Critical path-based oil-water two-phase flow model construction method and system, and medium

Abstract

The application discloses a critical path-based oil-water two-phase seepage model construction method and system and a medium, relates to the oil and gas field development technical field, and combines traditional black oil model simulation technology and critical radius technology based on critical path seepage theory, proposes an oil-water two-phase seepage characteristic oil reservoir simulation method considering microscale critical paths on the basis of ensuring the scale of the oil reservoir model, restores micro characteristics such as internal pore throat structures of real reservoir rocks to the maximum extent by using the critical radius, and studies factors such as the influence of the dominant channel (critical path) of oil-water two-phase fluid seepage in the pore throat and displacement efficiency on the phenomenon from the micro perspective, so that higher-precision oil reservoir simulation analysis results are obtained; the scheme directly calculates the flow and pressure of each component of oil and water based on the critical radius and the critical path length, does not need to input a static oil-water relative permeability curve in the simulation process, and can more directly reflect the stress state and change process of each part of the oil reservoir.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development technology, specifically to a method, system, and medium for constructing an oil-water two-phase flow model based on a critical path. Background Technology

[0002] Petroleum is an indispensable strategic resource for a nation's survival and development. Maximizing the extraction of underground energy and transforming it into a driving force for economic development is of paramount importance and occupies a crucial position in national energy planning. After years of research, reservoir development methods have matured. Researchers largely employ numerical simulation methods to reduce development costs and formulate reasonable development plans and provide scientific guidance based on simulation results. Reservoir numerical simulation refers to using models to study the dynamic changes of reservoirs, including physical simulation and mathematical (numerical) simulation. Physical simulation refers to laboratory studies of reservoir development dynamics, while the main principle of reservoir numerical simulation is to use partial differential equations to describe the reservoir's exploitation state and obtain changes in development indicators through computer numerical solutions. Reservoir numerical simulation can consider the dynamic impacts of reservoir geometry, heterogeneity, changes in rock and fluid properties, well pattern, and production, making it the method that considers the most factors to date in reservoir dynamics research and a crucial tool in reservoir development research. The main characteristic of numerical simulation is the analysis and prediction of development dynamics through simulation analysis of fluid and energy distribution within the reservoir.

[0003] In actual oil production, the application of oil-water two-phase models is crucial because they can accurately describe and predict the complex flow behavior of oil and water in reservoirs. By constructing mathematical models and employing numerical simulation techniques, these models can simulate dynamic changes such as water-driven oil recovery and oil-water front advancement. This provides a scientific basis for formulating and optimizing oilfield development plans, evaluating submersible pump performance, optimizing oil-water separation technology, and conducting reservoir dynamic monitoring and analysis, thereby effectively improving oilfield recovery and economic benefits.

[0004] Traditional black oil models employ a simplified two-phase flow model to simulate oil and water flow within reservoirs. While widely used as a fundamental tool in reservoir simulation, this model has several limitations in actual oil production: it neglects the heterogeneity of reservoir rocks; the geological heterogeneity, fractures, and small-scale characteristics of the reservoir are typically simplified using a grid (with side lengths usually tens of meters), failing to accurately describe actual reservoir conditions. Furthermore, it cannot directly consider the influence of microscopic factors such as rock pore throat characteristics and dynamic multiphase fluid flow characteristics at the pore scale (micrometers, centimeters) on the macroscopic flow process. Additionally, due to the simplification of complex flow mechanisms, such as gravity effects in multiphase flow, the handling of these complex mechanisms is rather coarse. Furthermore, traditional black oil models require static oil-water relative permeability curves for multiphase flow simulation. These curves describe the stress state of each grid point, including oil-water content, viscosity, and capillary forces, and are used to calculate grid conductivity. However, in actual flow, the oil-water relative permeability curve is dynamic, changing with time and fluid position. Therefore, the relative permeability curves input by traditional simulation methods have certain limitations. These limitations restrict the use of traditional black oil models under complex reservoir conditions. Summary of the Invention

[0005] The technical problem this invention aims to solve is that traditional oil-water two-phase flow models in black oil models rely on relative permeability curves for construction. However, in actual flow processes, the relative permeability curve of oil and water is dynamic data that changes dynamically with time and fluid position, resulting in significant application defects in oil-water two-phase flow models constructed by traditional simulation methods. The purpose of this invention is to provide a method, system, and medium for constructing an oil-water two-phase flow model based on a critical path. This method addresses the dynamic pore fluid pressure, gravity, and capillary force stress states of each grid (spatial location) in the reservoir during oil-water two-phase flow. It can directly calculate the flow rate and pressure of each oil and water component based on the critical radius and critical path length. The simulation process no longer requires inputting static relative permeability curves, and can more directly reflect the stress state and changes in various parts of the reservoir. The calculation results can directly reflect the pressure wave range, the spatial position and movement state of the oil-water two-phase fluid interface.

[0006] This invention is achieved through the following technical solution:

[0007] This solution provides a method for constructing an oil-water two-phase flow model based on the critical path, including:

[0008] Based on nuclear magnetic resonance logging technology and critical path flow theory, a critical radius model for the flow process of oil-water two-phase fluids is established.

[0009] Based on the critical radius model and under the equivalent assumptions, an oil-water two-phase numerical model applicable to the single-well scale of an oil reservoir is established.

[0010] Solving the numerical model of the oil-water two-phase system yields simulation results of the phase displacement between the oil and water.

[0011] The working principle of this scheme: Traditional black oil models rely on relative permeability curves for oil-water two-phase flow models. However, in actual flow processes, the relative permeability curves of oil and water are dynamic data that change dynamically with time and fluid position. This leads to significant application defects in oil-water two-phase flow models constructed by traditional simulation methods. The purpose of this invention is to provide a method, system, and medium for constructing oil-water two-phase flow models based on critical paths. Combining the advantages of traditional black oil model simulation technology and critical radius technology based on critical path theory, this invention proposes a reservoir simulation method that considers microscale critical paths for oil-water two-phase flow characteristics while ensuring the scale of the reservoir model. This method can utilize the critical radius to restore the microscopic features such as the pore throat structure inside the real reservoir rock to the greatest extent. It can also study the critical path (dominant channel) and displacement efficiency factors of oil-water two-phase fluid flow inside the pore throat from a microscopic perspective, thereby obtaining higher accuracy reservoir simulation analysis results. Furthermore, this invention addresses the dynamic pore fluid pressure, gravity, and capillary force stress states of each grid (spatial location) in the reservoir during oil-water two-phase flow. It can directly calculate the flow rate and pressure of each oil-water component based on the critical radius and critical path length. The simulation process no longer requires inputting static oil-water relative permeability curves, and can more directly reflect the stress state and changes in each part of the reservoir. The calculation results can directly reflect the pressure wave range, the spatial location and movement state of the oil-water two-phase fluid interface.

[0012] A further optimization scheme involves establishing a critical radius model based on nuclear magnetic resonance logging technology and critical path seepage theory, including the following methods:

[0013] Construct a well location grid model and calculate the permeability and porosity of each grid.

[0014] Based on the critical path seepage theory, a critical radius model for the oil-water two-phase fluid flow process is constructed by considering the actual rock pore throat characteristics and seepage channel characteristics in the well location grid model; the critical radius model includes:

[0015] The critical radius r between grids i and j cij for:

[0016]

[0017] Where, k ij m represents the permeability between adjacent grids i and j. 2 ;φ ij τ represents the porosity between adjacent grids i and j, dimensionless; τ represents the tortuosity, dimensionless; σz This represents the coefficient of variation of rock heterogeneity, and is dimensionless.

[0018] A further optimized solution is that the equivalent assumptions include:

[0019] a. In the critical radius model, the critical path is the main channel for fluid seepage, and the pressure drop generated by fluid flow mainly occurs in the critical path;

[0020] b. In the critical path, there is only one two-phase fluid interface between the oil and water phases.

[0021] c. The two fluids flowing in the network are immiscible;

[0022] d, Piston-like displacement occurs in the critical path.

[0023] A further optimization scheme involves establishing a numerical model of the oil-water two-phase system suitable for a single well scale in an oil reservoir, based on the aforementioned critical radius model and under equivalent assumptions; including the following methods:

[0024] Calculate the equivalent capillary force p of the reservoir grid caused by the oil-water interface within the critical path. cij (Unit: Pa): p cij =2γcosθ / r cij ; where r cij γ represents the critical radius of the critical path between grid i and grid j, in meters; γ represents the interfacial tension between the oil and water phases, in N / m; θ represents the wetting angle, in degrees.

[0025] The conductivity of the oil-water two-phase fluid between any two grids is calculated based on the critical path.

[0026] Obtain the effective viscosity and density of the oil-water two-phase fluid in the critical path between reservoir grids;

[0027] Based on the critical radius, the conductivity, effective viscosity, and density are input into the mass conservation equation to construct the differential equations for the flow rate and pressure diffusion of the oil-water two-phase system.

[0028] A numerical model of the oil-water two-phase system was obtained by numerically simulating the differential equations for flow rate and pressure diffusion.

[0029] A further optimization scheme involves calculating the conductivity of the oil-water two-phase fluid between any two grids based on the critical path; including the following method:

[0030] When oil and water coexist in the critical path between grid i and grid j, the conductivity ξ of the oil-water two-phase fluid within the equivalent capillary force of the reservoir grid is... ij [Unit: m] 3 / (Pa·s)] is:

[0031]

[0032] Then the pressure difference Δp between grid i and grid j ij Flow rate q of the oil-water two-phase mixture at (unit Pa) ij (unit: m) 3 / s) flow satisfies:

[0033]

[0034] Δp ij =p i -p j -p cij ;

[0035] Where, p i =p oi +ρ ow gZ i p oi Let ρ be the pore pressure of grid i, in Pa; ow For the density of the mixed fluid, kg / m³ 3 g is the acceleration due to gravity, 9.8 m / s². 2 ;p j =p oj +ρ ow gZ j p oj Z represents the pore pressure of grid j, in Pa; i Z is the vertical height of grid i, in meters. j Vertical height of grid j, m; p cij Reservoir grid equivalent capillary force, Pa; τ is tortuosity, dimensionless; l ij Let m be the grid side length; cij Effective porosity, dimensionless; r cij Let m be the critical radius; η be the η value. eff The effective viscosity of the mixed fluid is expressed in Pa·s.

[0036] A further optimized scheme involves obtaining the effective viscosity and density of the oil-water two-phase fluid in the critical path between reservoir grids; including the following method:

[0037] The effective viscosity η of the oil-water two-phase fluid in the critical path between reservoir grids is calculated using the following formula. eff :

[0038] η eff =B w μ w X ij +B o μ o (1-X ij )

[0039] Among them Bw B represents the volume coefficient of water, which is dimensionless; o μ represents the volume coefficient of oil and is dimensionless. w The viscosity of water is expressed in Pa·s; μ. o X represents the viscosity of oil, Pa·s; ij Denotes a dimensionless number related to the position of the oil-water interface, (0≤X) ij ≤1), which is the position of the concave meniscus divided by the length of the entire critical path;

[0040] The density ρow of the oil-water two-phase fluid in the critical path between reservoir grids is calculated using the following formula: ρ ow =ρ w X ij +ρ o (1-X ij );

[0041] Where, ρ w ρ represents the density of water. o This indicates the density of the oil.

[0042] A further optimized scheme, based on the mass conservation equation, includes the following differential equations for the oil-water two-phase flow rate and pressure diffusion:

[0043]

[0044] Where i represents any number from 1 to N, and N represents the total number of grid cells. m represents the conductivity between two adjacent grids i and j. 3 / (Pa·s); Δp ij The pressure difference between grid i and grid j is expressed in Pa; ψ = φ c0i V bi C tow ;φ c0i V represents the initial porosity of grid i, dimensionless; bi m represents the volume of grid i. 3 Δt is the simulation time step, in seconds; Δp i This represents the change in pressure at grid i over time Δt, in Pa and C. tow (Pa -1 C is the combined compressibility coefficient of the oil and water phases. Since the compressibility of oil and water is approximately equal, for the sake of simplifying the calculation, C is used here. tow The value can be the same as the compressibility coefficient of oil or water.

[0045] A further optimization scheme is as follows: the method for solving the oil-water two-phase numerical model to obtain the simulation results of the phase displacement of the oil and water phases includes:

[0046] In conjunction with the oil-water displacement process, during the numerical simulation of the differential equations for flow and pressure diffusion in the oil-water two-phase system, the fluid conductivity of all grids is updated according to the time step to update the movement process and distribution state of the computational interface.

[0047] The pressure and flow rate of different grids are solved, and the global pressure field at different time points is solved by the conjugate gradient method.

[0048] This solution provides a system for constructing an oil-water two-phase flow model based on a critical path. Its key feature is that it is used to implement the aforementioned method for constructing an oil-water two-phase flow model based on a critical path. The system includes:

[0049] The first module is used to establish a critical radius model of the oil-water two-phase fluid flow process based on nuclear magnetic resonance logging technology and critical path flow theory.

[0050] The second module is used to establish an oil-water two-phase numerical model applicable to the single-well scale of the reservoir based on the critical radius model under equivalent assumptions.

[0051] The solver module is used to solve the numerical model of the oil-water two-phase system to obtain the simulation results of the phase displacement of the oil and water two phases.

[0052] This solution also provides a computer-readable medium storing a computer program thereon, which, when executed by a processor, can implement the above-described method for constructing an oil-water two-phase flow model based on a critical path.

[0053] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0054] 1. The present invention provides a method, system, and medium for constructing an oil-water two-phase flow model based on critical paths. Combining the advantages of traditional black oil model simulation technology and critical radius technology based on critical path flow theory, this invention proposes a reservoir simulation method that considers the micro-scale critical path of oil-water two-phase flow characteristics while ensuring the scale of the reservoir model. This method can utilize the critical radius to restore the micro-scale features such as the pore throat structure inside the real reservoir rock to the greatest extent, and can study the critical path (dominant channel) and displacement efficiency of oil-water two-phase fluids in the pore throat from a micro-level perspective, thereby obtaining higher accuracy reservoir simulation analysis results.

[0055] 2. The present invention provides a method, system, and medium for constructing an oil-water two-phase flow model based on a critical path. It addresses the dynamic pore fluid pressure, gravity, and capillary force stress states of each grid (spatial location) in the oil-water two-phase flow process. The flow rate and pressure of each oil-water component can be directly calculated based on the critical radius and critical path length. The simulation process no longer requires inputting static oil-water relative permeability curves, and can more directly reflect the stress state and changes in various parts of the reservoir. The calculation results can directly reflect the pressure wave range, the spatial location of the oil-water two-phase fluid interface, and its movement. Attached Figure Description

[0056] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0057] Figure 1 A schematic diagram of the process for constructing an oil-water two-phase flow model based on the critical path;

[0058] Figure 2 A schematic diagram showing the location of the oil-water interface when water and the two phases coexist in the critical path.

[0059] Figure 3 A schematic diagram of waterflooding simulation at the single-well scale in a water-oil reservoir;

[0060] Figure 4 This is a schematic diagram of oil-drive water simulation at the scale of a single well in an oil reservoir. Detailed Implementation

[0061] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0062] Traditional oil-water two-phase flow models in black oil models rely on relative permeability curves for construction. However, in actual flow processes, the relative permeability curves of oil and water are dynamic data that move and change dynamically with time and fluid position. This results in significant application defects in oil-water two-phase flow models constructed by traditional simulation methods. In view of this, the present invention provides the following embodiments to solve the above-mentioned technical problems.

[0063] Example 1

[0064] This embodiment provides a method for constructing an oil-water two-phase flow model based on the critical path, such as... Figure 1 As shown, it includes:

[0065] Step one: Based on nuclear magnetic resonance logging technology and critical path flow theory, establish a critical radius model for the oil-water two-phase fluid flow process; this step specifically includes the following methods:

[0066] S11, construct the well location grid model and calculate the permeability and porosity of each grid;

[0067] S12, based on the critical path seepage theory, a critical radius model for the oil-water two-phase fluid flow process is constructed by considering the actual rock pore throat characteristics and seepage channel characteristics in the well location grid model; the critical radius model includes:

[0068] The critical radius r between grids i and j cij (Unit: m) is:

[0069]

[0070] Where, k ij m represents the permeability between adjacent grids i and j. 2 ;φ ij τ represents the porosity between adjacent grids i and j, dimensionless; τ represents the tortuosity, dimensionless; σ z This represents the coefficient of variation of rock heterogeneity, and is dimensionless.

[0071] Step two: Based on the critical radius model and under equivalent assumptions, establish an oil-water two-phase numerical model suitable for a single well scale in the reservoir; the equivalent assumptions include:

[0072] a. In the critical radius model, the critical path is the main channel for fluid seepage, and the pressure drop generated by fluid flow mainly occurs in the critical path;

[0073] b. In the critical path, there is only one two-phase fluid interface between the oil and water phases.

[0074] c. The two fluids flowing in the network are immiscible;

[0075] d, Piston-like displacement occurs in the critical path.

[0076] Based on the critical radius model and under equivalent assumptions, an oil-water two-phase numerical model applicable to the single-well scale of an oil reservoir is established; including the following methods:

[0077] S21, Calculate the equivalent capillary force p of the reservoir grid caused by the oil-water interface within the critical path. cij :p cij =2γcosθ / r cij ; where r cij γ represents the critical radius of the critical path between grid i and grid j, in meters; γ represents the interfacial tension between the oil and water phases, in N / m; θ represents the wetting angle, in degrees.

[0078] S22, Calculate the conductivity of the oil-water two-phase fluid between any two grids based on the critical path; including the method:

[0079] When oil and water coexist in the critical path between grids i and j, the conductivity ξ of the oil-water two-phase fluid in the critical path is... ij [unit m] 3 / (Pa·s)] is:

[0080]

[0081] Then the pressure difference Δp between grid i and grid j ij Flow rate q of the oil-water two-phase mixture at (unit Pa) ij (unit: m) 3 / s) flow satisfies:

[0082]

[0083] Δp ij =p i -p j -p cij ;

[0084] Where, p i =p oi +ρ ow gZ i p oi Let ρ be the pore pressure of grid i, in Pa. ow For the density of the mixed fluid, kg / m³ 3 g is the acceleration due to gravity, 9.8 m / s². 2 Z i Let m be the vertical height of grid i; p j =p oj +ρ ow gZ j p oj Let Z be the pore pressure of grid j, in Pa. j Vertical height of grid j, m; p cij The equivalent capillary force of the reservoir grid is Pa; τ is the tortuosity, dimensionless; l ij φ is the grid side length, in meters; ij Effective porosity, dimensionless; r cij Let m be the critical radius; η be the η value. eff The effective viscosity of the mixed fluid is expressed in Pa·s.

[0085] S23, Obtain the effective viscosity and density of the oil-water two-phase fluid in the critical path between reservoir grids; including the following methods:

[0086] The effective viscosity η of the oil-water two-phase fluid in the critical path between reservoir grids is calculated using the following formula. eff :

[0087] η eff =B w μ w X ij +B o μ o (1-X ij )

[0088] Among them B w B represents the volume coefficient of water, which is dimensionless; o μ represents the volume coefficient of oil and is dimensionless. w The viscosity of water is expressed in Pa·s; μ. o X represents the viscosity of oil, Pa·s; ij Denotes a dimensionless number related to the position of the oil-water interface, (0≤X) ij ≤1), which is the location of the concave liquid surface divided by the length of the entire street-facing path;

[0089] The density ρow of the oil-water two-phase fluid in the critical path between reservoir grids is calculated using the following formula: ρ ow =ρ w X ij +ρ o (1-X ij );

[0090] Where, ρ w ρ represents the density of water. o This indicates the density of the oil.

[0091] S24, based on the critical radius, inputs conductivity, effective viscosity, and density into the mass conservation equation to construct the differential equations for flow rate and pressure diffusion in the oil-water two-phase system:

[0092]

[0093] Where i represents any number from 1 to N, and N represents the total number of grid cells. m represents the conductivity between two adjacent grids i and j. 3 / (Pa·s); Δp ij The pressure difference between grid i and grid j is expressed in Pa; ψ = φ c0i V bi C tow ;φ c0i V represents the initial porosity of grid i, dimensionless; bi m represents the volume of grid i. 3 Δt is the simulation time step, in seconds; Δp i This represents the change in pressure at grid i over time Δt, in Pa and C.tow (Pa -1 C is the combined compressibility coefficient of the oil and water phases. Since the compressibility of oil and water is approximately equal, for the sake of simplifying the calculation, C is used here. tow The value can be the same as the compressibility coefficient of oil or water.

[0094] S25, numerical simulation of the differential equations for flow rate and pressure diffusion in the oil-water two-phase system yields a numerical model of the oil-water two-phase system.

[0095] Step 3: Solve the oil-water two-phase numerical model to obtain the simulation results of mutual displacement between the oil and water phases; the simulation results include water-driven oil displacement and oil-driven water displacement. This step specifically includes the following methods:

[0096] S31, combined with the oil-water displacement process, in the process of numerical simulation of the differential equations for flow and pressure diffusion of the oil-water two-phase flow, the fluid conductivity of all grids is updated according to the time step to update the calculation interface movement process and distribution state.

[0097] S32 solves for the pressure and flow rate of different grids, and uses the conjugate gradient method to solve for the global pressure field and oil-water flow rate data at different times.

[0098] For the oil-water displacement process in this scheme, when water acts as the displacing phase to displace oil, the initial oil-water two-phase flow model is entirely filled with oil phase, which is extracted as the displaced phase. The wetting angle of the oil-water two-phase flow model is 150° (oil-wet), and the water phase, as the non-wetting phase, is injected as the displacing phase. When oil acts as the displaced phase, the wetting angle of the oil-water two-phase flow model is 80° (water-wet), and the water phase is extracted as the displaced phase. During the numerical simulation, it is necessary to update the movement process and distribution state of the computational interface according to the time step, and update the fluid conductivity of all grids. The numerical simulation calculation process of oil-water two-phase flow can construct matrix equations at different times based on the law of conservation of mass. The simulation process described in this embodiment is to solve the pressure p of different grids. i With traffic q ij The global pressure field at different times can be solved using the conjugate gradient method. The two-phase flow process continues until the entire equivalent model is filled with infiltrated fluid (or the preset total simulation time is reached). The wellhead injection flow rate or injection pressure remains constant throughout the process. It is important to note that when the critical path between grid i and grid j contains only water, the critical path is marked as 1; when the critical path between grid i and grid j contains only oil, the critical path is marked as 0. The number of critical paths marked as 1 is counted, and divided by the total number of grids to obtain the water drive sweep efficiency E during the water-drive oil process. r Following the steps outlined above, and after visualizing fluid flow using computer language, this scheme achieves waterflooding simulation at the single-well scale of an oil reservoir (e.g., Figure 3 (as shown) and oil-driven water simulation as Figure 4As shown in the figure, the center of the model represents the injection well location, and different colors represent the flow field distribution of the displacing phase fluid. The black area represents the displaced phase that was not displaced. (Comparison) Figure 3 and Figure 4 This can clearly reflect the differences in the displacement process caused by the differences in the properties of oil and water.

[0099] This embodiment combines critical path seepage theory and considers the characteristics of the critical path as an advantageous seepage channel. It can directly reflect the dynamic changes in oil-water saturation during the simulation process and does not require input of capillary pressure curves and relative permeability curves. Through the above steps, a complete process of geological modeling, oil-water two-phase seepage theory model and numerical simulation solution can be established, which directly reflects the sweep range, spatial position and movement state of the oil-water two-phase fluid. Compared with the original black oil model, the simulation results are more reasonable.

[0100] The simulation technique in this embodiment calculates the pressure field distribution in the equivalent model using the implicit finite difference method, and then calculates the location of the two-phase fluid interface and the sweep efficiency. The reservoir model is simple and easy to use, and GPU-accelerated computing technology can be used to improve the number of grids, calculation speed, and simulation accuracy.

[0101] This approach combines reservoir grid models with critical path flow theory, which can greatly increase the model scale while ensuring modeling accuracy, and study the microscopic flow mechanism at the reservoir scale while ensuring the accuracy of simulation results.

[0102] Example 2

[0103] This embodiment provides a system for constructing an oil-water two-phase flow model based on the critical path flow theory, used to implement the oil-water two-phase flow model construction method based on the critical path described in Embodiment 1; the system includes:

[0104] The first module is used to establish a critical radius model for the flow process of oil-water two-phase fluid based on nuclear magnetic resonance logging technology and critical theory.

[0105] The second module is used to establish an oil-water two-phase numerical model applicable to the single-well scale of the reservoir based on the critical radius model under equivalent assumptions.

[0106] The solver module is used to solve the numerical model of the oil-water two-phase system to obtain the simulation results of the phase displacement of the oil and water two phases.

[0107] Example 3

[0108] This embodiment provides a computer-readable medium storing a computer program, which, when executed by a processor, can implement the oil-water two-phase flow model construction method based on critical path as described in Embodiment 1; specifically, the following steps are performed:

[0109] Step 1: Based on nuclear magnetic resonance logging technology and critical path flow theory, establish a critical radius model for the flow process of oil-water two-phase fluids;

[0110] Step 2: Based on the critical radius model and under the equivalent assumptions, establish a numerical model of oil-water two-phase flow suitable for single-well scale in oil reservoirs;

[0111] Step 3: Solve the numerical model of the oil-water two-phase system to obtain the simulation results of the phase displacement of the oil and water.

[0112] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for constructing an oil-water two-phase flow model based on a critical path, characterized in that, include: Based on nuclear magnetic resonance logging technology and critical path flow theory, a critical radius model for the flow process of oil-water two-phase fluids is established. Based on the critical radius model and under the equivalent assumptions, an oil-water two-phase numerical model applicable to the single-well scale of an oil reservoir is established. Solving the numerical model of the oil-water two-phase system yields simulation results of phase displacement between the oil and water phases; Methods for constructing numerical models of oil-water two-phase systems include: Calculate the equivalent capillary force p of the reservoir grid caused by the oil-water interface within the critical path. cij : ; where r cij The critical radius represents the critical path radius between grid i and grid j; γ represents the interfacial tension between the oil and water phases; θ represents the wetting angle. The conductivity of the oil-water two-phase fluid between any two grids is calculated based on the critical path. Obtain the effective viscosity and density of the oil-water two-phase fluid in the critical path between reservoir grids; Based on the critical radius, the conductivity, effective viscosity, and density are input into the mass conservation equation to construct the differential equations for the flow rate and pressure diffusion of the oil-water two-phase system. A numerical model of the oil-water two-phase system was obtained by numerically simulating the differential equations for flow rate and pressure diffusion.

2. The method for constructing an oil-water two-phase flow model based on a critical path according to claim 1, characterized in that, The method for constructing the critical radius model of the oil-water two-phase fluid flow process includes: Construct a well location grid model and calculate the permeability and porosity of each grid. Based on the critical path seepage theory, a critical radius model for the oil-water two-phase fluid flow process is constructed by considering the actual rock pore throat characteristics and seepage channel characteristics in the well location grid model; the critical radius model includes: The critical radius r between grids i and j cij for: ； Where, k ij This represents the permeability between adjacent grids i and j. τ represents the porosity between adjacent grids i and j; τ represents the tortuosity; σ represents the porosity between adjacent grids i and j. z This represents the coefficient of variation of rock heterogeneity.

3. The method for constructing an oil-water two-phase flow model based on a critical path according to claim 2, characterized in that, The equivalent assumptions include: a. In the critical radius model, the critical path is the main channel for fluid seepage, and the pressure drop generated by the fluid flow mainly occurs in the critical path; b. In the critical path, there is only one two-phase fluid interface between the oil and water phases. c. The two fluids flowing in the network are immiscible; d, Piston-like displacement occurs in the critical path.

4. The method for constructing an oil-water two-phase flow model based on a critical path according to claim 1, characterized in that, Calculate the conductivity of the oil-water two-phase fluid between any two grids based on the critical path; including: When oil and water coexist in the critical path between grid i and grid j, the conductivity of the oil and water fluids in the critical path is... for: ； The pressure difference between grid i and grid j The flow rate q of the oil-water two-phase mixture ij Flow satisfies: ； Where, p i =p oi +ρ ow gZ i p oi Let ρ be the pore pressure of grid i. ow For the density of the mixed fluid, Z i Let be the vertical height of grid i, and g be the acceleration due to gravity, 9.8 m / s². 2 ;p j =p oj +ρ ow gZ j p oj For grid j, Z j Vertical height of grid j, m; p cij τ is the equivalent capillary force of the reservoir grid; l is the tortuosity; ij The grid side length; Effective porosity; r cij The critical radius; The effective viscosity of the mixed fluid.

5. The method for constructing an oil-water two-phase flow model based on a critical path according to claim 1, characterized in that, The effective viscosity and density of the oil-water two-phase fluid in the critical path between reservoir grids are obtained; include: The effective viscosity of the oil-water two-phase fluid in the critical path between reservoir grids is calculated using the following formula. : ； Among them B w B represents the volume coefficient of water, which is dimensionless; o μ represents the volume coefficient of oil and is dimensionless. w The viscosity of water is expressed in Pa·s; μ. o Indicates the viscosity of the oil; X ij A dimensionless number relating to the position of the oil-water interface, 0 ≤ X ij ≤1, which means the position of the concave meniscus is divided by the length of the entire critical path; The density ρ of the oil-water two-phase fluid in the critical path between reservoir grids is calculated using the following formula. ow : ; Where, ρ w ρ represents the density of water. o This indicates the density of the oil.

6. The method for constructing an oil-water two-phase flow model based on a critical path according to claim 4, characterized in that, The differential equations for the flow rate and pressure diffusion of the oil-water two-phase system include: ； Where i represents any number from 1 to N, and N represents the total number of grid cells. Δp represents the conductivity between two adjacent grids i and j; ij This represents the pressure difference between grid i and grid j; ; V represents the initial porosity of grid i; bi Δt represents the volume of grid i; Δt is the simulation time step; Δp i C represents the change in pressure of grid i within Δt; tow Let C be the combined compressibility coefficient of the oil and water phases. Since the compressibility of oil and water is approximately equal, C is used here for simplified calculation. tow The value of is consistent with the compressibility coefficient of oil or water.

7. The method for constructing an oil-water two-phase flow model based on a critical path according to claim 1, characterized in that, The solution to the oil-water two-phase numerical model yields simulation results of the phase displacement between the oil and water phases, including: In conjunction with the oil-water displacement process, during the numerical simulation of the differential equations for flow and pressure diffusion in the oil-water two-phase system, the fluid conductivity of all grids is updated according to the time step to update the movement process and distribution state of the computational interface. The pressure and flow rates of different grids are solved, and the global pressure field and oil-water flow rate data at different times are obtained by using the conjugate gradient method.

8. A system for constructing an oil-water two-phase flow model based on a critical path, characterized in that, The system is used to implement the method for constructing an oil-water two-phase flow model based on a critical path as described in any one of claims 1-7; the system comprises: The first module is used to establish a critical radius model of the oil-water two-phase fluid flow process based on nuclear magnetic resonance logging technology and critical path flow theory. The second module is used to establish a numerical model of oil and water phases applicable to the single-well scale of the reservoir based on the critical radius model under equivalent assumptions. The solver module is used to solve the numerical model of the oil-water two-phase system to obtain the simulation results of the phase displacement of the oil and water two phases.

9. A computer-readable medium having a computer program stored thereon, characterized in that, The computer program, when executed by a processor, can implement the method for constructing an oil-water two-phase flow model based on a critical path as described in any one of claims 1-7.

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