Evaluation method and equipment for free adsorption ratio of deep coal gas

Abstract

The present invention provides a method and device for evaluating the free adsorption ratio of deep coal-rock gas, relating to the technical field of coal-rock gas development. The method comprises: constructing a microscopic pore composite model with different rock pore diameters based on a coal-rock sample to be evaluated; wherein the microscopic pore composite model is constructed based on the material composition of the coal-rock sample to be evaluated and the full-scale pore characteristics of the coal-rock sample; setting simulation environment parameters for the microscopic pore composite model, adsorbing a preset gas into the microscopic pore composite model, achieving equilibrium in the microscopic pore composite model based on density functional theory, and establishing a dynamic evolution model by varying the pore diameter of the microscopic pore composite model to obtain simulation data under different simulation environment parameters; and determining the free adsorption ratio of deep coal-rock gas based on the simulation data under different simulation environment parameters and a preset free adsorbed gas ratio model. The present invention can improve the accuracy of the free adsorption ratio of deep coal-rock gas.

Description

Technical Field

[0001] The present invention relates to the technical field of coal-rock gas development, and in particular to an evaluation method and evaluation equipment for the free adsorption ratio of deep coal-rock gas. Background Art

[0002] With the continuous growth of global energy demand, coal-rock gas (CLG) has gradually gained attention as a clean energy source. The acquisition of CLG mainly depends on the gas adsorption characteristics in coal rock. Therefore, the study of its adsorption and free behavior has become an important part of CLG development.

[0003] The formation and occurrence of coal-rock gas are closely related to the porous structure, composition, and burial depth of the coal rock. In deep coal seams, the physical and chemical properties of coal-rock gas vary with changes in temperature and pressure, which has a significant impact on the adsorption capacity and movement behavior of coal-rock gas. In addition, the high temperature and high pressure environment of deep coal seams will also change the movement mode of gas molecules, affecting their existence state in the coal rock. Studies have shown that the adsorption process of gas in coal rock is affected by many factors, including the specific surface area of ​​coal, pore structure, and the characteristics of gas molecules. In deep coal seams, due to the more complex geological conditions, the adsorption characteristics of gas may exhibit different behaviors from those in shallow layers.

[0004] Currently, the adsorption capacity of coal-rock gas, and thus the proportion of free gas, is primarily estimated by fitting adsorption models based on laboratory-measured coal sample adsorption isotherms. However, because the physical and chemical properties of coal are affected by complex factors such as formation temperature, pressure, coal seam structure, and composition, current evaluation methods cannot accurately determine the proportion of free adsorption of deep coal-rock gas. Summary of the Invention

[0005] The embodiment of the present invention provides an evaluation method and evaluation equipment for the free adsorption ratio of deep coal-rock gas, so as to solve the problem that the current evaluation method cannot accurately evaluate the free adsorption ratio of deep coal-rock gas.

[0006] In a first aspect, an embodiment of the present invention provides a method for evaluating the free adsorption ratio of deep coal gas, comprising:

[0007] A microscopic pore composite model of different rock pore sizes is constructed based on the coal rock sample to be evaluated; wherein the microscopic pore composite model is constructed based on the material composition of the coal rock sample to be evaluated and the full-scale pore characteristics of the coal rock sample;

[0008] The simulation environment parameters of the microporous composite model are set, and a preset gas is adsorbed into the microporous composite model. Based on density functional theory, the microporous composite model is brought into equilibrium. A dynamic evolution model is established by changing the pore size of the microporous composite model to obtain simulation data under different simulation environment parameters.

[0009] Based on the simulation data under different simulation environment parameters and the preset free adsorbed gas ratio model, the free adsorption ratio of deep coal gas is determined.

[0010] In one possible implementation, the microscopic pore composite model is constructed using a graphene plate as a medium, and the graphene plate has the same material composition as the coal rock sample to be evaluated;

[0011] Material composition includes total organic carbon and mineral composition.

[0012] In one possible implementation, the microscopic pore composite model includes a first box, a pore channel, and a second box, wherein the first box and the second box are connected via the pore channel, and the first box, the second channel, and the third box all use graphene as a medium;

[0013] The first box is an adsorption box, which is used to adsorb the preset gas to achieve dynamic equilibrium of the preset gas;

[0014] The pore channels include graphene circular channels with various pore sizes;

[0015] The second box is an empty box with graphene as the medium.

[0016] In one possible implementation, the full-scale pore characteristics of the coal rock sample include characteristics of the micropores, mesopores, and macropores of the coal rock sample.

[0017] In a possible implementation, the simulation environment parameters include normal temperature, ground temperature, high temperature, pressure, simulation time step, and aperture.

[0018] In a possible implementation, the preset gas is methane, and the simulation data includes the number of methane molecules at different positions in the microscopic pore composite model at different temperatures, pressures, and pore sizes.

[0019] In one possible implementation, the free adsorbed gas ratio model k is:

[0020]

[0021] in, is the number of free gas molecules in the micropores, R0 is the proportion of micropores, is the number of free gas molecules in the mesopores, R1 is the proportion of mesopores, is the number of free gas molecules in the macropores, R2 is the proportion of macropores, is the number of adsorbed gas molecules in the micropores, is the number of gas molecules adsorbed in the mesopores.

[0022] In one possible implementation, the number of free gases in the macropores is The calculation method is:

[0023]

[0024] Wherein, N is the total number of adsorbed preset gas molecules.

[0025] In one possible implementation, the number of free gases in micropores, the number of adsorbed gases in micropores, the number of free gases in mesopores, and the number of adsorbed gases in mesopores are determined based on simulation data under different parameters.

[0026] In the second aspect, an embodiment of the present invention provides an evaluation device for the free adsorption ratio of deep coal gas, including a memory and a processor, the memory storing a computer program, and the processor implementing the method in the first aspect or any possible implementation method of the first aspect when executing the computer program.

[0027] In an embodiment of the present invention, to more accurately reflect the material composition and full-scale pore characteristics of a coal rock sample, a microscopic pore composite model with different rock pore sizes was constructed based on the coal rock sample to be evaluated. To account for the environmental parameters of the actual on-site analysis process of the coal rock, the microscopic pore composite model was set with corresponding environmental simulation parameters. Preset gases were then adsorbed, and molecular dynamics simulation was used to recreate the gas adsorption behavior and dynamic migration process in the coal rock, generating simulated data under different simulated environmental parameters. Finally, based on the simulated data under different simulated environmental parameters and a pre-set free adsorbed gas ratio model, the free adsorbed ratio of deep coal rock gas can be determined. This improves the accuracy of the free adsorbed ratio calculation and provides a more reliable theoretical basis for the exploration and development of deep coal rock gas. Furthermore, compared with traditional experimental methods, the method provided by the present invention is not restricted by geological conditions and can be conducted anytime and anywhere, improving research efficiency. Furthermore, through molecular-level simulation, a deeper understanding of the microscopic behavior of methane molecules can be achieved, providing a scientific basis for resource exploration and development. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a flow chart for implementing a method for evaluating the free adsorption ratio of deep coal gas provided by an embodiment of the present invention;

[0029] Figure 2 is a schematic diagram of a microscopic pore composite model provided by an embodiment of the present invention;

[0030] Figure 3 Schematic diagram of the occurrence and migration pattern of methane gas after adsorption into a microscopic pore composite model provided by an embodiment of the present invention;

[0031] Figure 4It is a structural schematic diagram of a device for evaluating the free adsorption ratio of deep coal gas provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0032] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0033] As described in the background, the amount of coal-rock gas adsorption and the proportion of free gas can be estimated using the Langmuir or BET models based on laboratory-measured coal sample adsorption isotherms. However, this approach has limitations in practical applications. For example, it fails to fully account for the influence of complex factors such as formation temperature, pressure, coal seam structure, and composition, and lacks a detailed description of the dynamic migration and release of gas within coal.

[0034] Furthermore, using the Langmuir or BET models to estimate coal rock gas adsorption requires the collection of extensive experimental data, such as PVT sampling and isothermal adsorption data. This data collection then requires complex calculations and analysis. Furthermore, the Langmuir or Freundlich models may not accurately describe the complexity of the porous structure of coal rock and the behavior of gas molecules.

[0035] Currently, some calculations are performed under specific temperature and pressure conditions. However, the actual environment of deep coal seams is highly variable, which can lead to significant deviations between simulation results and actual conditions. Many studies also focus on microscopic or macroscopic scales, lacking the ability to connect different scales, hindering a comprehensive understanding of coal gas behavior.

[0036] In order to solve the above-mentioned technical problems, the present invention provides an evaluation method and evaluation equipment for the free adsorption ratio of deep coal gas.

[0037] See also Figure 1 , which shows a flow chart for implementing a method for evaluating the free adsorption ratio of deep coal gas provided by an embodiment of the present invention, as detailed below:

[0038] S110. Construct a microscopic pore composite model of different rock pore sizes based on the coal rock sample to be evaluated.

[0039] Among them, the microscopic pore composite model is constructed based on the material composition of the coal rock sample to be evaluated and the full-scale pore characteristics of the coal rock sample. The full-scale pore characteristics include micropores, mesopores and macropores.

[0040] In some embodiments, the microscopic pore composite model is constructed using a graphene plate as a medium, and the graphene plate has the same material composition as the coal rock sample to be evaluated, and the material composition includes total organic carbon and mineral composition.

[0041] In this embodiment, since the adsorption and migration of gas is relatively complex, it is necessary to simulate different conditions through a microscopic pore composite model to study its variation law.

[0042] like Figure 2 The figure shows a schematic diagram of the constructed microporous composite model, which includes a first box 210, a pore channel 220 and a second box 230. The first box 210 and the second box 230 are connected by the pore channel 220, and the first box 210, the second channel 220 and the third box 230 all use graphene as the medium.

[0043] The first adsorption box 210 is the initial box, used to adsorb a predetermined gas and achieve dynamic equilibrium. The pore channel 220 includes a plurality of circular graphene channels with different pore diameters, each with a circular cross-section. The third box 230 is an empty box containing graphene as the medium.

[0044] Current research primarily simulates density and pressure based on molecular dynamics, using the shape of the hysteresis loop for simulation. This invention, however, simulates and establishes a composite model of microscopic pores with varying pore sizes. By setting different pore sizes during the simulation process and selectively migrating them, the dynamic migration and release of a preset gas is simulated, creating a dynamic evolution model. Simulation data for a variety of pore sizes is generated using the number and distribution of preset gas molecules in the storage space.

[0045] By first establishing an initial simulation box on the left, namely the first box 210, and then connecting graphene circular channels of different pore sizes, namely the pore channel 220, and connecting the other end of the pore channel to the second box 230, a microscopic pore composite model with different pore sizes is obtained.

[0046] S120. Setting simulation environment parameters of the microporous composite model, adsorbing a preset gas into the microporous composite model, bringing the microporous composite model to equilibrium based on density functional theory, and establishing a dynamic evolution model by changing the pore size of the microporous composite model to obtain simulation data under different simulation environment parameters.

[0047] In order to accurately evaluate the coal and rock samples to be evaluated, it is necessary to comprehensively consider the environmental parameters during the on-site analysis of the coal and rock to ensure the accuracy and reliability of the evaluation.

[0048] In some embodiments, the simulation environment parameters include normal temperature, ground temperature, high temperature, pressure, simulation time step, and pore size.

[0049] For example, the normal temperature may be 20°C, the ground temperature 67°C, the high temperature 94°C, the pressure 28 MPa, the simulation time step 2500000 ps, ​​the pore size 1.5 nm, 3 nm, etc. may be selected.

[0050] After the simulation environment parameters are set, a certain amount of preset gas can be adsorbed into the microscopic pore composite model. The preset gas can be methane gas.

[0051] Through density functional theory and molecular dynamics simulation, we can analyze and compare the microscopic occurrence and migration behavior of preset gas molecules under different pore sizes and different simulation environment parameters.

[0052] In some embodiments, based on the microscopic pore composite model of different pore sizes constructed in the present invention, simulation data for various pore sizes is generated using the number and distribution of preset gas molecules in the storage space. The simulation data may include the number of methane molecules at different locations in the microscopic pore composite model at different temperatures, pressures, and pore sizes. For example, the number of adsorbed methane gas molecules within the pore channels of the microscopic pore composite model and the number of free methane gas molecules in the second box.

[0053] For example, the number of methane molecules in different storage spaces at room temperature of 20°C, formation pressure of 28 MPa, and pore size of 1.5 nm can be obtained, including the first box on the far left, the pore channel in the middle, and the second box on the far right.

[0054] like Figure 3 After setting the simulation environment parameters for the microporous composite model, the occurrence and migration patterns of methane molecules after a certain amount of methane gas is adsorbed into the microporous composite model are analyzed. Based on the location of the methane molecules, their occurrence states are defined as adsorbed and free. The methane gas in the pore channel 220 is adsorbed gas, i.e., in the adsorbed state. The methane gas in the second box 230 is free gas, i.e., in the free state.

[0055] S130. Determine the free adsorption ratio of deep coal rock gas based on simulation data under different simulation environment parameters and a preset free adsorbed gas ratio model.

[0056] Through the simulation in S120, simulation data under different simulation environment parameters are obtained and organized. The total number of preset gas molecules adsorbed into the microscopic pore composite model is set to N. From the above simulation data, the number of free and adsorbed gas molecules in the micropores and mesopores is obtained respectively.

[0057] In some embodiments, the free adsorbed gas fraction model k is:

[0058]

[0059] in, is the number of free gas molecules in the micropores, R0 is the proportion of micropores, is the number of free gas molecules in the mesopores, R1 is the proportion of mesopores, is the number of free gas molecules in the macropores, R2 is the proportion of macropores, is the number of adsorbed gas molecules in the micropores, is the number of adsorbed gas molecules in the mesopores, and all the gas in the macropores is assumed to be free.

[0060] Through the above simulation parameters, the number of free gas molecules in the micropores can be directly obtained The number of free gas molecules in the mesopores The number of free gas molecules in the macropores The number of adsorbed gas molecules in the micropores The number of adsorbed gas molecules in the mesopores However, the number of free gases in the macropores cannot be obtained. Therefore, it is also necessary to calculate the number of free gases in the macropores

[0061] The number of free gases in the macropores The calculation method is:

[0062]

[0063] Wherein, N is the total number of adsorbed preset gas molecules.

[0064] The present invention constructs a microscopic pore composite model of different rock pore sizes based on the full-scale pore characteristics and the material composition of the coal rock sample, and sets the environmental parameters for simulating the microscopic pore composite model based on the environmental parameters of the coal rock field analysis process. The molecular dynamics simulation is used to reproduce the adsorption behavior and dynamic migration process of the gas in the coal rock, thereby enabling an in-depth analysis of the different states of the gas in the coal rock, especially the ratio of free gas to adsorbed gas. By constructing a microscopic pore composite model and combining the environmental parameters for simulation, the obtained simulation data is more accurate. This not only improves the accuracy of the calculation, but also provides a more reliable theoretical basis for the exploration and development of deep coal-rock gas. In addition, compared with traditional experimental methods, the method provided by the present invention is not restricted by geological conditions and can be simulated anytime and anywhere, thereby improving the efficiency of the research. At the same time, through molecular-level simulation, the behavior of methane molecules at the microscale can be deeply understood, providing a scientific basis for resource exploration and development.

[0065] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0066] The following are device embodiments of the present invention. For details not fully described therein, reference may be made to the corresponding method embodiments described above.

[0067] Figure 4 The following is a schematic diagram showing the structure of a device for evaluating the free adsorption ratio of deep coal gas provided by an embodiment of the present invention. For ease of explanation, only the parts related to the embodiment of the present invention are shown, which are described in detail as follows:

[0068] like Figure 4 As shown, the evaluation device 400 for the free adsorption ratio of deep coal gas includes:

[0069] A model building module 410 is used to build a microscopic pore composite model of different rock pore sizes based on the coal rock sample to be evaluated; wherein the microscopic pore composite model is built based on the material composition of the coal rock sample to be evaluated and the full-scale pore characteristics of the coal rock sample;

[0070] The simulation module 420 is used to set simulation environment parameters of the microporous composite model, adsorb a preset gas into the microporous composite model, bring the microporous composite model to equilibrium based on density functional theory, and establish a dynamic evolution model by changing the pore size of the microporous composite model to obtain simulation data under different simulation environment parameters;

[0071] The ratio determination module 430 is used to determine the free adsorption ratio of deep coal rock gas based on simulation data under different simulation environment parameters and a preset free adsorption gas ratio model.

[0072] In one possible implementation, the microscopic pore composite model is constructed using a graphene plate as a medium, and the graphene plate has the same material composition as the coal rock sample to be evaluated;

[0073] Material composition includes total organic carbon and mineral composition.

[0074] In one possible implementation, the microscopic pore composite model includes a first box, a pore channel, and a second box, wherein the first box and the second box are connected via the pore channel, and the first box, the second channel, and the third box all use graphene as a medium;

[0075] The first box is an adsorption box, which is used to adsorb the preset gas and make the preset gas reach dynamic equilibrium;

[0076] The pore channels include graphene circular channels with various pore sizes;

[0077] The second box is an empty box with graphene as the medium.

[0078] In one possible implementation, the full-scale pore characteristics of the coal rock sample include characteristics of the micropores, mesopores, and macropores of the coal rock sample.

[0079] In a possible implementation, the simulation environment parameters include normal temperature, ground temperature, high temperature, pressure, simulation time step, and aperture.

[0080] In a possible implementation, the preset gas is methane, and the simulation data includes the number of methane molecules at different positions in the microscopic pore composite model at different temperatures, pressures, and pore sizes.

[0081] In one possible implementation, the free adsorbed gas ratio model k is:

[0082]

[0083] in, is the number of free gas molecules in the micropores, R0 is the proportion of micropores, is the number of free gas molecules in the mesopores, R1 is the proportion of mesopores, is the number of free gas molecules in the macropores, R2 is the proportion of macropores, is the number of adsorbed gas molecules in the micropores, is the number of gas molecules adsorbed in the mesopores.

[0084] In one possible implementation, the number of free gases in the macropores is The calculation method is:

[0085]

[0086] Wherein, N is the total number of adsorbed preset gas molecules.

[0087] In one possible implementation, the number of free gases in micropores, the number of adsorbed gases in micropores, the number of free gases in mesopores, and the number of adsorbed gases in mesopores are determined based on simulation data under different parameters.

[0088] An embodiment of the present invention also provides an evaluation device for the free adsorption ratio of deep coal gas, including a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, the method in the above method embodiment is implemented.

[0089] In the above embodiments, the descriptions of each embodiment have their own focus. For parts not described or recorded in detail in one embodiment, please refer to the relevant descriptions of other embodiments. Unless otherwise specified or there is a logical conflict, the terms and / or descriptions between different embodiments are consistent and can be referenced to each other. The technical features of different embodiments can be combined to form new embodiments based on their inherent logical relationships.

[0090] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention, and should all be included in the scope of protection of the present invention.

Claims

1. A method for evaluating the free adsorption ratio of deep coal gas, characterized in that: include: A microscopic pore composite model of different rock pore sizes is constructed based on the coal rock sample to be evaluated; wherein, the microscopic pore composite model is constructed based on the material composition of the coal rock sample to be evaluated and the full-scale pore characteristics of the coal rock sample; the microscopic pore composite model is constructed with a graphene plate as a medium, and the graphene plate has the same material composition as the coal rock sample to be evaluated; the microscopic pore composite model includes a first box, a pore channel and a second box, the first box and the second box are connected through the pore channel, and the first box, the second channel and the third box are all made of graphene plates as a medium; the first box is an adsorption box, which is used to adsorb a preset gas so that the preset gas reaches dynamic equilibrium; the pore channel includes a plurality of graphene circular channels with different pore sizes; the second box is an empty box with a graphene plate as a medium; the full-scale pore characteristics of the coal rock sample include the characteristics of the micropores, mesopores and macropores of the coal rock sample; Setting simulation environment parameters for the microporous composite model, adsorbing a preset gas into the microporous composite model, achieving equilibrium in the microporous composite model based on density functional theory, and establishing a dynamic evolution model by changing the pore size of the microporous composite model to obtain simulation data under different simulation environment parameters; the simulation environment parameters include normal temperature, ground temperature, high temperature, pressure, simulation time step, and pore size; the simulation data includes the number of methane molecules at different positions in the microporous composite model under different temperatures, pressures, and pore size; Determining the free adsorption ratio of deep coal rock gas based on the simulation data under the different simulation environment parameters and a preset free adsorbed gas ratio model; The free adsorbed gas ratio model k is: ； The number of free gases in the macropores The calculation method is: ； in, is the number of free gas molecules in the micropores, is the proportion of micropores, is the number of free gas molecules in the mesopores, is the proportion of mesopores, is the number of free gas molecules in the macropores, is the proportion of macropores, is the number of adsorbed gas molecules in the micropores, is the number of adsorbed gas molecules in the mesopores, and N is the total number of adsorbed preset gas molecules.

2. The method for evaluating the free adsorption ratio of deep coal gas according to claim 1, characterized in that: The material composition includes total organic carbon and mineral composition.

3. The method for evaluating the free adsorption ratio of deep coal gas according to claim 1 or 2, characterized in that: The preset gas is methane.

4. The method for evaluating the free adsorption ratio of deep coal gas according to claim 1, characterized in that: The number of free gas molecules in the micropores, the number of adsorbed gas molecules in the micropores, the number of free gas molecules in the mesopores, and the number of adsorbed gas molecules in the mesopores are determined based on simulation data under different parameters.

5. An evaluation device for the free adsorption ratio of deep coal gas, characterized in that: The method comprises a memory and a processor, wherein the memory stores a computer program, and the processor implements the method according to any one of claims 1 to 4 when executing the computer program.

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