Shale micro-nano pore multiphase multicomponent competitive adsorption data determination method and device

Abstract

The invention relates to the technical field of carbon dioxide sequestration and shale gas development, and particularly discloses a shale micro-nano pore multiphase multicomponent competitive adsorption data determination method and device, and the method comprises the steps: obtaining a shale core sample of a target area, and determining the type and relative content change characteristics of surface functional groups of the shale core sample; key structures and force field parameters of shale clay minerals in a target block are collected, and a shale clay mineral molecular model is established; establishing a plurality of fluid molecular models; establishing slit models, and establishing a multiphase fluid system model between the slit models to obtain a stable configuration; applying an external electric field to the stable configuration, and performing molecular dynamics calculation to obtain molecular trajectory coordinates and dynamics information of the multi-phase multi-component fluid; and calculating competitive adsorption data of the shale micro-nano pore multi-phase multi-component fluid under the action of the electric field. According to the scheme, the occurrence state and the competitive adsorption behavior of the shale micro-nano pore multi-phase multi-component fluid under the action of the electric field can be disclosed from the molecular scale.

Description

Technical Field

[0001] This specification relates to the technical fields of carbon dioxide sequestration and shale gas development, and particularly relates to a method and device for determining multi-phase and multi-component competitive adsorption data of shale micro-nano pores. Background Art

[0002] In recent years, global warming has posed a major threat to the earth's ecosystem, mainly due to excessive carbon dioxide emissions. In the carbon dioxide capture, utilization, and storage (CCUS) strategy, geological utilization and storage are an indispensable part, which can achieve the dual purposes of carbon sequestration and underground resource utilization, and thus have broad application potential. The shale gas resource reserve is very rich, and the shale reservoir has well-developed micro-nano pores, which can be used as a promising carbon dioxide storage site. In addition, according to the mechanism that CO2 is preferentially adsorbed over CH4 in shale, the injection of CO2 can promote the desorption of shale gas, making more adsorbed CH4 transform from the shale matrix surface into the free state. The technology of storing CO2 in shale gas reservoirs, using the competitive adsorption between CO2 and shale gas, can simultaneously improve the recovery rate of shale gas and achieve permanent geological storage of CO2.

[0003] The method of enhancing the adsorption of CO2 by porous solid materials with an electric field has been successfully applied in the fields of CO2 capture and electrochemistry. By applying an external electric field to change the physical and chemical properties of the adsorbent and adsorbate, the adsorption capacity of nano-materials for CO2 can be significantly improved, and the selective adsorption of CO2 in the CO2 / shale gas mixture can also be enhanced. According to the adsorption characteristics of shale for CO2 and the action mechanism of enhancing CO2 adsorption by porous materials with an electric field, the technology of enhancing the recovery rate of shale gas by injecting CO2 into shale gas reservoirs under the action of an electric field is proposed, with the expectation of achieving the synergistic enhancement of the recovery rate of shale gas and the CO2 sequestration capacity in shale reservoirs, which has great economic and environmental advantages. Therefore, the multi-phase and multi-component competitive adsorption mechanism of water-containing shale micro-nano pores under the action of an electric field is a basic geological and reservoir physics problem faced in shale gas development. However, at present, there is a lack of a molecular simulation method for multi-phase and multi-component competitive adsorption of shale micro-nano pores under reservoir temperature and pressure conditions with an external electric field, and it cannot simultaneously satisfy the research on the occurrence and adsorption behavior of multi-phase and multi-component fluids under an external electric field, resulting in relatively limited understanding of the adsorption characteristics of shale for single-phase gas or multi-component gas competitive adsorption 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 the recovery rate of shale gas.

[0004] In view of the above problems, no effective solution has been proposed yet. Summary of the Invention

[0005] The embodiments of this specification provide a method and device for determining the multi-phase and multi-component competitive adsorption data of shale micro-nano pores, so as to realize the research on the occurrence and adsorption behavior of multi-phase and multi-component fluids in shale micro-nano pores under an external electric field, which greatly promotes the application of the technology of enhancing the adsorption of CO2 by porous solid materials under an electric field in improving the recovery rate of shale gas.

[0006] The embodiments of this specification provide a method for determining the multi-phase and multi-component competitive adsorption data of shale micro-nano pores, including:

[0007] Obtain a shale core sample of the target area, and determine the types and relative content change characteristics of the surface functional groups of the shale core sample;

[0008] Collect the key structure and force field parameters of shale clay minerals in the target block, and establish a molecular model of shale clay minerals; according to the types and relative content changes of the surface 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 unit cell of the modified clay mineral molecules;

[0009] Establish multiple fluid molecular models; establish a slit model with the modified clay mineral molecules as the boundary, and establish a multi-phase fluid system model composed of the multiple fluid molecular models with different contents between the slit models to obtain the initial configuration of the multi-phase and multi-component competitive adsorption in shale micro-nano pores; optimize the structure of the initial configuration 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] Apply an external electric field to the stable configuration and perform molecular dynamics calculations to obtain the molecular trajectory coordinates and kinetic information of the multi-phase and multi-component fluid; based on the molecular trajectory coordinates and kinetic information of the multi-phase and multi-component fluid, calculate the competitive adsorption data of the multi-phase and multi-component fluid in shale micro-nano pores under the action of an electric field, so as to carry out shale gas exploitation and / or shale carbon dioxide sequestration based on the competitive adsorption data.

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

[0012] Saturate the shale core sample with formation water;

[0013] Use Fourier transform infrared spectroscopy to perform FTIR tests on the surface structure of the shale core sample after saturation with formation water before and after the action of an electric field to obtain the types and relative content change characteristics of the surface functional groups of the shale core sample.

[0014] In one embodiment, establishing multiple fluid molecular models includes:

[0015] Build water molecule models, carbon dioxide molecule models, and alkane molecule models using materials calculation software; among them, the force field of the water molecule model is the SPC / E force field, the force field of the carbon dioxide molecule model is the EPM2 force field, and the force field of the alkane molecule model is the OPLS-UA force field.

[0016] In one embodiment, perform structural optimization on the initial configuration to obtain a stable configuration, including:

[0017] Convert the initial configuration of the competitive adsorption of multi-phase and multi-component in shale micro-nano pores into a model file required by molecular dynamics simulation software;

[0018] Use molecular dynamics simulation software to perform structural optimization on the model file of the initial configuration, set simulation parameters, and perform energy minimization and position-restricted pre-equilibrium simulation in sequence to obtain a stable configuration.

[0019] In one embodiment, apply an external electric field to the stable configuration and perform molecular dynamics calculations to obtain the molecular trajectory coordinates and kinetic information of the multi-phase and multi-component fluid, including:

[0020] Using molecular dynamics simulation software, set the stable configuration as the NVT ensemble, apply an external electric field to the NVT ensemble, set the simulation electric field parameters, and perform molecular dynamics calculations to obtain the molecular trajectory coordinates and kinetic information of the multi-phase and multi-component fluid; among them, the formula for setting the electric field parameters is:

[0021]

[0022] Among them, E0 is the electric field strength; E is the electric field peak value; f is the electric field frequency; t is the time step.

[0023] In one embodiment, based on the molecular trajectory coordinates and kinetic information of the multi-phase and multi-component fluid, calculate the competitive adsorption data of the multi-phase and multi-component fluid in shale micro-nano pores under the action of an electric field, including:

[0024] Based on the molecular trajectory coordinates and kinetic information of the multi-phase and multi-component fluid, visualize the distribution of the multi-phase and multi-component fluid at different times, and generate real-time dynamic images of the occurrence state and competitive adsorption process of the multi-phase and multi-component fluid in shale micro-nano pores under the action of an electric field;

[0025] According to the molecular trajectory coordinates and kinetic information of the multi-phase and multi-component fluid, determine the absolute adsorption amount, selective adsorption coefficient, and interaction energy of each component in the multi-phase and multi-component fluid.

[0026] In one embodiment, the molecular trajectory coordinates and kinetic information of the multi-phase and multi-component fluid include: the density distribution curve, mole number distribution, and molecular number distribution of each component in the multi-phase and multi-component fluid;

[0027] Correspondingly, according to the molecular trajectory coordinates and kinetic information of the multiphase multi-component fluid, the absolute adsorption amount, selective adsorption coefficient, and interaction energy of each component in the multiphase multi-component fluid are determined, including:

[0028] According to the density distribution curves of the components in the multiphase multi-component fluid, the adsorption layer thickness of each component is determined, and based on the adsorption layer thickness of each component, the absolute adsorption amount of molecules is calculated;

[0029] Based on the absolute adsorption amount of each component in the multiphase multi-component fluid and the mole number distribution of each component, the selective adsorption coefficient of each component in the multiphase multi-component fluid is determined;

[0030] According to the molecular number distribution of the components in the multiphase multi-component fluid and the equilibrium configuration of each system, the interaction energy between each component and the modified wall surface is calculated.

[0031] The embodiments of the present specification also provide a device for determining the competitive adsorption data of multiphase multi-component in shale micro-nano pores, including:

[0032] An acquisition module, configured to acquire a shale core sample in a target area and determine the types and relative content change characteristics of the surface functional groups of the shale core sample;

[0033] A collection module, configured to collect the key structure and force field parameters of shale clay minerals in a target block, establish a molecular model of shale clay minerals; and also configured to modify and replace the molecular surface functional groups in the molecular model of shale clay minerals according to the types and relative content changes of the surface crown functional groups on the shale surface under the action of an electric field, and then expand the unit cell of the modified clay mineral molecules;

[0034] A building module, configured to build a variety of fluid molecular models; and also configured to build a slit model with the modified clay mineral molecules as the boundary, and establish a multiphase fluid system model composed of the variety of fluid molecular models with different contents between the slit models to obtain an initial configuration of competitive adsorption of multiphase multi-component in shale micro-nano pores; and also configured to optimize the structure of the initial configuration to obtain a stable configuration; the variety of fluid molecular models include a water molecule model, a carbon dioxide molecule model, and an alkane molecule model;

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

[0036] An embodiment of this specification also provides a computer device, including a processor and a memory for storing instructions executable by the processor. When the processor executes the instructions, the steps of the method for determining shale micro-nano pore multi-phase multi-component competitive adsorption data described in any of the above embodiments are implemented.

[0037] An embodiment of this specification also provides a computer-readable storage medium, on which computer instructions are stored. When the instructions are executed, the steps of the method for determining shale micro-nano pore multi-phase multi-component competitive adsorption data described in any of the above embodiments are implemented.

[0038] In an embodiment of this specification, a method for determining shale micro-nano pore multi-phase multi-component competitive adsorption data is provided. A shale core sample of a target area can be obtained, and the types and relative content change characteristics of surface functional groups of the shale core sample can be determined. Key structural and force field parameters of shale clay minerals in the target block are collected, and a molecular model of shale clay minerals is established. According to the types and relative content changes of surface functional groups on the shale surface under the action of an electric field, the molecular surface functional groups in the shale clay mineral molecular model are modified and replaced, and then the unit cell of the modified clay mineral molecule is expanded. Multiple fluid molecular models are established. A slit model with the modified clay mineral molecule as the boundary is established, and a multi-phase fluid system model composed of multiple fluid molecular models with different contents is established between the slit models to obtain an initial configuration of shale micro-nano pore multi-phase multi-component competitive adsorption. The initial configuration is 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 kinetic information of the multi-phase multi-component fluid. Based on the molecular trajectory coordinates and kinetic information of the multi-phase multi-component fluid, the competitive adsorption data of the shale micro-nano pore multi-phase multi-component fluid under the action of an electric field are calculated, so as to carry out shale gas exploitation and / or shale carbon dioxide sequestration based on the competitive adsorption data. Through the above method, the molecular simulation model of surface-modified shale micro-nano pore multi-phase multi-component competitive adsorption under the action of an electric field can be established by combining the change characteristics of surface functional groups on the shale surface under the action of an electric field, revealing the occurrence state and competitive adsorption behavior of the shale micro-nano pore multi-phase multi-component fluid under the action of an electric field from the molecular scale, realizing the selective adsorption of carbon dioxide in the mixed fluid by the shale under the enhanced action of an external electric field, and laying an important theoretical foundation for the application of the technology of enhancing the recovery rate of shale gas reservoirs by injecting carbon dioxide and carbon dioxide sequestration technology under the action of an electric field. Description of the Drawings

[0039] The drawings described herein are used to provide a further understanding of this specification, constitute a part of this specification, and do not limit this specification. In the drawings:

[0040] Figure 1Shows a flowchart of a method for determining multi-phase and multi-component competitive adsorption data in shale micro-nano pores in an embodiment of this specification;

[0041] Figure 2 Shows a flowchart of a method for determining multi-phase and multi-component competitive adsorption data in shale micro-nano pores in an embodiment of this specification;

[0042] Figure 3 Shows an initial distribution diagram of a multi-phase and multi-component system in shale micro-nano pores under the action of an electric field in an embodiment of this specification;

[0043] Figure 4 Shows the component distribution diagrams of shale micro-nano pores before and after the action of an electric field in an embodiment of this specification;

[0044] Figure 5 Shows the density distribution curves of each component in shale micro-nano pores under the action of different electric field intensities in an embodiment of this specification;

[0045] Figure 6 Shows the change diagram of CO2 / CH4 adsorption selectivity under different electric field intensities in an embodiment of this specification;

[0046] Figure 7 Shows the change diagram of the interaction energy between each component in shale micro-nano pores and the wall under different electric field intensities in an embodiment of this specification;

[0047] Figure 8 Shows the density distribution curves of each component in shale micro-nano pores under the action of different electric field frequencies in an embodiment of this specification;

[0048] Figure 9 Shows the change diagram of CO2 / CH4 adsorption selectivity under different electric field frequencies in an embodiment of this specification;

[0049] Figure 10 Shows the change diagram of the interaction energy between each component and the wall under different electric field frequencies in an embodiment of this specification;

[0050] Figure 11 Shows a structural block diagram of a device for determining multi-phase and multi-component competitive adsorption data in shale micro-nano pores in an embodiment of this specification;

[0051] Figure 12 Shows a schematic diagram of a computer device in an embodiment of this specification. Detailed implementation manners

[0052] The principles and spirit of this specification will be described below with reference to several exemplary embodiments. It should be understood that these embodiments are provided only to enable those skilled in the art to better understand and then implement this specification, rather than limiting the scope of this specification in any way. On the contrary, these embodiments are provided to make the disclosure of this specification more thorough and complete, and to be able to fully convey the scope of this disclosure to those skilled in the art.

[0053] Those skilled in the art know that the embodiments of this specification can be implemented as a system, device, equipment, method, or computer program product. Therefore, the disclosure of this specification can be specifically implemented in the following forms, namely: completely hardware, completely 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 is little research on molecular simulation of multi-phase and multi-component competitive adsorption in shale micro-nano pores under the action of an electric field, and it mainly focuses on the simulation research of single-component and multi-component competitive adsorption of shale gas without the action of an electric field. None of them have analyzed and explained the changes in surface functional groups of shale under the action of external DC and AC electric fields, the occurrence state of CO2 / shale gas / water in shale micro-pores under actual geological burial depth conditions of shale, and the competitive adsorption mechanism.

[0055] Based on the above problems, the embodiments of this specification provide a method for determining multi-phase and multi-component competitive adsorption data in shale micro-nano pores. It can realize the enhanced selective adsorption of CO2 in the mixed fluid by shale under the action of an external electric field, and combine the change characteristics of surface functional groups of shale under the action of an electric field to obtain a more accurate occurrence state and competitive adsorption behavior of CO2 / shale gas in water-bearing shale micro-nano pores, and strive to break through the technical bottlenecks of shale gas exploitation and CO2 sequestration.

[0056] Figure 1 The flowchart of the method for determining multi-phase and multi-component competitive adsorption data in shale micro-nano pores in an embodiment of this specification is shown. Although this specification provides method operation steps or device structures as shown in the following embodiments or drawings, more or fewer operation steps or module units may be included in the method or device based on routine or non-creative labor. In steps or structures where there is no necessary causal relationship logically, the execution order of these steps or the module structure of the device is not limited to the execution order or module structure described in the embodiments of this specification and shown in the drawings. When the method or module structure is applied to an actual device or terminal product, it can be executed sequentially or in parallel according to the method or module structure shown in the embodiments or drawings (for example, in an environment of parallel processors or multi-threaded processing, or even a distributed processing environment).

[0057] Specifically, asFigure 1 As shown in Figure 1 , the method for determining the multi-phase and multi-component competitive adsorption data of shale micro-nano pores provided by an embodiment of this specification may include the following steps.

[0058] Step S101: Obtain a shale core sample of the target area, and determine the types and relative content change characteristics of the surface functional groups of the shale core sample.

[0059] A shale core sample of the target area can be obtained. The target area can be the shale area to be observed. Collect the shale core sample from the target area, and this process needs to ensure the representativeness of the sample, so as to truly reflect the characteristics of the shale in the target area. Information such as the sampling location and depth should be recorded in detail because the mineral composition, pore structure, and surface properties of the shale at different locations and depths may vary. The types and relative content change characteristics of the surface functional groups of the shale core sample can be determined through experiments. Surface functional groups refer to atomic groups or chemical bonds existing on the surface of a substance with specific chemical properties and reaction activities. Combining the change characteristics of the surface functional groups of the shale under the action of an electric field to establish a relevant molecular simulation model helps to reveal the occurrence state and competitive adsorption behavior of multi-phase and multi-component fluids in shale micro-nano pores at the molecular scale.

[0060] In some embodiments of this specification, to determine the types and relative content change characteristics of the surface functional groups of the shale core sample, it may include: saturating the shale core sample with formation water; performing FTIR testing on the surface structure of the shale core sample saturated with formation water before and after the action of an electric field using Fourier transform infrared spectroscopy to obtain the types and relative content change characteristics of the surface functional groups of the shale core sample.

[0061] Specifically, the obtained shale core samples can be saturated with formation water. Simulating the actual water-bearing state of shale underground is because the presence of formation water will affect the physicochemical properties of the shale surface and the interaction between shale and gas molecules. By allowing the samples to fully absorb formation water and restoring their true underground environment, it lays a foundation for accurately studying the competitive adsorption behavior of multiple phases and components in shale pores in the subsequent steps. Different functional groups have specific vibration frequencies. When infrared light irradiates the sample, it will interact with the functional groups, causing some frequencies of infrared light to be absorbed. By detecting the absorption of infrared light of different frequencies by the sample, information related to the functional groups can be obtained. The shale samples saturated with formation water are subjected to FTIR tests before and after the application of an electric field. During the test, the samples are made into a form suitable for instrument detection (such as thin slices, powders, etc.) and placed into a Fourier transform infrared spectrometer. The instrument emits infrared light to penetrate the sample, and the detector records the absorption degree of infrared light of different frequencies, thereby obtaining an infrared spectrum. According to the characteristics of the position, intensity, and shape of the absorption peaks in the infrared spectrum, the types of surface functional groups of the shale are determined. For example, absorption peaks at specific positions correspond to different functional groups such as hydroxyl (-OH), carboxyl (-COOH), methyl (-CH3), etc. By comparing the intensity changes of each absorption peak before and after the application of the electric field, the change characteristics of the relative content 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 the electric field, it indicates that the relative content of this functional group increases; conversely, if the absorption peak intensity weakens, the relative content decreases. Through the above steps, the types and change characteristics of the relative content of surface functional groups of the shale core samples in the target area before and after the application of the electric field can be accurately obtained, providing key data support for establishing a more realistic molecular simulation model and further studying the competitive adsorption behavior of multiple phases and components in shale micro-nano pores under the action of an electric field.

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

[0063] Geological data of shale clay minerals in the target block can be obtained, including but not limited to information such as regional geological structure, stratigraphic distribution, and sedimentary environment. Shale samples collected from the target block can be subjected to XRD (X-ray diffraction) tests. XRD can determine the crystal structure type and lattice parameters of clay minerals by measuring the diffraction angle and intensity of X-rays in crystals. The microscopic morphology of shale clay minerals, such as particle size, shape, arrangement pattern, etc., can be observed using SEM (scanning electron microscope). Thermogravimetric analysis (TGA) can be used to determine the moisture content and thermal stability of clay minerals. Force field parameters describe the interactions between atoms in a molecule and are crucial for accurately simulating molecular behavior. Currently, there are many mature force fields, such as the CLAYFF force field (suitable for simulating multi-component mineral systems and their interfaces with fluids), the UFF force field (universal force field), etc. In this embodiment, the CLAYFF force field, a universal force field suitable for simulating multi-component mineral systems and their interfaces with fluids, is selected as the force field. A molecular model of shale clay minerals can be established using software such as Materials Studio (materials calculation software), CHARMM-GUI (multifunctional online platform for molecular dynamics simulation), or Avogadro (molecular editor and visualization tool). The types of clay minerals can be determined based on XRD and other analyses, and their basic structural units can be clarified. Based on the basic structural units and the unit cell parameters obtained from XRD, a complete unit cell structure can be extended and constructed in the modeling software. Considering that various functional groups exist on the surface of shale clay minerals, these functional groups have an important impact on their adsorption properties and interactions with fluids. After the preliminary model construction, the energy minimization function provided by the modeling software is used to optimize the structure of the model.

[0064] Under the action of an external electric field, the oxygen-containing functional groups of C elements in the surface structure of shale are modified, the content of C-C / C-H bonds decreases significantly, the C-C / C-H bonds break, and C-O bonds, C=O carbonyl functional groups, and COO- carboxyl functional groups are generated; as the electric field strength increases, the reduction amplitude of the C-C / C-H functional group content in the shale surface structure increases, the content of C=O carbonyl functional groups and COO- carboxyl functional groups continues to increase, and the content of C-O bonds shows a trend of increasing first and then decreasing. The functional groups on the shale surface (such as carbonyl, epoxy, amino, and hydroxyl groups, etc.) have different adsorption characteristics. These functional groups can affect the adsorption behavior of fluid molecules (such as methane, carbon dioxide, etc.) on the shale surface. The presence of functional groups can inhibit the adsorption of methane while promoting the adsorption of carbon dioxide. This may be because the interaction force between the functional groups and carbon dioxide molecules is stronger, thus enhancing the adsorption ability of carbon dioxide on the shale surface.

[0065] In the competitive adsorption process of multiphase and multicomponent fluids, functional groups will preferentially adsorb certain fluid molecules (such as carbon dioxide), thereby occupying the high-energy adsorption sites of these fluid molecules. This will lead to a decrease in the adsorption amount of other fluid molecules (such as methane) because their adsorption sites are occupied by functional groups. The 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 action of functional groups on fluid adsorption and diffusion, but also in the influence of functional groups on pore structure and competitive adsorption mechanism. At the same time, under the action of an external electric field, the interactions between different surface functional groups and fluid molecules are different, which will also affect multicomponent competitive adsorption. Therefore, according to the changes in the types and relative contents of surface functional groups on shale under the action of an electric field, the molecular surface functional groups in the shale clay mineral molecular model can be modified and replaced, and then the unit cell of the modified clay mineral molecule can be expanded. Thus, the accuracy of competitive adsorption data can be improved.

[0066] After determining the change characteristics of the types and relative contents of surface functional groups on shale before and after the action of an electric field (obtained through Fourier transform infrared spectroscopy FTIR testing), based on these data, determine the specific scheme for modifying and replacing the shale clay mineral molecular model. For example, if the FTIR test shows that the relative content of hydroxyl (-OH) functional groups on the shale surface increases after the action of an electric field and a new carboxyl (-COOH) functional group appears, then the number of -O groups needs to be increased accordingly in the molecular model, and the -COOH functional group needs to be introduced at an appropriate position.

[0067] Software for constructing shale clay mineral molecular models (such as Materials Studio, CHARMM-GUI, or Avogadro) can be used for functional group modification operations. Taking Materials Studio as an example, using its atomic editing tool, find the atomic sites suitable for adding or replacing functional groups on the surface of the established clay mineral molecular model. For example, for the layered montmorillonite clay mineral model, sites such as oxygen atoms or aluminum atoms on its surface may be suitable for connecting new functional groups. Select the appropriate chemical bond connection method, and according to the chemical structure principle, accurately add the new functional group to the model surface. During the addition process, strictly follow the chemical valence bond rules to ensure that parameters such as bond length and bond angle conform to the actual chemical structure. For the functional groups that need to be replaced, first delete the original functional groups, and then add the new functional groups according to the above method. At the same time, preliminarily optimize the local structure after adding or replacing functional groups to make the interaction energy between atoms in this area reach a relatively stable state. After completing the modification and replacement of functional groups, use the analysis function of the software again to check the structural rationality of the new model.

[0068] The appropriate cell expansion multiple can be determined according to the research purpose and the requirements 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. Usually, the selection of the cell expansion multiple needs to comprehensively consider the balance between computing resources and model accuracy. Taking the Materials Studio software as an example, select the functions related to unit cell operations in the menu bar and input the determined cell expansion multiple. The software will automatically expand the unit cell of the modified clay mineral molecules according to the set multiple. After the cell expansion is completed, due to the increase in the unit cell size, the interactions between atoms may change, and it is necessary to perform overall optimization on the expanded model.

[0069] Step S103, establish multiple fluid molecular models; establish a slit model with the modified clay mineral molecules as the boundary, and establish a multiphase fluid system model composed of multiple fluid molecular models with different contents between the slit models to obtain the initial configuration of competitive adsorption of multiple phases and multiple components in shale micro-nano pores; perform structural optimization on the initial configuration to obtain a stable configuration; the multiple fluid molecular models include a water molecular model, a carbon dioxide molecular model, and an alkane molecular model.

[0070] Specifically, fluid molecular models can be established through the Materials Studio software, including molecular models of water, CO2, alkanes, etc. Through the above steps, multiple fluid molecular models such as water, CO2, and alkanes can be established. These models will serve as the basis for constructing the multiphase fluid system model and are used to deeply study the competitive adsorption behavior of multiple phases and multiple components in shale micro-nano pores under the action of an electric field.

[0071] In some embodiments of this specification, establishing multiple fluid molecular models may include: using materials calculation software to establish a water molecular model, a carbon dioxide molecular model, and an alkane molecular model; wherein, the force field of the water molecular model is the SPC / E force field, the force field of the carbon dioxide molecular model is the EPM2 force field, and the force field of the alkane molecular model is the OPLS-UA force field. By setting like this, the competitive adsorption behavior of various fluids in micro-nano pores is made more accurate.

[0072] The specific size of the slit model can be set according to the actual size data of the target shale micro-nano pores, usually in the nanoscale range, considering the balance between research requirements and computing resources. The Packmol software can be used to construct the slit model. Packmol is a powerful software widely used in the field of molecular simulation, mainly for constructing the initial structures of complex molecular systems. Import the modified clay mineral molecular model after surface functional group modification and cell expansion treatment into the Packmol software. In the software, by setting relevant parameters, the modified clay mineral molecules are arranged in a parallel and opposite manner in space to form a slit-shaped boundary structure. The specific parameter settings include the positions, orientations of the molecules, and the spacing of the slits, etc., to ensure that the geometric shape and size of the slit model meet the preset requirements.

[0073] The content ratios of different fluid molecules in the multiphase fluid system can be set according to the actual fluid composition of the target shale reservoir. For example, for a specific shale gas reservoir, through geological analysis and experimental measurement, the content ratios of fluids such as water, CO2, and methane are determined, and based on this, the corresponding number of molecules is set in the model. The determination of these ratios should be as close to the actual situation as possible to ensure the authenticity and reliability of the simulation results. In the Packmol software, for the established slit model, according to the set content of fluid molecules, molecular models of various fluids such as water, CO2, and alkanes are filled into the space between the slit models. The software will randomly distribute these fluid molecules according to the set parameters, while ensuring that the distances between molecules conform to physical laws and avoiding unreasonable situations such as molecular overlap. During the filling process, some constraint conditions can be set as needed, such as the minimum distance between fluid molecules and the clay mineral surface, etc., to better simulate the distribution state of fluids in shale pores under actual conditions. After the construction of the multiphase fluid system model is completed, a comprehensive inspection of the obtained initial configuration is carried out. After inspection and optimization, the initial configuration of competitive adsorption of multiphase and multi-component in shale micro-nano pores is obtained.

[0074] After obtaining the initial configuration of competitive adsorption of multiphase and multi-component in shale micro-nano pores, to ensure the accuracy and reliability of the simulation results, its structure needs to be optimized to obtain a stable configuration. This process is usually achieved with the help of professional simulation software such as LAMMPS. LAMMPS (Large-scale Atomic / Molecular Massively Parallel Simulator) is an open-source molecular dynamics simulation software widely used in the fields of materials science, chemistry, biophysics, etc.

[0075] In some embodiments of this specification, optimizing the structure of the initial configuration to obtain a stable configuration may include: converting the initial configuration of the multi-phase and multi-component competitive adsorption in shale micro-nano pores into a model file required by molecular dynamics simulation software; using the molecular dynamics simulation software to optimize the structure of the model file of the initial configuration, setting simulation parameters, and performing energy minimization and position-restricted pre-equilibrium simulation in sequence to obtain a stable configuration.

[0076] Specifically, since the initial configuration is constructed by 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 simulation and plays an important role in the simulation research of complex molecular systems. It can convert the molecular structure model constructed by users into an input file that can be directly used by molecular dynamics simulation software (such as LAMMPS). Therefore, first use Moltemplate software 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), in which the number of particles (N), volume (V), and temperature (T) of the system remain constant. This choice is based on the fact that in the actual situation of the multi-phase and multi-component system in shale micro-nano pores, the pore volume is relatively fixed, and a constant temperature environment can be set during the simulation to simulate the situation under specific reservoir temperature conditions. According to the force fields selected when constructing the molecular models of shale clay minerals and fluid molecules before, 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, accurately set the corresponding force field parameters in LAMMPS software. These force field parameters determine the way and intensity of the interaction between atoms, including parameters such as bond length, bond angle, dihedral angle, etc., and the specific forms of potential energy functions such as van der Waals force and electrostatic interaction. Accurately setting the force field parameters can ensure that the description of the interaction between molecules during the simulation conforms to the actual physical and chemical 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 should ensure the stability of the simulation while guaranteeing the computational efficiency.

[0077] Before starting the molecular 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 there is a relatively high potential energy. The purpose of energy minimization is to adjust the atomic positions to minimize the total energy of the entire system, eliminate unreasonable overlaps or excessive intermolecular forces between atoms, and thus obtain a relatively stable structure. After energy minimization, although the system reaches a relatively low energy state, it may still not reach the true equilibrium state. The purpose of the position-restricted pre-equilibration simulation is to perform a molecular dynamics simulation on the system at a set temperature under certain constraints, allowing the molecules to move freely within a certain range, further adjusting their positions and orientations to reach a thermal equilibrium state. At the same time, by restricting the positions of certain atoms or molecular groups, unreasonable structural changes during the equilibration process can be avoided, ensuring the overall structural stability of the system. Based on the characteristics of the system and the simulation requirements, the atoms or molecular groups to be restricted are determined. After setting the position restriction conditions and temperature control parameters in the LAMMPS software, the pre-equilibration simulation is started. After energy minimization and position-restricted pre-equilibration 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 is 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 kinetic information of the multiphase multicomponent fluid; based on the molecular trajectory coordinates and kinetic information of the multiphase multicomponent fluid, calculate the competitive adsorption data of the multiphase multicomponent fluid in the shale micro-nano pores under the action of the electric field, so as to carry out shale gas exploitation and / or shale carbon dioxide sequestration based on the competitive adsorption data.

[0079] After obtaining the stable configuration, applying an external electric field and performing molecular dynamics calculations are key steps to deeply study the behavior of the multiphase multicomponent fluid in the shale micro-nano pores under the action of the electric field. An external electric field can be applied. In the LAMMPS software, an external electric field is applied along the Z-axis direction of the system. The parameters of the simulated electric field, including the electric field strength, electric field frequency, and electrification time, etc., need to be precisely set. 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 in the range to study the influence of electric fields with different strengths on the system. The electric field frequency affects the variation characteristics of the electric field. Different frequencies can be set according to the research needs, such as from low frequency to high frequency, to explore the influence of the electric field frequency on the behavior of fluid molecules. The electrification time needs to be determined based on the total simulation duration and the time required for the system to reach a stable state to ensure that the effect of the electric field on the system can be observed within a sufficient time.

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

[0081]

[0082] where E0 is the electric field strength; E is the electric field peak value; f is the electric field frequency; t is the time step. Through this formula, the LAMMPS software can calculate the electric field strength at each moment in real time according to the set parameters, so as to accurately simulate the effect of the electric field changing with time on the multiphase multicomponent fluid.

[0083] While applying an electric field, maintain the previously set NVT ensemble conditions, that is, the number of particles (N), volume (V), and temperature (T) of the system remain constant. This can ensure that when studying the influence of the electric field on the system, other factors (such as volume changes, increases or decreases in the number of particles, etc.) are excluded from interfering with the results, and focus on the interaction between the electric field and the multi-phase multi-component fluid. Continue to use the appropriate time step (such as 1 - 5 fs) determined during the previous optimization process to ensure the stability and computational efficiency of the simulation. Determine a sufficient number of simulation steps according to the research purpose and the time required for the system to reach a stable state. As the simulation steps progress, the multi-phase multi-component fluid molecules, under the combined action of the electric field force and intermolecular interaction forces, perform complex movements within the shale micro-nano pores. The software tracks the movement trajectories of each molecule in real time and records the position coordinates of the molecules at different times. At the same time, calculate its kinetic information, such as velocity, acceleration, kinetic energy, etc., according to the movement state of the molecule. These information reflect the energy changes and movement characteristics of the molecules under the action of the electric field, and are of great significance for deeply understanding the competitive adsorption behavior and dynamic distribution of multi-phase multi-component fluids in shale pores. During the simulation process, the LAMMPS software records the trajectory coordinates and kinetic information of the multi-phase multi-component fluid molecules according to the set output frequency and stores them in a specific file. The output frequency can be adjusted according to research needs. For example, data is output every certain number of steps (such as 100 - 1000 steps) to obtain sufficient detailed dynamic information of the system without occupying too much storage space. After the simulation is completed, the obtained molecular trajectory coordinates and kinetic information files are the basis for subsequent analysis. These data will be used for further processing and analysis. For example, through molecular dynamics simulation visualization software (such as VMD, Ovital, etc.), the distribution of multi-phase multi-component fluids at different times is visualized to intuitively observe the movement trajectories and distribution changes of fluid molecules in shale micro-nano pores under the action of the electric field; important parameters such as the absolute adsorption amount, selective adsorption coefficient, and change law of interaction energy of each component can also be calculated based on these data to deeply study the influence mechanism of the electric field on the competitive adsorption behavior of multi-phase multi-component fluids in shale micro-nano pores.

[0084] In the above embodiments, the molecular simulation model of competitive adsorption of multi-phase multi-component fluids in surface-modified shale micro-nano pores under the action of an electric field can be established by combining the change characteristics of surface functional groups on the shale under the action of the electric field, revealing the occurrence state and competitive adsorption behavior of multi-phase multi-component fluids in shale micro-nano pores at the molecular scale, realizing the enhanced selective adsorption of carbon dioxide in the mixed fluid by shale under the action of an external electric field, and laying an important theoretical foundation for the application of the technology of enhancing the recovery rate of shale gas reservoirs by injecting carbon dioxide and carbon dioxide sequestration technology.

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

[0086] In the field of molecular dynamics simulation, there are various software available for visualizing molecular trajectory data, such as VMD, Ovito, etc. Although software such as VMD and Ovito support various common molecular trajectory file formats, the data format output by LAMMPS may need to be converted to some extent. In the selected visualization software, the processed molecular trajectory file is imported through the corresponding file loading function. At the same time, other information related to the molecular structure and properties, such as atom types, force field parameters, etc., is loaded so that the software can correctly identify different multiphase and multicomponent fluid molecules and endow them with appropriate visualization features, such as colors, sizes, etc. According to the characteristics of the multiphase and multicomponent fluid molecules, a suitable representation method is selected to display the molecular structure. The parameters of the visualization scene, such as the background color, lighting conditions, etc., are adjusted to improve the clarity and visualization effect of the image. Using the time series function of the visualization software, the distribution of the multiphase and multicomponent fluid at different times is sequentially displayed according to the time order in the molecular trajectory data. In the visualization software, by using the animation recording function, the static images at different times are combined into an animation in sequence to generate a real-time dynamic image of the occurrence state and competitive adsorption process of the multiphase and multicomponent fluid in the shale micro-nano pores under the action of an electric field. Through the above steps, the abstract molecular trajectory coordinates and kinetic information can be converted into an intuitive real-time dynamic image, providing a powerful tool for researchers to deeply analyze the occurrence state and competitive adsorption process of the multiphase and multicomponent fluid in the shale micro-nano pores under the action of an electric field.

[0087] Important parameters such as the absolute adsorption amount, selective adsorption coefficient, and interaction energy can also be extracted from the molecular trajectory coordinates and kinetic information of the multiphase and multicomponent fluid, providing quantitative data support for deeply understanding the competitive adsorption behavior of the multiphase and multicomponent fluid in the shale micro-nano pores under the action of an electric field. These data have important guiding significance for practical applications such as evaluating shale gas recovery efficiency and CO2 sequestration capacity.

[0088] In some embodiments of the present specification, the molecular trajectory coordinates and kinetic information of the multiphase multicomponent fluid may include: the density distribution curve, mole number distribution, and molecule number distribution of each component in the multiphase multicomponent fluid; correspondingly, according to the molecular trajectory coordinates and kinetic information of the multiphase multicomponent fluid, determining the absolute adsorption amount, selective adsorption coefficient, and interaction energy of each component in the multiphase multicomponent fluid may include: determining the adsorption layer thickness of each component according to the density distribution curve 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 of each component in the multiphase multicomponent fluid and the mole number distribution of each component; calculating the interaction energy between each component and the modified wall surface according to the molecule 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 the multiphase multicomponent fluid in the shale micro-nano pores under the action of an electric field can be quantitatively analyzed, providing detailed quantitative data for deeply understanding the multiphase multicomponent competitive adsorption process and the influence of the electric field on shale gas recovery and CO2 sequestration. These calculations help to evaluate the effects of shale gas exploitation and CO2 sequestration under different electric field conditions, providing a theoretical basis for optimizing related technologies.

[0089] Each embodiment in this specification is described in a progressive manner. The same or similar parts among the embodiments can be referred to each other, and the differences between each embodiment and other embodiments are emphasized. Specifically, reference can be made to the description of the related processing related embodiments above, and details will not be repeated here.

[0090] The specific embodiments of this specification have been described above. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims can be executed in a different order than in the embodiments and still achieve the desired results. Additionally, the processes depicted in the drawings do not necessarily require the specific order or sequential order shown to achieve the desired results. In certain embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0091] The above method will be described below in conjunction with a specific embodiment. However, it should be noted that this specific embodiment is only for better explaining this specification and does not constitute an improper limitation to this specification.

[0092] In this specific embodiment, a method for determining multiphase multicomponent competitive adsorption data in shale micro-nano pores is provided. Please refer to Figure 2 , which shows the flow chart of the method for determining multiphase multicomponent competitive adsorption data in the shale micro-nano pores in this specific embodiment. As Figure 2 shown, the method in this embodiment may include the following content.

[0093] (1) Obtain the shale core samples of the target area. After saturating them with formation water, conduct FTIR tests on the surface structure of the shale samples before and after the action of the electric field using Fourier transform infrared spectroscopy to obtain the types and relative content change characteristics of their surface functional groups.

[0094] (2) Collect the key structural and force field parameters of the shale clay minerals in the target block. Establish a molecular model of the shale clay minerals through software such as Materials Studio, CHARMM-GUI, or Avogadro. Select the general force field CLAYFF force field applicable to multi-component mineral systems and their interface simulations with fluids. According to the types and relative content changes of the surface crown functional groups on the shale after the action of the electric field, modify and replace the surface functional groups of the clay mineral molecules, and then expand the unit cell of the modified clay mineral molecules. Establish fluid molecular models through Materials Studio software, including molecular models of water, CO2, alkanes, etc. In order to make the competitive adsorption behavior of various fluids in micro-nano pores more accurate, select the SPC / E force field for the H2O force field, the EPM2 force field for the CO2 force field, and the OPLS-UA force field for the alkane molecular force field; use Packmol software to establish a slit model with the modified clay mineral molecules as the boundary, and then establish a multi-phase fluid system model composed of different contents of water, CO2, alkanes, etc. between the slit models to obtain the initial configuration for observing the multi-phase multi-component competitive adsorption in the shale micro-nano pores.

[0095] (3) Use Moltemplate software to convert the initial configuration of the multi-phase multi-component competitive adsorption in the shale micro-nano pores into a model file required by Lammps software; use LAMMPS software to optimize the structure of the above system, set the simulation parameters, and obtain a stable configuration after sequential energy minimization and position-restricted pre-equilibrium simulation to ensure more accurate subsequent calculation results.

[0096] (4) Use LAMMPS software, set it to the NVT ensemble, apply an external electric field along the Z-axis of the system, and set the simulation electric field parameters, including parameters such as electric field strength, electric field frequency, and electrification time, to conduct molecular dynamics calculations to obtain molecular trajectory coordinates and kinetic information. The formula for setting the electric field parameters is:

[0097]

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

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

[0100] (6) According to the calculation results of the LAMMPS software, including the density distribution, mole number distribution, molecular number distribution, etc. of each component of the multiphase fluid in the shale micro-nano pores under the action of an external electric field, and further calculate the absolute adsorption amount, selective adsorption coefficient, and change law of interaction energy of each component.

[0101] Obtain the adsorption layer thickness of different molecules from the density distribution curve, and then calculate the absolute adsorption amount of different molecules:

[0102]

[0103] Where: V ab is the absolute adsorption amount, μmol / m 2 ; ρi is the density of molecule i in the model, g / cm 3 ; L1 and L2 are the starting length and ending length of the adsorption phase of molecule i in the model, nm; M i is the relative molecular mass of molecule i, g / mol; S is the specific surface area of the model pores, nm 2 .

[0104] According to the absolute adsorption amount results of different molecules, calculate the selective adsorption coefficient of different molecules:

[0105]

[0106] Where: S ij is the adsorption selectivity of molecule i relative to molecule j; X i , X j are the mole fractions of molecule i and molecule j in the adsorption phase respectively; Y i , Y j are the mole fractions of molecule i and molecule j in the free phase.

[0107] Calculate the interaction energy between the target fluid molecules and the modified wall surface according to the equilibrium configuration of each system, including the van der Waals energy and the electrostatic energy, which is expressed as:

[0108]

[0109] Where: E i represents the interaction energy between the wall surface and component i; E t represents the total energy of the system composed of component i and the wall surface; E b and E sDenote the thermodynamic energy of the wall surface and component i; N i Denote the number of molecules of component i. Usually, E i A negative value of E indicates an adsorbable state. The larger the absolute value, the stronger the interaction between component i and the wall surface, making the component more inclined to adsorb on the wall surface.

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

[0111] (1) Obtain the shale core sample of the target area. After saturating it with formation water, use Fourier transform infrared spectroscopy to conduct FTIR tests on the surface structure of the shale sample before and after the action of the electric field, and obtain the types and relative content change characteristics of its surface functional groups.

[0112] (2) The main clay mineral in the shale of the target block is montmorillonite. Obtain the key structure and force field parameters, and establish a montmorillonite molecular model through Materials Studio software. The molecular formula is Si8Al4O 20 (OH)4, select the CLAYFF force field, and use the Lennard-Jones (LJ) 12-6 type potential function for the van der Waals force; according to the types and relative content changes of the surface crown functional groups of the shale after the action of the electric field, modify and replace the surface functional groups of the montmorillonite molecule; then expand the unit cell (5×4×1) of the modified clay mineral molecule, and the size is Establish fluid molecular models through Materials Studio software, including water, CO2, and methane molecular models. Select the SPC / E force field for H2O, the EPM2 force field for CO2, and the OPLS-UA force field for the methane molecule, and optimize the fluid molecular models; use Packmol software to establish a slit model with the modified montmorillonite molecule as the boundary, and the slit distance is Denote the 3nm shale pores, and then establish a multiphase fluid system model composed of different contents of water, CO2, and methane molecules between the slit models to obtain the initial configuration of the competitive adsorption of CO2 / CH4 in micro-nano pores of water-bearing shale with different water contents and different CO2 / CH4 content ratios under reservoir temperature and pressure conditions.

[0113] (3) Use Moltemplate software to convert the initial configuration of the competitive adsorption of CO2 / CH4 in micro-nano pores of water-bearing shale into the model file required by Lammps software; use LAMMPS software to optimize the structure of the above system, set the simulation parameters, and obtain a stable configuration after energy minimization and position-restricted pre-equilibrium simulation in sequence, Figure 3 Is the optimized configuration of the competitive adsorption of CO2 / CH4 in micro-nano pores of water-bearing shale after optimization, ensuring more accurate subsequent calculation results.

[0114] (4) Use the LAMMPS software, set it to the NVT ensemble, apply an external electric field along the z-axis of the system, and set the simulation electric field parameters, including parameters such as electric field strength, electric field frequency, and electrification time, to perform molecular dynamics calculations to obtain molecular trajectory coordinates and kinetic information. After verifying that the running time reaches 3 ns, the entire system reaches an equilibrium state.

[0115] (5) Obtain the calculation results of the LAMMPS software, use the Ovital 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. Figure 4 It is a visualization diagram of the competitive adsorption distribution of each component in shale micro-nano pores before and after the action of the electric field. Figure 4 (a) in it is a visualization diagram of the competitive adsorption distribution of each component in shale micro-nano pores before applying the electric field. Figure 4 (b) in it is a visualization diagram of the competitive adsorption distribution of each component in shale micro-nano pores after applying the electric field.

[0116] (6) According to the calculation results of the LAMMPS software, further calculate the fluid density distribution, multicomponent competitive adsorption amount, selective adsorption coefficient, and interaction energy variation law of the CO2 / CH4 system in the water-containing shale micro-nano pores under the action of an external electric field.

[0117] Figure 5 It shows the density distribution curves of each component in shale micro-nano pores under different electric field strengths in this specific embodiment. Figure 5 (a) in it is for the electric field strength E = 0 The density distribution curves of each component in shale micro-nano pores under the action. Figure 5 (b) in it is for the electric field strength E = 0.1 The density distribution curves of each component in shale micro-nano pores under the action. Figure 5 (c) in it is for the electric field strength E = 0.25 The density distribution curves of each component in shale micro-nano pores under the action. Figure 5 (d) in it is for the electric field strength E = 0.5 The density distribution curves of each component in shale micro-nano pores under the action. From Figure 5 It can be seen that as a polar molecule, the H2O molecule is more easily driven by the electric field, and the electric field strength has the most obvious influence on the H2O molecule. 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 It shows the change diagram of CO2 / CH4 adsorption selectivity under different electric field strengths in this specific embodiment. From Figure 6It can be seen that the applied electric field increases the selective adsorption of shale to CO2. With the increase of the electric field strength, the adsorption selectivity of water-containing shale to CO2 increases. However, with the further increase of the electric field strength, the adsorption selectivity of water-containing shale to CO2 molecules gradually reaches equilibrium.

[0119] Figure 7 The change diagram of the interaction energy between each component of the shale micro-nano pores and the wall under different electric field strengths in this specific embodiment is shown. From Figure 7 it can be seen that with the increase of the electric field strength, the interaction energy between H2O and the shale wall increases, verifying the desorption of H2O molecules 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 change in the interaction energy between CH4 and the shale wall is very small.

[0120] Figure 8 The density distribution curves of each component of the shale micro-nano pores under the action of different electric field frequencies in this specific embodiment are shown. Figure 8 In (a), it is the density distribution curve of each component of the shale micro-nano pores under the action of the electric field frequency f = 0 GHz. Figure 8 In (b), it is the density distribution curve of each component of the shale micro-nano pores under the action of the electric field frequency f = 20 GHz. Figure 8 In (c), it is the density distribution curve of each component of the shale micro-nano pores under the action of the electric field frequency f = 60 GHz. Figure 8 In (d), it is the density distribution curve of each component of the shale micro-nano pores under the action of the electric field frequency f = 100 GHz. From Figure 8 it can be seen that the influence of the electric field frequency on H2O molecules is the most obvious. The oscillating electric field promotes the desorption of some H2O molecules, and the H2O molecules gradually tend to be symmetrically distributed. And too high an electric field frequency causes some CO2 to change from the adsorbed state to the free state.

[0121] Figure 9 The change diagram of the CO2 / CH4 adsorption selectivity under different electric field frequencies in this specific embodiment is shown. From Figure 9 it can be seen that when the electric field frequency is lower than 40 GHz, the applied electric field increases the selective adsorption of water-containing shale to CO2. However, when the electric field frequency increases to higher than 40 GHz, the applied electric field will reduce the selective adsorption of water-containing shale to CO2.

[0122] Figure 10 The change diagram of the interaction energy between each component and the wall under different electric field frequencies in this specific embodiment is shown. From Figure 10It can be seen that with the increase of the electric field frequency, the interaction energy between CO2 molecules and the shale wall gradually increases, the adsorption of CO2 molecules is inhibited, the interaction energy between H2O and the shale wall gradually decreases, the adsorption of H2O molecules by the shale wall increases, and the interaction energy between CH4 and the shale wall changes little.

[0123] From the description of the above embodiments, those skilled in the art can combine the characteristics of the changes in the surface functional groups of shale under the action of an electric field to establish a molecular simulation model for the competitive adsorption of multiphase and multicomponent fluids in the micro-nano pores of surface-modified shale under the action of an electric field, reveal the occurrence state and competitive adsorption behavior of multiphase and multicomponent fluids in the micro-nano pores of shale under the action of an electric field at the molecular scale, realize the enhanced selective adsorption of CO2 in the mixed fluid by shale under the applied electric field, and lay an important theoretical foundation for the application of the technology of enhancing the recovery rate of shale gas reservoirs by injecting CO2 and CO2 sequestration technology under the electric field.

[0124] Combined with the test experiment on the changes of surface functional groups of shale under the action of an electric field, establish a molecular simulation model for the competitive adsorption of multiphase and multicomponent fluids in the micro-nano pores of surface-modified shale under the action of an electric field, and reveal the occurrence state and competitive adsorption behavior of multiphase and multicomponent fluids in the micro-nano pores of shale under the action of an electric field at the molecular scale.

[0125] Based on the same inventive concept, an apparatus for determining competitive adsorption data of multiphase and multicomponent fluids in micro-nano pores of shale is also provided in the embodiments of this specification, as described in the following embodiments. Since the principle of solving problems by the apparatus for determining competitive adsorption data of multiphase and multicomponent fluids in micro-nano pores of shale is similar to that of the method for determining competitive adsorption data of multiphase and multicomponent fluids in micro-nano pores of shale, the implementation of the apparatus for determining competitive adsorption data of multiphase and multicomponent fluids in micro-nano pores of shale can refer to the implementation of the method for determining competitive adsorption data of multiphase and multicomponent fluids in micro-nano pores of shale, and the repeated parts will not be elaborated. As used hereinafter, the term "unit" or "module" can be a combination of software and / or hardware that can achieve a predetermined function. Although the apparatuses described in the following embodiments are preferably implemented in software, implementation in hardware, or a combination of software and hardware is also possible and contemplated. Figure 11 is a structural block diagram of the apparatus for determining competitive adsorption data of multiphase and multicomponent fluids in micro-nano pores of shale in the embodiments of this specification, as Figure 11 shown, including: an acquisition module 1101, a collection module 1102, an establishment module 1103, and a calculation module 1104. The following describes this structure.

[0126] The acquisition module 1101 is used to acquire a shale core sample of a target area and determine the types and relative content change characteristics of the surface functional groups of the shale core sample.

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

[0128] The establishment module 1103 is used to establish multiple fluid molecular models; it is also used to establish a slit model with the modified clay mineral molecules as the boundary, and establish a multiphase fluid system model composed of multiple fluid molecular models with different contents between the slit models to obtain the initial configuration of competitive adsorption of multiphase and multicomponent fluids in the shale micro-nano pores; it is also used to optimize the structure of the initial configuration 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.

[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 kinetic information of the multiphase and multicomponent fluids; it is also used to calculate the competitive adsorption data of the multiphase and multicomponent fluids in the shale micro-nano pores under the action of an electric field based on the molecular trajectory coordinates and kinetic information of the multiphase and multicomponent fluids, so as to carry out shale gas exploitation and / or shale carbon dioxide sequestration based on the competitive adsorption data.

[0130] In some embodiments of the present specification, the acquisition module is specifically used for: saturating the shale core sample with formation water; performing FTIR tests on the surface structure of the shale core sample after saturating it with formation water before and after the action of an electric field using Fourier transform infrared spectroscopy to obtain the types and relative content change characteristics of the surface functional groups of the shale core sample.

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

[0132] In some embodiments of the present specification, the establishment module is specifically used for: converting the initial configuration of competitive adsorption of multiphase and multicomponent fluids in the shale micro-nano pores into a model file required by molecular dynamics simulation software; using molecular dynamics simulation software to optimize the structure 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.

[0133] In some embodiments of this specification, the calculation module is specifically configured to: use molecular dynamics simulation software, set the stable configuration as the NVT ensemble, apply an external electric field to the NVT ensemble, set the simulation electric field parameters, perform molecular dynamics calculations, and obtain the molecular trajectory coordinates and kinetic information of the multi-phase multi-component fluid; where the formula for setting the electric field parameters is:

[0134]

[0135] where E0 is the electric field strength; E is the electric field peak 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 configured to: based on the molecular trajectory coordinates and kinetic information of the multi-phase multi-component fluid, visualize the distribution of the multi-phase multi-component fluid at different times, generate a real-time dynamic image of the occurrence state and competitive adsorption process of the multi-phase multi-component fluid in the shale micro-nano pores under the action of the electric field; and determine the absolute adsorption amount, selective adsorption coefficient, and interaction energy of each component in the multi-phase multi-component fluid according to the molecular trajectory coordinates and kinetic information of the multi-phase multi-component fluid.

[0137] In some embodiments of this specification, the molecular trajectory coordinates and kinetic information of the multi-phase multi-component fluid may include: the density distribution curve, mole number distribution, and molecule number distribution of each component in the multi-phase multi-component fluid; correspondingly, determining the absolute adsorption amount, selective adsorption coefficient, and interaction energy of each component in the multi-phase multi-component fluid according to the molecular trajectory coordinates and kinetic information of the multi-phase multi-component fluid may include: determining the adsorption layer thickness of each component according to the density distribution curve of each component in the multi-phase multi-component fluid, and calculating the absolute adsorption amount of the molecule based on the adsorption layer thickness of each component; determining the selective adsorption coefficient of each component in the multi-phase multi-component fluid based on the absolute adsorption amount of each component in the multi-phase multi-component fluid and the mole number distribution of each component; and calculating the interaction energy between each component and the modified wall surface according to the molecule number distribution of each component in the multi-phase multi-component fluid and the equilibrium configuration of each system.

[0138] The embodiments of this specification also provide a computer device, which can specifically refer to Figure 12 the schematic diagram of the composition structure of the computer device based on the method for determining the competitive adsorption data of the multi-phase multi-component in the shale micro-nano pores provided in the embodiments of this specification as shown. The computer device may specifically include an input device 121, a processor 122, and a memory 123. Among them, the memory 123 is used to store instructions executable by the processor. When the processor 122 executes the instructions, it implements the steps of the method for determining the competitive adsorption data of the multi-phase multi-component in the shale micro-nano pores described in any of the above embodiments.

[0139] In this embodiment, the input device may specifically be one of the main devices for information exchange between a user and a computer system. The input device may include a keyboard, a mouse, a camera, a scanner, a light pen, a handwriting input board, a 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 may also acquire and receive data transmitted from other modules, units, and devices. The processor may be implemented in any suitable manner. For example, the processor may take the form of, for example, a microprocessor or a processor and a computer-readable medium storing computer-readable program code (such as software or firmware) executable by the (micro)processor, logic gates, switches, an application specific integrated circuit (ASIC), a programmable logic controller, and a form embedded microcontroller, etc. The memory may specifically be a memory device for storing information in modern information technology. The memory may include multiple levels. In a digital system, anything that can store binary data can be a memory; in an integrated circuit, a circuit with a storage function without a physical form is also called a memory, such as RAM, FIFO, etc.; in a system, a storage device with a physical form is also called a memory, such as a memory module, a TF card, etc.

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

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

[0142] In this embodiment, the above storage medium includes but is not limited to a random access memory (RAM), a read-only memory (ROM), a cache, a hard disk drive (HDD), or a memory card. The memory may be used to store computer program instructions. The network communication unit may be set according to the standards specified by the communication protocol and is an interface for network connection communication.

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

[0144] Obviously, those skilled in the art should understand that the various modules or steps of the embodiments of the present specification described above can be implemented by a general-purpose computing device. They can be concentrated on a single computing device or distributed over a network composed of multiple computing devices. Optionally, they can be implemented with program codes executable by the computing device. Thus, they can be stored in a storage device and executed by the computing device. And in some cases, the steps shown or described can be executed in a sequence different from that here, or they can be separately fabricated into individual integrated circuit modules, or multiple modules or steps among them can be fabricated into a single integrated circuit module for implementation. In this way, the embodiments of the present specification are not limited to any specific 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 many applications other than the examples provided will be obvious to those skilled in the art upon reading the above description. Therefore, the scope of this specification should not be determined with reference to the above description, but should be determined with reference to the full scope of the foregoing claims and the equivalents thereof.

[0146] The above are only the preferred embodiments of this specification and are not used to limit this specification. For those skilled in the art, the embodiments of this specification can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this specification shall be included within the protection scope of this specification.

Claims

1. A method for determining multi-phase and multi-component competitive adsorption data of shale micro-nano pores, characterized in that Including: Obtain a shale core sample of the target area, and determine the types and relative content change characteristics of the surface functional groups of the shale core sample; Collect the key structural and force field parameters of the shale clay minerals in the target block, and establish a molecular model of the shale clay minerals; according to the types and relative content changes of the surface crown 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 the shale clay minerals, and then expand the unit cell of the modified clay mineral molecules; Establish multiple fluid molecular models; establish a slit model with the modified clay mineral molecules as the boundary, and establish a multiphase fluid system model composed of the multiple fluid molecular models with different contents between the slit models to obtain the initial configuration of competitive adsorption of multiphase and multicomponent in the shale micro-nano pores; optimize the structure of the initial configuration 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; Apply an external electric field to the stable configuration and perform molecular dynamics calculations to obtain the molecular trajectory coordinates and kinetic information of the multiphase and multicomponent fluid; based on the molecular trajectory coordinates and kinetic information of the multiphase and multicomponent fluid, calculate the competitive adsorption data of the multiphase and multicomponent fluid in the shale micro-nano pores under the action of an electric field, so as to carry out shale gas exploitation and / or shale carbon dioxide sequestration based on the competitive adsorption data.

2. The method for determining shale micro-nano pore multiphase and multicomponent competitive adsorption data according to claim 1, wherein Determine the types and relative content change characteristics of the surface functional groups of the shale core sample, including: Saturate the shale core sample with formation water; Use Fourier transform infrared spectroscopy to perform FTIR tests on the surface structure of the shale core sample after saturation with formation water before and after the action of an electric field, and obtain the types and relative content change characteristics of the surface functional groups of the shale core sample.

3. The method for determining the multi-phase and multi-component competitive adsorption data of shale micro-nano pores according to claim 1, characterized in that Establish multiple fluid molecular models, including: Use material calculation software to establish a water molecule model, a carbon dioxide molecule model, and an alkane molecule model; among them, the force field of the water molecule model is the SPC / E force field, the force field of the carbon dioxide molecule model is the EPM2 force field, and the force field of the alkane molecule model is the OPLS-UA force field.

4. The method for determining the shale micro-nano pore multiphase multi-component competitive adsorption data according to claim 1, characterized in that Optimize the structure of the initial configuration to obtain a stable configuration, including: Convert the initial configuration of competitive adsorption of multiphase and multicomponent in the shale micro-nano pores into a model file required by the molecular dynamics simulation software; Use the molecular dynamics simulation software to optimize the structure of the model file of the initial configuration, set the simulation parameters, and perform energy minimization and position-restricted pre-equilibrium simulations in sequence to obtain a stable configuration.

5. The method for determining shale micro-nano pore multi-phase and multi-component competitive adsorption data according to claim 1, characterized in that Apply an external electric field to the stable configuration and perform molecular dynamics calculations to obtain the molecular trajectory coordinates and kinetic information of the multiphase and multicomponent fluid, including: Use the molecular dynamics simulation software to set the stable configuration as the NVT ensemble, apply an external electric field to the NVT ensemble, set the simulation electric field parameters, and perform molecular dynamics calculations to obtain the molecular trajectory coordinates and kinetic information of the multiphase and multicomponent fluid; among them, the formula for setting the electric field parameters is: Where, E0 is the electric field strength; E is the electric field peak value; f is the electric field frequency; t is the time step.

6. The method for determining the multi-phase and multi-component competitive adsorption data of shale micro-nano pores according to claim 1, wherein Based on the molecular trajectory coordinates and kinetic information of the multiphase and multicomponent fluid, calculate the competitive adsorption data of the multiphase and multicomponent fluid in the shale micro-nano pores under the action of an electric field, including: Based on the molecular trajectory coordinates and kinetic information of the multiphase and multicomponent fluid, visualize the distribution of the multiphase and multicomponent fluid at different times, and generate a real-time dynamic image of the occurrence state and competitive adsorption process of the multiphase and multicomponent fluid in the shale micro-nano pores under the action of an electric field; According to the molecular trajectory coordinates and kinetic information of the multiphase and multicomponent fluid, determine the absolute adsorption amount, selective adsorption coefficient, and interaction energy of each component in the multiphase and multicomponent fluid.

7. The method for determining the shale micro-nano pore multi-phase multi-component competitive adsorption data according to claim 1, wherein The molecular trajectory coordinates and kinetic information of the multiphase and multicomponent fluid include: the density distribution curve, mole number distribution, and molecule number distribution of each component in the multiphase and multicomponent fluid; Correspondingly, according to the molecular trajectory coordinates and kinetic information of the multiphase and multicomponent fluid, determining the absolute adsorption amount, selective adsorption coefficient, and interaction energy of each component in the multiphase and multicomponent fluid includes: According to the density distribution curve of each component in the multiphase and multicomponent fluid, determine the adsorption layer thickness of each component, and based on the adsorption layer thickness of each component, calculate the absolute adsorption amount of molecules; Based on the absolute adsorption amount of each component in the multiphase and multicomponent fluid and the mole number distribution of each component, determine the selective adsorption coefficient of each component in the multiphase and multicomponent fluid; According to the molecule number distribution of each component in the multiphase and multicomponent fluid and the equilibrium configuration of each system, calculate the interaction energy between each component and the modified wall surface.

8. An apparatus for determining multi-phase and multi-component competitive adsorption data of shale micro-nano pores, characterized in that, Including: An acquisition module, used to acquire a shale core sample in the target area, and determine the types and relative content change characteristics of the surface functional groups of the shale core sample; A collection module, used to collect the key structure and force field parameters of the shale clay minerals in the target block, and establish a molecular model of the shale clay minerals; also used to modify and replace the molecular surface functional groups in the molecular model of the shale clay minerals according to the types and relative content changes of the surface crown functional groups on the shale under the action of an electric field, and then expand the unit cell of the modified clay mineral molecules; A construction module, used to construct molecular models of multiple fluids; also used to construct a slit model with the modified clay mineral molecules as the boundary, and establish a multiphase fluid system model composed of molecular models of the multiple fluids with different contents between the slit models, to obtain the initial configuration of the competitive adsorption of the multiphase and multicomponent in the shale micro-nano pores; also used to optimize the structure of the initial configuration to obtain a stable configuration; the molecular models of the multiple fluids include a water molecule model, a carbon dioxide molecule model, and an alkane molecule model; A calculation module, used to apply an external electric field to the stable configuration and perform molecular dynamics calculations to obtain the molecular trajectory coordinates and kinetic information of the multiphase and multicomponent fluid; also used to calculate the competitive adsorption data of the multiphase and multicomponent fluid in the shale micro-nano pores under the action of an electric field based on the molecular trajectory coordinates and kinetic information of the multiphase and multicomponent fluid, so as to carry out shale gas exploitation and / or shale carbon dioxide sequestration based on the competitive adsorption data.

9. A computer device, characterized in that, Comprising a processor and a memory for storing processor-executable instructions, when the processor executes the instructions, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having computer instructions stored thereon, characterized in that, When the instructions are executed by the processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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