Simulation experiment device and method for coal measure gas enrichment

Abstract

The embodiment of the invention provides a simulation experiment device and method for coal-series gas enrichment, and relates to the technical field of natural gas exploration and development. The simulation experiment device for coal series gas enrichment comprises a first reaction cabin, a second reaction cabin and a third reaction cabin which are sequentially communicated and stacked, the first reaction cabin is used for containing a bottom rock sample, the second reaction cabin is used for containing a coal seam sample, and the third reaction cabin is used for containing a top rock sample; the injection system is communicated with the first reaction cabin; the first reaction cabin, the second reaction cabin and the third reaction cabin are respectively provided with at least one stress loader and at least one heater. Through collaborative design of multi-cabin layered sample bearing and independent stress and temperature regulation, confining pressure constraint and interlayer stress transfer of a top plate rock sample and a bottom layer rock sample to a coal seam sample are accurately simulated, the real occurrence environment of coal series gas in a stratum is reduced, the influence of interlayer stress on coal series gas enrichment is prevented from being ignored, and obtained experimental data are more reliable.

Description

Technical Field

[0001] This application relates to the field of natural gas exploration and development technology, and in particular to a simulation experimental apparatus and method for coalbed methane enrichment. Background Technology

[0002] Coal-bearing gas refers to various types of natural gas found in coal-bearing reservoirs, primarily unconventional natural gas such as coalbed methane, coalbed shale gas, and coalbed sandstone gas. Gas-bearing shale and coalbed methane are mostly located below 1,000 meters and are influenced by stress and temperature fields. During the enrichment process of coal-bearing gas, different stress and temperature fields are key factors affecting the efficient accumulation of coal-bearing gas within the strata. Therefore, experimental studies on the enrichment capacity of coal-bearing gas under different geological conditions are necessary.

[0003] In related technologies, the simulation experimental device for coalbed methane enrichment includes an injection system, a reaction chamber, a pressurization device, and a heating device. The reaction chamber is used to fix the coal seam sample, the pressurization device and the heating device are used to provide the coal seam sample with a triaxial stress and temperature field consistent with the formation, and the injection system is used to transport natural gas into the coal seam sample to simulate the formation environment, thereby conducting natural gas enrichment experiments.

[0004] However, the coal seam is located thousands of meters underground, and there are rocks above and below the coal seam. The interlayer pressure between the rocks and the coal seam affects the coalbed methane enrichment process, which leads to errors in the coalbed methane experimental results. Summary of the Invention

[0005] This application provides a simulation experimental apparatus and method for coalbed methane enrichment, which overcomes the limitations of existing technologies that only conduct experiments on individual coal seams. However, actual coal seams are located thousands of meters underground, with rocks above and below them. The interlayer pressure between the rocks and the coal seam affects the coalbed methane enrichment process, resulting in errors in the coalbed methane experimental results.

[0006] In a first aspect, embodiments of this application provide a simulation experimental device for coalbed methane enrichment, comprising: a reaction system, the reaction system comprising a first reaction chamber, a second reaction chamber and a third reaction chamber connected in series, the first reaction chamber being used to contain bottom rock samples, the second reaction chamber being used to contain coal seam samples, and the third reaction chamber being used to contain roof rock samples, wherein the first reaction chamber, the second reaction chamber and the third reaction chamber are arranged in a stacked manner.

[0007] An injection system, which is connected to the first reaction chamber, is used to deliver coalbed methane into the bottom rock sample.

[0008] Multiple stress loaders and multiple heaters are provided, and the first reaction chamber, the second reaction chamber and the third reaction chamber are each provided with at least one stress loader and at least one heater.

[0009] In one possible implementation, the first reaction chamber and the second reaction chamber, as well as the second reaction chamber and the third reaction chamber, are connected by annular sealing rings. The annular sealing rings have annular openings that form a flow path between the first reaction chamber, the second reaction chamber, and the third reaction chamber.

[0010] In one possible implementation, the injection system includes a first gas storage tank, a second gas storage tank, and a water storage tank.

[0011] The first gas storage tank is connected to the first reaction chamber through a first gas transmission pipe. A first regulating valve is installed on the first gas transmission pipe. The first gas storage tank is used to store coal-based gas.

[0012] The second gas storage tank is connected to the first reaction chamber through a second gas supply pipe. A second regulating valve is installed on the second gas supply pipe. The second gas storage tank is used to store rare gases.

[0013] The water storage tank is connected to the first reaction chamber via a water supply pipe, and a water supply regulating valve is installed on the water supply pipe.

[0014] In one possible implementation, a recovery system is also included, comprising a gas-liquid separator and a dryer. The third reaction chamber is connected to the inlet of the gas-liquid separator via a discharge pipe. The gas-liquid separator has a gas outlet and a liquid outlet. The liquid outlet is connected to the water storage tank via a return pipe, and the gas outlet is connected to the inlet of the dryer.

[0015] In one possible implementation, a backpressure device is also included, comprising a backpressure valve and a backpressure control pump. The backpressure valve is disposed on the discharge pipe, and the backpressure control pump is connected to the backpressure valve. The backpressure control pump is used to control the opening degree of the backpressure valve.

[0016] In one possible implementation, a data acquisition and monitoring system is also included, which includes multiple strain gauges, multiple pressure sensors, and multiple temperature sensors. At least one strain gauge, at least one pressure sensor, and at least one temperature sensor are provided in each of the first reaction chamber, the second reaction chamber, and the third reaction chamber.

[0017] Both the strain gauge and the pressure sensor are used to be installed on the surface of the bottom rock sample, the coal seam sample, and the roof rock sample.

[0018] In one possible implementation, a first pressure gauge and a second pressure gauge are also included, with the first pressure gauge located at the inlet end of the first reaction chamber.

[0019] The second pressure gauge is installed on the discharge pipe between the back pressure valve and the third reaction chamber.

[0020] In one possible implementation, the stress loader includes a lateral loading mechanism and an axial loading mechanism. The lateral loading mechanism includes a first pressure block and a first driving member. The output end of the first driving member is connected to the first pressure block. The first driving member is used to drive the first pressure block to apply lateral pressure to the side of one of the bottom rock sample, the coal seam sample, and the roof rock sample.

[0021] The axial loading mechanism includes a second pressure block and a second driving member. The output end of the second driving member is connected to the second pressure block. The second driving member is used to drive the second pressure block to apply axial pressure to the end face of one of the bottom rock sample, the coal seam sample, and the roof rock sample.

[0022] In one possible implementation, the heater includes a heating element and an insulation layer, and the insulation layer is provided on the outer periphery of the first reaction chamber, the second reaction chamber, and the third reaction chamber.

[0023] Secondly, embodiments of this application provide a simulation experimental method for coalbed methane enrichment, employing a simulation experimental apparatus for coalbed methane enrichment as provided in the first aspect. The simulation experimental apparatus for coalbed methane enrichment includes a reaction system, an injection system, multiple stress loaders, and multiple heaters. The reaction system includes a first reaction chamber, a second reaction chamber, and a third reaction chamber connected in series. The experimental method includes the following steps.

[0024] The first reaction chamber contains bottom rock samples, the second reaction chamber contains coal seam samples, and the third reaction chamber contains roof rock samples.

[0025] The stress loaders apply stress to the bottom rock sample in the first reaction chamber until a first preset stress is reached, to the coal seam sample in the second reaction chamber until a second preset stress is reached, and to the roof rock sample in the third reaction chamber until a third preset stress is reached.

[0026] The bottom rock sample in the first reaction chamber is heated by multiple heaters until it reaches a first preset temperature, the coal seam sample in the second reaction chamber is heated until it reaches a second preset temperature, and the roof rock sample in the third reaction chamber is heated until it reaches a third preset temperature.

[0027] Coal-bearing gas is introduced into the first reaction chamber through an injection system until the bottom rock sample, the coal seam sample, and the roof rock sample in the reaction system are all filled with coal-bearing gas.

[0028] This application provides a simulation experimental device and method for coalbed methane enrichment. The simulation experimental device consists of a first reaction chamber, a second reaction chamber, and a third reaction chamber connected in series and stacked sequentially. Each chamber is used to hold bottom rock samples, coal seam samples, and roof rock samples corresponding to the strata, respectively. Each chamber is equipped with a stress loader and a heater. By layering and independently controlling the stress and temperature of the samples in multiple reaction chambers, the confining pressure constraint of the roof rock samples and bottom rock samples on the coal seam samples, as well as the interlayer stress transfer, is accurately simulated. This restores the true stress field of the coal seam under the combined action of the top and bottom rock samples, thereby restoring the true occurrence environment of coalbed methane in the strata. This avoids the situation where stress is only applied to the coal seam samples, which may lead to the neglect of the enrichment deviation caused by coalbed methane channeling under the action of interlayer stress. Through the collaborative design of multi-chamber segmented sample holding and independent stress and temperature control, this application restores the true occurrence environment of coalbed methane in the strata. The experimental data obtained are more reliable and practical, providing strong support for the study of coalbed methane enrichment mechanism and field exploration and development. Attached Figure Description

[0029] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0030] Figure 1 A schematic diagram of the structure of the simulation experimental device for coalbed methane enrichment provided in this application;

[0031] Figure 2 for Figure 1 A schematic diagram of the structure of the first, second, or third reaction chamber in the simulation experimental device for coalbed methane enrichment provided in the paper;

[0032] Figure 3 for Figure 1 A partial cross-sectional view of the first reaction chamber in the simulation experimental device for coalbed methane enrichment provided in China.

[0033] Explanation of reference numerals in the attached figures:

[0034] 100 - Reaction system; 110 - First reaction chamber; 120 - Second reaction chamber; 130 - Third reaction chamber;

[0035] 200 - Injection system; 210 - First gas storage tank; 211 - First gas supply pipe; 212 - First regulating valve; 220 - Second gas storage tank; 221 - Second gas supply pipe; 222 - Second regulating valve; 230 - Water storage tank; 231 - Water supply pipe; 232 - Water supply regulating valve;

[0036] 300 - Stress loader; 310 - Lateral loading mechanism; 311 - First pressure block; 312 - First driving member; 320 - Axial loading mechanism; 321 - Second pressure block; 322 - Second driving member;

[0037] 400 - Heater; 410 - Heating element; 420 - Insulation layer;

[0038] 500 - Annular seal; 510 - Annular opening;

[0039] 600 - Recovery system; 610 - Gas-liquid separator; 611 - Gas outlet; 612 - Liquid outlet; 620 - Dryer; 630 - Discharge pipe;

[0040] 700 - Back pressure device; 710 - Back pressure valve; 720 - Back pressure control pump;

[0041] 800 - Data acquisition and monitoring system; 810 - Strain gauge; 820 - Pressure sensor; 830 - Temperature sensor; 840 - First pressure gauge; 850 - Second pressure gauge; 860 - Chromatograph; 870 - Gas flow meter.

[0042] The accompanying drawings have illustrated specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to specific embodiments. Detailed Implementation

[0043] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0044] The terms "first," "second," "third," etc. (if present) in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein.

[0045] Secondly, it should be noted that in the description of this application, the terms "inner", "outer", "first direction", "second direction", etc., indicating the direction or positional relationship are based on the direction or positional relationship shown in the drawings. This is only for the convenience of description and does not indicate or imply that the device or component must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this application.

[0046] Furthermore, it should be noted that, in the description of this application, unless otherwise expressly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0047] As shown in the background art, the simulation experimental device for coalbed methane enrichment includes an injection system, a reaction chamber, a pressurization device, and a heating device. The reaction chamber is used to fix the coal seam sample, the pressurization device and the heating device are used to provide the coal seam sample with a triaxial stress and temperature field consistent with the formation, and the injection system is used to deliver natural gas into the coal seam sample to simulate the formation environment and then conduct natural gas enrichment experiments.

[0048] However, the coal seam is located thousands of meters underground, and there are rocks above and below the coal seam. The interlayer pressure between the rocks and the coal seam affects the coalbed methane enrichment process, which leads to errors in the coalbed methane experimental results.

[0049] Understandably, in coal-bearing strata, coal seams are mostly located below 1,000 meters, with rock strata on both sides. The bottom strata below the coal seam are mostly dense mudstone, limestone, or siltstone, while the top strata are mostly more plastic mudstone and shale, or sometimes permeable sandstone. Most natural gas is stored in coal seams. The coal-bearing gas enrichment process refers to the migration of natural gas (both free and adsorbed) within the coal seam from its formation area to a favorable storage space (within the coal seam) under the combined influence of geological conditions (pressure, temperature, tectonic movement) and its own conditions (porosity, permeability), continuously accumulating until it reaches a concentration with industrial exploitability (or an experimentally observable effective concentration).

[0050] However, the enrichment of coalbed methane is controlled by a variety of geological factors, including its own conditions, the influence of tectonic movements on the migration of coalbed methane, and the influence of the pressure difference between rock strata and coal seams on coalbed methane.

[0051] Therefore, conventional experiments using a single coal seam can only detect the flow and accumulation of gas within the coal seam, making it difficult to reproduce the actual state of coal-bearing gas in the strata. Furthermore, the pressure difference between the rock strata and the coal seam can easily cause coal-bearing gas to penetrate vertically into the rock strata and flow along the transverse fractures of the rock strata, leading to gas leakage. Consequently, the experimental results obtained by using only a coal seam may differ from those of the actual strata.

[0052] To address the aforementioned technical problems, this application provides a simulation experimental apparatus and method for coalbed methane enrichment, comprising: a reaction system including a first reaction chamber, a second reaction chamber, and a third reaction chamber connected in series, wherein the first reaction chamber is used to contain bottom rock samples, the second reaction chamber is used to contain coal seam samples, and the third reaction chamber is used to contain roof rock samples, and the first reaction chamber, the second reaction chamber, and the third reaction chamber are arranged in a stacked manner; an injection system connected to the first reaction chamber, the injection system being used to deliver coalbed methane into the bottom rock samples; and multiple stress loaders and multiple heaters, wherein each of the first reaction chamber, the second reaction chamber, and the third reaction chamber is equipped with at least one stress loader and at least one heater.

[0053] The simulation experimental device comprises a first reaction chamber, a second reaction chamber, and a third reaction chamber, connected in series and stacked sequentially. Each chamber holds bottom rock samples, coal seam samples, and roof rock samples corresponding to the strata, respectively. Each chamber is equipped with a stress loader and a heater. By layering and independently controlling the stress and temperature of the samples within each chamber, the device accurately simulates the confining pressure constraints and interlayer stress transfer exerted on the coal seam samples by the roof and bottom rock samples. This recreates the true stress field of the coal seam samples under the combined action of the top and bottom rock samples, thus reproducing the true occurrence environment of coal-bearing gas in the strata. This avoids the situation where stress is applied only to the coal seam samples, neglecting the enrichment deviation caused by coal-bearing gas channeling under interlayer stress. This application, through the synergistic design of multi-chamber segmented sample holding and independent stress and temperature control, recreates the true occurrence environment of coal-bearing gas in the strata. The experimental data obtained are more reliable and practical, providing strong support for the study of coal-bearing gas enrichment mechanisms and field exploration and development.

[0054] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will be described below with reference to the accompanying drawings.

[0055] In a first aspect, embodiments of this application provide a simulation experimental apparatus for coalbed methane enrichment, referring to... Figure 1 and Figure 2As shown, it includes: a reaction system 100, which includes a first reaction chamber 110, a second reaction chamber 120 and a third reaction chamber 130 connected in sequence. The first reaction chamber 110 is used to contain bottom rock samples, the second reaction chamber 120 is used to contain coal seam samples, and the third reaction chamber 130 is used to contain roof rock samples. The first reaction chamber 110, the second reaction chamber 120 and the third reaction chamber 130 are arranged in a stacked manner.

[0056] The injection system 200 is connected to the first reaction chamber 110 and is used to deliver coalbed methane into the bottom rock sample.

[0057] Multiple stress loaders 300 and multiple heaters 400 are provided in the first reaction chamber 110, the second reaction chamber 120 and the third reaction chamber 130, each equipped with at least one stress loader 300 and at least one heater 400.

[0058] The second reaction chamber 120 is equipped with a third reaction chamber 130 and a first reaction chamber 110 on its upper and lower sides, corresponding to the actual geological environment. The second reaction chamber 120 can hold coal seam samples, the third reaction chamber 130 located above the coal seam samples can hold roof rock samples, and the first reaction chamber 110 located below the coal seam samples can hold bottom rock samples. The three of them constitute a closed geological system.

[0059] Each reaction chamber is equipped with a stress loader 300 and a heater 400. The stress loader 300 and the heater 400 can be precisely adjusted according to the stress and temperature experienced by samples at different depths in the real strata to recreate the stratum environment.

[0060] Furthermore, the injection system 200 can be connected to the first reaction chamber 110. By using the injection system 200 to inject coalbed methane into the bottom rock sample, the coalbed methane can move along the bottom rock sample toward the coal seam sample in the second reaction chamber 120, so that it stores coalbed methane, simulating the real occurrence environment of coalbed methane in the strata, so as to conduct experiments.

[0061] Specifically, refer to Figure 1As shown, the simulation experimental device consists of a first reaction chamber 110, a second reaction chamber 120, and a third reaction chamber 130 arranged in a sequentially connected and stacked manner. Each chamber is used to hold bottom rock samples, coal seam samples, and roof rock samples corresponding to the strata, respectively. Each chamber is equipped with a stress loader 300 and a heater 400. By layering and independently controlling the stress and temperature of the samples in each reaction chamber, the device accurately simulates the confining pressure constraint of the roof rock samples and bottom rock samples on the coal seam samples, as well as the interlayer stress transfer. This restores the true stress field of the coal seam samples under the combined action of the roof rock samples and bottom rock samples, thereby restoring the true occurrence environment of coalbed methane in the strata. This avoids the situation where stress is only applied to the coal seam samples, which leads to the neglect of the enrichment deviation caused by coalbed methane channeling under the action of interlayer stress. This application, through the collaborative design of multi-compartment segmented sample bearing and independent stress and temperature control, restores the real occurrence environment of coalbed methane in the strata. The experimental data obtained are more reliable and practical, providing strong support for the study of coalbed methane enrichment mechanism and field exploration and development.

[0062] In one possible implementation, combining Figure 1 and Figure 2 As shown, the first reaction chamber 110 and the second reaction chamber 120, as well as the second reaction chamber 120 and the third reaction chamber 130, are connected by annular sealing rings 500. The annular sealing ring 500 has an annular opening 510, which forms a flow path between the first reaction chamber 110, the second reaction chamber 120 and the third reaction chamber 130.

[0063] Combination Figure 1 and Figure 2 As shown, the first reaction chamber 110, the second reaction chamber 120 and the third reaction chamber 130 are arranged in a sequential stacked manner, and the corresponding bottom rock samples, coal seam samples and roof rock samples are also stacked vertically, with annular sealing rings 500 placed between the end faces.

[0064] The annular sealing ring 500 has an annular opening 510, which forms a flow path between the first reaction chamber 110, the second reaction chamber 120 and the third reaction chamber 130, preventing coal-based gas and water from leaking out of the gaps between the chambers, and ensuring that the water, coal-based gas and rare gas delivered by the injection system 200 are transported only through the annular opening 510.

[0065] Furthermore, the annular sealing ring 500 fits into the mating surface of the adjacent compartments to form a sealing barrier. On the one hand, the annular sealing ring 500 can firmly lock the high-pressure environment inside the compartment, prevent the interlayer pressure in the three compartments from leaking outward, ensure the stable transmission of pressure from the bottom layer to the coal seam to the roof, and avoid the distortion of enrichment dynamic simulation caused by pressure loss.

[0066] In one possible implementation, reference is made to Figure 1 As shown, the injection system 200 includes a first gas storage tank 210, a second gas storage tank 220, and a water storage tank 230.

[0067] The first gas storage tank 210 is connected to the first reaction chamber 110 through the first gas transmission pipe 211. The first gas transmission pipe 211 is equipped with a first regulating valve 212. The first gas storage tank 210 is used to store coal-based gas.

[0068] The second gas storage tank 220 is connected to the first reaction chamber 110 through the second gas supply pipe 221. The second gas supply pipe 221 is equipped with a second regulating valve 222. The second gas storage tank 220 is used to store rare gases.

[0069] The water storage tank 230 is connected to the first reaction chamber 110 through the water supply pipe 231, and the water supply pipe 231 is equipped with a water supply regulating valve 232.

[0070] The first gas storage tank 210 is used to store coal-bearing gas, and the second gas storage tank 220 is used to store rare gases. The rare gases are stable and do not react with the bottom rock samples, coal seam samples, or roof rock samples, and do not interfere with the adsorption and desorption of coal-bearing gas.

[0071] The first gas storage tank 210 and the second gas storage tank 220 can be switched via their respective regulating valves (first regulating valve 212 and second regulating valve 222) to realize the coalbed methane enrichment experiment.

[0072] Understandably, the second regulating valve 222 can be opened first to transport the rare gas in the second gas storage tank 220 to the bottom rock sample in the first reaction chamber 110 along the second gas transmission pipe 221, and the transmission can continue so that the bottom rock sample, coal seam sample and roof rock sample all contain rare gas, and the airtightness of the reaction system 100 can be tested to avoid gas leakage during the experiment and cause errors.

[0073] Furthermore, the first regulating valve 212 can precisely control the rate and pressure of coalbed methane delivery, and the coalbed methane supply intensity can be set as needed. Similarly, a water storage tank 230 can be set up, and the water supply regulating valve 232 on the water supply pipe 231 can precisely control the water injection volume and pressure, so that water is injected into the bottom rock sample, coal seam sample, and roof rock sample, simulating the formation water and gas occurrence state, restoring the real geological environment of "coalbed methane-formation water" coexistence, avoiding the large deviation between the simulated coalbed methane adsorption amount and migration resistance and the actual situation due to only storing coalbed methane, so as to improve the enrichment mechanism research under multi-factor coupling during the experiment.

[0074] In one possible implementation, such as Figure 1As shown, it also includes a recovery system 600, which includes a gas-liquid separator 610 and a dryer 620. The third reaction chamber 130 is connected to the inlet of the gas-liquid separator 610 through a discharge pipe 630. The gas-liquid separator 610 has a gas outlet 611 and a liquid outlet 612. The liquid outlet 612 is connected to the water storage tank 230 through a return pipe 640, and the gas outlet 611 is connected to the inlet of the dryer 620.

[0075] Combination Figure 1 As shown, the recovery system 600 uses a gas-liquid separator 610 to separate the mixed medium (coal gas and water) discharged from the third reaction chamber 130. The gas-liquid separator 610 is equipped with an independent gas outlet 611 and a liquid outlet 612 to avoid gas composition detection distortion and liquid metering deviation caused by gas-liquid mixing, so as to make the calculation of coal seam enrichment and inter-layer flow more accurate.

[0076] The outlet 612 of the gas-liquid separator 610 is connected to the water storage tank 230 through the return pipe 640. The water separated by the gas-liquid separator 610 can be returned to the water storage tank 230 for recycling, which not only restores the real geological environment, but also realizes the recycling of water media and avoids water waste.

[0077] Furthermore, referring to Figure 1 As shown, the outlet 611 of the gas-liquid separator 610 is connected to the dryer 620. The dryer 620 can remove moisture and impurities from the recovered coal gas. On the one hand, it avoids moisture from interfering with the detection of the composition and concentration of the coal gas (such as moisture affecting the detection accuracy of the chromatograph 860), ensuring the accuracy of experimental data such as the coal gas loss rate. On the other hand, the dried gas has stable properties and can be used as needed, avoiding pipeline blockage or gas source pollution caused by impurities.

[0078] In one possible implementation, such as Figure 1 As shown, it also includes a back pressure device 700, which includes a back pressure valve 710 and a back pressure control pump 720. The back pressure valve 710 is disposed on the discharge pipe 630, and the back pressure control pump 720 is connected to the back pressure valve 710. The back pressure control pump 720 is used to control the opening degree of the back pressure valve 710.

[0079] like Figure 1 As shown, the back pressure control pump 720 can precisely adjust the opening of the back pressure valve 710. During the experiment, a gradient back pressure value can be set as needed. In conjunction with the independent stress loaders 300 in the first reaction chamber 110, the second reaction chamber 120, and the third reaction chamber 130, it can simulate the back pressure of stable formations at normal burial depths, as well as the abnormal back pressure in structural zones such as faults and folds. It can also realize the step-like rise and fall of back pressure, and accurately observe the influence of back pressure changes on the enrichment of coal seam samples, the sealing properties of roof rock samples, and the interlayer flow.

[0080] In one possible implementation, combining Figure 1 and Figure 2 As shown, it also includes a data acquisition and monitoring system 800, which includes multiple strain gauges 810, multiple pressure sensors 820 and multiple temperature sensors 830. At least one strain gauge 810, at least one pressure sensor 820 and at least one temperature sensor 830 are installed in each of the first reaction chamber 110, the second reaction chamber 120 and the third reaction chamber 130.

[0081] Both strain gauge 810 and pressure sensor 820 are used to be placed on the surface of bottom rock samples, coal seam samples and roof rock samples.

[0082] Combination Figure 1 and Figure 2 As shown, pressure sensors 820 in the first reaction chamber 110, the second reaction chamber 120, and the third reaction chamber 130 are all deployed on the surface or inside the corresponding bottom rock sample, coal seam sample, and roof rock sample to capture the pressure distribution of the bottom rock sample, coal seam sample, and roof rock sample in real time, so as to confirm whether the pore pressure is consistent with the formation and maintains balance, thereby ensuring that the structural simulation environment is completed for subsequent experimental operations.

[0083] Strain gauges 810 in the first reaction chamber 110, the second reaction chamber 120, and the third reaction chamber 130 are arranged on the surface of the corresponding bottom rock sample, coal seam sample, and roof rock sample. The strain gauges 810 can monitor the elastic and plastic deformation of the samples under pressure and temperature in real time (such as the expansion of the coal seam sample after adsorbing coal gas and the development of cracks in the roof rock sample after being compressed).

[0084] Temperature sensor 830 detects the temperature in the three reaction chambers to ensure stable heating conditions and avoid abnormal adsorption and desorption characteristics of coal-based gas caused by temperature fluctuations.

[0085] The data acquisition and monitoring system 800, injection system 200, stress loader 300, and heater 400 can all be electrically connected to a controller (not shown in the figure). The strain gauge 810, pressure sensor 820, and temperature sensor 830 of the data acquisition and monitoring system 800 can transmit the detected pressure, strain, and temperature data back to the injection system 200, stress loader 300, and heater 400 in real time. The controller dynamically adjusts the injection intensity of the injection system 200, the loading force of the stress loader 300, and the heating power of the heater 400 to ensure that the stress field and temperature field in the three reaction chambers are consistent with the actual strata, thereby improving the accuracy and stability of the simulation.

[0086] In addition, it should be noted that, in combination Figure 1As shown, a chromatograph 860 can also be installed, which is connected to a dryer 620. The dryer 620 can remove moisture and impurities from the recovered coal gas.

[0087] The chromatograph 860 can accurately separate and detect various components in coalbed methane (the core component of coalbed methane, methane or ethane, as well as impurity gases, etc.) to detect changes in the concentration and proportion of each component, thereby forming a closed loop for accounting of data such as "injected gas volume - enriched gas volume - lost gas volume".

[0088] Specifically, the chromatograph 860 can receive the changes in concentration and composition of coalbed methane discharged from the reaction system 100 and dried by the dryer 620. It can not only verify whether the composition of the coalbed methane delivered to the reaction system 100 changes during the experiment (such as whether it reacts with the sample), but also calculate the specific proportion of coalbed methane loss during the migration of coalbed methane from the bottom rock sample to the top rock sample, the adsorption and enrichment of coal seam samples, and the crossflow loss of top rock samples. This clarifies the main control link of coalbed methane enrichment and solves the problem that traditional experiments cannot trace the destination of coalbed methane.

[0089] In addition, a gas flow meter 870 can be installed at the outlet of the dryer 620. This gas flow meter 870 can monitor the flow rate of coal gas output from the dryer 620 in real time. Furthermore, the gas flow meter 870 can also function as a monitoring instrument. If the gas-liquid separator 610 fails (liquid level too high or drain valve stuck), liquid will rush into the gas flow meter 870, causing a sudden drop or excessive fluctuation in flow rate. This will trigger an immediate alarm and stop the flow, preventing any impact on experimental results.

[0090] Furthermore, in combination Figure 1 As shown, it also includes a first pressure gauge 840 and a second pressure gauge 850, with the first pressure gauge 840 located at the inlet end of the first reaction chamber 110.

[0091] The second pressure gauge 850 is installed on the discharge pipe 630 between the back pressure valve 710 and the third reaction chamber 130.

[0092] Reference Figure 1 As shown, the first pressure gauge 840 is located at the inlet of the first reaction chamber 110 to accurately monitor the initial injection pressure of the medium (coal-bearing gas, rare gas, and formation water) input by the injection system 200 into the bottom rock sample in the first reaction chamber 110, clarify the dynamic benchmark for bottom gas and water supply, and avoid the distortion of interlayer pressure supply caused by the failure to detect injection pressure fluctuations in time.

[0093] The second pressure gauge 850 is installed on the discharge pipe 630 between the third reaction chamber 130 and the back pressure valve 710. It accurately monitors the end discharge pressure after the complete transfer through the "bottom layer-coal seam-roof" and captures the pressure status at the outlet of the third reaction chamber 130, thus avoiding back pressure control deviation caused by the lack of benchmark monitoring of the end pressure.

[0094] The first pressure gauge 840 and the second pressure gauge 850 are compared with the pressure sensors 820 in the three reaction chambers at any time to provide real-time feedback on the initial and final pressures of the reaction system 100. Secondary pressure calibration is performed to prevent excessively high final pressure from causing fracture development and flow in the roof rock sample, or excessively low pressure from causing pressure imbalance in the chamber. This ensures dynamic balance in the three reaction chambers, avoids sudden pressure changes that could damage the physical properties of coal and rock samples, and guarantees the stability and repeatability of the experiment.

[0095] In one possible implementation, reference is made to Figure 2 As shown, the stress loader 300 includes a lateral loading mechanism 310 and an axial loading mechanism 320. The lateral loading mechanism 310 includes a first pressure block 311 and a first driving member 312. The output end of the first driving member 312 is connected to the first pressure block 311. The first driving member 312 is used to drive the first pressure block 311 to apply lateral pressure to the side of one of the bottom rock sample, the coal seam sample and the roof rock sample.

[0096] The axial loading mechanism 320 includes a second pressure block 321 and a second driving member 322. The output end of the second driving member 322 is connected to the second pressure block 321. The second driving member 322 is used to drive the second pressure block 321 to apply axial pressure to the end face of one of the bottom rock sample, the coal seam sample and the roof rock sample.

[0097] Understandably, each reaction chamber is independently equipped with a stress loader 300, and each stress loader 300 can apply confining pressure to the corresponding rock or coal sample in the chamber to simulate the pressure experienced by the actual strata.

[0098] Specifically, the stress loader 300 can be divided into a lateral loading mechanism 310 and an axial loading mechanism 320. The first pressure block 311 of the lateral loading mechanism 310 matches the outer periphery of the corresponding bottom rock sample, coal seam sample or roof rock sample. The first pressure block 311 is driven by the first driving member 312 to apply lateral pressure to the side of the corresponding rock sample or coal sample to simulate the horizontal tectonic stress and interlayer shear stress in the strata.

[0099] The axial loading mechanism 320 drives the second pressure block 321 through the second driving member 322 to apply axial pressure to the end face of the corresponding rock or coal sample, simulating the vertical burial pressure of the stratum.

[0100] The lateral loading mechanism 310 and the axial loading mechanism 320 can be independently set to pressure values ​​and loading rates. All three reaction chambers are equipped with the lateral loading mechanism 310 and the axial loading mechanism 320. The appropriate axial pressure (corresponding to vertical pressure at different burial depths) and lateral pressure (corresponding to horizontal tectonic stress in different rock strata) can be set for the different physical properties of bottom rock samples, coal seam samples, and roof rock samples. This accurately simulates the differential distribution and transmission process of interlayer stress (such as the transmission of axial pressure from the roof to the coal seam and the influence of interlayer lateral shear stress on gas migration channels). This solves the problem that traditional methods of loading only the coal seam cannot adapt to interlayer differences, which leads to ignoring the influence of interlayer pressure on the coalbed methane enrichment process and thus causing large errors in experimental results.

[0101] In one possible implementation, reference is made to Figure 2 and Figure 3 As shown, the heater 400 includes a heating element 410 and an insulation layer 420. The outer periphery of the first reaction chamber 110, the second reaction chamber 120 and the third reaction chamber 130 are all provided with an insulation layer 420.

[0102] Understandably, in combination Figure 2 and Figure 3 As shown, each of the first reaction chamber 110, the second reaction chamber 120, and the third reaction chamber 130 is individually equipped with a heating element 410 and an insulation layer 420.

[0103] Heating element 410 provides a stable heat source for rock and coal samples inside the chamber to regulate the temperature inside the chamber. Insulation layer 420 covers the outer periphery of each of the three reaction chambers, which can effectively prevent heat loss from the chamber to the outside and isolate the external ambient temperature interference, avoiding sudden temperature fluctuations inside the chamber. This ensures that each chamber containing bottom rock samples, coal seam samples, and roof rock samples can maintain a stable set temperature, so that the formation temperature field simulation is more accurate and temperature fluctuations do not affect the experimental results.

[0104] Secondly, embodiments of this application provide a simulation experimental method for coalbed methane enrichment, employing the simulation experimental apparatus for coalbed methane enrichment as provided in the first aspect. The simulation experimental apparatus for coalbed methane enrichment includes a reaction system 100, an injection system 200, multiple stress loaders 300, and multiple heaters 400. The reaction system 100 includes a first reaction chamber 110, a second reaction chamber 120, and a third reaction chamber 130 connected in sequence. The experimental method includes the following steps.

[0105] The first reaction chamber 110 contains bottom rock samples, the second reaction chamber 120 contains coal seam samples, and the third reaction chamber 130 contains roof rock samples.

[0106] Multiple stress loaders 300 apply stress to the bottom rock sample in the first reaction chamber 110 until the first preset stress is reached, apply stress to the coal seam sample in the second reaction chamber 120 until the second preset stress is reached, and apply stress to the roof rock sample in the third reaction chamber 130 until the third preset stress is reached.

[0107] Multiple heaters 400 respectively heat the bottom rock sample in the first reaction chamber 110 until it reaches the first preset temperature, heat the coal seam sample in the second reaction chamber 120 until it reaches the second preset temperature, and heat the roof rock sample in the third reaction chamber 130 until it reaches the third preset temperature.

[0108] Coal-bearing gas is introduced into the first reaction chamber 110 through the injection system 200 until the bottom rock sample, coal seam sample and roof rock sample in the reaction system 100 are filled with coal-bearing gas.

[0109] Specifically, firstly, top slab samples, coal seam samples, and bottom slab samples that are consistent with the actual strata lithology can be selected and placed in the third reaction chamber 130, the second reaction chamber 120, and the first reaction chamber 110 in sequence.

[0110] Then, the back pressure valve 710 at the outlet of the third reaction chamber 130 can be closed, the second regulating valve 222 can be opened, and the rare gas in the second gas storage tank 220 can be injected into the bottom rock sample in the first reaction chamber 110. The rare gas can continue to be introduced so that the rare gas moves along the bottom rock sample toward the coal seam sample in the second reaction chamber 120. After the three reaction chambers are filled with rare gas, the second regulating valve 222 can be closed and left to stand. The first pressure gauge 840 and the second pressure gauge 850 can be observed to see if there is any change. If there is no change, the airtightness is good.

[0111] Then, stress can be applied to the samples using stress loaders 300 in the three corresponding chambers to achieve the same stress as the formation. Specifically, the stress loader 300 in the first reaction chamber 110 applies stress to the bottom rock sample until it reaches the first preset stress, the stress loader 300 in the second reaction chamber 120 applies stress to the coal seam sample until it reaches the second preset stress, and the stress loader 300 in the third reaction chamber 130 applies stress to the roof rock sample until it reaches the third preset stress.

[0112] Among them, the first preset stress, the second preset stress, and the third preset stress are different stresses that are borne according to different actual stratum depths.

[0113] Similarly, the heater 400 located in the first reaction chamber 110 can be used to heat the bottom rock sample until it reaches the first preset temperature, the heater 400 located in the second reaction chamber 120 can be used to heat the coal seam sample until it reaches the second preset temperature, and the heater 400 located in the third reaction chamber 130 can be used to heat the roof rock sample until it reaches the third preset temperature, so that the preset temperature in the three chambers is consistent with the actual temperature of the real strata.

[0114] This setup is intended to create a realistic stress and temperature field environment for the geological strata.

[0115] Subsequently, the backpressure valve 710 can be adjusted to match the formation pressure, and the first regulating valve 212 can be opened to inject coalbed methane from the first gas storage tank 210 into the bottom rock sample in the first reaction chamber 110. The injection rate is controlled by the first regulating valve 212 to continue introducing coalbed methane, allowing it to move along the bottom rock sample towards the coal seam sample in the second reaction chamber 120. Simultaneously, the pore pressure of the samples in each chamber is monitored by the pressure sensor 820. When the pore pressure of the sample reaches the preset pressure value of the backpressure valve 710 and remains stable, it can be determined that the samples in the three chambers have reached adsorption equilibrium, and there is no need to continue injecting coalbed methane. This simulates the actual coalbed methane occurrence environment in the formation, facilitating subsequent experiments.

[0116] In addition, after the coalbed methane reaches adsorption equilibrium, the water supply regulating valve 232 can be opened, and the water in the water storage tank 230 can be injected into the bottom rock sample in the first reaction chamber 110. The injection rate can be controlled by the water supply regulating valve 232 to continue injecting water until water flows out of the outlet of the third reaction chamber 130. Then the water supply regulating valve 232 is closed to simulate the water content of the formation.

[0117] After the simulation environment is constructed, the pressure can be reduced in stages by adjusting the back pressure valve 710, and data such as the enrichment gas production flow rate and cumulative gas production under the pressure steps can be recorded to provide support for the study of coalbed methane enrichment mechanism.

[0118] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A simulation experimental apparatus for coalbed methane enrichment, characterized in that, include: The reaction system (100) includes a first reaction chamber (110), a second reaction chamber (120), and a third reaction chamber (130) connected in series. The first reaction chamber (110) is used to contain bottom rock samples, the second reaction chamber (120) is used to contain coal seam samples, and the third reaction chamber (130) is used to contain roof rock samples. The first reaction chamber (110), the second reaction chamber (120), and the third reaction chamber (130) are arranged in a stacked manner. An injection system (200) is connected to the first reaction chamber (110) and is used to deliver coalbed methane into the bottom rock sample; Multiple stress loaders (300) and multiple heaters (400) are provided in the first reaction chamber (110), the second reaction chamber (120) and the third reaction chamber (130), each equipped with at least one stress loader (300) and at least one heater (400).

2. The simulation experimental apparatus for coalbed methane enrichment according to claim 1, characterized in that, The first reaction chamber (110) and the second reaction chamber (120), as well as the second reaction chamber (120) and the third reaction chamber (130), are connected by annular sealing rings (500). The annular sealing rings (500) have annular openings (510), which form a flow path between the first reaction chamber (110), the second reaction chamber (120), and the third reaction chamber (130).

3. The simulation experimental apparatus for coalbed methane enrichment according to claim 1, characterized in that, The injection system (200) includes a first gas storage tank (210), a second gas storage tank (220), and a water storage tank (230). The first gas storage tank (210) is connected to the first reaction chamber (110) through the first gas transmission pipe (211). The first gas transmission pipe (211) is equipped with a first regulating valve (212). The first gas storage tank (210) is used to store coal-based gas. The second gas storage tank (220) is connected to the first reaction chamber (110) through the second gas supply pipe (221). The second gas supply pipe (221) is equipped with a second regulating valve (222). The second gas storage tank (220) is used to store rare gases. The water storage tank (230) is connected to the first reaction chamber (110) through a water supply pipe (231), and a water supply regulating valve (232) is provided on the water supply pipe (231).

4. The simulation experimental apparatus for coalbed methane enrichment according to claim 3, characterized in that, It also includes a recovery system (600), which includes a gas-liquid separator (610) and a dryer (620). The third reaction chamber (130) is connected to the inlet of the gas-liquid separator (610) through a discharge pipe (630). The gas-liquid separator (610) has an air outlet (611) and a liquid outlet (612). The liquid outlet (612) is connected to the water storage tank (230) through a return pipe (640). The air outlet (611) is connected to the inlet of the dryer (620).

5. The simulation experimental apparatus for coalbed methane enrichment according to claim 4, characterized in that, It also includes a back pressure device (700), which includes a back pressure valve (710) and a back pressure control pump (720). The back pressure valve (710) is disposed on the discharge pipe (630), and the back pressure control pump (720) is connected to the back pressure valve (710). The back pressure control pump (720) is used to control the opening degree of the back pressure valve (710).

6. The simulation experimental apparatus for coalbed methane enrichment according to claim 5, characterized in that, It also includes a data acquisition and monitoring system (800), which includes multiple strain gauges (810), multiple pressure sensors (820) and multiple temperature sensors (830). At least one strain gauge (810), at least one pressure sensor (820) and at least one temperature sensor (830) are provided in the first reaction chamber (110), the second reaction chamber (120) and the third reaction chamber (130). The strain gauge (810) and the pressure sensor (820) are both used to be installed on the surface of the bottom rock sample, the coal seam sample and the roof rock sample.

7. The simulation experimental apparatus for coalbed methane enrichment according to claim 6, characterized in that, It also includes a first pressure gauge (840) and a second pressure gauge (850), wherein the first pressure gauge (840) is located at the inlet end of the first reaction chamber (110); The second pressure gauge (850) is located on the discharge pipe (630) between the back pressure valve (710) and the third reaction chamber (130).

8. The simulation experimental apparatus for coalbed methane enrichment according to any one of claims 1-7, characterized in that, The stress loader (300) includes a lateral loading mechanism (310) and an axial loading mechanism (320). The lateral loading mechanism (310) includes a first pressure block (311) and a first driving member (312). The output end of the first driving member (312) is connected to the first pressure block (311). The first driving member (312) is used to drive the first pressure block (311) to apply lateral pressure to the side of one of the bottom rock sample, the coal seam sample, and the roof rock sample. The axial loading mechanism (320) includes a second pressure block (321) and a second driving member (322). The output end of the second driving member (322) is connected to the second pressure block (321). The second driving member (322) is used to drive the second pressure block (321) to apply axial pressure to the end face of one of the bottom rock sample, the coal seam sample and the roof rock sample.

9. The simulation experimental apparatus for coalbed methane enrichment according to any one of claims 1-7, characterized in that, The heater (400) includes a heating element (410) and an insulation layer (420), and the insulation layer (420) is provided on the outer periphery of the first reaction chamber (110), the second reaction chamber (120) and the third reaction chamber (130).

10. A simulation experimental method for coalbed methane enrichment, characterized in that, The simulation experimental apparatus for coalbed methane enrichment as described in any one of claims 1-9 is used. The apparatus comprises a reaction system (100), an injection system (200), multiple stress loaders (300), and multiple heaters (400). The reaction system (100) includes a first reaction chamber (110), a second reaction chamber (120), and a third reaction chamber (130) connected in series. The experimental method includes the following steps: The first reaction chamber (110) contains bottom rock samples, the second reaction chamber (120) contains coal seam samples, and the third reaction chamber (130) contains roof rock samples; The stress loaders (300) respectively apply stress to the bottom rock sample in the first reaction chamber (110) until the first preset stress is reached, apply stress to the coal seam sample in the second reaction chamber (120) until the second preset stress is reached, and apply stress to the roof rock sample in the third reaction chamber (130) until the third preset stress is reached. The bottom rock sample in the first reaction chamber (110) is heated by multiple heaters (400) until it reaches a first preset temperature, the coal seam sample in the second reaction chamber (120) is heated until it reaches a second preset temperature, and the roof rock sample in the third reaction chamber (130) is heated until it reaches a third preset temperature. Coal-bearing gas is introduced into the first reaction chamber (110) through the injection system (200) until the bottom rock sample, the coal seam sample and the roof rock sample in the reaction system (100) are filled with coal-bearing gas.

Images