Shale oil reservoir CO2 injection multiphase multicomponent flow law analysis method considering fluid confinement phase change and related device
Through molecular simulation experiments and thermodynamic phase equilibrium theory, a fluid confined phase transition model was constructed when CO2 was injected in shale reservoirs, which solved the problem of unknown impact of fluid confined phase transition on the flow characteristics of multiphase and multicomponents, and achieved dynamic prediction and production optimization of CO2 development in shale reservoirs.
Patent Information
- Application Number
- CN202510276665.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-10
- Publication Date
- 2025-06-27
AI Technical Summary
During the CO2 injection development process of shale reservoirs, the impact of fluid limit phase transformation on the flow characteristics of multiphase and multicomponents is unknown, resulting in challenges in the design and optimization of development plans.
The relationship between shale pore size, pore wall surface and boundary effect was obtained by molecular simulation experiments, and the fluid boundary phase change model of the shale oil-CO2 system was constructed based on the thermodynamic phase equilibrium theory. A multi-phase multi-component flow model of shale reservoir injection was constructed that considered the fluid boundary phase change. The flow velocity and flow direction were solved by the feature line method, and the jumping conditions, entropy conditions and velocity constraints were combined to obtain the multi-phase multi-component flow path.
The multiphase and multi-component flow law of CO2-shale oil system under confined phase transformation is accurately described, providing theoretical guidance for dynamic prediction and production optimization of CO2 injection development in shale reservoirs.
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Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of oil and gas reservoir development, and particularly relates to a method for analyzing the multiphase and multicomponent flow law of CO2 injection in shale oil reservoirs considering fluid confinement phase change and related devices. Background Art
[0002] Driven by the breakthrough and innovation of petroleum geology theory, significant breakthroughs have been made in the exploration of unconventional reservoirs, indicating that shale oil and gas resources are abundant. Efficient development of shale oil reservoirs can effectively solve the problem of energy shortage. CO2 injection is one of the main effective methods for developing shale oil reservoirs. Conducting multiphase and multicomponent flow analysis of the CO2 - shale oil hydrocarbon system is helpful for the scheme design and optimization of CO2 injection development in shale oil reservoirs, and is of great significance for the efficient development of shale oil reservoirs.
[0003] During the process of CO2 injection for developing shale oil reservoirs, the dynamic changes of fluid composition and temperature and pressure will cause fluid phase change. In particular, the confinement effects such as adsorption and capillary force in the nano - pores of shale oil reservoirs change the mass transfer process between multiphase fluids, resulting in confined phase change of fluids in shale nano - pores. The fluid confined phase change not only changes the number of phases of the flowing fluids in the shale oil reservoir, but also changes the composition and flow characteristics of each phase. These changes will all affect the multiphase and multicomponent flow of CO2 injection development in shale oil reservoirs. Therefore, in order to deeply understand the flow characteristics of CO2 injection development in shale oil reservoirs, it is necessary to analyze the influence of fluid confined phase change on the multiphase and multicomponent flow of the CO2 - shale oil system. Summary of the Invention
[0004] To solve the problems existing in the prior art, the purpose of the present invention is to provide a method for analyzing the multiphase and multicomponent flow law of CO2 injection in shale oil reservoirs considering fluid confinement phase change and related devices, which can accurately describe the multiphase and multicomponent flow law of the CO2 - shale oil system under confined phase change, and provide theoretical guidance for the dynamic prediction and production optimization of CO2 injection development in shale oil reservoirs.
[0005] The above object of the present invention is achieved by the following technical solutions: A method for analyzing the multiphase and multicomponent flow law of CO2 injection in shale oil reservoirs considering fluid confinement phase change includes the following processes: Through molecular simulation experiments, using the basic parameters of the target shale oil reservoir obtained, obtain the relationship between shale pore size, pore wall surface and confinement effect; According to the relationship between shale pore size, pore wall surface and confinement effect, obtain the molar fraction of each phase and the composition of each phase in the shale oil - CO2 system under confined phase change; Based on the multiphase and multicomponent flow theory, combined with the molar fraction of each phase and the composition of each phase in the shale oil - CO2 system under confined phase change, construct a multiphase and multicomponent flow model of CO2 injection in shale oil reservoirs considering fluid confinement phase change; Using the method of characteristics, a multi-phase and multi-component flow model of CO2 injection in a shale oil reservoir considering fluid-confined phase change is established to obtain the flow velocity and flow direction of multi-phase and multi-component fluids during CO2 injection in the shale oil reservoir. Based on the flow velocity and flow direction of multi-phase and multi-component fluids during CO2 injection in the shale oil reservoir, combined with the jump condition, entropy condition, and velocity constraint, a solution model for the multi-phase and multi-component flow path of the shale oil-CO2 system with confined phase change is obtained. Based on the solution model for the multi-phase and multi-component flow path of the shale oil-CO2 system with confined phase change, the multi-phase and multi-component flow law during CO2 injection in the target shale oil reservoir is obtained.
[0006] Preferably, the basic parameters of the target shale oil reservoir include: shale pore size distribution, shale mineral composition, and shale oil components.
[0007] Preferably, the pore wall includes quartz, kaolinite, and kerogen.
[0008] Preferably, the relationship between shale pore size, pore wall, and confinement effect includes the relationship equations between shale pore size, pore wall, and capillary force and adsorption amount of the shale oil-CO2 system. Based on the relationship equations between shale pore size, pore wall, and capillary force and adsorption amount of the shale oil-CO2 system, combined with the thermodynamic phase equilibrium theory, a fluid-confined phase change model of the shale oil-CO2 system is constructed, and the molar fractions and compositions of each phase of the shale oil-CO2 system under confined phase change are obtained according to the fluid-confined phase change model of the shale oil-CO2 system.
[0009] Preferably, the gas-phase molar fraction during the fluid-confined phase change of the shale oil-CO2 system under confined phase change is as follows:
[0010] where, λ V is the gas-phase molar fraction; N is the total number of components; is the total molar fraction of component i ; is the gas-liquid equilibrium constant; The gas-liquid equilibrium constant is calculated by the following formula:
[0011] where, and are the fugacity coefficients of component i in the liquid phase and gas phase, respectively; P L and P V are the liquid-phase and gas-phase pressures, respectively; When the fluid confined phase transition occurs in the shale oil-CO2 system under confined phase transition, the composition of each phase is as follows:
[0012]
[0013] Among them, and are the mole fractions of component i in the liquid phase and gas phase, respectively.
[0014] Preferably, the multi-phase and multi-component flow model for injecting CO2 into the shale oil reservoir is as follows:
[0015] Among them, ; is the mole fraction of component i in the j phase; is the j phase mole fraction; is the total volume fraction of component i ; is a dimensionless length; is the dimensionless time of the injected pore volume; The matrix A is a function of the total components; is the number of components.
[0016] Preferably, the multi-phase and multi-component flow laws during the process of injecting CO2 into the target shale oil reservoir include: the multi-phase and multi-component flow law considering the influence of the confinement effect on the fluid phase transition and the multi-phase and multi-component flow law of the confined phase transition of the fluid contained in pores with the same aperture.
[0017] The present invention also provides an analysis system for the multi-phase and multi-component flow law of injecting CO2 into a shale oil reservoir considering fluid confined phase transition. This system is used to implement the above method of the present invention and includes: The first data processing module: used to obtain the relationship between the shale pore size, pore wall surface and confinement effect through molecular simulation experiments by using the basic parameters of the target shale oil reservoir already obtained; The second data processing module: used to obtain the mole fraction and composition of each phase in the shale oil-CO2 system under confined phase transition according to the relationship between the shale pore size, pore wall surface and confinement effect; The first model construction module: used to construct a multi-phase and multi-component flow model for injecting CO2 into a shale oil reservoir considering fluid confined phase transition based on the multi-phase and multi-component flow theory and combining the mole fraction and composition of each phase in the shale oil-CO2 system under confined phase transition; The third data processing module: It is used to utilize the method of characteristic lines to obtain the multiphase and multicomponent flow velocity and flow direction during CO₂ injection in a shale oil reservoir by considering a multiphase and multicomponent flow model of CO₂ injection in a shale oil reservoir with fluid-confined phase change; The second model construction module: It is used to obtain a solution model for the multiphase and multicomponent flow path of a shale oil-CO₂ system with confined phase change based on the multiphase and multicomponent flow velocity and flow direction during CO₂ injection in a shale oil reservoir, combined with jump conditions, entropy conditions, and velocity constraints; The fourth data processing module: It is used to obtain the multiphase and multicomponent flow law during CO₂ injection in the target shale oil reservoir based on the solution model for the multiphase and multicomponent flow path of a shale oil-CO₂ system with confined phase change.
[0018] The present invention also provides an electronic device, including: One or more processors; A storage device on which one or more programs are stored; When the one or more programs are executed by the one or more processors, the one or more processors implement the method for analyzing the multiphase and multicomponent flow law of CO₂ injection in a shale oil reservoir considering fluid-confined phase change as described above in the present invention.
[0019] The present invention also provides a storage medium on which a computer program is stored, wherein the computer program, when executed by a processor, implements the method for analyzing the multiphase and multicomponent flow law of CO₂ injection in a shale oil reservoir considering fluid-confined phase change as described above in the present invention.
[0020] The present invention has the following beneficial effects: (1) The molecular simulation method is adopted to conduct interfacial tension and adsorption tests in nano-pores. By changing the pore size and pore wall composition, shale pores with different pore sizes and wall compositions are simulated. It is difficult to carry out nano-scale physical experiments due to the limitations of experimental materials and measurement, and conventional physical experiments are carried out under bulk-phase conditions, unable to consider the influence of nano-confined effects, resulting in the experimental results being difficult to accurately reflect the actual situation inside nano-pores. However, the molecular simulation method adopted in the present invention well overcomes the problems of experimental materials and measurement, and at the same time can consider the influence of confined effects.
[0021] (2) Based on the thermodynamic phase equilibrium theory, a fluid-confined phase change model of the shale oil-CO₂ system is derived, which can be used for predicting the phase change of multicomponent fluids during CO₂ injection in a shale oil reservoir, providing a basis for subsequent multiphase and multicomponent flow prediction.
[0022] (3) A multiphase and multicomponent flow model of shale oil-CO2 system with confined phase change was constructed, and a flow path solution method was proposed. The flow characteristics of each phase and each component in the shale oil-CO2 system under confined phase change were analyzed, which has important guiding significance for the CO2 injection development of shale oil reservoirs. Description of the Drawings
[0023] Figure 1 It is a flow chart of the analysis method for the multiphase and multicomponent flow law of CO2 injection in shale oil reservoirs considering fluid confined phase change according to the present invention; Figure 2(a) shows the variation of different pore sizes and interfacial tensions in a specific embodiment of the present invention; Figure 2(b) shows the variation of different pore walls and interfacial tensions in a specific embodiment of the present invention; Figure 3(a) shows the variation of adsorption amounts with different pore sizes in a specific embodiment of the present invention; Figure 3(b) shows the variation of adsorption amounts with different pore walls in a specific embodiment of the present invention; Figure 4(a) is the multiphase and multicomponent (C10) flow profile considering the influence of confinement effect on fluid phase change in a specific embodiment of the present invention; Figure 4(b) is the multiphase and multicomponent (CH4) flow profile considering the influence of confinement effect on fluid phase change in a specific embodiment of the present invention; Figure 4(c) is the multiphase and multicomponent (Sg) flow profile considering the influence of confinement effect on fluid phase change in a specific embodiment of the present invention; Figure 4(d) is the multiphase and multicomponent (CO2) flow profile considering the influence of confinement effect on fluid phase change in a specific embodiment of the present invention; Figure 5(a) is the multiphase and multicomponent (C10) flow profile with fluid confined phase change in pores of different sizes in a specific embodiment of the present invention; Figure 5(b) is the multiphase and multicomponent (CH4) flow profile with fluid confined phase change in pores of different sizes in a specific embodiment of the present invention; Figure 5(c) is the multiphase and multicomponent (Sg) flow profile with fluid confined phase change in pores of different sizes in a specific embodiment of the present invention; Figure 5(d) is the multiphase and multicomponent (CO2) flow profile with fluid confined phase change in pores of different sizes in a specific embodiment of the present invention. Detailed Embodiments
[0024] The present invention will be clearly and completely described below in conjunction with the drawings and embodiments of the present invention. The described embodiments are only a part of the embodiments of the present invention, not all of the embodiments.
[0025] Refer to Figure 1 , the analysis method for the multiphase and multicomponent flow law of CO2 injection in shale oil reservoirs considering fluid confined phase change in this embodiment specifically includes the following steps: Step 1: Obtain the basic parameters of the target shale reservoir. The basic parameters of the target shale reservoir include: shale pore size distribution, shale mineral composition, and shale oil components. Among them, the pore size distribution is measured by adsorption experiments and nuclear magnetic resonance experiments, the shale minerals are analyzed by an X-ray diffractometer, and the main components of shale oil and their proportions are measured by the four-component analysis method and gas chromatography.
[0026] Step 2: Through molecular simulation experiments, obtain the relationship between shale pore size, wall surface, and confinement effect. The relationship between shale pore size, wall surface, and confinement effect specifically includes the relationship equations of pore size, wall surface, and capillary force and adsorption amount in the shale oil-CO2 system. Based on the relationship equations of shale pore size, wall surface, and capillary force and adsorption amount, combined with the thermodynamic phase equilibrium theory, construct a fluid confinement phase change model of the shale oil-CO2 system, and obtain the molar fractions of each phase and the composition of each phase.
[0027] Specifically, in Step 2, the molecular simulation experiment is carried out using the open-source LAMMPS program. Based on the molecular dynamics simulation technology, pore walls with different characteristics are constructed. The pore walls include quartz, kaolinite, and kerogen, etc. Then, according to the shale pore size distribution results, pore sizes of 5 nm - 50 nm are selected to establish pore models with different pore sizes and wall surface characteristics.
[0028] Apply the periodic boundary condition in the established pore models with different pore sizes and wall surface characteristics to generate the initial structure. Initialize CO2 molecules and shale oil component molecules in the pore models, and obtain a stable initial system configuration through energy minimization. Set the temperature and pressure for equilibration in the NVT ensemble, simulate and collect data in the NVE ensemble, and calculate the interfacial tension according to the components of the pressure tensor in the x, y, and z directions. The relationship equation between the components of the pressure tensor and the interfacial tension is:
[0029] Among them, is the gas-liquid interfacial tension in the pore with a pore size of r and a wall surface of χ ; n is the number of interfaces in the system; L z is the length of the Z direction of the pore model; P xx , P yy , P zz are the pressure tensors in each direction.
[0030] Through molecular simulation experiments, the pressure tensors of the gas-liquid interfaces in different pore sizes and within the wall can be obtained in all directions. According to the relationship equation between the components of the pressure tensor and the interfacial tension, the variation of the interfacial tension in different pore sizes and within the wall is shown in Figures 2(a) and 2(b). It can be seen from the results that within different pore sizes and the wall, the interfacial tension increases with the decrease of pressure; at the same pressure, the interfacial tension decreases with the decrease of pore size, and the interfacial tension value within the kerogen wall is the largest.
[0031] By changing the pore size and wall properties of the shale, and based on the change of the interaction energy between the fluid molecules and the wall in the system, the adsorption amount of each component on the pore wall of the shale is determined. Based on the Langmuir model, the parameters are respectively fitted for single components of CO2 and hydrocarbons 、 , and according to the partial pressures of the components in the mixture, the multi-component adsorption model is established as:
[0032] where, V is the adsorption amount; is the maximum adsorption amount of the component in the pore with a pore size of r and a wall of χ ; b is the coefficient; P is the equilibrium pressure.
[0033] Through molecular simulation experiments, the adsorption amount data of components in different pore sizes and within the wall can be obtained. Through the multi-component adsorption model, the variation of the adsorption amount in different pore sizes and within the wall is shown in Figures 3(a) and 3(b). It can be seen from the results that within different pore sizes and the wall, the adsorption amount increases with the increase of pressure; at the same pressure, the larger the pore size, the larger the specific surface area, increasing the contact opportunity with each component, resulting in a larger adsorption amount; among different walls, the interaction force between kerogen and each component is strong, resulting in the largest adsorption amount inside it.
[0034] According to the actual adsorption amount and the maximum adsorption amount, the adsorption layer thickness t is:
[0035] where, ; ν is the molar volume; N A is the Avogadro constant.
[0036] According to the adsorption layer thickness and the molecular diameter of the solid wall, the effective pore radius is:
[0037] where, is the molecular diameter of the solid wall.
[0038] Based on the above interfacial tension and the effective pore radius, through the Young-Laplace equation, the capillary force expressions for fluids in pores with different pore diameters and wall pores are obtained as follows:
[0039] where is the capillary force in the pore with a pore diameter of r and a wall of χ ; γ is the interfacial tension; is the effective pore radius; θ is the contact angle between the liquid phase and the gas phase.
[0040] Through the capillary force and the liquid phase pressure, the gas phase pressure can be expressed as:
[0041] where is the liquid phase pressure.
[0042] Based on the phase equilibrium theory, according to the fugacity coefficients and pressures of each phase, the gas-liquid equilibrium constants of each component during the fluid-confined phase transition of the shale oil-CO2 system can be obtained as:
[0043] where and are the fugacity coefficients of component i in the liquid phase and the gas phase, respectively; and are the liquid phase pressure and the gas phase pressure, respectively.
[0044] Based on the gas-liquid equilibrium constants of each component and the Rachford–Rice equation, through Newton iteration calculation, the gas phase mole fraction during the fluid-confined phase transition of the shale oil-CO2 system can be obtained as:
[0045] where is the gas phase mole fraction; N is the total number of components; is the total mole fraction of component i ; is the gas-liquid equilibrium constant.
[0046] According to the gas phase mole fraction and the gas-liquid equilibrium constants of each component, the compositions of each phase during the fluid-confined phase transition of the shale oil-CO2 system can be obtained as: ,
[0047] Among them, and are the mole fractions of component i in the liquid phase and the gas phase, respectively; is the gas-phase mole fraction.
[0048] Step 3: Based on the multiphase and multicomponent flow theory, construct a multiphase and multicomponent flow model for the shale oil-CO2 system, and use the method of characteristics to solve it to obtain the flow velocity and flow direction of the multiphase and multicomponent during CO2 injection into the shale oil reservoir.
[0049] Specifically, in Step 3, based on the multiphase and multicomponent seepage theory, combined with the mole fractions and compositions of each phase in the shale oil-CO2 system under confined phase change, the multiphase and multicomponent flow equation for CO2 injection into the shale oil reservoir considering fluid confined phase change can be obtained as follows:
[0050] Among them, ; is the mole fraction of component i in j phase; is j phase mole fraction; is the total volume fraction of component i ; is the dimensionless length; is the dimensionless time of the injected pore volume; The matrix A is a function of the total components; is the number of components.
[0051] Let n c = 3, and the multiphase and multicomponent flow equation for the three-component shale oil-CO2 system can be obtained as follows:
[0052] Among them, ; is the total fractional flow rate of component i ; is the mole fraction of component i in j phase; is j phase fractional flow rate.
[0053] According to the method of characteristics, the flow velocities of each phase and each component in the connected path and the non-connected path are given by the eigenvalues of the coefficient matrix of the above equation as follows:
[0054] Among them, is the speed of the connected line path; is the speed of the non-connected line path; a is the ratio of the slope and intercept of the non-connected line.
[0055] Step 4: According to the confined phase transition model of the shale oil-CO2 system and the flow velocities and flow directions of multiple phases and multiple components, combined with additional physical conditions, a method for solving the multi-phase and multi-component flow path of the shale oil-CO2 system with confined phase transition is proposed. This solution method selects the only correct multi-phase and multi-component flow path through the molar fractions and compositions of each phase in the confined phase transition, as well as the flow velocities and flow directions of the multi-phase and multi-component, combined with additional physical conditions.
[0056] Specifically, in Step 4, the flow directions of each phase and each component can be given by the eigenvector corresponding to the eigenvalue. The eigenvalue The corresponding eigenvector is determined by the following formula:
[0057] The eigenvector related to the eigenvalue v nt is determined by the following formula:
[0058] Based on the above flow velocities and flow directions of the multi-phase and multi-component, combined with three additional physical conditions: jump condition, entropy condition and velocity constraint, a solution model for the multi-phase and multi-component flow path of the shale oil-CO2 system with confined phase transition can be formed.
[0059] Step 5: Based on the solution model for the multi-phase and multi-component flow path with confined phase transition, analyze the multi-component flow law during the CO2 injection process in the target shale reservoir. The multi-component flow law during the CO2 injection process in the target shale reservoir includes: the multi-phase and multi-component flow law considering the influence of the confinement effect on fluid phase transition, and the multi-phase and multi-component flow law of the fluid confined phase transition in different pore sizes. Finally, the flow characteristics of each phase and each component in the CO2 injection development of the target area are obtained.
[0060] Figures 4(a)-4(d) are the multi-component flow profiles considering the influence of the confinement effect on fluid phase transition. It can be seen that compared with not considering the confinement effect, when considering the influence of capillary force on fluid phase transition in the confinement effect, the flow of each component and the front velocity of gas saturation are faster. When both capillary force and adsorption effect exist in the confinement effect, the influence on the flow of each component and each phase is more obvious. The adsorption effect will reduce the effective nano-pore size, thereby enhancing the confinement effect and further increasing the flow velocity of each phase and each component, indicating that the influence of capillary force and adsorption effect on the multi-phase and multi-component flow must be considered simultaneously in the actual development process of shale reservoirs.
[0061] Figures 5(a) - 5(d) show the multi-component flow profiles with fluid phase change in pores of different apertures. It can be seen that as the aperture decreases, the migration speed of the leading edge of gas saturation becomes faster. At the same time, as the aperture decreases, the two-phase region gradually reduces. Fluid-confined phase change can make the migration speed of gas saturation faster and reduce the range of the two-phase region, enabling crude oil to be produced at a faster speed and with a higher recovery rate.
[0062] Figures 4(a) - 5(d) show the influence of fluid-confined phase change on multi-phase and multi-component flow during CO2 injection in shale oil reservoirs under different conditions. Before actually exploiting shale oil reservoirs, based on the basic parameters of shale oil reservoirs and combining with the method for analyzing multi-phase and multi-component flow during CO2 injection in shale oil reservoirs considering fluid-confined phase change provided by the present invention, theoretical guidance can be provided for the development of shale oil reservoirs by CO2 injection.
[0063] In addition, the embodiment of the present invention also provides a system for implementing the above-mentioned method for analyzing the multi-phase and multi-component flow law during CO2 injection in shale oil reservoirs considering fluid-confined phase change of the present invention, including: The first data processing module: used to obtain the relationship between shale pore size, pore wall surface and confinement effect through molecular simulation experiments by using the basic parameters of the target shale oil reservoir obtained; The second data processing module: used to obtain the mole fraction and composition of each phase in the shale oil - CO2 system under confinement phase change according to the relationship between shale pore size, pore wall surface and confinement effect; The first model construction module: used to construct a multi-phase and multi-component flow model for CO2 injection in shale oil reservoirs considering fluid-confined phase change based on the multi-phase and multi-component flow theory and combining the mole fraction and composition of each phase in the shale oil - CO2 system under confinement phase change; The third data processing module: used to obtain the flow velocity and flow direction of multi-phase and multi-component during CO2 injection in shale oil reservoirs through the multi-phase and multi-component flow model for CO2 injection in shale oil reservoirs considering fluid-confined phase change by using the method of characteristics; The second model construction module: used to obtain a solution model for the multi-phase and multi-component flow path of the shale oil - CO2 system with confinement phase change based on the flow velocity and flow direction of multi-phase and multi-component during CO2 injection in shale oil reservoirs and combining the jump condition, entropy condition and velocity constraint; The fourth data processing module: used to obtain the multi-phase and multi-component flow law during CO2 injection in the target shale oil reservoir based on the solution model for the multi-phase and multi-component flow path of the shale oil - CO2 system with confinement phase change.
[0064] The embodiment of the present invention also provides a corresponding electronic device and a computer-readable storage medium for implementing the solution provided by the embodiment of the present invention.
[0065] Among them, the device includes a memory and a processor. The memory is used to store instructions or codes, and the processor is used to execute the instructions or codes so that the device executes the method for analyzing the multiphase and multicomponent flow law of CO2 injection in shale reservoirs considering fluid confinement phase change according to any embodiment of the present application.
[0066] A computer program is stored on the storage medium. Among them, when the computer program is executed by a processor, it implements the method for analyzing the multiphase and multicomponent flow law of CO2 injection in shale reservoirs considering fluid confinement phase change according to any embodiment of the present application.
[0067] Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.
[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: still can modify the specific implementation manners of the present invention or make equivalent substitutions, and any modification or equivalent substitution without departing from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.
Claims
1. A method for analyzing multiphase and multicomponent flow laws of CO2 injection in shale oil reservoirs considering fluid confined phase change, characterized in that: The process includes the following: Through molecular simulation experiments, the relationship between shale pore size, pore wall and confinement effect is obtained using the basic parameters of the target shale reservoir. According to the relationship between shale pore size, pore wall and confinement effect, the mole fraction and composition of each phase in the shale oil-CO2 system under confinement phase transition are obtained; Based on the multiphase and multicomponent flow theory, combined with the mole fraction and composition of each phase in the shale oil-CO2 system under confined phase change, a multiphase and multicomponent flow model for CO2 injection in shale reservoirs considering fluid confined phase change is constructed. The characteristic line method is used to obtain the multi-phase and multi-component flow velocity and flow direction of CO2 injection in shale reservoirs by considering the multi-phase and multi-component flow model of CO2 injection in shale reservoirs with fluid confined phase change. Based on the flow velocity and direction of multi-phase and multi-component during CO2 injection into shale oil reservoirs, combined with jump conditions, entropy conditions and velocity constraints, a multi-phase and multi-component flow path solution model for the shale oil-CO2 system with confined phase transition is obtained. Based on the multiphase and multicomponent flow path solution model of shale oil-CO2 system with confined phase change, the multiphase and multicomponent flow laws during CO2 injection in the target shale oil reservoir are obtained.
2. The method for analyzing multiphase and multicomponent flow rules of CO2 injection into shale oil reservoirs considering fluid confined phase change according to claim 1 is characterized in that: The basic parameters of the target shale reservoir include: shale pore size distribution, shale mineral composition and shale oil components.
3. The method for analyzing multiphase and multicomponent flow rules of CO2 injection into shale oil reservoirs considering fluid confined phase change according to claim 1 is characterized in that: The pore walls consist of quartz, kaolinite and kerogen.
4. The method for analyzing multiphase and multicomponent flow rules of CO2 injection into shale oil reservoirs considering fluid confined phase change according to claim 1 is characterized in that: The relationship between shale pore size, pore wall and confinement effect includes the relationship equation between shale pore size, pore wall and capillary force and adsorption amount of shale oil-CO2 system; Based on the relationship equation between shale pore size, pore wall and capillary force and adsorption amount of shale oil-CO2 system, combined with thermodynamic phase equilibrium theory, a fluid confined phase transition model of shale oil-CO2 system is constructed. According to the fluid confined phase transition model of shale oil-CO2 system, the molar fraction and composition of each phase in the shale oil-CO2 system under confined phase transition are obtained.
5. The method for analyzing multiphase and multicomponent flow rules of CO2 injection into shale oil reservoirs considering fluid confined phase change according to claim 4 is characterized in that: The gas phase mole fraction of the shale oil-CO2 system during the fluid confined phase transition under confined phase transition is as follows: in, 𝜆 V is the gas phase mole fraction; N is the total number of components; It is a component i The total mole fraction of is the gas-liquid equilibrium constant; Vapor-liquid equilibrium constant Calculated by the following formula: in, and The components are i Fugacity coefficients in the liquid and gas phases; P L and P V are the liquid and gas phase pressures, respectively; The compositions of each phase in the shale oil-CO2 system fluid during confined phase transition are as follows: in, and The components i The mole fractions in the liquid and vapor phases.
6. The method for analyzing multiphase and multicomponent flow rules of CO2 injection into shale oil reservoirs considering fluid confined phase change according to claim 1 is characterized in that: The multiphase and multicomponent flow model of CO2 injection in shale oil reservoirs is as follows: in, ; It is a component i exist j Mole fraction of the phase; for j phase mole fraction; It is a component i The total volume fraction of is the dimensionless length; is the dimensionless time of injection into the pore volume; the matrix A is a function of the total components; is the number of components.
7. The method for analyzing multiphase and multicomponent flow rules of CO2 injection into shale oil reservoirs considering fluid confined phase change according to claim 1 is characterized in that: The multiphase and multicomponent flow laws during CO2 injection in the target shale oil reservoir include: the multiphase and multicomponent flow laws considering the influence of confinement effect on fluid phase change and the multiphase and multicomponent flow laws considering the confined phase change of fluid in the same pore size.
8. A multi-phase and multi-component flow law analysis system for CO2 injection into shale oil reservoirs considering fluid confined phase change, characterized in that: include: The first data processing module is used to obtain the relationship between shale pore size, pore wall and confinement effect by using the basic parameters of the target shale reservoir obtained through molecular simulation experiments; The second data processing module is used to obtain the mole fraction and composition of each phase of the shale oil-CO2 system under confined phase transition according to the relationship between shale pore size, pore wall and confinement effect; The first model building module is used to build a multiphase and multicomponent flow model for CO2 injection in shale oil reservoirs considering fluid confined phase change based on the multiphase and multicomponent flow theory and the mole fraction and composition of each phase in the shale oil-CO2 system under confined phase change; The third data processing module is used to obtain the multi-phase and multi-component flow velocity and flow direction of CO2 injection into shale oil reservoirs by using the characteristic line method and the multi-phase and multi-component flow model of CO2 injection into shale oil reservoirs considering the phase change of fluid confinement; The second model building module is used to obtain a multi-phase and multi-component flow path solution model of the shale oil-CO2 system with confined phase change based on the flow velocity and flow direction of multi-phase and multi-component when injecting CO2 into shale oil reservoirs, combined with jump conditions, entropy conditions and velocity constraints; The fourth data processing module is used to solve the multiphase and multicomponent flow path model of the shale oil-CO2 system based on confined phase change, and obtain the multiphase and multicomponent flow law during the CO2 injection process in the target shale oil reservoir.
9. An electronic device, characterized in that: include: one or more processors; a storage device having one or more programs stored thereon; When the one or more programs are executed by the one or more processors, the one or more processors implement the multi-phase and multi-component flow law analysis method for CO2 injection into shale oil reservoirs considering fluid confined phase change as described in any one of claims 1-7.
10. A storage medium, characterized in that: A computer program is stored thereon, wherein when the computer program is executed by a processor, the method for analyzing multi-phase and multi-component flow laws of CO2 injection in shale oil reservoirs considering fluid confined phase change as described in any one of claims 1 to 7 is implemented.