Method, device and equipment for predicting displacement effect of shale oil reservoir and medium
By constructing a three-phase displacement model of CO2-oil-water at the pore scale in shale oil reservoirs using the phase-field method, the problem of three-phase flow and displacement behavior of CO2-oil-water in shale oil reservoirs was solved, thereby improving the recovery rate of shale oil.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- PETROCHINA CO LTD
- Filing Date
- 2024-11-04
- Publication Date
- 2026-05-08
AI Technical Summary
Existing technologies are insufficient to effectively predict the three-phase flow and displacement behavior of CO2-oil-water in shale oil reservoirs, resulting in high difficulty in shale oil development and low recovery rates.
A three-phase displacement model of carbon dioxide, oil, and water at the pore scale in shale oil was constructed using the phase field method. By obtaining the volume fraction and capillary pressure of each phase, a momentum conservation equation was established, and the fluid velocity and mixture density were calculated to predict the three-phase displacement effect.
It enables efficient prediction of three-phase displacement effects in shale oil under conditions of extremely low permeability and non-connected pores, thereby improving the recovery rate of shale oil.
Smart Images
Figure CN121997786A_ABST
Abstract
Description
Technical Field
[0001] This disclosure belongs to the field of shale oil displacement technology, and specifically relates to a method, apparatus, equipment and medium for predicting the displacement effect of shale oil reservoirs. Background Technology
[0002] Shale oil, as an abundant unconventional energy source, is crucial for ensuring energy supply through effective development. However, the reservoir properties of shale oil differ significantly from those of conventional reservoirs. Shale reservoirs have very small pore sizes, primarily composed of nanopores. Due to the narrow flow channels within these nanopores, fluid transport behavior is easily influenced by the pore wall surface. This makes the effective development of shale oil reservoirs more challenging compared to conventional oil and gas reservoirs. To improve shale oil recovery, carbon dioxide flooding technology has received widespread attention and research in recent years. By injecting carbon dioxide into the formation, crude oil viscosity is effectively reduced, displacement efficiency is improved, and thus oil and gas production is increased.
[0003] In shale oil reservoirs, the presence of micropores makes the three-phase flow and displacement behavior of CO2-oil-water highly complex, affecting overall recovery efficiency. To achieve effective development of shale oil reservoirs, it is urgent to elucidate the CO2 displacement mechanism at the nanoscale. Due to extremely low permeability and the lack of pore connectivity, core displacement experiments are difficult to conduct. Therefore, developing an efficient and accurate predictive method for the three-phase displacement behavior of CO2-oil-water within the micropores of shale oil is of great significance for improving shale oil recovery. Summary of the Invention
[0004] In view of the above problems, this disclosure proposes a method, apparatus, equipment and medium for predicting the displacement effect of shale oil reservoirs, which can predict the three-phase displacement effect of shale oil through modeling for small-pore shale oil reservoirs.
[0005] The technical solution provided in this disclosure is as follows:
[0006] This disclosure provides a method for predicting the displacement effect of shale oil reservoirs, including:
[0007] The volume fraction and capillary pressure of each phase in the three phases of carbon dioxide, oil and water were obtained, and a three-phase displacement model of carbon dioxide, oil and water at the pore scale of shale oil was constructed by the phase field method.
[0008] A simulation domain is drawn based on the pore size distribution of shale oil reservoirs. The simulation domain is then meshed and initial and boundary conditions are set.
[0009] The displacement behavior of nanoporous shale oil under three-phase displacement was calculated, and the three-phase displacement effect was predicted based on the displacement behavior of nanoporous shale oil under three-phase displacement.
[0010] Furthermore, the construction of the three-phase displacement model of carbon dioxide, oil, and water at the pore scale of shale oil using the phase-field method includes:
[0011] Establish the momentum conservation equations for a three-phase fluid consisting of carbon dioxide, oil, and water;
[0012] Among them, the momentum conservation equation between fluid surface tension and volume force and fluid velocity and density is established.
[0013] Furthermore, the flow velocity of the three-phase fluid during displacement in the same shale reservoir pore size is determined based on the momentum conservation equation.
[0014] Furthermore, the construction of the three-phase displacement model of carbon dioxide, oil, and water at the pore scale of shale oil using the phase-field method includes:
[0015] The density of a mixture of carbon dioxide, oil, and water is determined based on the volume fraction and density of each phase.
[0016] Furthermore, the construction of the three-phase displacement model of carbon dioxide, oil, and water at the pore scale of shale oil using the phase-field method also includes:
[0017] The viscosity of a mixture of carbon dioxide, oil, and water is determined by the volume fraction and viscosity of each phase in the three phases of carbon dioxide, oil, and water.
[0018] Furthermore, the construction of the three-phase displacement model of carbon dioxide, oil, and water at the pore scale of shale oil using the phase-field method includes:
[0019] The free energy of the three-phase displacement model is defined as a function of the phase field variables;
[0020] The volume force is determined based on the surface tension coefficient of each phase interface, the additional free volume energy parameter, and the capillary parameters of each phase.
[0021] Furthermore, the method also includes:
[0022] The chemical potential of each phase in the three phases of carbon dioxide, oil, and water is determined based on the aforementioned three-phase displacement model.
[0023] The surface tension applied to the pores of shale oil by fluid forces is calculated based on chemical potential.
[0024] Based on the same inventive concept, another aspect of this disclosure provides a device for predicting the displacement effect of shale oil reservoirs, comprising:
[0025] The model building unit is used to obtain the volume fraction and capillary pressure of each phase in the three phases of carbon dioxide, oil and water, and to construct a three-phase displacement model of carbon dioxide, oil and water at the pore scale of shale oil using the phase field method.
[0026] The condition setting unit is used to draw a simulation domain based on the pore size distribution of shale oil reservoirs, perform meshing of the simulation domain, and set initial and boundary conditions.
[0027] The calculation and prediction unit is used to calculate the displacement behavior of nanoporous shale oil under three-phase displacement mode, and predict the three-phase displacement effect based on the displacement behavior of nanoporous shale oil under three-phase displacement mode.
[0028] Based on the same inventive concept, another aspect of the present disclosure provides an electronic device, including: a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other through the communication bus;
[0029] Memory, which stores computer programs;
[0030] A method for predicting the displacement effect of shale oil reservoirs when the processor executes a program stored in memory.
[0031] Based on the same inventive concept, this disclosure also provides, in another aspect, a computer-readable storage medium storing a computer program, which, when executed by a processor, realizes a method for predicting the displacement effect of shale oil reservoirs.
[0032] The above-described one or more technical solutions in the embodiments of this disclosure have at least the following technical effects:
[0033] This application constructs a shale oil pore-scale three-phase displacement model by obtaining the volume fraction and capillary pressure of each phase (carbon dioxide, oil, and water) using the phase-field method. A simulation domain is drawn based on the pore size distribution of the shale oil reservoir, and meshes are generated for this domain, with initial and boundary conditions set. The displacement behavior of nanoporous shale oil under the three-phase displacement method is calculated, and the three-phase displacement effect is predicted based on this behavior. Therefore, it is possible to predict the three-phase displacement effect of shale oil in small-pore shale reservoirs through modeling, solving the problem of difficult shale oil development under extremely low permeability and pore discontinuity, thereby improving the efficiency of shale oil displacement development.
[0034] Other features and advantages of this disclosure will be set forth in the following description and will be apparent in part from the description or may be learned by practicing the disclosure. The objects and other advantages of this disclosure may be realized and obtained by means of the structures pointed out in the description and the accompanying drawings. Attached Figure Description
[0035] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0036] Figure 1 A flowchart of a method for predicting the displacement effect of shale oil reservoirs is shown;
[0037] Figure 2 A schematic diagram of a device for predicting the displacement effect of shale oil reservoirs is shown.
[0038] Figure 3 A schematic diagram of the displacement process in a shale oil reservoir model is shown.
[0039] Figure 4 The diagram shows the evolution of three-phase displacement saturation calculated by the model.
[0040] Figure 5 A schematic diagram of an electronic device is shown. Detailed Implementation
[0041] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.
[0042] It should be noted that the terms "first," "second," etc., used in this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," "longitudinal," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings.
[0043] This disclosure provides, in one aspect, a method for predicting the displacement effect in shale oil reservoirs, see [link to relevant documentation]. Figure 1 ,include:
[0044] S101: Obtain the volume fraction and capillary pressure of each phase in the three phases of carbon dioxide, oil, and water, and construct a three-phase displacement model of carbon dioxide, oil, and water at the pore scale of shale oil using the phase field method.
[0045] S102: Draw a simulation domain based on the pore size distribution of shale oil reservoirs, and perform meshing and set initial and boundary conditions for the simulation domain;
[0046] S103: Calculate the displacement behavior of nanoporous shale oil under three-phase displacement, and predict the three-phase displacement effect based on the displacement behavior of nanoporous shale oil under three-phase displacement.
[0047] It should be noted that this application establishes a three-phase displacement model for shale oil at the pore scale based on the phase-field method. The three-phase displacement referred to in this application is the displacement of shale oil by carbon dioxide, oil, and water. Whether described verbally or by chemical formula, carbon dioxide refers to the same substance. The phase-field method used in this application uses differential equations to represent the combined effects of diffusion, ordering potential, and thermodynamic driving forces with specific physical mechanisms. These equations are solved through computer programming to obtain the instantaneous state of the studied system in time and space. It is used to simulate the microstructure of materials, especially describing the arrangement and potential defects of different phases at the nanometer and micrometer scales. It is suitable for describing boundary motions during phase transitions, such as the melting of solids. Compared to traditional sharp interface models, the phase-field method avoids some of the problems associated with sharp interface models. The phase-field method is a simulation method that mainly uses continuous variables to simulate discontinuous phenomena, and has the advantages of simple algorithms and powerful functionality.
[0048] Specifically, in step S101, the construction of a three-phase displacement model of carbon dioxide, oil, and water at the pore scale of shale oil using the phase field method includes:
[0049] Establish the momentum conservation equations for a three-phase fluid consisting of carbon dioxide, oil, and water;
[0050] Among them, the momentum conservation equation between fluid surface tension and volume force and fluid velocity and density is established.
[0051] Specifically, the momentum conservation equation for the CO2-oil-water three-phase fluid is expressed as follows:
[0052]
[0053] Where ρ is density; u is velocity; p is pressure; σ is dynamic viscosity; T is temperature; F st is the surface tension; F is the volume force.
[0054] The flow velocity of the three-phase fluid during displacement in the same pore size of shale reservoir is determined based on the momentum conservation equation.
[0055] In some specific embodiments, the construction of a three-phase displacement model of carbon dioxide, oil, and water at the pore scale of shale oil using the phase field method includes:
[0056] The density of a mixture of carbon dioxide, oil, and water is determined based on the volume fraction and density of each phase.
[0057] Specifically, the CO2-oil-water three-phase field model can be described as follows:
[0058]
[0059] In the formula ∑ represents the volume fraction of each phase; i n represents the capillary pressure of each phase; i ε is the chemical potential; M0 is the molecular mobility parameter; ε is the parameter that determines the interface thickness.
[0060] The construction of a three-phase displacement model of carbon dioxide, oil, and water at the pore scale in shale oil using the phase field method also includes:
[0061] The viscosity of a mixture of carbon dioxide, oil, and water is determined by the volume fraction and viscosity of each phase in the three phases of carbon dioxide, oil, and water.
[0062] Specifically, the density and viscosity of a CO2-oil-water three-phase mixture are defined as follows:
[0063]
[0064] Where ρ is density; denoted as volume fraction; μ represents dynamic viscosity.
[0065] In some specific embodiments, the construction of a three-phase displacement model of carbon dioxide, oil, and water at the pore scale of shale oil using the phase field method includes:
[0066] The free energy of the three-phase displacement model is defined as a function of the phase field variables;
[0067] The volume force is determined based on the surface tension coefficient of each phase interface, the additional free volume energy parameter, and the capillary parameters of each phase.
[0068] Specifically, the free energy of a CO2-oil-water three-phase system is defined as a function of the phase field variables:
[0069]
[0070] In the formula σ ij is the surface tension coefficient of the interface between phase i and phase j; ∧ is a parameter specifying the additional free volume energy.
[0071] The capillary parameters for each phase are defined as follows:
[0072] ∑ A =σ AB +σAC -σ BC
[0073] ∑ B =σ AB +σ BC -σ AC
[0074] ∑ C =σ AC +σ BC -σ AB
[0075]
[0076] Furthermore, the method also includes:
[0077] The chemical potential of each phase in the three phases of carbon dioxide, oil, and water is determined based on the aforementioned three-phase displacement model.
[0078] The surface tension applied to the pores of shale oil by fluid forces is calculated based on chemical potential.
[0079] Specifically, the surface tension applied as a physical force is calculated based on the chemical potential:
[0080]
[0081] This application establishes a three-phase displacement model of CO2-oil-water at the pore scale for shale oil based on the phase-field method. Subsequently, a simulation domain is drawn according to the pore size distribution of the shale reservoir, and meshing, initial conditions, and boundary conditions are set. Finally, the displacement behavior of shale oil within nanopores under different displacement methods (water drive, CO2 drive) is calculated. For details of the working process, please refer to [link to relevant documentation]. Figure 3 Three-phase displacement fluid is injected into the pores to allow shale oil to flow out. The reservoir model used in this embodiment is as follows: Figure 3 As shown, the simulation domain has a width of 5 nm and a horizontal length of 15 nm. Initially, the simulation domain is filled with shale oil, and water is injected from the left boundary at a rate of 0.01 m / s. After 1.26 s, water injection stops, and CO2 is injected from the left boundary at a rate of 0.01 m / s.
[0082] For details on the displacement effects under different displacement methods, please refer to Figure 4 A schematic diagram illustrating the evolution of CO2, oil, and water saturation during water flooding and CO2 flooding processes. This demonstrates that water saturation exhibits characteristics similar to both carbon dioxide and oil saturation.
[0083] Based on the same inventive concept, another aspect of this disclosure provides a device for predicting the displacement effect of shale oil reservoirs, see [link to relevant documentation]. Figure 2 ,include:
[0084] Model 201 was established to obtain the volume fraction and capillary pressure of each phase in the three phases of carbon dioxide, oil and water. A three-phase displacement model of carbon dioxide, oil and water at the pore scale of shale oil was constructed by the phase field method.
[0085] The condition setting unit 202 is used to draw a simulation domain according to the pore size distribution of shale oil reservoirs, perform meshing for the simulation domain, and set initial and boundary conditions.
[0086] The calculation and prediction unit 203 is used to calculate the displacement behavior of nanoporous shale oil under the three-phase displacement mode, and predict the three-phase displacement effect based on the displacement behavior of nanoporous shale oil under the three-phase displacement mode.
[0087] Based on the same inventive concept, this disclosure also provides an electronic device 161, see [link to previous document]. Figure 5 It includes a processor 164, a communication interface 165, a memory 162, and a communication bus, wherein the processor 164, the communication interface 165, and the memory 162 communicate with each other through the communication bus;
[0088] Memory 162 stores computer program 163;
[0089] When processor 164 executes the program stored in memory 162, it implements a method for predicting the displacement effect of shale oil reservoirs.
[0090] The aforementioned communication bus can be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus, etc. This communication bus can be divided into address bus, data bus, control bus, etc.
[0091] The communication interface 165 is used for communication between the aforementioned electronic device 161 and other devices.
[0092] The memory 162 may include random access memory (RAM) or non-volatile memory, such as at least one disk storage device. Optionally, the memory 162 may also be at least one storage device located remotely from the aforementioned processor 164.
[0093] The processor 164 mentioned above can be a general-purpose processor 164, including a central processing unit (CPU), a network processor 164 (NP), etc.; it can also be a digital signal processor 164 (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.
[0094] Based on the same inventive concept, another aspect of the present disclosure provides a computer-readable storage medium storing a computer program 163, which, when executed by a processor 164, implements a method for predicting the displacement effect of shale oil reservoirs.
[0095] The computer-readable storage medium may be included in the device / apparatus described in the above embodiments; or it may exist independently and not assembled into the device / apparatus. The computer-readable storage medium carries one or more programs that, when executed, implement the method for predicting the displacement effect of shale oil reservoirs according to embodiments of this disclosure.
[0096] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.
Claims
1. A method for predicting the displacement effect of shale oil reservoirs, characterized in that, include: The volume fraction and capillary pressure of each phase in the three phases of carbon dioxide, oil and water were obtained, and a three-phase displacement model of carbon dioxide, oil and water at the pore scale of shale oil was constructed by the phase field method. A simulation domain is drawn based on the pore size distribution of shale oil reservoirs. The simulation domain is then meshed and initial and boundary conditions are set. The displacement behavior of nanoporous shale oil under three-phase displacement was calculated, and the three-phase displacement effect was predicted based on the displacement behavior of nanoporous shale oil under three-phase displacement.
2. The method according to claim 1, characterized in that, The construction of a three-phase displacement model of carbon dioxide, oil, and water at the pore scale in shale oil using the phase-field method includes: Establish the momentum conservation equations for a three-phase fluid consisting of carbon dioxide, oil, and water; Among them, the momentum conservation equation between fluid surface tension and volume force and fluid velocity and density is established.
3. The method according to claim 2, characterized in that, The flow velocity of the three-phase fluid during displacement in the same pore size of shale reservoir is determined based on the momentum conservation equation.
4. The method according to claim 2, characterized in that, The construction of a three-phase displacement model of carbon dioxide, oil, and water at the pore scale in shale oil using the phase-field method includes: The density of a mixture of carbon dioxide, oil, and water is determined based on the volume fraction and density of each phase.
5. The method according to claim 4, characterized in that, The construction of a three-phase displacement model of carbon dioxide, oil, and water at the pore scale in shale oil using the phase field method also includes: The viscosity of a mixture of carbon dioxide, oil, and water is determined by the volume fraction and viscosity of each phase in the three phases of carbon dioxide, oil, and water.
6. The method according to claim 5, characterized in that, The construction of a three-phase displacement model of carbon dioxide, oil, and water at the pore scale in shale oil using the phase-field method includes: The free energy of the three-phase displacement model is defined as a function of the phase field variables; The volume force is determined based on the surface tension coefficient of each phase interface, the additional free volume energy parameter, and the capillary parameters of each phase.
7. The method according to any one of claims 1 to 6, characterized in that, The method further includes: The chemical potential of each phase in the three phases of carbon dioxide, oil, and water is determined based on the aforementioned three-phase displacement model. The surface tension applied to the pores of shale oil by fluid forces is calculated based on chemical potential.
8. A device for predicting the displacement effect of shale oil reservoirs, characterized in that, include: The model building unit is used to obtain the volume fraction and capillary pressure of each phase in the three phases of carbon dioxide, oil and water, and to construct a three-phase displacement model of carbon dioxide, oil and water at the pore scale of shale oil using the phase field method. The condition setting unit is used to draw a simulation domain based on the pore size distribution of shale oil reservoirs, perform meshing of the simulation domain, and set initial and boundary conditions. The calculation and prediction unit is used to calculate the displacement behavior of nanoporous shale oil under three-phase displacement mode, and predict the three-phase displacement effect based on the displacement behavior of nanoporous shale oil under three-phase displacement mode.
9. An electronic device, characterized in that, include: The processor, communication interface, memory, and communication bus are connected, with the processor, communication interface, and memory communicating with each other via the communication bus. Memory, which stores computer programs; When the processor executes the program stored in the memory, it implements the method for predicting the displacement effect of shale oil reservoirs as described in any one of claims 1 to 7.
10. A computer-readable storage medium, characterized in that, The system contains a computer program that, when executed by a processor, implements the method for predicting the displacement effect of shale oil reservoirs as described in any one of claims 1 to 7.