the extraction hole of the extraction tube (10) and the injection hole of the injection tube (9); S3. Inject liquid CO2 into the coal seam injection hole; Adjust the three-way valve (3) to connect the liquid CO2 storage tank (1) to the high-pressure pump (4), and control the flow rate of liquid CO2 injected into the coal seam according to the monitoring data of the pressure detection module (5) and the liquid flow detection module (8); S4. Inject biodegradable liquid into the coal seam injection hole; Adjust the three-way valve (3) to connect the biodegradation storage tank (2) to the high-pressure pump (4), and control the flow rate of the biodegradation liquid injected into the coal seam according to the monitoring data of the pressure detection module (5) and the liquid flow detection module (8); S5. Verify the permeability enhancement effect of the coal seam; The gas extraction effect after coal seam permeability enhancement is verified based on the gas flow rate and gas concentration monitored by the gas online detection module (11).
10. The method for a coal seam CO2 phase change displacement coupled with microbial degradation and permeability enhancement process according to claim 9, characterized in that: Step S3 is performed for 7 to 10 days before step S4 is performed.