Method and apparatus for determining multiphase and multicomponent competitive adsorption data in shale micro-nanopores

Abstract

This specification relates to the fields of carbon dioxide sequestration and shale gas development technology, specifically disclosing a method and apparatus for determining multiphase and multicomponent competitive adsorption data in shale micro- and nanoporous structures. The method includes: acquiring shale core samples from a target area and determining the types and relative content variations of surface functional groups in the shale core samples; collecting key structural and force field parameters of shale clay minerals from the target block and establishing a molecular model of the shale clay minerals; establishing multiple fluid molecular models; establishing slit models and establishing multiphase fluid system models between the slit models to obtain a stable configuration; applying an external electric field to the stable configuration and performing molecular dynamics calculations to obtain the molecular trajectory coordinates and dynamic information of the multiphase and multicomponent fluids; and calculating the competitive adsorption data of the multiphase and multicomponent fluids in shale micro- and nanoporous structures under the action of the electric field. This method can reveal the occurrence state and competitive adsorption behavior of multiphase and multicomponent fluids in shale micro- and nanoporous structures under the action of an electric field at the molecular scale.

Description

Technical Field

[0001] This specification relates to the fields of carbon dioxide sequestration and shale gas development technology, and in particular to a method and apparatus for determining multiphase and multicomponent competitive adsorption data of shale micro-nano pores. Background Technology

[0002] In recent years, global warming has been primarily caused by excessive carbon dioxide emissions. Geological utilization and storage are indispensable components of the carbon dioxide capture, utilization, and storage (CCUS) strategy, achieving the dual goals of carbon sequestration and underground resource utilization, thus possessing broad application potential. Shale gas resources are abundant, and shale reservoirs have well-developed micro- and nano-pores, making them promising carbon dioxide storage sites. Furthermore, based on the mechanism of CO2 preferential adsorption over CH4 in shale, CO2 injection can promote shale gas desorption, allowing more adsorbed CH4 to be converted into a free state from the shale matrix surface. Shale gas reservoir CO2 storage technology utilizes the competitive adsorption of CO2 and shale gas to simultaneously achieve enhanced shale gas recovery and permanent CO2 geological storage.

[0003] The technique of enhancing CO2 adsorption using porous solid materials with electric fields has been successfully applied in CO2 capture and electrochemistry. By altering the physicochemical properties of the adsorbent and adsorbate through an applied electric field, the adsorption capacity of nanomaterials for CO2 can be significantly improved, and the selective adsorption of CO2 in CO2 / shale gas mixtures can also be enhanced. Based on the CO2 adsorption characteristics of shale and the mechanism of CO2 adsorption using porous materials enhanced by electric fields, a technology for enhancing CO2 injection into shale gas reservoirs with electric fields is proposed. This aims to achieve a synergistic enhancement of shale gas recovery and CO2 sequestration capacity in shale reservoirs, offering significant economic and environmental advantages. Therefore, the multiphase, multi-component competitive adsorption mechanism of micro- and nanopores in water-bearing shale under the action of an electric field is a fundamental geological and reservoir physics problem faced in shale gas development. However, there is currently a lack of molecular simulation methods for the competitive adsorption of multiphase and multicomponent gases in shale micro-nano pores under reservoir temperature and pressure conditions under an applied electric field. Furthermore, it is not possible to simultaneously study the occurrence and adsorption behavior of multiphase and multicomponent fluids under an applied electric field. This results in a limited understanding of the adsorption characteristics of single-phase gases or competitive adsorption of multicomponent gases in shale under the action of an electric field in a high-temperature and high-pressure environment, which greatly limits the application of this technology in enhancing shale gas recovery.

[0004] There is currently no effective solution to the above problems. Summary of the Invention

[0005] This specification provides a method and apparatus for determining competitive adsorption data of multiphase and multicomponent shale micro- and nanoporous structures, enabling the study of the occurrence and adsorption behavior of multiphase and multicomponent fluids in shale micro- and nanoporous structures under an applied electric field. This greatly promotes the application of electric field-enhanced porous solid material CO2 adsorption technology in improving shale gas recovery.

[0006] This specification provides an embodiment of a method for determining multiphase, multicomponent competitive adsorption data of shale micro- and nanopores, including:

[0007] Obtain shale core samples from the target area and determine the types and relative content variations of surface functional groups in the shale core samples;

[0008] Key structural and force field parameters of shale clay minerals in the target block were collected, and a molecular model of shale clay minerals was established. Based on the changes in the types and relative contents of functional groups on the shale surface under the action of an electric field, the molecular surface functional groups in the molecular model of shale clay minerals were modified and replaced, and the cell of the modified clay mineral molecules was expanded.

[0009] Multiple fluid molecular models were established; a slit model with the modified clay mineral molecules as boundaries was established, and a multiphase fluid system model composed of different contents of the multiple fluid molecular models was established between the slit models to obtain the initial configuration of multiphase and multi-component competitive adsorption in shale micro-nano pores; the initial configuration was structurally optimized to obtain a stable configuration; the multiple fluid molecular models include a water molecule model, a carbon dioxide molecule model, and an alkane molecule model;

[0010] An external electric field is applied to the stable configuration, and molecular dynamics calculations are performed to obtain the molecular trajectory coordinates and dynamic information of the multiphase and multicomponent fluid. Based on the molecular trajectory coordinates and dynamic information of the multiphase and multicomponent fluid, competitive adsorption data of the shale micro- and nano-porous multiphase and multicomponent fluid under the action of the electric field are calculated, so as to carry out shale gas extraction and / or shale carbon dioxide sequestration based on the competitive adsorption data.

[0011] In one embodiment, determining the types and relative content variations of surface functional groups in the shale core sample includes:

[0012] The shale core samples were saturated with formation water.

[0013] Fourier transform infrared spectroscopy was used to test the surface structure of shale core samples after saturation with formation water before and after the application of an electric field, and the changes in the types and relative contents of surface functional groups of the shale core samples were obtained.

[0014] In one embodiment, multiple fluid molecule models are established, including:

[0015] A water molecule model, a carbon dioxide molecule model, and an alkane molecule model were established using materials calculation software. The force field of the water molecule model was an SPC / E force field, the force field of the carbon dioxide molecule model was an EPM2 force field, and the force field of the alkane molecule model was an OPLS-UA force field.

[0016] In one embodiment, structural optimization of the initial configuration to obtain a stable configuration includes:

[0017] The initial configuration of multiphase and multicomponent competitive adsorption in shale micro- and nanopores is converted into a model file required by molecular dynamics simulation software.

[0018] The model file of the initial configuration was structurally optimized using molecular dynamics simulation software. Simulation parameters were set, and energy minimization and position-restricted pre-equilibrium simulations were performed sequentially to obtain a stable configuration.

[0019] In one embodiment, an external electric field is applied to the stable configuration, and molecular dynamics calculations are performed to obtain the molecular trajectory coordinates and dynamic information of the multiphase, multicomponent fluid, including:

[0020] Using molecular dynamics simulation software, the stable configuration was set as an NVT ensemble. An external electric field was applied to the NVT ensemble, and the simulated electric field parameters were set. Molecular dynamics calculations were performed to obtain the molecular trajectory coordinates and dynamic information of the multiphase, multi-component fluid. The formula for setting the electric field parameters is as follows:

[0021]

[0022] Where E0 is the electric field intensity; E is the peak electric field value; f is the electric field frequency; and t is the time step.

[0023] In one embodiment, based on the molecular trajectory coordinates and dynamic information of the multiphase multicomponent fluid, competitive adsorption data of the shale micro / nanopore multiphase multicomponent fluid under the action of an electric field are calculated, including:

[0024] Based on the molecular trajectory coordinates and dynamic information of the multiphase and multicomponent fluid, the distribution of the multiphase and multicomponent fluid at different times is visualized to generate real-time dynamic images of the occurrence state and competitive adsorption process of the multiphase and multicomponent fluid in the micro-nano pores of shale under the action of an electric field.

[0025] Based on the molecular trajectory coordinates and dynamic information of the multiphase multicomponent fluid, the absolute adsorption amount, selective adsorption coefficient, and interaction energy of each component in the multiphase multicomponent fluid are determined.

[0026] In one embodiment, the molecular trajectory coordinates and dynamic information of the multiphase multicomponent fluid include: the density distribution curves, molar number distributions, and molecular number distributions of each component in the multiphase multicomponent fluid;

[0027] Accordingly, based on the molecular trajectory coordinates and dynamic information of the multiphase multicomponent fluid, the absolute adsorption amount, selective adsorption coefficient, and interaction energy of each component in the multiphase multicomponent fluid are determined, including:

[0028] Based on the density distribution curves of each component in the multiphase multicomponent fluid, the adsorption layer thickness of each component is determined, and the absolute adsorption amount of molecules is calculated based on the adsorption layer thickness of each component.

[0029] Based on the absolute adsorption amount of each component in the multiphase multicomponent fluid and the molar number distribution of each component, the selective adsorption coefficient of each component in the multiphase multicomponent fluid is determined.

[0030] Based on the molecular number distribution of each component in the multiphase multicomponent fluid and the equilibrium configuration of each system, the interaction energy between each component and the modified wall is calculated.

[0031] This specification also provides an embodiment of a device for determining multiphase, multicomponent competitive adsorption data of shale micro-nano pores, comprising:

[0032] The acquisition module is used to acquire shale core samples from the target area and determine the types and relative content variation characteristics of the surface functional groups of the shale core samples.

[0033] The collection module is used to collect key structural and force field parameters of shale clay minerals in the target block and establish a molecular model of shale clay minerals. It is also used to modify and replace the molecular surface functional groups in the molecular model of shale clay minerals according to the changes in the types and relative contents of functional groups on the shale surface under the action of an electric field, and then expand the cell of the modified clay mineral molecules.

[0034] The module is used to establish multiple fluid molecule models; it is also used to establish slit models with the modified clay mineral molecules as boundaries, and to establish multiphase fluid system models composed of different contents of the multiple fluid molecule models between the slit models, to obtain the initial configuration of multiphase and multi-component competitive adsorption in shale micro-nano pores; it is also used to optimize the structure of the initial configuration to obtain a stable configuration; the multiple fluid molecule models include water molecule models, carbon dioxide molecule models, and alkane molecule models;

[0035] The calculation module is used to apply an external electric field to the stable configuration and perform molecular dynamics calculations to obtain the molecular trajectory coordinates and dynamic information of the multiphase and multicomponent fluid; it is also used to calculate the competitive adsorption data of the multiphase and multicomponent fluid in the micro- and nano-pores of shale under the action of the electric field based on the molecular trajectory coordinates and dynamic information of the multiphase and multicomponent fluid, so as to carry out shale gas extraction and / or shale carbon dioxide sequestration based on the competitive adsorption data.

[0036] This specification also provides a computer device, including a processor and a memory for storing processor-executable instructions, wherein the processor executes the instructions to implement the steps of the method for determining multiphase and multicomponent competitive adsorption data of shale micro-nano pores described in any of the above embodiments.

[0037] This specification also provides a computer-readable storage medium storing computer instructions that, when executed, implement the steps of the method for determining multiphase and multicomponent competitive adsorption data of shale micro-nano pores described in any of the above embodiments.

[0038] This specification provides a method for determining multiphase and multicomponent competitive adsorption data in shale micro- and nanopores. This method allows for the acquisition of shale core samples from a target region and the determination of the types and relative content variations of surface functional groups in the shale core samples. Key structural and force field parameters of shale clay minerals from the target block are collected, and a molecular model of the shale clay minerals is established. Based on the changes in the types and relative content of shale surface functional groups under the action of an electric field, the molecular surface functional groups in the shale clay mineral molecular model are modified and replaced, and the cell of the modified clay mineral molecules is expanded. Multiple fluid molecular models are established. A slit model with modified clay mineral molecules as boundaries is established, and a multiphase fluid system model composed of multiple fluid molecular models with different contents is established between the slit models to obtain the initial configuration of multiphase and multicomponent competitive adsorption in shale micro- and nanopores. The initial configuration is structurally optimized to obtain a stable configuration. The multiple fluid molecular models include a water molecule model, a carbon dioxide molecule model, and an alkane molecule model. An external electric field is applied to a stable configuration, and molecular dynamics calculations are performed to obtain the molecular trajectory coordinates and dynamic information of the multiphase and multicomponent fluid. Based on the molecular trajectory coordinates and dynamic information of the multiphase and multicomponent fluid, competitive adsorption data of the multiphase and multicomponent fluid in shale micro- and nanopores under the action of the electric field are calculated. This data is then used for shale gas extraction and / or shale carbon dioxide sequestration. By combining the above method with the characteristics of functional group changes on the shale surface under the action of the electric field, a molecular simulation model of competitive adsorption of multiphase and multicomponent fluids in surface-modified shale micro- and nanopores under the action of the electric field can be established. This model reveals the occurrence state and competitive adsorption behavior of multiphase and multicomponent fluids in shale micro- and nanopores under the action of the electric field at the molecular scale. It enables the selective adsorption of carbon dioxide in mixed fluids by shale enhanced by an external electric field, laying an important theoretical foundation for the application of electric field-enhanced carbon dioxide injection technology for shale gas reservoirs to improve recovery and for carbon dioxide sequestration. Attached Figure Description

[0039] The accompanying drawings, which are included to provide a further understanding of this specification and form part of it, do not constitute a limitation thereof. In the drawings:

[0040] Figure 1A flowchart of a method for determining multiphase, multicomponent competitive adsorption data of shale micro-nano pores in one embodiment of this specification is shown;

[0041] Figure 2 A flowchart of a method for determining multiphase, multicomponent competitive adsorption data of shale micro-nano pores in one embodiment of this specification is shown;

[0042] Figure 3 The diagram shows the initial distribution of a multiphase, multicomponent shale micro-nano porous system under the influence of an electric field in one embodiment of this specification.

[0043] Figure 4 The diagram shows the distribution of various components in the micro- and nano-pores of shale before and after the application of an electric field in one embodiment of this specification.

[0044] Figure 5 The following are density distribution curves of various components in shale micro- and nano-pores under different electric field intensities in one embodiment of this specification;

[0045] Figure 6 The diagram shows the variation of CO2 / CH4 adsorption selectivity under different electric field strengths in one embodiment of this specification.

[0046] Figure 7 This specification shows a graph illustrating the variation of interaction energy between the components of shale micro / nanopores and the wall under different electric field intensities in one embodiment of the present specification.

[0047] Figure 8 The following are density distribution curves of various components in shale micro- and nano-pores under different electric field frequencies in one embodiment of this specification;

[0048] Figure 9 This specification shows a graph illustrating the variation in CO2 / CH4 adsorption selectivity under different electric field frequencies in one embodiment of the invention.

[0049] Figure 10 This specification shows a graph illustrating the variation of the interaction energy between each component and the wall at different electric field frequencies in one embodiment of the present specification.

[0050] Figure 11 A structural block diagram of a device for determining multiphase and multicomponent competitive adsorption data of shale micro-nano pores is shown in one embodiment of this specification;

[0051] Figure 12 A schematic diagram of a computer device according to one embodiment of this specification is shown. Detailed Implementation

[0052] The principles and spirit of this specification will now be described with reference to several exemplary embodiments. It should be understood that these embodiments are given merely to enable those skilled in the art to better understand and implement this specification, and are not intended to limit the scope of this specification in any way. Rather, these embodiments are provided to make this disclosure more thorough and complete, and to fully convey the scope of this disclosure to those skilled in the art.

[0053] Those skilled in the art will recognize that the embodiments described in this specification can be implemented as a system, apparatus, method, or computer program product. Therefore, the disclosure of this specification can be specifically implemented in the following forms: entirely hardware, entirely software (including firmware, resident software, microcode, etc.), or a combination of hardware and software.

[0054] Since the exploration and development of shale gas, molecular simulation of shale gas adsorption in shale has gradually become a research hotspot. However, there are few studies on molecular simulation of multiphase and multi-component competitive adsorption in shale micro- and nano-pores under the action of an electric field. These studies mainly focus on simulations of single-component and multi-component competitive adsorption of shale gas without an electric field. None of these studies have analyzed and explained the changes in functional groups on the shale surface under applied DC and AC electric fields, the occurrence state of CO2 / shale gas / water in the micropores of shale under actual geological burial depth conditions, and the competitive adsorption mechanism.

[0055] To address the above issues, this specification provides a method for determining multiphase, multicomponent competitive adsorption data in shale micro- and nanopores. This method enables the selective adsorption of CO2 from a mixed fluid by shale under an applied electric field. By combining this with the characteristics of functional group changes on the shale surface under the influence of the electric field, a more accurate determination of the occurrence state and competitive adsorption behavior of CO2 / shale gas in the micro- and nanopores of water-bearing shale can be obtained, aiming to overcome the technological bottlenecks in shale gas extraction and CO2 sequestration.

[0056] Figure 1 A flowchart illustrating a method for determining multiphase, multicomponent competitive adsorption data of shale micro / nanopores according to an embodiment of this specification is provided. While this specification provides method operation steps or apparatus structures as shown in the following embodiments or figures, more or fewer operation steps or module units may be included in the method or apparatus based on conventional or non-inventive effort. In steps or structures where there is no logically necessary causal relationship, the execution order of these steps or the module structure of the apparatus is not limited to the execution order or module structure described in the embodiments and figures of this specification. When the method or module structure is applied in actual devices or end products, it can be executed sequentially or in parallel according to the method or module structure shown in the embodiments or figures (e.g., in a parallel processor or multithreaded processing environment, or even a distributed processing environment).

[0057] Specifically, such as Figure 1 As shown in the figure, the method for determining multiphase and multicomponent competitive adsorption data of shale micro-nano pores provided in one embodiment of this specification may include the following steps.

[0058] Step S101: Obtain shale core samples from the target area and determine the types and relative content variation characteristics of surface functional groups in the shale core samples.

[0059] Shale core samples can be obtained from the target area. The target area can be the shale region to be observed. The process of collecting shale core samples from the target area must ensure the representativeness of the samples and their ability to accurately reflect the characteristics of the shale in the target area. Sampling location, depth, and other information should be recorded in detail, as shale at different locations and depths may exhibit differences in mineral composition, pore structure, and surface properties. The types and relative content variations of surface functional groups in shale core samples can be determined experimentally. Surface functional groups refer to atomic groups or chemical bonds existing on the surface of a material and possessing specific chemical properties and reactivity. By combining the characteristics of shale surface functional group changes under an electric field, a relevant molecular simulation model can be established, which helps to reveal the multiphase, multicomponent fluid occurrence state and competitive adsorption behavior of shale micro- and nanopores under an electric field at the molecular scale.

[0060] In some embodiments of this specification, determining the types and relative content variations of surface functional groups in the shale core sample may include: saturating the shale core sample with formation water; and performing Fourier transform infrared spectroscopy (FTIR) tests on the surface structure of the shale core sample after saturation with formation water before and after the application of an electric field to obtain the types and relative content variations of surface functional groups in the shale core sample.

[0061] Specifically, shale core samples can be saturated with formation water. This simulates the actual water-bearing state of shale underground because the presence of formation water affects the physicochemical properties of the shale surface and the interaction between shale and gas molecules. By allowing the sample to fully absorb formation water, the true underground environment is recreated, laying the foundation for subsequent accurate research on the competitive adsorption behavior of multiphase and multicomponent molecules in shale pores. Different functional groups have specific vibrational frequencies. When infrared light irradiates the sample, it interacts with the functional groups, causing the absorption of infrared light at certain frequencies. By detecting the absorption of infrared light at different frequencies by the sample, information related to the functional groups can be obtained. Shale samples saturated with formation water are subjected to FTIR tests before and after the application of an electric field. During the test, the sample is prepared into a form suitable for instrument detection (such as thin slices, powder, etc.) and placed in a Fourier transform infrared spectrometer. The instrument emits infrared light that penetrates the sample, and the detector records the degree of absorption of infrared light at different frequencies, thus obtaining an infrared spectrum. Based on the position, intensity, and shape of absorption peaks in the infrared spectrum, the types of functional groups on the shale surface can be determined. For example, absorption peaks at specific positions correspond to different functional groups such as hydroxyl (-OH), carboxyl (-COOH), and methyl (-CH3). By comparing the intensity changes of each absorption peak before and after the application of an electric field, the relative content changes of surface functional groups can be quantitatively analyzed. For instance, if the intensity of the absorption peak corresponding to a certain functional group increases after the application of an electric field, it indicates that the relative content of that functional group increases; conversely, if the intensity of the absorption peak decreases, the relative content decreases. Through these steps, the types and relative content changes of surface functional groups in shale core samples from the target area before and after the application of an electric field can be accurately obtained. This provides crucial data support for establishing more realistic molecular simulation models and for in-depth research on the multiphase and multi-component competitive adsorption behavior of shale micro- and nanopores under the influence of an electric field.

[0062] Step S102: Collect key structural and force field parameters of shale clay minerals in the target block and establish a molecular model of shale clay minerals; based on the changes in the types and relative contents of functional groups on the shale surface under the action of an electric field, modify and replace the molecular surface functional groups in the molecular model of shale clay minerals, and then expand the cell of the modified clay mineral molecules.

[0063] Geological data on shale clay minerals in the target block can be obtained, including but not limited to information on regional geological structure, stratigraphic distribution, and sedimentary environment. XRD (X-ray diffraction) tests can be performed on shale samples collected from the target block. XRD can determine the crystal structure type and lattice parameters of clay minerals by measuring the diffraction angle and intensity of X-rays in the crystal. SEM (scanning electron microscopy) can be used to observe the microscopic morphology of shale clay minerals, such as particle size, shape, and arrangement. Thermogravimetric analysis (TGA) can be used to determine the water content and thermal stability of clay minerals. Force field parameters describe the interactions between atoms in molecules and are crucial for accurately simulating molecular behavior. Many mature force fields are available, such as the CLAYFF force field (suitable for simulating multi-component mineral systems and their fluid interfaces) and the UFF force field (universal force field). In this embodiment, the CLAYFF force field, a universal force field suitable for simulating multi-component mineral systems and their fluid interfaces, is selected. Molecular models of shale clay minerals can be built using software such as Materials Studio (materials calculation software), CHARMM-GUI (a multi-functional online platform for molecular dynamics simulation), or Avogadro (a molecular editor and visualization tool). Based on the clay mineral species identified through XRD and other analyses, their basic structural units can be determined. Based on these basic structural units, and using the unit cell parameters obtained from XRD, a complete unit cell structure is constructed in the modeling software. Considering the various functional groups present on the surface of shale clay minerals, which significantly influence their adsorption properties and interactions with fluids, after completing the initial model construction, the energy minimization function provided by the modeling software is used to optimize the model's structure.

[0064] Under an applied electric field, the oxygen-containing functional groups of carbon in the shale surface structure undergo modification, with a significant decrease in the content of CC / CH bonds and the breakage of CC / CH bonds, generating CO bonds, C=O carbonyl functional groups, and COO-carboxyl functional groups. With increasing electric field strength, the decrease in the content of CC / CH functional groups in the shale surface structure increases, while the contents of C=O carbonyl and COO-carboxyl functional groups continuously increase, and the CO bond content shows a trend of first increasing and then decreasing. The functional groups on the shale surface (such as carbonyl, epoxy, nitrogen, and hydroxyl groups) possess different adsorption characteristics. These functional groups can influence the adsorption behavior of fluid molecules (such as methane and carbon dioxide) on the shale surface. The presence of functional groups can inhibit methane adsorption while promoting carbon dioxide adsorption. This may be due to the stronger interaction force between the functional groups and carbon dioxide molecules, thereby enhancing the adsorption capacity of carbon dioxide on the shale surface.

[0065] In the competitive adsorption process of multiphase and multicomponent fluids, functional groups preferentially adsorb certain fluid molecules (such as carbon dioxide), thereby occupying the high-energy adsorption sites of these fluid molecules. This leads to a decrease in the adsorption of other fluid molecules (such as methane), as their adsorption sites are occupied by functional groups. Functional groups on the shale surface have a significant impact on the competitive adsorption of multiphase and multicomponent fluids. These effects are not only reflected in the direct influence of functional groups on fluid adsorption and diffusion, but also in their influence on pore structure and competitive adsorption mechanisms. Furthermore, under the influence of an applied electric field, the different interactions between different surface functional groups and fluid molecules also affect multicomponent competitive adsorption. Therefore, based on the changes in the types and relative contents of functional groups on the shale surface under an electric field, the molecular surface functional groups in the shale clay mineral molecular model can be modified and replaced, and the cell size of the modified clay mineral molecules can be expanded. This can improve the accuracy of the competitive adsorption data.

[0066] After determining the changes in the types and relative contents of functional groups on the shale surface before and after the application of an electric field (obtained through Fourier Transform Infrared Spectroscopy (FTIR)), specific schemes for modifying and replacing the molecular model of shale clay minerals were determined based on these data. For example, if FTIR tests show that the relative content of hydroxyl (-OH) functional groups on the shale surface increases after the application of an electric field, and new carboxyl (-COOH) functional groups appear, then the number of -O groups needs to be increased accordingly in the molecular model, and -COOH functional groups need to be introduced in appropriate positions.

[0067] Functional group modification can be performed using software for building molecular models of shale clay minerals (such as Materials Studio, CHARMM-GUI, or Avogadro). Taking Materials Studio as an example, its atom editing tools are used to find suitable atomic sites on the surface of the established clay mineral molecular model for adding or replacing functional groups. For instance, for a layered montmorillonite clay mineral model, oxygen or aluminum atoms on its surface might be suitable for connecting new functional groups. Appropriate chemical bonding methods are selected, and the new functional groups are accurately added to the model surface according to chemical structure principles. During the addition process, chemical valence rules must be strictly followed to ensure that bond lengths, bond angles, and other parameters conform to the actual chemical structure. For functional groups that need to be replaced, the original functional group is deleted first, and then the new functional group is added using the above method. Simultaneously, the local structure after adding or replacing functional groups is initially optimized to achieve a relatively stable interatomic interaction energy in that region. After completing the modification and replacement of functional groups, the software's analysis function is used again to check the structural rationality of the new model.

[0068] The appropriate cell expansion factor can be determined based on the research objectives and the needs of subsequent simulation calculations. The purpose of cell expansion is to more accurately reflect the macroscopic properties of clay minerals and their interactions with surrounding fluid molecules in the simulation, while avoiding the influence of boundary effects. Typically, the selection of the cell expansion factor requires a balance between computational resources and model accuracy. Taking Materials Studio software as an example, select the cell operation function in the menu bar and enter the desired cell expansion factor. The software will automatically expand the modified clay mineral molecular cell according to the set factor. After cell expansion, due to the increased cell size, the interactions between atoms may change, requiring overall optimization of the expanded model.

[0069] Step S103: Establish multiple fluid molecule models; establish slit models with the modified clay mineral molecules as boundaries, and establish multiphase fluid system models composed of different contents of the multiple fluid molecule models between the slit models to obtain the initial configuration of multiphase and multicomponent competitive adsorption of shale micro-nano pores; optimize the structure of the initial configuration to obtain a stable configuration; the multiple fluid molecule models include water molecule models, carbon dioxide molecule models and alkane molecule models.

[0070] Specifically, fluid molecular models, including those for water, CO2, and alkanes, can be established using Materials Studio software. Through these steps, various fluid molecular models, such as those for water, CO2, and alkanes, can be created. These models will serve as the foundation for constructing multiphase fluid system models, enabling in-depth research into the competitive adsorption behavior of multiphase and multi-component systems within the micro- and nano-pores of shale under the influence of an electric field.

[0071] In some embodiments of this specification, various fluid molecule models are established, which may include: establishing water molecule models, carbon dioxide molecule models, and alkane molecule models using materials calculation software; wherein the force field of the water molecule model is an SPC / E force field, the force field of the carbon dioxide molecule model is an EPM2 force field, and the force field of the alkane molecule model is an OPLS-UA force field. This setup makes the competitive adsorption behavior of various fluids in micro- and nano-pores more accurate.

[0072] Based on the actual size data of the micro- and nano-pores in the target shale, typically within the nanoscale range, and considering the balance between research needs and computational resources, the specific dimensions of the slit model can be set. The slit model can be constructed using Packmol software. Packmol is a powerful software widely used in molecular simulation, primarily for constructing the initial structures of complex molecular systems. The modified clay mineral molecular model, previously modified with surface functional groups and subjected to cell expansion, is imported into Packmol software. In the software, relevant parameters are set to arrange the modified clay mineral molecules in a parallel and relative manner in space, forming a slit-like boundary structure. Specific parameter settings include the position and orientation of the molecules, as well as the spacing of the slits, ensuring that the geometry and size of the slit model meet the pre-defined requirements.

[0073] Based on the actual fluid composition of the target shale reservoir, the proportions of different fluid molecules in the multiphase fluid system can be set. For example, for a specific shale gas reservoir, the proportions of fluids such as water, CO2, and methane are determined through geological analysis and experimental measurements, and the corresponding number of molecules is set in the model accordingly. These proportions should be as close as possible to the actual situation to ensure the authenticity and reliability of the simulation results. In Packmol software, for the established slit model, various fluid molecules such as water, CO2, and alkanes are filled into the space between the slit models according to the set fluid molecule contents. The software will randomly distribute these fluid molecules according to the set parameters, while ensuring that the distance between molecules conforms to physical laws and avoids unreasonable situations such as molecular overlap. During the filling process, some constraints can be set as needed, such as the minimum distance between fluid molecules and the surface of clay minerals, to better simulate the distribution of fluids in shale pores under actual conditions. After the multiphase fluid system model is built, the initial configuration is comprehensively checked. After checking and optimization, the initial configuration of multiphase and multi-component competitive adsorption in shale micro- and nano-pores is obtained.

[0074] After obtaining the initial configuration of multiphase, multicomponent competitive adsorption in shale micro- and nanopores, structural optimization is needed to obtain a stable configuration to ensure the accuracy and reliability of the simulation results. This process is typically achieved using specialized simulation software, such as LAMMPS. LAMMPS (Large-Scale Atomic / Molecular Parallel Simulator) is an open-source molecular dynamics simulation software widely used in materials science, chemistry, biophysics, and other fields.

[0075] In some embodiments of this specification, structural optimization of the initial configuration to obtain a stable configuration may include: converting the initial configuration of multiphase and multicomponent competitive adsorption in shale micro- and nanopores into a model file required by molecular dynamics simulation software; using molecular dynamics simulation software to perform structural optimization of the model file of the initial configuration, setting simulation parameters, and sequentially performing energy minimization and position-restricted pre-equilibrium simulations to obtain a stable configuration.

[0076] Specifically, since the initial configuration is constructed using software such as Packmol, its file format may not be directly applicable to LAMMPS software (i.e., molecular dynamics simulation software). Moltemplate is a tool for preparing input files for molecular dynamics simulations and plays an important role in the simulation study of complex molecular systems. It can convert user-built molecular structure models into input files that can be directly used by molecular dynamics simulation software (such as LAMMPS). Therefore, Moltemplate software is first used to convert the initial configuration file into a model file that LAMMPS software can recognize and process. In LAMMPS software, choosing an appropriate ensemble is crucial for the stability and accuracy of the simulation system. It is usually set to the NVT ensemble (canonical ensemble), under which the particle number (N), volume (V), and temperature (T) of the system remain constant. This choice is based on the fact that in actual shale micro-nano porous multiphase multicomponent systems, the pore volume is relatively fixed, and a constant temperature environment can be set during the simulation to simulate conditions under specific reservoir temperature conditions. Based on the force fields previously selected when constructing the molecular models of shale clay minerals and fluids, such as the CLAYFF force field for shale clay minerals, the SPC / E force field for water, the EPM2 force field for CO2, and the OPLS-UA force field for alkanes, the corresponding force field parameters are accurately set in the LAMMPS software. These force field parameters determine the mode and intensity of interatomic interactions, including bond lengths, bond angles, dihedral angles, and the specific forms of potential energy functions such as van der Waals forces and electrostatic interactions. Accurately setting the force field parameters ensures that the description of intermolecular interactions during the simulation conforms to actual physicochemical laws. In addition to the ensemble and force field parameters, some parameters related to the simulation process also need to be set. For example, the choice of time step must ensure both computational efficiency and simulation stability.

[0077] Before starting the dynamics simulation, the system is first subjected to energy minimization. This is because the atomic positions in the initial configuration may not be in the lowest energy state, and may possess relatively high potential energy. The purpose of energy minimization is to adjust the positions of atoms to reduce the total energy of the entire system to a minimum, eliminating unreasonable overlap or excessive interaction forces between atoms, thereby obtaining a relatively stable structure. After energy minimization, although the system reaches a relatively low energy state, it may still not have reached a true equilibrium state. The purpose of position-restricted pre-equilibrium simulation is to allow the system to undergo dynamics simulation at a set temperature under certain restrictive conditions, enabling molecules to move freely within a certain range and further adjust their positions and orientations to reach thermal equilibrium. At the same time, by restricting the positions of certain atoms or molecular groups, unreasonable structural changes can be avoided during the equilibrium process, ensuring the overall structural stability of the system. Based on the characteristics of the system and the simulation requirements, the atoms or molecular groups that need to be restricted are determined. After setting the position restriction conditions and temperature control parameters in the LAMMPS software, the pre-equilibrium simulation is started. After energy minimization and position-restricted pre-equilibrium simulation, the system is comprehensively checked to determine whether a stable configuration has been obtained. If all indicators show that the system is in a stable state, then a stable configuration has been confirmed.

[0078] Step S104: Apply an external electric field to the stable configuration and perform molecular dynamics calculations to obtain the molecular trajectory coordinates and dynamic information of the multiphase and multicomponent fluid; based on the molecular trajectory coordinates and dynamic information of the multiphase and multicomponent fluid, calculate the competitive adsorption data of the shale micro-nano pore multiphase and multicomponent fluid under the action of the electric field, so as to carry out shale gas extraction and / or shale carbon dioxide sequestration based on the competitive adsorption data.

[0079] After obtaining a stable configuration, applying an external electric field and performing molecular dynamics calculations are crucial steps in studying the behavior of multiphase, multicomponent fluids in the micro- and nano-pores of shale under an electric field. An external electric field can be applied. In LAMMPS software, the external electric field is applied along the Z-axis of the system. Precise settings are required for various parameters of the simulated electric field, including electric field strength, electric field frequency, and application time. The electric field strength determines the magnitude of the force exerted by the electric field on the molecules of the multiphase, multicomponent fluid. For example, the electric field strength can be set at... Within a certain range, the influence of electric fields of varying intensities on the system can be studied. The frequency of the electric field affects its changing characteristics; different frequencies can be set according to research needs, such as from low to high frequencies, to explore the effect of electric field frequency on the behavior of fluid molecules. The energizing time needs to be determined based on the total simulation duration and the time required for the system to reach a steady state, ensuring that the effect of the electric field on the system is observed within a sufficient timeframe.

[0080] In some embodiments of this specification, applying an external electric field to the stable configuration and performing molecular dynamics calculations to obtain the molecular trajectory coordinates and dynamic information of the multiphase, multicomponent fluid may include: using molecular dynamics simulation software, setting the stable configuration as an NVT ensemble, applying an external electric field to the NVT ensemble, setting the simulated electric field parameters, and performing molecular dynamics calculations to obtain the molecular trajectory coordinates and dynamic information of the multiphase, multicomponent fluid; wherein, the formula for setting the electric field parameters is:

[0081]

[0082] Where E0 is the electric field strength; E is the peak electric field value; f is the electric field frequency; and t is the time step. Using this formula, the LAMMPS software can calculate the electric field strength at each moment in real time during the simulation, based on the set parameters, thus accurately simulating the effect of time-varying electric fields on multiphase, multi-component fluids.

[0083] While applying the electric field, the previously set NVT ensemble conditions are maintained, i.e., the number of particles (N), volume (V), and temperature (T) of the system remain constant. This ensures that when studying the effect of the electric field on the system, interference from other factors (such as volume changes, changes in the number of particles, etc.) is eliminated, allowing focus on the interaction between the electric field and the multiphase multicomponent fluid. The appropriate time step determined in the previous optimization process (e.g., 1-5 fs) is continued to ensure the stability and computational efficiency of the simulation. A sufficient number of simulation steps is determined based on the research objectives and the time required for the system to reach a stable state. As the simulation progresses, the multiphase multicomponent fluid molecules undergo complex motions within the micro- and nanopores of shale under the combined influence of the electric field and intermolecular forces. The software tracks the trajectory of each molecule in real time, recording its position coordinates at different moments. Simultaneously, the dynamic information of the molecules, such as velocity, acceleration, and kinetic energy, is calculated based on their motion states. This information reflects the energy changes and motion characteristics of molecules under the influence of the electric field, which is of great significance for a deeper understanding of the competitive adsorption behavior and dynamic distribution of multiphase multicomponent fluids in shale pores. During the simulation, the LAMMPS software records the trajectory coordinates and dynamic information of multiphase and multicomponent fluid molecules at a set output frequency and stores them in a specific file. The output frequency can be adjusted according to research needs; for example, data can be output every certain number of steps (e.g., 100-1000 steps) to obtain sufficiently detailed system dynamic information without consuming excessive storage space. After the simulation, the obtained molecular trajectory coordinates and dynamic information files form the basis for subsequent analysis. These data will be used for further processing and analysis, such as visualizing the distribution of multiphase and multicomponent fluids at different times using molecular dynamics simulation visualization software (e.g., VMD, Ovital), intuitively observing the motion trajectory and distribution changes of fluid molecules in shale micro- and nano-pores under the influence of an electric field; and calculating important parameters such as the absolute adsorption amount of each component, selective adsorption coefficient, and interaction energy variation based on these data, to further study the influence mechanism of the electric field on the competitive adsorption behavior of multiphase and multicomponent fluids in shale micro- and nano-pores.

[0084] In the above embodiments, by combining the characteristics of functional group changes on the shale surface under the action of an electric field, a molecular simulation model of multiphase and multicomponent competitive adsorption of shale micro-nano pores under the action of an electric field can be established. This model reveals the occurrence state and competitive adsorption behavior of multiphase and multicomponent fluids in shale micro-nano pores under the action of an electric field at the molecular scale. This enables the selective adsorption of carbon dioxide in mixed fluids by shale enhanced by an external electric field, laying an important theoretical foundation for the application of carbon dioxide injection and carbon dioxide sequestration technology in shale gas reservoirs enhanced by electric field.

[0085] In some embodiments of this specification, calculating the competitive adsorption data of the multiphase multi-component fluid in shale micro-nanopores under the action of an electric field, based on the molecular trajectory coordinates and dynamic information of the multiphase multi-component fluid, may include: visualizing the distribution of the multiphase multi-component fluid at different times based on the molecular trajectory coordinates and dynamic information of the multiphase multi-component fluid, generating a real-time dynamic image of the occurrence state and competitive adsorption process of the multiphase multi-component fluid in shale micro-nanopores under the action of an electric field; and determining the absolute adsorption amount, selective adsorption coefficient, and interaction energy of each component in the multiphase multi-component fluid based on the molecular trajectory coordinates and dynamic information of the multiphase multi-component fluid.

[0086] In the field of molecular dynamics simulation, various software programs are available for visualizing molecular trajectory data, such as VMD and Ovito. While VMD and Ovito support many common molecular trajectory file formats, the data format output by LAMMPS may require some conversion. In the selected visualization software, the processed molecular trajectory file is imported using the appropriate file loading function. Simultaneously, other information related to molecular structure and properties, such as atom types and force field parameters, is loaded to ensure the software can correctly identify different multiphase and multicomponent fluid molecules and assign them appropriate visualization features, such as color and size. Based on the characteristics of the multiphase and multicomponent fluid molecules, a suitable representation method is selected to display the molecular structure. Parameters of the visualization scene, such as background color and lighting conditions, are adjusted to improve image clarity and visualization effects. Using the time-series function of the visualization software, the distribution of multiphase and multicomponent fluids at different times is displayed sequentially according to the time sequence in the molecular trajectory data. In the visualization software, the animation recording function is used to sequentially combine static images from different times into an animation, generating a real-time dynamic image of the occurrence state and competitive adsorption process of multiphase and multicomponent fluids in shale micro- and nano-porous structures under the influence of an electric field. Through the above steps, abstract molecular trajectory coordinates and dynamic information can be transformed into intuitive real-time dynamic images, providing researchers with a powerful tool for in-depth analysis of the occurrence state and competitive adsorption process of multiphase and multicomponent fluids in shale micro- and nanopores under the action of an electric field.

[0087] Furthermore, important parameters such as absolute adsorption capacity, selective adsorption coefficient, and interaction energy can be extracted from the molecular trajectory coordinates and kinetic information of multiphase and multicomponent fluids. This provides quantitative data support for a deeper understanding of the competitive adsorption behavior of multiphase and multicomponent fluids in shale micro- and nanopores under the influence of an electric field. These data have significant guiding significance for practical applications such as evaluating shale gas recovery and CO2 sequestration capabilities.

[0088] In some embodiments of this specification, the molecular trajectory coordinates and dynamic information of the multiphase multicomponent fluid may include: the density distribution curves, molar number distributions, and molecular number distributions of each component in the multiphase multicomponent fluid; correspondingly, determining the absolute adsorption amount, selective adsorption coefficient, and interaction energy of each component in the multiphase multicomponent fluid based on the molecular trajectory coordinates and dynamic information may include: determining the adsorption layer thickness of each component based on the density distribution curves of each component in the multiphase multicomponent fluid, and calculating the absolute adsorption amount of molecules based on the adsorption layer thickness of each component; determining the selective adsorption coefficient of each component in the multiphase multicomponent fluid based on the absolute adsorption amount and molar number distribution of each component; and calculating the interaction energy between each component and the modified wall surface based on the molecular number distribution of each component in the multiphase multicomponent fluid and the equilibrium configuration of each system. Through the above steps, the adsorption characteristics of multiphase, multicomponent fluids in shale micro- and nanopores under the influence of an electric field can be quantitatively analyzed. This provides detailed quantitative data for a deeper understanding of the competitive adsorption process of multiphase and multicomponent fluids and the impact of the electric field on shale gas recovery and CO2 sequestration. These calculations help evaluate the effectiveness of shale gas extraction and CO2 sequestration under different electric field conditions, providing a theoretical basis for optimizing related technologies.

[0089] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. For details, please refer to the foregoing descriptions of the relevant processing embodiments; they will not be repeated here.

[0090] The foregoing has described specific embodiments of this specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims may be performed in a different order than that shown in the embodiments and may still achieve the desired result. Furthermore, the processes depicted in the drawings do not necessarily require the specific or sequential order shown to achieve the desired result. In some embodiments, multitasking and parallel processing are possible or may be advantageous.

[0091] The above method will be described below with reference to a specific embodiment. However, it is worth noting that this specific embodiment is only for better illustration of this specification and does not constitute an improper limitation of this specification.

[0092] This specific embodiment provides a method for determining multiphase, multicomponent competitive adsorption data in shale micro- and nanopores. Please refer to... Figure 2 The flowchart illustrates the method for determining multiphase, multicomponent competitive adsorption data of shale micro- and nanopores in this specific embodiment. Figure 2 As shown, the method in this embodiment may include the following.

[0093] (1) Obtain shale core samples from the target area. After saturating the formation water, use Fourier transform infrared spectroscopy to test the surface structure of the shale samples before and after the electric field to obtain the characteristics of the changes in the types and relative contents of surface functional groups.

[0094] (2) Collect key structural and force field parameters of shale clay minerals in the target block, establish shale clay mineral molecular models using Materials Studio, CHARMM-GUI or Avogadro software, select the CLAYFF force field, a general force field suitable for simulating multi-component mineral systems and their interfaces with fluids, modify and replace the surface functional groups of clay mineral molecules according to the changes in the types and relative contents of functional groups on the shale surface after the electric field is applied, and then expand the cell of the modified clay mineral molecules. Fluid molecular models, including water, CO2, and alkanes, were established using Materials Studio software. To make the competitive adsorption behavior of various fluids in micro- and nano-pores more accurate, the SPC / E force field was selected for H2O, the EPM2 force field for CO2, and the OPLS-UA force field for alkane molecules. A slit model with modified clay mineral molecules as boundaries was established using Packmol software. Then, a multiphase fluid system model composed of different contents of water, CO2, and alkanes was established between the slit models to obtain the initial configuration of the multiphase and multi-component competitive adsorption in the micro- and nano-pores of shale.

[0095] (3) The initial configuration of multiphase and multicomponent competitive adsorption of shale micro-nano pores was converted into the model file required by the LAMMPS software using the Moltemplate software; the above system was structurally optimized using the LAMMPS software, simulation parameters were set, and a stable configuration was obtained after energy minimization and position-restricted pre-equilibrium simulation, so as to ensure that the subsequent calculation results are more accurate.

[0096] (4) Using LAMMPS software, set to the NVT ensemble, an external electric field was applied along the Z-axis of the system. Simulated electric field parameters, including electric field strength, electric field frequency, and application time, were set. Molecular dynamics calculations were then performed to obtain molecular trajectory coordinates and dynamic information. The formula for setting the electric field parameters is as follows:

[0097]

[0098] In the formula: E0 is the electric field strength. E is the peak value of the electric field. f is the electric field frequency (Hz); t is the time step (fs).

[0099] (5) Obtain the calculation results of LAMMPS software, and use molecular dynamics simulation visualization software to visualize the distribution of multiphase and multicomponent fluids at different times, and obtain real-time dynamic images of the occurrence state and competitive adsorption process of multiphase fluids in shale micro-nano pores under different electric fields.

[0100] (6) Based on the calculation results of LAMMPS software, including the density distribution, molar number distribution, and molecular number distribution of each component of the shale micro-nano porous multiphase fluid under the action of an applied electric field, the absolute adsorption amount, selective adsorption coefficient, and interaction energy variation law of each component are further calculated.

[0101] The adsorption layer thickness of different molecules is obtained from the density distribution curve, and then the absolute adsorption amount of different molecules is calculated:

[0102]

[0103] In the formula: V ab This is the absolute adsorption capacity, in μmol / m³. 2 ρi is the density of molecule i in the model, in g / cm³. 3 L1 and L2 are the initial and final lengths of the adsorbed phase of molecule i in the model, respectively, in nm; M i Let be the relative molecular mass of molecule i, in g / mol; and S be the specific surface area of ​​the model pores, in nm. 2 .

[0104] Based on the absolute adsorption amounts of different molecules, the selective adsorption coefficients of different molecules are calculated:

[0105]

[0106] In the formula: S ij X represents the adsorption selectivity of molecule i relative to molecule j; i X j These represent the mole fractions of molecules i and j in the adsorbed phase, respectively; Y i Y j Let i and j be the mole fractions of molecules i and j in the free phase.

[0107] The interaction energy between the target fluid molecules and the modified wall, including van der Waals energy and electrostatic energy, is calculated based on the equilibrium configuration of each system and expressed as:

[0108]

[0109] In the formula: E i E represents the interaction energy between the wall and component i; t E represents the total energy of the system consisting of component i and the wall; b and E sN represents the wall energy and the thermodynamic energy of component i; i This represents the number of molecules of component i. Typically, E... i A negative value indicates an adsorbable state. The larger the absolute value, the stronger the interaction between component i and the wall, making the component more inclined to adsorb onto the wall.

[0110] The following is a specific embodiment to illustrate this solution. Specifically, this embodiment takes the competitive adsorption of CO2 / CH4 in the micro-nano pores of water-bearing shale under the action of an electric field as an example, and includes the following steps.

[0111] (1) Obtain shale core samples from the target area. After saturating the formation water, use Fourier transform infrared spectroscopy to test the surface structure of the shale samples before and after the electric field to obtain the characteristics of the changes in the types and relative contents of surface functional groups.

[0112] (2) The main clay mineral in the shale of the target block is montmorillonite. Key structural and force field parameters were obtained, and a molecular model of montmorillonite was established using Materials Studio software. The molecular formula is Si8Al4O3. 20 (OH)4, the force field selected is the CLAYFF field, and the van der Waals force adopts the Lennard-Jones (LJ) 12-6 type potential energy function; based on the changes in the types and relative contents of functional groups on the shale surface after the electric field, the functional groups on the surface of montmorillonite molecules are modified and replaced; then the cell of the modified clay mineral molecules is expanded (5×4×1), with a size of... Fluid molecular models, including water, CO2, and methane molecule models, were established using Materials Studio software. The SPC / E force field was selected for H2O, the EPM2 force field for CO2, and the OPLS-UA force field for methane molecules. The fluid molecular models were then optimized. A slit model with modified montmorillonite molecules as boundaries was established using Packmol software, with a slit distance of [missing information]. The pore size of shale is represented by 3 nm. Then, a multiphase fluid system model composed of water, CO2 and methane molecules with different contents is established between the slit models to obtain the initial configuration of CO2 / CH4 competitive adsorption in the micro-nano pores of water-bearing shale under different water contents and different CO2 / CH4 content ratios under reservoir temperature and pressure conditions.

[0113] (3) The initial configuration of CO2 / CH4 competitive adsorption in the micro-nano pores of hydrous shale was converted into a model file required by the LAMMPS software using Moltemplate software; the system structure was optimized using LAMMPS software, simulation parameters were set, and a stable configuration was obtained after energy minimization and position-restricted pre-equilibrium simulations. Figure 3 To optimize the CO2 / CH4 competitive adsorption configuration in the micro-nano pores of the water-bearing shale, and to ensure more accurate subsequent calculation results.

[0114] (4) Using LAMMPS software, set as NVT ensemble, apply an external electric field along the z-axis of the system, set the simulated electric field parameters, including electric field strength, electric field frequency, electric application time, etc., and perform molecular dynamics calculations to obtain molecular trajectory coordinates and dynamic information. It was verified that the entire system reached equilibrium after a runtime of 3ns.

[0115] (5) Obtain the calculation results from LAMMPS software, and use Ovital software to visualize the multiphase and multicomponent fluid distribution at different times. Obtain real-time dynamic images of the multiphase fluid occurrence state and competitive adsorption process in shale micro- and nano-pores under different electric fields. Figure 4 This is a visualization of the competitive adsorption distribution of various components in the micro- and nano-pores of shale before and after the application of an electric field. Figure 4 (a) is a visualization of the competitive adsorption distribution of various components in the micro- and nano-pores of shale before the application of an electric field. Figure 4 (b) is a visualization of the competitive adsorption distribution of various components in the micro- and nano-pores of shale after the application of an electric field.

[0116] (6) Based on the calculation results of LAMMPS software, the fluid density distribution, multi-component competitive adsorption amount, selective adsorption coefficient and interaction energy variation law of the CO2 / CH4 system with micro-nano pores in water-bearing shale under the action of an external electric field were further calculated.

[0117] Figure 5 The density distribution curves of various components in the micro- and nano-pores of shale under different electric field intensities are shown in this specific embodiment. Figure 5 In the figure, (a) represents the electric field strength. Density distribution curves of various components in the micro-nano pores of shale under the action of [unclear]. Figure 5 (b) represents the electric field strength. Density distribution curves of various components in the micro-nano pores of shale under the action of [unclear]. Figure 5 (c) represents the electric field strength. Density distribution curves of various components in the micro-nano pores of shale under the action of [unclear]. Figure 5 (d) represents the electric field strength. Density distribution curves of various components in the micro- and nano-pores of shale under the influence of [unspecified action]. Figure 5 It is known that H2O molecules, as polar molecules, are more easily driven by electric fields. The electric field strength has the most significant effect on H2O molecules. As the electric field strength increases, the adsorption state of a large number of water molecules is destroyed, and free H2O molecules gradually form aggregated water in the pores.

[0118] Figure 6 The diagram illustrates the variation in CO2 / CH4 adsorption selectivity under different electric field intensities in this specific embodiment. Figure 6It can be seen that the applied electric field increases the selective adsorption of CO2 by shale, and the adsorption selectivity of water-bearing shale for CO2 increases with the increase of electric field strength. However, with the further increase of electric field strength, the adsorption selectivity of water-bearing shale for CO2 molecules gradually reaches equilibrium.

[0119] Figure 7 This diagram illustrates the variation in interaction energy between various components of the shale micro / nanopores and the shale wall under different electric field intensities in this specific embodiment. Figure 7 It can be seen that as the electric field strength increases, the interaction energy between H2O and the shale wall increases, verifying that H2O molecules desorb from the shale wall. The interaction energy between CO2 and the shale wall decreases, verifying that increasing the electric field strength can increase the adsorption selectivity of CO2. The interaction energy between CH4 and the shale wall changes very little.

[0120] Figure 8 The density distribution curves of various components in the micro- and nano-pores of shale under different electric field frequencies are shown in this specific embodiment. Figure 8 (a) in the figure is the density distribution curve of each component in the micro-nano pores of shale under the action of an electric field frequency f = 0 GHz. Figure 8 (b) in the figure is the density distribution curve of each component in the micro-nano pores of shale under the action of an electric field frequency f = 20 GHz. Figure 8 (c) in the figure represents the density distribution curves of various components in the micro- and nano-pores of shale under the action of an electric field frequency of f = 60 GHz. Figure 8 In Figure (d), the density distribution curves of various components in the micro- and nano-pores of shale are shown under an electric field frequency of f = 100 GHz. Figure 8 It can be seen that the electric field frequency has the most significant effect on H2O molecules. The oscillating electric field causes some H2O molecules to desorb, and the H2O molecules gradually tend to be symmetrically distributed. Furthermore, the excessively high electric field frequency causes some CO2 to change from the adsorbed state to the free state.

[0121] Figure 9 The diagram illustrates the variation in CO2 / CH4 adsorption selectivity under different electric field frequencies in this specific embodiment. Figure 9 It can be seen that when the electric field frequency is below 40 GHz, the applied electric field increases the selective adsorption capacity of water-bearing shale for CO2, but as the electric field frequency increases to above 40 GHz, the applied electric field reduces the selective adsorption capacity of water-bearing shale for CO2.

[0122] Figure 10 The diagram illustrates the variation of the interaction energy between each component and the wall at different electric field frequencies in this specific embodiment. Figure 10It can be seen that as the frequency of the electric field increases, the interaction energy between CO2 molecules and the shale wall gradually increases, and the adsorption of CO2 molecules is inhibited. The interaction energy between H2O and the shale wall gradually decreases, increasing the adsorption of H2O molecules on the shale wall. The interaction energy between CH4 and the shale wall changes very little.

[0123] As can be seen from the above description of the embodiments, those skilled in the art can combine the changes in functional groups on the shale surface under the action of an electric field to establish a molecular simulation model of multiphase and multicomponent competitive adsorption in shale micro-nano pores under the action of an electric field. This model reveals the occurrence state and competitive adsorption behavior of multiphase and multicomponent fluids in shale micro-nano pores under the action of an electric field at the molecular scale. This enables the selective adsorption of CO2 in mixed fluids by shale enhanced by an external electric field, laying an important theoretical foundation for the application of electric field-enhanced CO2 injection and CO2 sequestration technology in shale gas reservoirs.

[0124] Based on the experimental test of functional group changes on shale surface under electric field, a molecular simulation model of multiphase and multicomponent competitive adsorption in shale micro-nano pores under electric field was established. This model reveals the occurrence state and competitive adsorption behavior of multiphase and multicomponent fluids in shale micro-nano pores under electric field at the molecular scale.

[0125] Based on the same inventive concept, this specification also provides a device for determining multiphase and multicomponent competitive adsorption data of shale micro- and nanoporous structures, as described in the following embodiments. Since the principle of the device for determining multiphase and multicomponent competitive adsorption data of shale micro- and nanoporous structures is similar to that of the method for determining multiphase and multicomponent competitive adsorption data of shale micro- and nanoporous structures, the implementation of the device can refer to the implementation of the method for determining multiphase and multicomponent competitive adsorption data of shale micro- and nanoporous structures, and will not be repeated. As used below, the terms "unit" or "module" can refer to a combination of software and / or hardware that performs a predetermined function. Although the device described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated. Figure 11 This is a structural block diagram of a shale micro / nanopore multiphase multicomponent competitive adsorption data determination device according to an embodiment of this specification, such as... Figure 11 As shown, it includes: acquisition module 1101, collection module 1102, establishment module 1103 and calculation module 1104. The structure is described below.

[0126] The acquisition module 1101 is used to acquire shale core samples from the target area and determine the types and relative content variation characteristics of surface functional groups in the shale core samples.

[0127] The collection module 1102 is used to collect key structural and force field parameters of shale clay minerals in the target block and establish a molecular model of shale clay minerals. It is also used to modify and replace the molecular surface functional groups in the molecular model of shale clay minerals according to the changes in the types and relative contents of functional groups on the shale surface under the action of an electric field, and then expand the cell of the modified clay mineral molecules.

[0128] The module 1103 is used to establish multiple fluid molecule models; it is also used to establish slit models with the modified clay mineral molecules as boundaries, and to establish multiphase fluid system models composed of different contents of the multiple fluid molecule models between the slit models, so as to obtain the initial configuration of multiphase and multi-component competitive adsorption of shale micro-nano pores; it is also used to optimize the structure of the initial configuration to obtain a stable configuration; the multiple fluid molecule models include water molecule models, carbon dioxide molecule models and alkane molecule models.

[0129] The calculation module 1104 is used to apply an external electric field to the stable configuration and perform molecular dynamics calculations to obtain the molecular trajectory coordinates and dynamic information of the multiphase and multicomponent fluid; it is also used to calculate the competitive adsorption data of the multiphase and multicomponent fluid in the micro-nano pores of shale under the action of the electric field based on the molecular trajectory coordinates and dynamic information of the multiphase and multicomponent fluid, so as to carry out shale gas extraction and / or shale carbon dioxide sequestration based on the competitive adsorption data.

[0130] In some embodiments of this specification, the acquisition module is specifically used for: saturating the shale core sample with formation water; and performing Fourier transform infrared spectroscopy (FTIR) tests on the surface structure of the shale core sample after saturation with formation water before and after the application of an electric field, to obtain the characteristics of the changes in the types and relative contents of surface functional groups of the shale core sample.

[0131] In some embodiments of this specification, the establishment module is specifically used to: establish water molecule models, carbon dioxide molecule models, and alkane molecule models using materials calculation software; wherein the force field of the water molecule model is an SPC / E force field, the force field of the carbon dioxide molecule model is an EPM2 force field, and the force field of the alkane molecule model is an OPLS-UA force field.

[0132] In some embodiments of this specification, the establishment module is specifically used to: convert the initial configuration of multiphase and multicomponent competitive adsorption in shale micro- and nanopores into a model file required by molecular dynamics simulation software; optimize the structure of the model file of the initial configuration using molecular dynamics simulation software, set simulation parameters, and perform energy minimization and position-restricted pre-equilibrium simulations in sequence to obtain a stable configuration.

[0133] In some embodiments of this specification, the calculation module is specifically used for: using molecular dynamics simulation software, setting the stable configuration as an NVT ensemble, applying an external electric field to the NVT ensemble, setting the simulated electric field parameters, performing molecular dynamics calculations, and obtaining the molecular trajectory coordinates and dynamic information of the multiphase, multicomponent fluid; wherein, the formula for setting the electric field parameters is:

[0134]

[0135] Where E0 is the electric field intensity; E is the peak electric field value; f is the electric field frequency; and t is the time step.

[0136] In some embodiments of this specification, the calculation module is specifically used to: visualize the distribution of the multiphase multicomponent fluid at different times based on the molecular trajectory coordinates and dynamic information of the multiphase multicomponent fluid, and generate a real-time dynamic image of the occurrence state and competitive adsorption process of the shale micro-nano pore multiphase multicomponent fluid under the action of an electric field; and determine the absolute adsorption amount, selective adsorption coefficient and interaction energy of each component in the multiphase multicomponent fluid according to the molecular trajectory coordinates and dynamic information of the multiphase multicomponent fluid.

[0137] In some embodiments of this specification, the molecular trajectory coordinates and dynamic information of the multiphase multicomponent fluid may include: the density distribution curves, molar number distributions, and molecular number distributions of each component in the multiphase multicomponent fluid; correspondingly, determining the absolute adsorption amount, selective adsorption coefficient, and interaction energy of each component in the multiphase multicomponent fluid based on the molecular trajectory coordinates and dynamic information may include: determining the adsorption layer thickness of each component based on the density distribution curves of each component in the multiphase multicomponent fluid, and calculating the absolute adsorption amount of molecules based on the adsorption layer thickness of each component; determining the selective adsorption coefficient of each component in the multiphase multicomponent fluid based on the absolute adsorption amount and molar number distribution of each component; and calculating the interaction energy between each component and the modified wall surface based on the molecular number distribution of each component in the multiphase multicomponent fluid and the equilibrium configuration of each system.

[0138] This specification also provides a computer device, which can be found in the following description. Figure 12 The diagram shown illustrates the computer device structure for determining shale micro / nanopore multiphase and multicomponent competitive adsorption data based on the embodiments of this specification. Specifically, the computer device may include an input device 121, a processor 122, and a memory 123. The memory 123 stores processor-executable instructions. When the processor 122 executes the instructions, it implements the steps of the shale micro / nanopore multiphase and multicomponent competitive adsorption data determination method described in any of the above embodiments.

[0139] In this embodiment, the input device can specifically be one of the main devices for information exchange between the user and the computer system. The input device may include a keyboard, mouse, camera, scanner, light pen, handwriting input tablet, voice input device, etc.; the input device is used to input raw data and programs for processing these data into the computer. The input device can also receive data transmitted from other modules, units, and devices. The processor can be implemented in any suitable manner. For example, the processor can take the form of a microprocessor or processor and a computer-readable medium storing computer-readable program code (e.g., software or firmware) executable by the (micro)processor, logic gates, switches, application-specific integrated circuits (ASICs), programmable logic controllers, and embedded microcontrollers, etc. The memory can specifically be a memory device used to store information in modern information technology. The memory can include multiple layers; in digital systems, anything that can store binary data can be considered memory; in integrated circuits, a circuit without physical form but with storage function is also called memory, such as RAM, FIFO, etc.; in a system, a storage device with physical form is also called memory, such as a memory stick, TF card, etc.

[0140] In this embodiment, the specific functions and effects implemented by the computer device can be explained in comparison with other embodiments, and will not be repeated here.

[0141] This specification also provides a computer storage medium for determining shale micro-nano pore multiphase multi-component competitive adsorption data based on the method. The computer storage medium stores computer program instructions, which, when executed, implement the steps of the shale micro-nano pore multiphase multi-component competitive adsorption data determination method described in any of the above embodiments.

[0142] In this embodiment, the storage medium includes, but is not limited to, Random Access Memory (RAM), Read-Only Memory (ROM), cache, hard disk drive (HDD), or memory card. The memory can be used to store computer program instructions. The network communication unit can be an interface configured according to standards specified in the communication protocol for network connection communication.

[0143] In this embodiment, the specific functions and effects implemented by the program instructions stored in the computer storage medium can be explained by comparison with other embodiments, and will not be repeated here.

[0144] Obviously, those skilled in the art will understand that the modules or steps of the embodiments described above can be implemented using general-purpose computing devices. They can be centralized on a single computing device or distributed across a network of multiple computing devices. Optionally, they can be implemented using computer-executable program code, thereby storing them in a storage device for execution by a computing device. In some cases, the steps shown or described can be performed in a different order than those presented herein, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. Thus, the embodiments of this specification are not limited to any particular combination of hardware and software.

[0145] It should be understood that the above description is for illustrative purposes and not for limitation. Many embodiments and applications beyond the provided examples will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of this specification should not be determined by reference to the above description, but rather by reference to the foregoing claims and the full scope of their equivalents.

[0146] The above description is merely a preferred embodiment of this specification and is not intended to limit this specification. Various modifications and variations can be made to the embodiments described herein by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this specification should be included within the scope of protection of this specification.

Claims

1. A method for determining multiphase, multicomponent competitive adsorption data of shale micro / nanopores, characterized in that, include: Obtain shale core samples from the target area and determine the types and relative content variations of surface functional groups in the shale core samples; Key structural and force field parameters of shale clay minerals in the target block were collected, and a molecular model of shale clay minerals was established. Based on the changes in the types and relative contents of functional groups on the shale surface under the action of an electric field, the molecular surface functional groups in the molecular model of shale clay minerals were modified and replaced, and the cell of the modified clay mineral molecules was expanded. Multiple fluid molecular models were established; a slit model with the modified clay mineral molecules as boundaries was established, and a multiphase fluid system model composed of different contents of the multiple fluid molecular models was established between the slit models to obtain the initial configuration of multiphase and multi-component competitive adsorption in shale micro-nano pores; the initial configuration was structurally optimized to obtain a stable configuration; the multiple fluid molecular models include a water molecule model, a carbon dioxide molecule model, and an alkane molecule model; An external electric field is applied to the stable configuration, and molecular dynamics calculations are performed to obtain the molecular trajectory coordinates and dynamic information of the multiphase and multicomponent fluid. Based on the molecular trajectory coordinates and dynamic information of the multiphase and multicomponent fluid, competitive adsorption data of the shale micro- and nano-porous multiphase and multicomponent fluid under the action of the electric field are calculated, so as to carry out shale gas extraction and / or shale carbon dioxide sequestration based on the competitive adsorption data. The determination of the types and relative content variations of surface functional groups in the shale core samples includes: The shale core samples were saturated with formation water. Fourier transform infrared spectroscopy was used to test the surface structure of shale core samples after saturation with formation water before and after the application of an electric field, and the changes in the types and relative contents of surface functional groups of the shale core samples were obtained.

2. The method for determining multiphase, multicomponent competitive adsorption data of shale micro-nano pores according to claim 1, characterized in that, Establish various fluid molecular models, including: A water molecule model, a carbon dioxide molecule model, and an alkane molecule model were established using materials calculation software. The force field of the water molecule model was an SPC / E force field, the force field of the carbon dioxide molecule model was an EPM2 force field, and the force field of the alkane molecule model was an OPLS-UA force field.

3. The method for determining multiphase and multicomponent competitive adsorption data of shale micro-nano pores according to claim 1, characterized in that, Structural optimization is performed on the initial configuration to obtain a stable configuration, including: The initial configuration of multiphase and multicomponent competitive adsorption in shale micro- and nanopores is converted into a model file required by molecular dynamics simulation software. The model file of the initial configuration was structurally optimized using molecular dynamics simulation software. Simulation parameters were set, and energy minimization and position-restricted pre-equilibrium simulations were performed sequentially to obtain a stable configuration.

4. The method for determining multiphase, multicomponent competitive adsorption data of shale micro-nano pores according to claim 1, characterized in that, An external electric field is applied to the stable configuration, and molecular dynamics calculations are performed to obtain the molecular trajectory coordinates and dynamic information of the multiphase, multicomponent fluid, including: Using molecular dynamics simulation software, the stable configuration was set as an NVT ensemble. An external electric field was applied to the NVT ensemble, and the simulated electric field parameters were set. Molecular dynamics calculations were performed to obtain the molecular trajectory coordinates and dynamic information of the multiphase, multi-component fluid. The formula for setting the electric field parameters is as follows: Where E0 is the electric field intensity; E is the peak electric field value; f is the electric field frequency; and t is the time step.

5. The method for determining multiphase, multicomponent competitive adsorption data of shale micro-nano pores according to claim 1, characterized in that, Based on the molecular trajectory coordinates and dynamic information of the multiphase and multicomponent fluid, competitive adsorption data of the shale micro- and nano-porous multiphase and multicomponent fluid under the action of an electric field are calculated, including: Based on the molecular trajectory coordinates and dynamic information of the multiphase and multicomponent fluid, the distribution of the multiphase and multicomponent fluid at different times is visualized to generate real-time dynamic images of the occurrence state and competitive adsorption process of the multiphase and multicomponent fluid in the micro-nano pores of shale under the action of an electric field. Based on the molecular trajectory coordinates and dynamic information of the multiphase multicomponent fluid, the absolute adsorption amount, selective adsorption coefficient, and interaction energy of each component in the multiphase multicomponent fluid are determined.

6. The method for determining multiphase and multicomponent competitive adsorption data of shale micro-nano pores according to claim 1, characterized in that, The molecular trajectory coordinates and dynamic information of the multiphase multicomponent fluid include: the density distribution curves, molar number distributions, and molecular number distributions of each component in the multiphase multicomponent fluid; Accordingly, based on the molecular trajectory coordinates and dynamic information of the multiphase multicomponent fluid, the absolute adsorption amount, selective adsorption coefficient, and interaction energy of each component in the multiphase multicomponent fluid are determined, including: Based on the density distribution curves of each component in the multiphase multicomponent fluid, the adsorption layer thickness of each component is determined, and the absolute adsorption amount of molecules is calculated based on the adsorption layer thickness of each component. Based on the absolute adsorption amount of each component in the multiphase multicomponent fluid and the molar number distribution of each component, the selective adsorption coefficient of each component in the multiphase multicomponent fluid is determined. Based on the molecular number distribution of each component in the multiphase multicomponent fluid and the equilibrium configuration of each system, the interaction energy between each component and the modified wall is calculated.

7. A device for determining multiphase and multicomponent competitive adsorption data of shale micro- and nanopores, characterized in that, include: The acquisition module is used to acquire shale core samples from the target area and determine the types and relative content variation characteristics of the surface functional groups of the shale core samples. The collection module is used to collect key structural and force field parameters of shale clay minerals in the target block and establish a molecular model of shale clay minerals. It is also used to modify and replace the molecular surface functional groups in the molecular model of shale clay minerals according to the changes in the types and relative contents of functional groups on the shale surface under the action of an electric field, and then expand the cell of the modified clay mineral molecules. The module is used to establish multiple fluid molecule models; it is also used to establish slit models with the modified clay mineral molecules as boundaries, and to establish multiphase fluid system models composed of different contents of the multiple fluid molecule models between the slit models, to obtain the initial configuration of multiphase and multi-component competitive adsorption in shale micro-nano pores; it is also used to optimize the structure of the initial configuration to obtain a stable configuration; the multiple fluid molecule models include water molecule models, carbon dioxide molecule models, and alkane molecule models; The calculation module is used to apply an external electric field to the stable configuration and perform molecular dynamics calculations to obtain the molecular trajectory coordinates and dynamic information of the multiphase and multicomponent fluid; it is also used to calculate the competitive adsorption data of the multiphase and multicomponent fluid in the micro-nano pores of shale under the action of the electric field based on the molecular trajectory coordinates and dynamic information of the multiphase and multicomponent fluid, so as to carry out shale gas extraction and / or shale carbon dioxide sequestration based on the competitive adsorption data. Specifically, the collection module is used to: saturate the shale core sample with formation water; and perform Fourier transform infrared spectroscopy (FTIR) tests on the surface structure of the shale core sample after saturation with formation water before and after the application of an electric field, thereby obtaining the characteristics of the changes in the types and relative contents of surface functional groups of the shale core sample.

8. A computer device, characterized in that, It includes a processor and a memory for storing processor-executable instructions, wherein the processor, when executing the instructions, implements the steps of the method according to any one of claims 1 to 6.

9. A computer-readable storage medium storing computer instructions thereon, characterized in that, When the instructions are executed by the processor, they implement the steps of the method according to any one of claims 1 to 6.

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