Visualization method for simulating micro occurrence and flow of deep coal rock gas
By conducting physicochemical property tests and molecular dynamics simulations on deep coal and rock samples, and constructing molecular models based on drilling data, the problem of reproducing multi-field coupling conditions of deep coal and rock gas was solved. This enabled the visualization of the microscopic occurrence and flow of deep coal and rock gas, providing more accurate simulation and research tools.
Patent Information
- Application Number
- CN202610038721.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-13
- Publication Date
- 2026-05-26
AI Technical Summary
Existing technologies cannot accurately reproduce the multi-field coupling conditions of deep coal and rock gas, resulting in significant deviations between laboratory data and actual conditions. Furthermore, traditional methods cannot reveal the occurrence and flow patterns of methane in micropores and fractures, making it difficult to understand the enrichment mechanism and mining dynamics of deep coal and rock gas.
By testing the physicochemical properties of deep coal and rock samples and estimating in-situ pressure, temperature, and geostress parameters using drilling and logging data, a molecular model is constructed using molecular dynamics simulation methods. Simulated boundary conditions are then applied to simulate the occurrence and flow of methane, and its trajectory is recorded in real time. Finally, the results are displayed through a visualization module.
It achieves a simulation boundary consistent with the deep environment, improves the accuracy and reliability of simulation results, breaks through the limitations of macroscopic equivalence and microscopic fuzziness, provides an intuitive research tool for the microscopic mechanism of deep coal and rock gas, and is adapted to the characteristic of high proportion of free methane.
Smart Images
Figure CN122084861A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of coalbed methane exploration technology, and in particular to a visualization method for simulating the microscopic occurrence and flow of deep coalbed methane. Background Technology
[0002] Deep coalbed methane, as an important replacement resource for conventional oil and gas, is characterized by its huge reserves and clean, efficient production. However, its development faces significantly different technical challenges compared to shallow coalbed methane. Deep coal reservoirs are subjected to the combined effects of high pressure, high temperature, and high stress fields, causing compression and reconstruction of the coal pore-fracture system. Furthermore, the proportion of free gas in the total methane content is significantly increased, and its flow characteristics differ markedly from those of shallow coal seams. This means that research methods used for shallow coal seams are not applicable to deep coal seams.
[0003] On the one hand, laboratory experimental devices are limited by their pressure-bearing, temperature-controlling, and stress-loading capabilities, making it impossible to accurately reproduce the multi-field coupling conditions in deep in-situ conditions. This results in significant deviations between the measured occurrence and flow data and the actual in-situ state, making it difficult to reflect the true characteristics of the coexistence of multiple methane states. On the other hand, traditional methods (such as volumetric methods and simplified numerical simulations) can only obtain macroscopic equivalent parameters, failing to reveal the distribution of methane occurrence forms in microscopic pores and fractures, and also making it difficult to visualize the methane flow path and dynamic migration patterns. This leads to insufficient understanding of the enrichment mechanism and mining dynamics of deep coal and rock gas.
[0004] Therefore, there is a need to provide an improved technical solution that addresses the shortcomings of the existing technology. Summary of the Invention
[0005] The purpose of this application is to provide a visualization method for simulating the microscopic occurrence and flow of coalbed methane, so as to solve or alleviate the problems existing in the prior art.
[0006] To achieve the above objectives, this application provides the following technical solution: A visualization method for simulating the microscopic occurrence and flow of deep coal and rock gas, the visualization method comprising the following steps: Step 1: Conduct physicochemical property tests on deep coal and rock samples to obtain measured data on the physicochemical properties of deep coal and rock samples; Step 2: Estimate the in-situ pressure, in-situ temperature and geostress parameters of the reservoir at the preset burial depth based on drilling and logging data, so as to determine the simulated boundary conditions; Step 3: Based on the measured data of physicochemical properties in Step 1, construct a molecular model using molecular dynamics simulation methods; Then, the simulated boundary conditions from step 2 are loaded into the molecular model; Then the reliability of the molecular model was verified; Step 4: Perform deep methane occurrence simulation on the validated molecular model to obtain the occurrence simulation results; Step 5: Based on the simulation results of the molecular model in Step 4, simulate the flow process of methane in the molecular model and record the trajectory of methane molecules in real time. Step 6: Use the visualization module in the molecular simulation software to visualize the simulation results from Steps 4 and 5.
[0007] The visualization method for simulating the microscopic occurrence and flow of deep coal and rock gas as described above, preferably, involves performing elemental analysis on the deep coal and rock sample in step 1 to obtain the elemental composition and atomic ratio of the deep coal and rock sample; Solid-state nuclear magnetic resonance (NMR) tests were performed on deep coal and rock samples, and deconvolution analysis was conducted to obtain the carbon skeleton structure parameters of the deep coal and rock samples. Low-temperature adsorption tests were conducted on deep coal and rock samples to obtain their pore structure parameters. Mechanical property tests were conducted on deep coal and rock samples to obtain their mechanical response parameters. Density tests were conducted on deep coal and rock samples to obtain their density parameters.
[0008] The visualization method for simulating the microscopic occurrence and flow of deep coal and rock gas, as described above, preferably involves obtaining formation pressure gradient, geothermal gradient, and geostress monitoring data based on drilling logging data in step 2. Estimate the in-situ pressure of the reservoir at the preset burial depth based on the formation pressure gradient; Estimate the in-situ temperature of the reservoir at the preset burial depth based on the geothermal gradient; Estimate the ratio of horizontal stress to vertical stress based on ground stress monitoring data, and set the total stress range; Then, the pressure-temperature-stress synergistic relationship can be established through the multi-field coupling module of molecular simulation software, and simulation boundary conditions consistent with the in-situ environment can be set.
[0009] The visualization method for simulating the microscopic occurrence and flow of deep coal and rock gas, as described above, preferably involves constructing a molecular model in step 3 using molecular dynamics simulation. Specifically, based on the elemental composition and carbon skeleton structural parameters of the deep coal and rock sample, a two-dimensional coal molecular unit is constructed. The two-dimensional coal molecular unit is then assembled into a three-dimensional model box containing initial pores using an amorphous polymerization method to form an initial model. Then, the initial model was optimized by annealing kinetics to form a molecular model.
[0010] In the visualization method for simulating the microscopic occurrence and flow of deep coal and rock gas as described above, preferably, in step 3, the simulation boundary conditions determined in step 2 are loaded into the annealed and optimized molecular model to simulate the compression and reconstruction process of micro and nano pores in coal and rock under deep environment.
[0011] In the visualization method for simulating the microscopic occurrence and flow of deep coal and rock gas as described above, preferably, in step 3, the elemental composition, density, pore structure parameters and mechanical response parameters of the molecular model with loaded model boundary conditions are compared and analyzed with the measured physicochemical properties data in step 1 to verify the molecular model.
[0012] The visualization method for simulating the microscopic occurrence and flow of deep coal and rock gas, as described above, preferably involves, in step 4, under the simulation boundary conditions determined in step 2, using the giant canonical ensemble simulation method based on the molecular model verified in step 3, to study the adsorption and desorption equilibrium process of methane. After the molecular model reaches adsorption equilibrium, the distribution location and number of adsorbed methane molecules are statistically analyzed, and the proportion of free methane is determined.
[0013] In the visualization method for simulating the microscopic occurrence and flow of deep coal and rock gas as described above, preferably, in step 5, based on the occurrence simulation results of the molecular model in step 4, the molecular dynamics simulation method is used to study the flow process of methane in the molecular model, and the motion trajectory of methane molecules is recorded in real time.
[0014] The visualization method for simulating the microscopic occurrence and flow of deep coal and rock gas, as described above, preferably involves, in step 6, using the visualization module in the molecular simulation software, converting the occurrence simulation results from step 4 into a three-dimensional occurrence state distribution map and an occurrence morphology partition cloud map.
[0015] In the visualization method for simulating the microscopic occurrence and flow of deep coal and rock gas as described above, preferably, in step 6, the methane molecule trajectory in step 5 is converted into a dynamic trajectory animation through the visualization module in the molecular simulation software.
[0016] Compared with the closest prior art, the technical solution of this application has the following beneficial effects: In this visualization method for simulating the microscopic occurrence and flow of deep coal and rock gas, the in-situ pressure, temperature, and geostress parameters at a preset burial depth are estimated, and the simulation boundary conditions including the in-situ pressure, temperature, and geostress parameters are loaded into the molecular model. This directly establishes a simulation boundary consistent with the actual deep environment, solving the technical bottleneck that the laboratory cannot reproduce complex in-situ conditions. This makes the simulation results closer to engineering practice and ensures the accuracy and reliability of the visualization results.
[0017] This method transforms the methane occurrence forms and methane movement trajectories from molecular models into visualization results, breaking through the limitations of traditional methods that focus on macroscopic equivalence and microscopic ambiguity. It provides a more intuitive research tool for understanding the microscopic mechanisms of deep coal and shale gas. Furthermore, this visualization method specifically incorporates the calculation of free methane, making it more suitable for the characteristic of a high proportion of free methane in deep coal and shale gas, ensuring that the visualization method can more accurately simulate the actual situation of deep coal and shale gas. Attached Figure Description
[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. Wherein: Figure 1 A flowchart illustrating the visualization method for simulating the microscopic occurrence and flow of deep coal and rock gas in this application; Figure 2 Molecular model diagrams of deep coal and rock provided according to some embodiments of this application; Figure 3 A visualization of the microscopic occurrence state of deep coal and rock gas provided according to some embodiments of this application; Figure 4 This is a microscopic flow trajectory diagram of deep coal and rock gas provided according to some embodiments of this application. Detailed Implementation
[0019] The present application will now be described in detail with reference to the accompanying drawings and embodiments. Various examples are provided by way of interpretation and not by way of limitation. In fact, those skilled in the art will recognize that modifications and variations can be made to the present application without departing from the scope or spirit thereof. For example, a feature represented or described as part of one embodiment may be used in another embodiment to produce yet another embodiment. Therefore, it is desirable that the present application encompass such modifications and variations that fall within the scope of the appended claims and their equivalents.
[0020] In the following description, the terms "first / second / third" are used merely to distinguish similar objects and do not represent a specific order of objects. It is understood that "first / second / third" may be interchanged in a specific order or sequence where permitted, so that the embodiments of this application described herein can be implemented in an order other than that illustrated or described herein.
[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terminology used herein is for the purpose of describing embodiments of this disclosure only and is not intended to limit this disclosure.
[0022] In the description of this application, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," and "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and do not require that this application be constructed and operated in a specific orientation, and therefore should not be construed as limiting this application. The terms "connected," "linked," and "set up" used in this application should be interpreted broadly. For example, they can refer to fixed connections or detachable connections; direct connections or indirect connections through intermediate components; wired connections, radio connections, or wireless communication signal connections. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.
[0023] The present application will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present application can be combined with each other.
[0024] According to specific embodiments of this application, such as Figure 1-4 As shown, this application provides a visualization method for simulating the microscopic occurrence and flow of deep coal and rock gas. The visualization method includes the following steps: Step 1: Conduct physicochemical property tests on deep coal and rock samples to obtain measured data on the physicochemical properties of deep coal and rock samples.
[0025] Step 2: Estimate the in-situ pressure, in-situ temperature, and geostress parameters of the reservoir at the preset depth based on drilling and logging data, in order to determine the simulated boundary strip.
[0026] Step 3: Based on the measured physicochemical properties data from Step 1, construct a molecular model using molecular dynamics simulation methods; load the simulation boundary conditions from Step 2 into the molecular model; and then verify the reliability of the molecular model.
[0027] Step 4: Perform deep methane occurrence simulation on the validated molecular model to obtain the occurrence simulation results.
[0028] Step 5: Based on the simulation results of the molecular model in Step 4, simulate the flow process of methane in the molecular model and record the trajectory of methane molecules in real time.
[0029] Step 6: Use the visualization module in the molecular simulation software to visualize the simulation results from Steps 4 and 5.
[0030] In this visualization method for simulating the microscopic occurrence and flow of deep coal and rock gas, the in-situ pressure, temperature, and geostress parameters at a preset burial depth are estimated, and the simulation boundary conditions including the in-situ pressure, temperature, and geostress parameters are loaded into the molecular model. This directly establishes a simulation boundary consistent with the actual deep environment, solving the technical bottleneck that the laboratory cannot reproduce complex in-situ conditions. This makes the simulation results closer to engineering practice and ensures the accuracy and reliability of the visualization results.
[0031] This method transforms the methane occurrence forms and methane movement trajectories from molecular models into visualization results, breaking through the limitations of traditional methods that focus on macroscopic equivalence and microscopic ambiguity. It provides a more intuitive research tool for understanding the microscopic mechanisms of deep coal and shale gas. Furthermore, this visualization method specifically incorporates the calculation of free methane, making it more suitable for the characteristic of a high proportion of free methane in deep coal and shale gas, ensuring that the visualization method can more accurately simulate the actual situation of deep coal and shale gas.
[0032] In step 1, elemental analysis is performed on the deep coal and rock samples to obtain the elemental composition and atomic ratios of the deep coal and rock samples.
[0033] Solid-state nuclear magnetic resonance (NMR) tests were performed on deep coal and rock samples, and deconvolution analysis was conducted to obtain the carbon skeleton structure parameters of the deep coal and rock samples.
[0034] Low-temperature adsorption tests were conducted on deep coal and rock samples to obtain their pore structure parameters.
[0035] Mechanical property tests were conducted on deep coal and rock samples to obtain their mechanical response parameters.
[0036] Density tests were conducted on deep coal and rock samples to obtain their density parameters.
[0037] In this embodiment, deep coal and rock samples with a burial depth of ≥1500m were selected.
[0038] The elemental composition and atomic ratio of C, H, O, N, and S in deep coal and rock samples were determined by using an elemental analyzer to clarify the basic chemical composition for molecular structure construction.
[0039] Acquiring deep coal and rock samples using solid-state nuclear magnetic resonance (NMR) spectroscopy 13 C NMR spectra were used to calculate the proportions of aromatic and alkyl carbons through deconvolution, thus determining the carbon skeleton structure characteristics of deep coal and rock samples.
[0040] Low-temperature liquid nitrogen-carbon dioxide adsorption experiments were conducted on deep coal and rock samples to determine the pore size distribution, specific surface area, and pore volume of mesopores (2-50 nm) and micropores (<2 nm), revealing the quantitative characteristics of the dense pores in deep coal and rock samples.
[0041] Uniaxial compressive strength test and triaxial compression test were conducted on deep coal and rock samples to determine the elastic modulus and Poisson's ratio of the deep coal and rock samples under different stress levels, and to obtain the mechanical response parameters of the deep coal and rock samples under deep stress environment.
[0042] Density tests can also be performed on deep coal and rock samples to serve as relevant indicators for density matching of molecular models.
[0043] In step 2, formation pressure gradient, geothermal gradient and geostress monitoring data are obtained based on drilling logging data.
[0044] The in-situ pressure of the reservoir at the preset burial depth is estimated based on the formation pressure gradient.
[0045] The in-situ temperature of the reservoir at the preset burial depth is estimated based on the geothermal gradient.
[0046] The ratio of horizontal stress to vertical stress is estimated based on ground stress monitoring data, and the total stress range is set.
[0047] Then, the pressure-temperature-stress synergistic relationship can be established through the multi-field coupling module of molecular simulation software, and simulation boundary conditions consistent with the in-situ environment can be set.
[0048] In this embodiment, by introducing response estimations of in-situ pressure, in-situ temperature, and geostress parameters of reservoirs at a preset burial depth, a more accurate basis for limiting the complex deep environment is provided for the establishment of molecular models and subsequent simulations, which is beneficial to the accuracy of simulation results.
[0049] In this embodiment, the pressure-temperature-stress synergistic relationship is established through the multi-field coupling module of molecular simulation software, and the simulation boundary conditions consistent with the in-situ environment are set, thereby enabling the reproduction of deep complex multi-field environments that are difficult to reproduce in the laboratory.
[0050] In step 3, molecular dynamics simulation is used to construct a molecular model. Specifically, based on the elemental composition and carbon skeleton structure parameters of the deep coal and rock samples, two-dimensional coal molecular units are constructed. The two-dimensional coal molecular units are then assembled into a three-dimensional model box containing initial pores using an amorphous polymerization method to form an initial model. Then, the initial model is optimized by annealing dynamics to form a molecular model.
[0051] In this embodiment, molecular dynamics simulation is used, and the measured data of the physicochemical properties of the deep coal and rock samples determined in step 1 are incorporated to ensure the reliability of the initial model construction.
[0052] The initial model was optimized by annealing kinetics by cycling it 3-5 times in the temperature range of 300-600K. The internal stress of the model was eliminated by the energy minimization algorithm, so that the structural energy was reduced to a minimum, thereby constructing a structurally stable molecular model.
[0053] In step 3, the simulated boundary conditions determined in step 2 are loaded into the annealed and optimized molecular model to simulate the compression and reconstruction process of micro- and nano-pores in coal and rock under deep environment.
[0054] In this embodiment, after loading simulated boundary conditions including in-situ pressure, temperature and geostress parameters onto the molecular model, it is possible to simulate the compression and reconstruction process of coal and rock micro-nano pores in deep environments, forming a three-level pore structure including micropores, mesopores and fractures in the molecular model.
[0055] In step 3, the elemental composition, density, pore structure parameters, and mechanical response parameters of the molecular model with applied boundary conditions are compared and analyzed with the measured physicochemical properties data from step 1 to validate the molecular model. Deviations can be quantitatively analyzed item by item for each measured physicochemical property to verify the reliability and accuracy of the molecular model.
[0056] In step 4, under the simulation boundary conditions determined in step 2, based on the molecular model verified in step 3, the adsorption and desorption equilibrium process of methane is studied using the grand canonical ensemble simulation method. After the molecular model reaches the adsorption equilibrium state, the distribution position and number of adsorbed methane molecules are statistically analyzed, and the proportion of free methane is determined.
[0057] In this embodiment, based on the actual gas saturation of the deep coal reservoir, a corresponding number of methane molecules are loaded into the system of the molecular model, and the simulation duration is set to ensure that the system of the molecular model reaches the adsorption equilibrium state. After equilibrium is reached, the number of adsorbed methane molecules on the coal surface and in the micropores is counted, and the number of unadsorbed free methane molecules in the pore space is counted by molecular counting method. The amount of free methane is converted by combining the ideal gas law, the proportion of free methane is calculated, and the differences in the methane occurrence forms in different micro- and nano-pore scales are analyzed.
[0058] In this embodiment, the amount of adsorbed methane can be determined by fitting GCMC simulation data using the Langmuir model, and the amount of free methane can be calculated by subtracting the number of adsorbed methane molecules from the total number of methane molecules and combining this with the ideal gas law, thus ensuring the accuracy of the free methane percentage calculation.
[0059] In step 5, based on the simulation results of the molecular model in step 4, the flow process of methane in the molecular model is studied using molecular dynamics simulation method, so as to realize the simulation of the diffusion and permeation process of methane in the micropore-mesopore-crack three-level pore structure of the molecular model, and record the motion trajectory of methane molecules in real time.
[0060] In step 6, the simulation results from step 4 are transformed into a three-dimensional distribution map of the occurrence state and a cloud map of the occurrence morphology using the visualization module in the molecular simulation software. The methane molecule trajectory from step 5 is also transformed into a dynamic trajectory animation using the visualization module in the molecular simulation software. This visually demonstrates the dynamic changes in occurrence morphology and flow characteristics under different pressure and temperature conditions, thereby achieving an intuitive presentation and interactive analysis of the microscopic occurrence and flow processes of deep coal and rock gas.
[0061] In this embodiment, the molecular simulation software can be Materials Studio software.
[0062] The following example uses coal and rock buried at a depth of 2000m in a certain area as an illustration. The specific visualization method includes the following steps: Step 1, Precise characterization of the physical and chemical properties of deep coal and rock: Coal and rock samples buried at a depth of 2000m were selected for testing.
[0063] Elemental analysis revealed a carbon content of 82.5%, a hydrogen content of 4.2%, an oxygen content of 11.3%, a nitrogen content of 1.2%, and a sulfur content of 0.8%, with atomic ratios of H / C and O / C of 1.02 and 0.083, respectively. Solid-state nuclear magnetic resonance (NMR) analysis, calculated via deconvolution, showed an aromatic carbon content of 78.3% and an alkyl carbon content of 21.7%. Low-temperature adsorption experiments determined the micropore volume to be 0.032 cm³. 3 / g, mesopore volume 0.085cm³ 3 / g, total pore volume 0.238 cm³ 3 / g; mechanical tests showed an elastic modulus of 12.5 GPa, a Poisson's ratio of 0.28, and a compressive strength of 38.6 MPa.
[0064] Step 2, Coupling of deep in-situ condition parameters and setting of boundary conditions: Based on geological data at a burial depth of 2000 m, the formation pressure gradient is 0.015 MPa / m, and the simulated pressure is set to 30 MPa.
[0065] The geothermal gradient is 3 ℃ / 100m, the surface temperature is 20℃, and the converted simulated temperature is 90℃.
[0066] Vertical stress 40 MPa, horizontal stress 56 MPa, total stress range set at 40-56 MPa.
[0067] By using the mechanical-thermal coupling module of the molecular simulation software, pressure, temperature, and stress parameters are input to establish the synergistic relationship among the three, ensuring that the boundary conditions are consistent with the in-situ environment.
[0068] Step 3: Construction and validation of deep coal and rock macromolecular models adapted to the proportion of free state: Based on the physicochemical property data from step 1, eight two-dimensional coal molecular units were constructed. These units were then assembled into a three-dimensional initial model using an amorphous polymerization method, with an initial density of 1.30 g / cm³. 3 The initial model was optimized by cyclic annealing at temperatures ranging from 300 K to 600 K and back to 300 K, with each cycle holding for 2 ns, reducing the model energy to 2856 kJ / mol. Subsequently, the simulation chamber was subjected to a pressure of 30 MPa, a temperature of 90 °C, and a stress of 40–56 MPa, compressing the model's pore volume to 0.221 cm³. 3 / g, with an error of 6.3% compared to the experimental total pore volume; the reliability of the model was verified by quantitative analysis of the model's elemental composition, density, and pore distribution, and comparison with experimental results. The final molecular model is as follows. Figure 2 As shown.
[0069] Step 4, Molecular simulation of the microscopic occurrence characteristics of deep coal and rock gas: The grand canonical ensemble (GCMC) simulation method was used to conduct adsorption-desorption equilibrium simulations of the validated model under conditions of 90℃ and 30 MPa. Based on a gas saturation of 85%, each structural unit was calculated to contain 81 methane molecules. The GCMC simulation duration was 15 ns, with data recorded every 100 ps. After equilibrium was reached, the number of adsorbed and free methane molecules were counted, and the proportion of free methane molecules was calculated. The visualization results of methane occurrence are shown below. Figure 3 As shown.
[0070] Step 5, Molecular simulation of microscopic flow characteristics of deep coal and rock gas: Molecular dynamics (MD) simulations were performed on the simulated model at 90°C for a duration of 8 ns and a time step of 1 fs. The trajectory of methane molecules was recorded in real time during the simulation. Animation screenshots of the trajectory from the 1-3 ns dynamics simulation are shown below. Figure 4 As shown.
[0071] Step 6, Visualization of microscopic attribution and flow: Output the state diagram (e.g., through the visualization module of the molecular simulation software) Figure 3 As shown), the trajectory file simulated by MD is imported into the auxiliary software, and the animation frame rate is set to generate the flowing trajectory animation (as shown). Figure 4 As shown in the figure, the microscopic processes of coalbed methane occurrence and flow are presented intuitively. The molecular simulation software used can be Materials Studio.
[0072] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A visualization method for simulating the microscopic occurrence and flow of deep coal and rock gas, characterized in that, The visualization method includes the following steps: Step 1: Conduct physicochemical property tests on deep coal and rock samples to obtain measured data on the physicochemical properties of deep coal and rock samples; Step 2: Estimate the in-situ pressure, in-situ temperature and geostress parameters of the reservoir at the preset burial depth based on drilling and logging data, so as to determine the simulated boundary conditions; Step 3: Based on the measured data of physicochemical properties in Step 1, construct a molecular model using molecular dynamics simulation methods; Then, the simulated boundary conditions from step 2 are loaded into the molecular model; Then the reliability of the molecular model was verified; Step 4: Perform deep methane occurrence simulation on the validated molecular model to obtain the occurrence simulation results; Step 5: Based on the simulation results of the molecular model in Step 4, simulate the flow process of methane in the molecular model and record the trajectory of methane molecules in real time. Step 6: Use the visualization module in the molecular simulation software to visualize the simulation results from Steps 4 and 5.
2. The visualization method for simulating the microscopic occurrence and flow of deep coal and rock gas according to claim 1, characterized in that, In step 1, elemental analysis is performed on the deep coal and rock samples to obtain the elemental composition and atomic ratio of the deep coal and rock samples; Solid-state nuclear magnetic resonance (NMR) tests were performed on deep coal and rock samples, and deconvolution analysis was conducted to obtain the carbon skeleton structure parameters of the deep coal and rock samples. Low-temperature adsorption tests were conducted on deep coal and rock samples to obtain their pore structure parameters. Mechanical property tests were conducted on deep coal and rock samples to obtain their mechanical response parameters. Density tests were conducted on deep coal and rock samples to obtain their density parameters.
3. The visualization method for simulating the microscopic occurrence and flow of deep coal and rock gas according to claim 2, characterized in that, In step 2, formation pressure gradient, geothermal gradient and geostress monitoring data are obtained based on drilling logging data; Estimate the in-situ pressure of the reservoir at the preset burial depth based on the formation pressure gradient; Estimate the in-situ temperature of the reservoir at the preset burial depth based on the geothermal gradient; Estimate the ratio of horizontal stress to vertical stress based on ground stress monitoring data, and set the total stress range; Then, the pressure-temperature-stress synergistic relationship can be established through the multi-field coupling module of molecular simulation software, and simulation boundary conditions consistent with the in-situ environment can be set.
4. The visualization method for simulating the microscopic occurrence and flow of deep coal and rock gas according to claim 3, characterized in that, In step 3, molecular model construction is carried out using molecular dynamics simulation methods. Specifically, based on the elemental composition and carbon skeleton structural parameters of deep coal and rock samples, two-dimensional coal molecular units are constructed. The two-dimensional coal molecular units are then assembled into a three-dimensional model box containing initial pores through amorphous polymerization method to form an initial model. Then, the initial model was optimized by annealing kinetics to form a molecular model.
5. The visualization method for simulating the microscopic occurrence and flow of deep coal and rock gas according to claim 4, characterized in that, In step 3, the simulated boundary conditions determined in step 2 are loaded into the annealed and optimized molecular model to simulate the compression and reconstruction process of micro- and nano-pores in coal and rock under deep environment.
6. The visualization method for simulating the microscopic occurrence and flow of deep coal and rock gas according to claim 5, characterized in that, In step 3, the elemental composition, density, pore structure parameters, and mechanical response parameters of the molecular model with the model boundary conditions applied are compared and analyzed with the measured physicochemical properties data from step 1 to verify the molecular model.
7. The visualization method for simulating the microscopic occurrence and flow of deep coal and rock gas according to claim 6, characterized in that, In step 4, under the simulation boundary conditions determined in step 2, based on the molecular model verified in step 3, the adsorption and desorption equilibrium process of methane is studied using the grand canonical ensemble simulation method. After the molecular model reaches the adsorption equilibrium state, the distribution position and number of adsorbed methane molecules are statistically analyzed, and the proportion of free methane is determined.
8. The visualization method for simulating the microscopic occurrence and flow of deep coal and rock gas according to claim 7, characterized in that, In step 5, based on the simulation results of the molecular model in step 4, the flow process of methane in the molecular model is studied using molecular dynamics simulation, and the trajectory of methane molecules is recorded in real time.
9. The visualization method for simulating the microscopic occurrence and flow of deep coal and rock gas according to claim 8, characterized in that, In step 6, the simulation results from step 4 are transformed into a three-dimensional distribution map of storage state and a cloud map of storage morphology partitions using the visualization module in the molecular simulation software.
10. The visualization method for simulating the microscopic occurrence and flow of deep coal and rock gas according to claim 8, characterized in that, In step 6, the methane molecule trajectory from step 5 is converted into a dynamic trajectory animation using the visualization module in the molecular simulation software.