In-situ coal microorganism yield increasing and permeability increasing simulation experiment device and experiment method

Abstract

The invention discloses an in-situ coal microorganism yield increasing and permeability increasing simulation experiment device and method. The device comprises a clamp holder, a flora culture system and a reaction system, a containing cavity for containing the fixing assembly is formed in the clamping device, and a clamping cavity which is used for containing a coal sample and is adjustable in space volume is formed in the fixing assembly. The flora culture system is communicated with the clamping cavity and is used for injecting a microorganism culture solution into the clamping cavity; the reaction system comprises a gas source assembly and a monitoring assembly; the gas source assembly comprises a buffer tank which is used for mixing carbon dioxide and methane and is communicated with the clamping cavity; the monitoring assembly comprises a pressure sensor and a water drainage and gas collection device which are communicated with the clamping cavity, and the water drainage and gas collection device is used for collecting and metering gas generated by reaction in the clamping cavity when the pressure in the clamping cavity is larger than preset pressure; an adjusting valve for adjusting the pressure in the clamping cavity is arranged on a communicating pipeline of the buffer tank and the clamping cavity, and a reference tank for sampling to analyze the change of gas components in the clamping cavity is arranged on the downstream side of the adjusting valve in the flow path direction.

Description

Technical Field

[0001] The present application belongs to the field of natural gas development technology, and specifically relates to an in-situ coal body microbial production and permeability enhancement simulation experimental device and experimental method. Background Art

[0002] As a crucial component of traditional energy, the clean and efficient development and utilization of coal resources has long been a research hotspot in the energy sector. Unconventional coal-bearing mineral resources (such as low-rank coal and shale gas) are subject to challenges such as low efficiency, high costs, and significant environmental disruption caused by traditional physical mining methods due to their complex occurrence and low permeability.

[0003] Microbial production enhancement technology, by introducing specific bacterial communities (such as methanogens and metabolic gas-producing bacteria), leverages microbial metabolic activity to improve coal pore structure and promote gas (methane) desorption and production, offering a new, green and efficient approach to developing unconventional coal resources. However, currently, there is no experimental device capable of simulating the in-situ environment of coal reservoirs, exploring the interaction mechanisms between microorganisms and coal, and optimizing production enhancement process parameters. Summary of the Invention

[0004] In view of this, the present application provides an in-situ coal microbial production and permeability enhancement simulation experimental device and experimental method, the main purpose of which is to simulate the in-situ environment of the coal reservoir, explore the interaction mechanism between microorganisms and coal, and optimize the production enhancement process parameters.

[0005] To achieve the above objectives, this application mainly provides the following technical solutions:

[0006] In one aspect of the present application, an in-situ coal microbial production and permeability enhancement simulation experimental device is provided, comprising:

[0007] A holder, wherein a receiving cavity is formed inside the holder, a fixing assembly is provided inside the receiving cavity, a clamping cavity for placing the coal sample is formed inside the fixing assembly, and the spatial volume of the clamping cavity is adjustable;

[0008] a bacterial colony culture system, the bacterial colony culture system being in communication with the clamping cavity and being used for injecting a microbial culture solution into the clamping cavity;

[0009] A reaction system, the reaction system comprising a gas source assembly and a monitoring assembly; the gas source assembly comprising a buffer tank for mixing carbon dioxide and methane, the buffer tank being in communication with the clamping chamber; the monitoring assembly comprising a pressure sensor and a drainage and gas collecting device, each in communication with the clamping chamber, the pressure sensor being configured to monitor the pressure within the clamping chamber, the drainage and gas collecting device being configured to collect and measure the gas generated by the reaction within the clamping chamber when the pressure within the clamping chamber exceeds a preset pressure;

[0010] The communication pipeline between the buffer tank and the clamping cavity is provided with an adjusting valve for adjusting the pressure in the clamping cavity, and a reference tank is arranged on the downstream side of the adjusting valve along the flow path direction for sampling to analyze the change of gas composition in the clamping cavity.

[0011] Optionally, the in-situ coal body microbial production and permeability enhancement simulation experiment device further comprises:

[0012] A pressure supply system comprising a water source and a pressure pump, the pressure pump being in communication with the water source and the containing cavity of the holder respectively, and the pressure pump being used for applying axial pressure and confining pressure to the fixed assembly respectively to simulate different formation pressure environments.

[0013] A thermostat, the holder being arranged in the thermostat, and the thermostat being used for simulating different formation temperature environments.

[0014] Optionally, the fixed assembly comprises:

[0015] A plurality of movable plates, the movable plates being uniformly distributed on the inner wall of the clamping cavity in a circumferential direction, the inner side surface of each movable plate being a curved surface structure adapted to the outer shape of the coal sample, and each movable plate being independently movable in a radial direction.

[0016] An axial constraint ring, the axial constraint ring being arranged at the axial two ends of the movable plate and being used for limiting the axial displacement of the movable plate.

[0017] A radial guide mechanism, the radial guide mechanism connecting the movable plate and the inner wall of the holder and being used for guiding the movable plate to move linearly in a radial direction.

[0018] An elastic sealing layer, the elastic sealing layer being covered on the inner side surface of the movable plate and being used for forming a sealed contact with the surface of the coal sample during the force application process.

[0019] Optionally, the in-situ coal body microbial production and permeability enhancement simulation experiment device further comprises:

[0020] A vacuum system comprising a vacuum pump and a vacuum tank, the vacuum pump being in communication with the clamping cavity and the bacterial population culture system respectively, and the vacuum tank being arranged on the communication pipeline between the vacuum pump and the clamping cavity and the bacterial population culture system.

[0021] Optionally, the in-situ coal body microbial production and permeability enhancement simulation experiment device further comprises:

[0022] A pore anti-reflection volume measurement system, the pore anti-reflection volume measurement system includes a gas cylinder and a standard tank, the gas cylinder, the standard tank and the clamping cavity are connected in sequence along the flow direction, a first stop valve is provided on the connecting pipeline between the gas cylinder and the standard tank, a second stop valve is provided on the connecting pipeline between the standard tank and the clamping cavity, and a pressure gauge is provided on the connecting pipeline between the second stop valve and the standard tank.

[0023] Optionally, the bacterial colony culture system includes:

[0024] a culture tank, the culture tank being used to contain a mixture of bacterial liquid and nutrient solution;

[0025] A water bath, wherein the culture tank is disposed in the water bath, and the water bath is used to control the temperature in the culture tank;

[0026] A piston pump, wherein the output end of the piston pump is arranged in the culture tank, and the piston pump is used to drive the microbial culture solution from the culture tank to be injected into the clamping cavity, and to make the microbial culture solution contact the coal sample.

[0027] Optionally, the bacterial colony culture system further comprises:

[0028] A sampling tube, the sampling tube is connected to the culture tank, and the end of the sampling tube is a sampling port;

[0029] A pH monitor is connected to the sampling tube.

[0030] Optionally, the in-situ coal microbial production and permeability enhancement simulation experimental device further comprises:

[0031] A control system is provided, wherein the control system is used to collect parameter data during the experiment, wherein the parameter data at least includes the real-time temperature and real-time pressure in the containing chamber, the real-time pressure in the clamping chamber, the total gas production and gas production rate measured by the drainage and gas collecting device, the pH value of the microbial culture solution, and the real-time temperature and real-time pressure in the culture tank used to cultivate the microbial culture solution.

[0032] Optionally, the in-situ coal microbial production and permeability enhancement simulation experimental device further comprises:

[0033] A drying tank is used to dry the coal sample before the experiment.

[0034] Another aspect of the present application provides an in-situ coal microbial production and permeability enhancement simulation experimental method, comprising:

[0035] The coal sample is placed in a drying tank for drying;

[0036] Transferring the dried coal sample into a clamping cavity of a clamper, and evacuating the clamping cavity through a vacuum system;

[0037] Axial pressure and confining pressure are applied to the fixed components through the pressure supply system, and the temperature is adjusted using a constant temperature box to simulate the pressure and temperature environment of the target formation;

[0038] Injecting gas into the clamping cavity through a pore permeability enhancement volume measurement system, and calculating the initial pore volume of the coal sample based on pressure gauge data;

[0039] The clamping cavity is evacuated again by the vacuum system to remove residual gas;

[0040] Injecting microbial culture fluid into the clamping cavity through a bacterial culture system, monitoring the pressure in the clamping cavity in real time using a control system, measuring the total amount of gas produced and the gas production rate through a drainage and gas collection device, and analyzing changes in gas composition by sampling through a reference tank;

[0041] After the reaction is completed, the clamping chamber is vacuumed again;

[0042] measuring a final pore volume of the coal sample;

[0043] Based on the difference between the initial pore volume and the final pore volume, combined with gas production data and gas composition changes, the impact of the production-increasing effect of the microbial culture solution on the pore structure and gas production performance of the coal sample is analyzed.

[0044] By means of the above technical solution, this application has at least the following beneficial effects:

[0045] The in-situ coal body microbial production and permeability enhancement simulation experimental device and experimental method provided in the embodiments of the present application, by setting the clamping cavity space volume of the fixed component to be adjustable, can adapt to the fixation of irregular-shaped coal samples, avoid the destruction of the pore structure caused by the regularization of the coal sample, and truly restore the underground occurrence form of the coal body, ensuring that the original pore and fracture characteristics of the coal sample in the experiment are complete, so that the interaction between the microorganism and the coal body is closer to the actual formation conditions, and improve the reliability of the experimental results. At the same time, the gas source component mixes carbon dioxide and methane through the buffer tank to simulate the original gas composition of the coal reservoir; the regulating valve on the connecting pipeline between the buffer tank and the clamping cavity can dynamically adjust the pressure in the clamping cavity, which can reproduce the formation pressure environment of the coal reservoir, thereby constructing physical and chemical conditions that are highly consistent with the actual coal reservoir, providing a basis for studying the metabolic activities of microorganisms in the real formation environment. The bacterial colony cultivation system is connected to the holding chamber, allowing for quantitative injection of a specific microbial culture solution. Fluid diffusion allows for uniform distribution of the bacterial colony within the pores of the coal sample, ensuring sufficient contact between the microorganisms and the coal mass, avoiding experimental errors caused by localized concentration variations, and improving the reproducibility of reaction efficiency. Furthermore, a pressure sensor monitors pressure changes within the holding chamber in real time, reflecting the impact of microbial metabolic activity on the coal pore pressure. A drainage gas collection device automatically collects gas when pressure exceeds a preset threshold, quantifying microbial gas production efficiency by measuring gas production. A reference tank is used to sample and analyze gas composition and identify the types of microbial metabolites, enabling dynamic tracking of the reaction process and providing real-time data support for understanding the mechanisms of microbial gas production. Specifically, the device integrates pressure monitoring, gas production metering, and gas composition analysis, enabling simultaneous acquisition of pressure-gas production rate-gas composition correlation data. Multi-dimensional data cross-analysis reveals the coupling mechanism between microbial metabolic activity, coal pore structure changes, and gas desorption. Furthermore, by adjusting variables such as the holding chamber volume, gas source component ratio, pressure conditions, and bacterial colony type, single- or multi-factor comparative experiments can be conducted. Therefore, by evaluating the impact of various parameters on the microbial production increase effect, the optimal process combination is screened out to provide quantitative guidance for field application. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a structural schematic diagram of an in-situ coal microbial production and permeability enhancement simulation experimental device according to an optional embodiment of the present application;

[0047] Figure 2 This is a flow chart of an in-situ coal microbial production and permeability enhancement simulation experimental method according to an optional embodiment of the present application.

[0048] The reference numerals indicate:

[0049] 1. Clamp; 11. Receiving chamber; 2. Fixing assembly; 21. Clamping chamber; 3. Bacteria culture system; 31. Culture tank; 32. Water bath; 33. Piston pump; 34. Sampling tube; 35. pH monitor; 4. Reaction system; 41. Gas source assembly; 411. Buffer tank; 412. Regulating valve; 413. Reference tank; 42. Monitoring assembly; 421. Pressure sensor; 422. Drainage and gas collecting device; 5. Pressure supply system; 51. Water source; 52. Pressure pump; 6. Constant temperature box; 7. Vacuum system; 71. Vacuum pump; 72. Vacuum tank; 8. Porosity anti-reflection volume measurement system; 81. Gas cylinder; 82. Standard tank; 83. First stop valve; 84. Second stop valve; 85. Pressure gauge; 9. Control system. DETAILED DESCRIPTION

[0050] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0051] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0052] In this application, unless otherwise specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they can refer to fixed connection, detachable connection, or integral connection; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0053] The preferred embodiments of the present application are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present application and are not used to limit the present application.

[0054] See also Figure 1As shown, according to an embodiment of the present application, an in-situ coal body microbial production and permeability enhancement simulation experimental device is provided, comprising a holder 1, a bacterial colony culture system 3 and a reaction system 4; a holding chamber 11 is formed inside the holder 1, a fixing component 2 is provided in the holding chamber 11, a clamping chamber 21 for placing a coal sample is formed inside the fixing component 2, and the spatial volume of the clamping chamber 21 is adjustable; the bacterial colony culture system 3 is connected to the clamping chamber 21 and is used to inject a microbial culture solution into the clamping chamber 21; the reaction system 4 comprises an air source component 41 and a monitoring component 42; the air source component 41 comprises a buffer tank 411 for mixing carbon dioxide and methane, and the buffer tank 411 is connected to the clamping chamber 21; the monitoring component 42 includes a pressure sensor 421 and a drainage and gas collecting device 422 respectively connected to the clamping chamber 21, the pressure sensor 421 is used to monitor the pressure in the clamping chamber 21, and the drainage and gas collecting device 422 is used to collect and measure the gas generated by the reaction in the clamping chamber 21 when the pressure in the clamping chamber 21 is greater than the preset pressure; wherein, a regulating valve 412 for adjusting the pressure in the clamping chamber 21 is provided on the connecting pipeline between the buffer tank 411 and the clamping chamber 21, and a reference tank 413 for sampling to analyze the changes in gas composition in the clamping chamber 21 is provided on the downstream side of the regulating valve 412 along the flow direction.

[0055] In this embodiment, by providing an adjustable volume for the clamping chamber 21 of the fixing assembly 2, it can accommodate irregularly shaped coal samples (such as natural coal fragments and coal samples containing fractures), avoiding the destruction of pore structure caused by regularization of the coal sample, and truly restoring the coal's underground morphology. This ensures that the original pore and fracture characteristics of the coal sample in the experiment are intact, making the interaction between microorganisms and the coal more similar to actual formation conditions, thereby improving the reliability of the experimental results. Simultaneously, the gas source assembly 41 mixes carbon dioxide and methane through a buffer tank 411 to simulate the original gas composition of the coal reservoir (such as the CO2 / CH4 ratio commonly found in coalbed methane). The regulating valve 412 on the connecting line between the buffer tank 411 and the clamping chamber 21 can dynamically adjust the pressure within the clamping chamber 21, reproducing the formation pressure environment of the coal reservoir (such as the high pressure state of deep coal seams), thereby establishing physical and chemical conditions (gas composition and pressure) that are highly consistent with actual coal reservoirs, providing a basis for studying the metabolic activities of microorganisms in real formation environments. At the same time, the bacterial colony culture system 3 is connected to the clamping chamber 21, and can quantitatively inject specific microbial culture fluids (such as methanogens and metabolic gas-producing bacteria), and achieve uniform distribution of the bacterial colony in the pores of the coal sample through fluid diffusion, ensuring full contact between the microorganisms and the coal body, avoiding experimental errors caused by local uneven concentrations, and improving the repeatability of the reaction efficiency. At the same time, the pressure sensor 421 monitors the pressure changes in the clamping chamber 21 in real time, reflecting the impact of microbial metabolic activity (such as gas production rate) on the pore pressure of the coal sample; the drainage gas collection device 422 automatically collects gas when the pressure exceeds the preset threshold, and the gas production efficiency of the microorganism can be quantified by measuring the gas production volume; the reference tank 413 is used to sample and analyze gas components (such as CH4 concentration changes), determine the type of microbial metabolites, and realize dynamic tracking of the reaction process, providing real-time data support for analyzing the microbial gas production mechanism (such as methane generation path). Specifically, the device integrates functions such as pressure monitoring, gas production metering, and gas composition analysis, and can simultaneously obtain correlation data of pressure-gas production rate-gas component. Through multi-dimensional data cross-analysis, the coupling mechanism between microbial metabolic activity, changes in coal pore structure, and gas desorption is revealed (for example, gas production leading to increased pressure promotes gas desorption). Furthermore, by adjusting variables such as the volume of the clamping chamber 21 (simulating different coal densities), the ratio of gas source components (CO2 / CH4 concentration), pressure conditions, and bacterial community type, single-factor or multi-factor comparative experiments can be conducted. Thus, by evaluating the impact of various parameters on the microbial yield enhancement effect, the optimal process combination (such as the optimal pressure threshold and bacterial community ratio) can be screened, providing quantitative guidance for field applications.

[0056] The holder 1 is used to fix the coal sample and provide a controllable reaction space.

[0057] Specifically, the accommodating cavity 11 inside the holder 1 is used to place the fixing assembly 2. The clamping cavity 21 of the fixing assembly 2 provides a space for placing the coal sample, and the volume of the clamping cavity 21 can be adjusted (for example, by an elastic material or a movable baffle) to directly fix the coal sample, so as to avoid the destruction of the original pore structure of the coal body due to the processing into a regular shape. At the same time, by adjusting the volume of the clamping cavity 21, different pressures can be applied to simulate the ground stress environment of the coal reservoir.

[0058] The microbial culture system 3 is used to inject the microbial culture solution to promote the reaction between the coal sample and the microorganisms.

[0059] Specifically, the microbial culture system 3 has a culture solution delivery pipeline, a culture container, and the like, which are in communication with the clamping cavity 21. The microbial culture solution can be methanogenic bacteria, metabolic gas-producing bacteria, and the like, and the microorganisms are delivered into the pores of the coal sample through the microbial culture solution. In actual application scenarios, parameters such as flow rate and concentration can be adjusted to study the effects of the microbial culture solution on the coal sample under different conditions.

[0060] The reaction system 4 is used to simulate a gas environment and monitor the reaction process.

[0061] Specifically, the buffer tank 411 mixes carbon dioxide (CO2) and methane (CH4) to simulate the gas composition in the coal reservoir. The regulating valve 412 controls the gas flow between the buffer tank 411 and the clamping cavity 21 to adjust the pressure in the clamping cavity 21. The reference tank 413 is located downstream of the regulating valve 412 and is used to sample and analyze the gas composition (for example, the change in CH4 concentration). The pressure sensor 421 is used to monitor the pressure change in the clamping cavity 21 in real time. The drainage gas collection device 422 collects and measures the gas (for example, CH4 and CO2) generated by the reaction through the drainage method.

[0062] It can be understood that the working process of the device and the experimental principle are as follows: the coal sample is placed in the clamping cavity 21, and the volume of the clamping cavity 21 is adjusted to fix the coal sample; the buffer tank 411 mixes carbon dioxide (CO2) and methane (CH4), and the regulating valve 412 controls the pressure to inject the simulated gas into the clamping cavity 21; the microbial culture system 3 injects the microbial culture solution into the clamping cavity 21, and the microorganisms in the microbial culture solution reproduce in the pores of the coal sample and react with the coal body. In this process, the pressure sensor 421 records the pressure change in real time. If the microorganisms produce gas to cause the pressure to rise, and when the pressure exceeds a preset value, the drainage gas collection device 422 collects the gas and measures the volume. At the same time, the reference tank 413 is regularly sampled to analyze the gas composition (for example, an increase in CH4 concentration indicates the effect of microbial gas production). Through the data of pressure, gas production, and gas composition, the improvement of the pore structure of the coal body by the microorganisms and the promotion of gas desorption are studied.

[0063] In some possible implemented embodiments disclosed in the present application, referring to Figure 1As shown, the in-situ coal microbial production enhancement and permeability enhancement simulation experimental device also includes a pressure supply system 5 and a constant temperature box 6. The pressure supply system 5 includes a water source 51 and a pressure pump 52. The pressure pump 52 is connected to the water source 51 and the accommodating cavity 11 of the clamp 1 respectively. The pressure pump 52 is used to apply axial pressure and confining pressure to the fixed component 2 respectively to simulate different formation pressure environments; the clamp 1 is arranged in the constant temperature box 6, and the constant temperature box 6 is used to simulate different formation temperature environments.

[0064] In this embodiment, a pressure supply system 5 and a constant temperature box 6 are added to further enhance the device's ability to restore all elements of the in-situ environment of the coal reservoir by simulating the synergistic effect of the formation pressure field and temperature field.

[0065] The water source 51 is used to provide a pressurized medium (usually water).

[0066] The pressure pump 52 is connected to the water source 51 and the accommodating chamber 11 of the clamp 1 , and applies axial pressure (axial pressure) and confining pressure (circumferential pressure) to the fixing assembly 2 by pumping high-pressure water.

[0067] Specifically, in actual application scenarios, when the clamp 1 is cylindrical, the pressure pump 52 is provided with an axial pipe connected to the axial end of the clamp 1 (i.e., the two end faces of the cylinder). The axial pipe is used to apply axial stress to the fixed component 2 inside the clamp 1 to simulate the vertical pressure of the overlying rock formation. An independent switch valve (such as a stop valve) and a pressure gauge (such as a pressure gauge) are provided on the axial pipe to control the start and stop of the axial pressure and monitor the pressure value in real time. In addition, the pressure pump 52 is also provided with an annular pipe connected to the circumferential outer side of the clamp 1 (i.e., the side wall of the cylinder). The annular pipe is used to apply annular stress (confining pressure) to the accommodating cavity 11 of the clamp 1 to simulate the lateral ground stress of the formation. The annular pipe is also equipped with an independent switch valve and a pressure gauge, which do not interfere with the control components of the axial pipe, ensuring that the confining pressure can be adjusted independently of the axial pressure. Therefore, through the independent control of the axial pipe and the annular pipe, stress path simulation and accurate quantification of stress state can be achieved.

[0068] It is understood that during stress path simulation, confining pressure can be applied first, followed by axial pressure, or both simultaneously. To accurately quantify the stress state, the pressure gauges on the axial and annular pipes display the specific values ​​of the axial and confining pressures, respectively, in real time, ensuring the accuracy of the stress conditions during the experiment.

[0069] The thermostat 6 is a closed box with a temperature control system 9 (such as a heating element and a temperature control sensor) disposed therein, and the holder 1 is completely placed inside the thermostat 6. In practical application scenarios, the temperature inside the thermostat 6 can be adjusted by the temperature control system.

[0070] As can be seen, the device can compare gas production curves under different temperature and pressure conditions to assess the adaptability of microorganisms in complex formation environments. Simulating real-world formation conditions also allows the selection of strains that combine temperature and pressure tolerance with high gas production efficiency, thus avoiding the disconnect between ideal laboratory conditions and field applications.

[0071] In some possible embodiments disclosed in the present application, the fixing assembly 2 includes multiple movable plates, axial constraint rings, radial guide mechanisms and elastic sealing layers. The multiple movable plates are evenly distributed on the inner wall of the clamping cavity 21 along the circumferential direction. The inner surface of each movable plate is a curved surface structure adapted to the shape of the coal sample, and each movable plate can move radially independently; the axial constraint rings are arranged at both axial ends of the movable plate to limit the axial displacement of the movable plate; the radial guide mechanism connects the movable plate and the inner wall of the clamp 1 to guide the movable plate to perform linear motion in the radial direction; the elastic sealing layer covers the inner surface of the movable plate to form a sealed contact with the surface of the coal sample during the force application process.

[0072] In this embodiment, a plurality of movable plates evenly distributed along the circumference are provided with a curved surface structure on the inner side, which can independently move radially according to the concave and convex contours of the coal sample and fit closely to the surface of the coal sample, thereby avoiding the clamping gap or stress concentration caused by the irregular shape of the coal sample in the traditional fixing method, ensuring that the coal sample is uniformly stressed during the experiment, and truly simulating the original constraint state of the coal body in the stratum. At the same time, the inner side of the movable plate is covered with an elastic sealing layer (such as flexible materials such as rubber and silicone), which can adaptively fill the micropores on the surface of the coal sample when radial force is applied to form a dynamic seal. At the same time, axial constraint rings are provided at both axial ends of the movable plate, which only allow the movable plate to move radially and limit its axial sliding. At the same time, the movable plate is connected to the inner wall of the clamp 1 through a radial guide mechanism, which is used to guide the movable plate to move in a radial straight line to avoid circumferential offset or jamming.

[0073] Multiple movable plates (e.g., 4, 6, or 8) are evenly arranged around the circumference of the clamping cavity 21, forming a cylindrical clamping space. The inner surface of each movable plate is curved, with the shape of the curved surface matching the local contour of the coal sample (e.g., convex or concave). The movable plates can independently move radially (i.e., along the radius of the clamping cavity 21), without mechanical linkage between them, and their positions can be adjusted independently.

[0074] Specifically, in actual application scenarios, when installing coal samples, the movable plate wraps the coal sample through radial movement, and its curved surface fits the concave and convex surface of the coal sample, achieving precise adaptation to irregular shapes and avoiding the damage to the pore structure of the coal sample by traditional rigid clamping.

[0075] The axial restraint rings are fixed to the axial ends of the movable plate and are fixedly connected to the inner wall of the clamp 1 .

[0076] Specifically, in actual application scenarios, the axial constraint ring limits the movable plate from moving in the axial direction (the length direction of the clamping cavity 21 ) through physical contact, and only allows it to move in the radial direction.

[0077] The radial guide mechanism may be a rail-slider mechanism, a screw-nut mechanism, or a ball guide column.

[0078] Specifically, in actual application scenarios, the radial guide mechanism is a slide rail-slider mechanism, which includes a radial guide rail opened on the inner wall of the clamp 1 and a slider arranged on the outer side of the movable plate. The slider and the guide rail constitute a sliding pair.

[0079] The elastic sealing layer may be made of rubber, silicone or elastic polymer, and is firmly bonded to the inner curved surface of the movable plate through a vulcanization process, with a thickness of about 1 to 3 mm.

[0080] Specifically, in actual application scenarios, the elastic sealing layer has a microporous structure or a corrugated shape to enhance its fit with the surface of the coal sample.

[0081] It can be understood that when the pressure pump 52 of the pressure supply system 5 applies axial pressure to the accommodating chamber 11 of the clamp 1: the axial pressure is transmitted to the axial end surface of each movable plate through the axial constraint ring; due to the special wedge-shaped structure of the movable plate (the outer thickness is greater than the inner thickness), the axial force is decomposed into a radial component, forcing the movable plate to move inward along the radial guide mechanism; each movable plate contracts toward the center synchronously, and its inner surface is tightly attached to the surface of the coal sample through the elastic sealing layer; the elastic sealing layer elastically deforms, adaptively filling the concave and convex areas of the coal sample surface, forming a stable constraint state with multiple points of contact. When the pressure pump 52 of the pressure supply system 5 applies confining pressure to the accommodating chamber 11 of the clamp 1: the confining pressure acts on the inner wall of the clamp 1 and is evenly transmitted to the outer surface of each movable plate through the pressurized medium (such as water); under the action of the radial pressure, the movable plate moves further inward along the radial guide mechanism, strengthening the constraint force on the coal sample; the elastic sealing layer undergoes plastic deformation under higher pressure, further optimizing the contact state with the coal sample surface, ensuring sealing performance and uniform constraint force. In this embodiment, through the synergistic effect of axial pressure and confining pressure, the fixing assembly 2 can simulate the triaxial stress state of the coal body at different stratum depths.

[0082] In some possible implementations disclosed in this application, see Figure 1 As shown, the in-situ coal microbial production enhancement and permeability enhancement simulation experimental device also includes a vacuum system 7, which includes a vacuum pump 71 and a vacuum tank 72. The vacuum pump 71 is connected to the clamping chamber 21 and the bacterial culture system 3 respectively, and the vacuum tank 72 is arranged on the connecting pipeline between the vacuum pump 71 and the clamping chamber 21 and the bacterial culture system 3.

[0083] In this embodiment, the vacuum pump 71 can create a negative pressure environment close to the original situ by evacuating the clamping chamber 21 and the bacterial culture system 3, making the experimental conditions closer to the actual geological scene and ensuring that the growth and metabolic characteristics of microorganisms in a similar real environment can be accurately simulated.

[0084] The vacuum pump 71 is used to generate a negative pressure environment and is the power source of the vacuum system 7. Through the suction action, the air pressure in the experimental device is reduced to a state lower than the atmospheric pressure.

[0085] The vacuum tank 72 is a container connected between the vacuum pump 71 and the experimental device (clamping chamber 21, bacterial culture system 3), which plays the role of buffering airflow and stabilizing negative pressure.

[0086] Specifically, in actual application scenarios, vacuum pump 71 is connected to clamping chamber 21 and bacterial culture system 3 through pipelines, forming two negative pressure pathways. Vacuum tank 72 is connected in series to the pipelines connecting vacuum pump 71 and the above two, located downstream of vacuum pump 71. Vacuum tank 72 is equipped with a vacuum gauge for measuring the vacuum level.

[0087] In some possible implementations disclosed in this application, see Figure 1 As shown, the in-situ coal body microbial production enhancement and permeability enhancement simulation experimental device also includes a pore permeability enhancement volume measurement system 8, which includes a gas cylinder 81 and a standard tank 82. The gas cylinder 81, the standard tank 82 and the clamping chamber 21 are connected in sequence along the flow direction. A first stop valve 83 is provided on the connecting pipeline between the gas cylinder 81 and the standard tank 82, a second stop valve 84 is provided on the connecting pipeline between the standard tank 82 and the clamping chamber 21, and a pressure gauge 85 is provided on the connecting pipeline between the second stop valve 84 and the standard tank 82.

[0088] In this embodiment, pressure changes are monitored by pressure gauge 85. Combined with the volume of standard tank 82 and the gas state equation, the effective permeability-enhancing volume of the coal sample (i.e., the pore space actually occupied by the gas) can be calculated. By repeatedly opening and closing first and second shut-off valves 83 and 84, changes in pore volume at different experimental stages (e.g., before and after microbial incubation) can be monitored in real time, allowing for a quantitative assessment of the effect of microbial metabolites (e.g., gas, acid) on pore permeability enhancement.

[0089] The gas cylinder 81 is used to store high-pressure gas as a measuring medium, which is an inert gas such as nitrogen or helium that is chemically stable and does not react with the coal sample or microorganisms.

[0090] The standard tank 82 is a sealed container with a known volume, serving as a gas volume reference.

[0091] The clamping cavity 21 is a cavity for placing the coal sample, and the internal pore structure of the coal sample is the measurement object.

[0092] The first stop valve 83 is used to control the connection and disconnection between the gas cylinder 81 and the standard tank 82 so as to realize the filling of the standard tank 82 or isolate the gas source.

[0093] The second stop valve 84 is used to control the opening and closing of the standard tank 82 and the clamping cavity 21 to realize the release of gas into the internal pores of the coal sample or the isolated pores to enhance the permeability volume measurement system 8 .

[0094] The pressure gauge 85 is used to monitor the outlet pressure of the standard tank 82 in real time. The outlet pressure can be used as the system pressure of the pore anti-reflection volume measurement system 8.

[0095] It is understood that the operating principle of the pore permeability enhancement volume measurement system 8 is as follows: close the second shut-off valve 84 and open the first shut-off valve 83; inflate the standard tank 82 with gas from the gas cylinder 81 to a preset pressure, at which point the gas state within the standard tank 82 is: P1, V1; close the first shut-off valve 83 to isolate the gas source; record the initial pressure (P1); open the second shut-off valve 84, allowing gas to flow into the internal pores of the coal sample within the clamping chamber 21; after the pressures equilibrate, record the stabilized pressure (P2), at which point the total system volume is V2. Based on the ideal gas equation: P1V1 = P2V2, the total system volume (V2) can be calculated, thereby solving for the internal pore volume of the coal sample (V2 - V1).

[0096] In some possible implementations disclosed in this application, see Figure 1 As shown, the bacterial culture system 3 includes a culture tank 31, a water bath 32 and a piston pump 33; the culture tank 31 is used to contain a mixture of bacterial liquid and nutrient solution; the culture tank 31 is arranged in the water bath 32, and the water bath 32 is used to control the temperature in the culture tank 31; the output end of the piston pump 33 is arranged in the culture tank 31, and the piston pump 33 is used to drive the microbial culture liquid from the culture tank 31 to be injected into the clamping cavity 21, and make the microbial culture liquid contact the coal sample.

[0097] The culture tank 31 is used to contain a mixture of bacterial liquid and nutrient solution, serving as a carrier for the growth and reproduction of microorganisms.

[0098] The water bath 32 provides a suitable growth environment for the microorganisms in the culture tank 31 by controlling the temperature.

[0099] The piston pump 33 is used to inject the microbial culture fluid from the culture tank 31 into the clamping chamber 21, bringing it into contact with the coal sample. By adjusting the output pressure of the piston pump 33, the permeability of the microbial culture fluid under different formation pressures can be simulated. For example, increasing the pump pressure can drive the microbial culture fluid into the pores of the coal sample.

[0100] In some possible implementations disclosed in this application, see Figure 1As shown, the bacterial culture system 3 further includes a sampling tube 34 and a pH monitor 35 ; the sampling tube 34 is connected to the culture tank 31 , and the end of the sampling tube 34 is a sampling port; the pH monitor 35 is connected to the sampling tube 34 .

[0101] Among them, one end of the sampling tube 34 is connected to the lower middle part of the tank body to ensure that the evenly mixed culture solution is extracted, and the other end extends to the outside of the equipment to form a sampling port.

[0102] Specifically, a valve (e.g., a ball valve or a stopcock) is provided on the sampling tube 34 to control the opening / closing of the sampling port, thereby preventing outside air or bacteria from entering the culture tank 31 during the sampling process. The sampling port can be equipped with a sealing cap or a sterile interface to ensure that the system is sealed when not sampling, thereby maintaining the sterility of the culture environment.

[0103] The pH monitor 35 is directly connected to the sampling tube 34 to provide real-time feedback of pH data.

[0104] Specifically, the pH monitor 35 is connected in parallel to the sampling tube 34 via a three-way interface, directly contacts the culture solution, and detects the pH value in real time.

[0105] In some possible implementations disclosed in this application, see Figure 1 As shown, the in-situ coal body microbial production enhancement and permeability enhancement simulation experimental device also includes a control system 9, which is used to collect parameter data during the experiment. The parameter data at least include the real-time temperature and real-time pressure in the accommodating chamber 11, the real-time pressure in the clamping chamber 21, the total gas production and gas production rate measured by the drainage and gas collecting device 422, the pH value of the microbial culture solution, and the real-time temperature and real-time pressure in the culture tank 31 used to cultivate the microbial culture solution.

[0106] Among them, the control system 9 can adopt a computer-data acquisition card architecture to realize the automatic collection and processing of parameters of the entire experimental process.

[0107] Specifically, in order to collect the real-time temperature and real-time pressure data in the accommodating chamber 11, a pressure and temperature sensor connected to the data acquisition card is set in the accommodating chamber 11; in order to collect the real-time pressure data in the clamping chamber 21, the pressure sensor 421 connected to the clamping chamber 21 is also connected to the data acquisition card; in order to collect the total gas production and gas production rate data measured by the drainage gas collecting device 422, a flow meter is set upstream of the drainage gas collecting device 422, and the flow meter and the drainage gas collecting device 422 are connected to the data acquisition card; in order to collect the pH value data of the microbial culture solution, the pH monitor 35 is connected to the data acquisition card; in order to collect the real-time temperature and real-time pressure data in the culture tank 31, a pressure and temperature sensor connected to the data card is set in the culture tube.

[0108] In some possible embodiments disclosed in the present application, the in-situ coal microbial production and permeability enhancement simulation experimental device further includes a drying tank, which is used to dry the coal sample before the experiment.

[0109] In this embodiment, the free water and part of the bound water in the coal sample are removed by drying, so that the initial conditions of the experiment can be made uniform, and the data accuracy, repeatability and engineering relevance of the coal sample microbial yield enhancement experiment can be improved.

[0110] Furthermore, in order to fully illustrate the specific implementation process of the in-situ coal body microbial production and permeability enhancement simulation experimental device, an in-situ coal body microbial production and permeability enhancement simulation experimental method is provided, see Figure 2 As shown, the method includes:

[0111] Step S101: placing the coal sample in a drying tank for drying.

[0112] Here, the coal sample is placed in a drying tank for drying. The main purpose is to remove moisture from the pores of the coal sample to ensure that the data measured in subsequent experiments can reflect the actual pore structure and gas adsorption characteristics of the coal sample.

[0113] Step S201 : The dried coal sample is transferred into the clamping cavity 21 of the clamper 1 , and the clamping cavity 21 is evacuated by the vacuum system 7 .

[0114] Here, the clamping chamber 21 is evacuated by the vacuum system 7. This not only removes the air in the clamping chamber 21, preventing it from interfering with the analysis results of the gas composition in subsequent experiments, but also allows the coal sample to be placed in a low-pressure environment similar to that of the formation, paving the way for subsequent simulation of the formation pressure environment.

[0115] Step S301: applying axial pressure and confining pressure to the fixing assembly 2 through the pressure supply system 5, and adjusting the temperature through the constant temperature box 6 to simulate the pressure environment and temperature environment of the target formation.

[0116] Here, axial and confining pressures are applied to the fixed assembly 2 via a pressure supply system 5, while the temperature is adjusted using a constant temperature chamber 6 to simulate the pressure and temperature environment of the target formation. Axial pressure simulates the vertical stress of the formation, while confining pressure simulates the lateral stress. The temperature is set based on the actual temperature of the target formation. This ensures that the coal sample environment during the experiment is similar to that of the actual formation, thereby ensuring that the experimental results are more valuable.

[0117] Step S401 : injecting gas into the clamping cavity 21 through the pore anti-permeability volume measurement system 8 , and calculating the initial pore volume of the coal sample according to the data of the pressure gauge 85 .

[0118] Here, the pore volume measurement system 8 injects gas of known pressure and volume into the holding chamber 21. The initial pore volume of the coal sample is then calculated based on the data from the pressure gauge 85. This data serves as a key parameter for subsequent analysis of the microbial yield enhancement effect. By comparing the changes in pore volume before and after the experiment, the effect of microorganisms on the pore structure of the coal sample can be assessed.

[0119] Step S501: The clamping chamber 21 is evacuated again by the vacuum system 7 to remove residual gas.

[0120] Here, the clamping chamber 21 is evacuated again by the vacuum system 7 to remove the residual gas, ensure that the reaction between the subsequently injected microbial culture solution and the coal sample will not be affected by the previous residual gas, ensure the purity of the experimental environment, and make the experimental results more accurate and reliable.

[0121] Step S601: inject microbial culture fluid into the clamping cavity 21 through the bacterial culture system 3, use the control system 9 to monitor the pressure in the clamping cavity 21 in real time, measure the total gas production and gas production rate through the drainage and gas collection device 422, and sample and analyze the changes in gas composition through the reference tank 413.

[0122] Here, the microbial culture fluid is injected into the holding chamber 21 via the bacterial colony cultivation system 3, and the pressure within the holding chamber 21 is monitored in real time by the control system 9. Simultaneously, the total amount and rate of gas production are measured by the drainage and gas collection device 422, and gas composition changes are analyzed by sampling in the reference tank 413. During this process, microorganisms decompose organic matter in the coal, producing gases such as methane. By monitoring and analyzing this data, we can understand the metabolic activity of the microorganisms and their gas production.

[0123] Step S701: After the reaction is completed, the clamping chamber 21 is vacuumed again.

[0124] Here, after the reaction is completed, the clamping chamber 21 is evacuated again, mainly to collect the residual gas so as to conduct a comprehensive analysis of the gas composition after the reaction, and also to prepare for the subsequent measurement of the final pore volume.

[0125] Step S801: measuring the final pore volume of the coal sample.

[0126] Here, the final pore volume of the coal sample is measured using a method similar to step S401. Comparing the final pore volume with the initial pore volume can intuitively show the impact of microbial activity on the pore structure of the coal sample, such as whether the pores have increased or enlarged.

[0127] Step S901: Based on the difference between the initial pore volume and the final pore volume, combined with the gas production data and the change in gas composition, the effect of the microbial culture fluid on the pore structure and gas production performance of the coal sample is analyzed.

[0128] Here, we analyze the impact of microbial culture fluid on the pore structure and gas production performance of coal samples based on the difference between initial and final pore volumes, combined with gas production data and gas composition changes. This comprehensive analysis of these data allows us to assess the feasibility and effectiveness of microbial production enhancement technology in practical applications, providing a theoretical basis for coalbed methane development.

[0129] It is easy for those skilled in the art to understand that, under the premise of no conflict, the above-mentioned advantageous methods can be freely combined and superimposed.

[0130] The above are merely preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application. The above are merely preferred embodiments of the present application. It should be noted that those skilled in the art may make various improvements and variations without departing from the technical principles of the present application, and such improvements and variations shall also be considered within the scope of protection of the present application.

Claims

1. An in-situ coal microbial production and permeability enhancement simulation experimental device, characterized in that: include: A holder, wherein a receiving cavity is formed inside the holder, a fixing assembly is provided inside the receiving cavity, a clamping cavity for placing the coal sample is formed inside the fixing assembly, and the spatial volume of the clamping cavity is adjustable; a bacterial colony culture system, the bacterial colony culture system being in communication with the clamping cavity and being used for injecting a microbial culture solution into the clamping cavity; A reaction system, the reaction system comprising a gas source assembly and a monitoring assembly; the gas source assembly comprising a buffer tank for mixing carbon dioxide and methane, the buffer tank being in communication with the clamping chamber; the monitoring assembly comprising a pressure sensor and a drainage and gas collecting device, each in communication with the clamping chamber, the pressure sensor being configured to monitor the pressure within the clamping chamber, the drainage and gas collecting device being configured to collect and measure the gas generated by the reaction within the clamping chamber when the pressure within the clamping chamber exceeds a preset pressure; A regulating valve for adjusting the pressure in the clamping cavity is provided on the connecting pipeline between the buffer tank and the clamping cavity, and a reference tank for sampling to analyze the changes in gas composition in the clamping cavity is provided on the downstream side of the regulating valve along the flow direction.

2. The in-situ coal microbial production and permeability enhancement simulation experimental device according to claim 1 is characterized in that: Also includes: a pressure supply system comprising a water source and a pressure pump, the pressure pump being in communication with the water source and the accommodating chamber of the clamp, respectively, and being configured to apply axial pressure and confining pressure to the fixing assembly, respectively, to simulate different formation pressure environments; A constant temperature box, wherein the clamp is arranged in the constant temperature box, and the constant temperature box is used to simulate different formation temperature environments.

3. The in-situ coal microbial production and permeability enhancement simulation experimental device according to claim 2 is characterized in that: The fixing assembly includes: A plurality of movable plates, the plurality of movable plates being evenly distributed along the circumferential direction on the inner wall of the clamping cavity, the inner surface of each movable plate being a curved surface structure adapted to the shape of the coal sample, and each movable plate being independently movable radially; Axial restraint rings, which are provided at both axial ends of the movable plate and are used to limit the axial displacement of the movable plate; a radial guide mechanism, the radial guide mechanism connecting the movable plate and the inner wall of the clamper, and used for guiding the movable plate to perform linear motion in a radial direction; An elastic sealing layer, which covers the inner surface of the movable plate and is used to form a sealed contact with the surface of the coal sample during the force application process.

4. The in-situ coal microbial production and permeability enhancement simulation experimental device according to claim 1 is characterized in that: Also includes: The vacuum system includes a vacuum pump and a vacuum tank. The vacuum pump is connected to the clamping cavity and the bacterial culture system respectively. The vacuum tank is arranged on the connecting pipeline between the vacuum pump, the clamping cavity and the bacterial culture system.

5. The in-situ coal microbial production and permeability enhancement simulation experimental device according to claim 1 is characterized in that: Also includes: A pore anti-reflection volume measurement system, the pore anti-reflection volume measurement system includes a gas cylinder and a standard tank, the gas cylinder, the standard tank and the clamping cavity are connected in sequence along the flow direction, a first stop valve is provided on the connecting pipeline between the gas cylinder and the standard tank, a second stop valve is provided on the connecting pipeline between the standard tank and the clamping cavity, and a pressure gauge is provided on the connecting pipeline between the second stop valve and the standard tank.

6. The in-situ coal microbial production and permeability enhancement simulation experimental device according to claim 1 is characterized in that: The bacterial colony culture system comprises: a culture tank, the culture tank being used to contain a mixture of bacterial liquid and nutrient solution; A water bath, wherein the culture tank is disposed in the water bath, and the water bath is used to control the temperature in the culture tank; A piston pump, wherein the output end of the piston pump is arranged in the culture tank, and the piston pump is used to drive the microbial culture solution from the culture tank to be injected into the clamping cavity, and to make the microbial culture solution contact the coal sample.

7. The in-situ coal microbial production and permeability enhancement simulation experimental device according to claim 6 is characterized in that: The bacterial colony culture system further comprises: A sampling tube, the sampling tube is connected to the culture tank, and the end of the sampling tube is a sampling port; A pH monitor is connected to the sampling tube.

8. The in-situ coal microbial production and permeability enhancement simulation experimental device according to claim 1 is characterized in that: Also includes: A control system is provided, wherein the control system is used to collect parameter data during the experiment, wherein the parameter data at least includes the real-time temperature and real-time pressure in the containing chamber, the real-time pressure in the clamping chamber, the total gas production and gas production rate measured by the drainage and gas collecting device, the pH value of the microbial culture solution, and the real-time temperature and real-time pressure in the culture tank used to cultivate the microbial culture solution.

9. The in-situ coal microbial production and permeability enhancement simulation experimental device according to claim 1 is characterized in that: Also includes: A drying tank is used to dry the coal sample before the experiment.

10. An in-situ coal microbial production and permeability enhancement simulation experimental method, characterized in that: include: The coal sample is placed in a drying tank for drying; Transferring the dried coal sample into a clamping cavity of a clamper, and evacuating the clamping cavity through a vacuum system; Axial pressure and confining pressure are applied to the fixed components through the pressure supply system, and the temperature is adjusted using a constant temperature box to simulate the pressure and temperature environment of the target formation; Injecting gas into the clamping cavity through a pore permeability enhancement volume measurement system, and calculating the initial pore volume of the coal sample based on pressure gauge data; The clamping cavity is evacuated again by the vacuum system to remove residual gas; Injecting microbial culture fluid into the clamping cavity through a bacterial culture system, monitoring the pressure in the clamping cavity in real time using a control system, measuring the total amount of gas produced and the gas production rate through a drainage and gas collection device, and analyzing changes in gas composition by sampling through a reference tank; After the reaction is completed, the clamping chamber is vacuumed again; measuring a final pore volume of the coal sample; Based on the difference between the initial pore volume and the final pore volume, combined with gas production data and gas composition changes, the impact of the production-increasing effect of the microbial culture solution on the pore structure and gas production performance of the coal sample is analyzed.

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