Single-phase seepage model construction method, system and medium based on critical path seepage

Abstract

The present invention discloses a method, system and medium for constructing a single-phase seepage model based on critical path seepage; relates to the field of oil reservoir simulation technology; for oil and gas reservoirs whose heavy oil layers and light oil layers have large viscosity changes with formation pressure, the method is improved on the basis of traditional single-phase seepage model construction technology, on the one hand, a critical radius model is established based on nuclear magnetic resonance logging technology and critical theory, and a single-phase flow and pressure diffusion model of the oil reservoir is established according to the critical radius model and the mass conservation equation, thereby improving the modeling rate; on the other hand, the scheme also adjusts the single-phase flow and pressure diffusion model of the oil reservoir according to actual fluid and actual formation pressure, and in the process of heavy oil layers and light oil layers changing with formation pressure viscosity, timely adjusts to an adaptive single-phase flow and pressure diffusion model of the oil reservoir, thereby improving the modeling rate and accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of oil reservoir simulation, and in particular to a method, system and medium for constructing a single-phase seepage model based on critical path seepage. Background Art

[0002] After years of research, reservoir development methods have matured. Researchers generally use numerical simulation methods to reduce development costs and formulate reasonable development plans and provide scientific guidance based on simulation results. Numerical reservoir simulation methods use models to study the dynamic changes of reservoirs, including physical simulation and mathematical (numerical) simulation. Physical simulation refers to the indoor study of reservoir development dynamics, while the main principle of numerical reservoir simulation methods is to describe the reservoir production status using a set of partial differential equations and obtain changes in development indicators through computer numerical solution. Numerical reservoir simulation methods can consider the impact of factors such as reservoir geometry, heterogeneity, changes in rock and fluid properties, well patterns, and production on dynamics. To date, this method considers the most factors in reservoir dynamics research and has become one of the important means of reservoir development research. The main feature of numerical simulation methods is the analysis and prediction of development dynamics through simulation analysis of fluid and energy distribution within the reservoir.

[0003] In the early stages of offshore oil and gas reservoir development, the viscosity of heavy oil layers and light oil layers changes greatly with formation pressure. Conventional single-phase seepage models are independent of each other for heavy oil layer models and light oil layer models. Different layers need to be replaced with different models, which affects the efficiency of oil and gas reservoir development. It is not suitable for scenarios where the viscosity of heavy oil layers and light oil layers changes greatly with formation pressure, and has large accuracy defects. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: in the early stage of offshore oil and gas reservoir development, the viscosity of heavy oil layers and light oil layers changes greatly with formation pressure, and conventional single-phase seepage models have great accuracy deficiencies; the purpose of the present invention is to provide a single-phase seepage model construction method, system and medium based on critical path seepage, and for oil and gas reservoirs where the viscosity of heavy oil layers and light oil layers changes greatly with formation pressure, the method is improved on the basis of traditional single-phase seepage model construction technology. On the one hand, a critical radius model is established based on nuclear magnetic resonance logging technology and critical theory, and a single-phase flow and pressure diffusion model of the reservoir is established based on the critical radius model and the mass conservation equation, thereby improving the modeling rate; on the other hand, this scheme also adjusts the single-phase flow and pressure diffusion model of the reservoir according to actual fluid and actual formation pressure, and timely adjusts it to an adaptive single-phase flow and pressure diffusion model of the reservoir in the process of viscosity change of heavy oil layers and light oil layers with formation pressure, thereby improving the modeling rate and accuracy.

[0005] The present invention is achieved through the following technical solutions:

[0006] This solution provides a method for constructing a single-phase seepage model based on critical path seepage, including:

[0007] Establish a critical radius model based on nuclear magnetic logging technology and critical theory;

[0008] Establishing a reservoir single-phase flow and pressure diffusion model based on the critical radius model and mass conservation equation;

[0009] Acquiring actual fluid and actual formation pressure, and adjusting the reservoir single-phase flow and pressure diffusion model according to the actual fluid and actual formation pressure;

[0010] Based on the finite difference method, the adjusted single-phase flow and pressure diffusion model is transformed into a set of nonlinear algebraic equations, and the flow rate of the single-phase fluid in each grid is obtained by solving them.

[0011] Working principle of this scheme: In the early stage of offshore oil and gas reservoir development, the viscosity of heavy oil layers and light oil layers changes greatly with the formation pressure, and the conventional single-phase seepage model has a large accuracy deficiency; the purpose of the present invention is to provide a single-phase seepage model construction method, system and medium based on critical path seepage, and for oil and gas reservoirs where the viscosity of heavy oil layers and light oil layers changes greatly with the formation pressure, the method is improved on the basis of the traditional single-phase seepage model construction technology. On the one hand, a critical radius model is established based on nuclear magnetic resonance logging technology and critical theory, and a single-phase flow and pressure diffusion model of the reservoir is established according to the critical radius model and the mass conservation equation to improve the modeling rate; on the other hand, this scheme also adjusts the single-phase flow and pressure diffusion model of the reservoir according to the actual fluid and actual formation pressure, and in the process of the viscosity of the heavy oil layer and light oil layer changing with the formation pressure, it is timely adjusted to an adaptive single-phase flow and pressure diffusion model of the reservoir to improve the modeling rate and accuracy.

[0012] A further optimization scheme is to establish a critical radius model based on nuclear magnetic logging technology and critical 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, the actual rock pore throat characteristics and seepage channel characteristics are considered in the well location grid model to construct a critical radius model. The critical radius model includes:

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

[0016]

[0017] Among them, φ ij represents the porosity between adjacent grids i and j; k ij represents the permeability between adjacent grids i and j; σ / <r>is the rock pore throat variation coefficient, where σ represents the standard deviation of the pore throat radius distribution curve, <r>is the mean value; z represents the rock pore throat coordination number, τ is the tortuosity;

[0018] The volume flow rate q between grid i and grid j is expressed based on the critical radius model ij :

[0019]

[0020] Δp ij =(p i -p j )=(p oi -p oj +ρgZ i -ρgZ j )

[0021] Among them, κ ij is the conductivity of the critical path between grid i and grid j; B s is the volume coefficient of the single-phase fluid; μ s is the fluid viscosity; p i represents the integrated pressure of grid i, p i =p oi +ρgZ i , p oi is the pore pressure of grid i, ρgZ i is the gravity of the fluid in grid i, ρ is the fluid density, g is the acceleration due to gravity; p j represents the integrated pressure at grid j, p j =p oj +ρgZ j , p oj is the pore pressure of grid j, ρgZ j is the gravity of the fluid in grid j; Z i is the vertical height of grid i; Z j is the vertical height of grid j; l ij is the distance between the center points of grid i and grid j; Δp ij represents the pressure difference between grid i and grid j, r cij is the critical radius between grids i and j; τ is the tortuosity; φ cij represents the effective porosity between adjacent grids i and j.

[0022] A further optimization scheme is to establish a reservoir single-phase flow and pressure diffusion model based on the critical radius model and mass conservation equation; including the following methods:

[0023] S21, obtain the grid element of the critical radius model, and express the fluid seepage velocity in three dimensions based on the grid element:

[0024]

[0025] Among them, v x , v y , v z are the components of the seepage velocity in the x-axis direction, y-axis direction, and z-axis direction respectively; l x , l y , l z are the lengths of the grid edge of the grid element in the x-axis direction, y-axis direction, and z-axis direction respectively; The conductivity gradient of the critical path between grid i and grid j is expressed as

[0026] S22, based on the law of conservation of mass and fluid seepage velocity, expresses the fluid mass flow rate in three dimensions:

[0027]

[0028] Among them, the center coordinates of the microelement of grid i are (x i ,y i , z i );Δl x , Δl y , Δl z are the lengths of the sides of the microelement in the x, y, and z directions respectively; ρ is the density of the single-phase fluid; v x 、v y 、v z are the flow velocities of the single-phase fluid in the x, y, and z directions respectively; Δx, Δy, and Δz are the distances that the single-phase fluid flows in the x, y, and z directions of the microelement respectively;

[0029] S23, considering the state of the porous medium and the state of the elastic liquid, constructing a state equation of the grid element, and determining the change of the fluid mass flow rate in the grid element according to the state equation;

[0030] S24, converting the mass flow rate and its change of the fluid in the grid micro-element into volume flow rate, and obtaining the flow exchange satisfaction between grid i and adjacent grid j;

[0031] S25, finally, in grid i, according to the law of conservation of mass, the single-phase flow and pressure diffusion equations are obtained.

[0032] A further optimization scheme is that the change of the fluid mass flow rate in the grid micro-element includes:

[0033]

[0034] Among them, φ c Indicates the porosity that changes with the average pressure p, p = (p i +p j ) / 2), p i and p j are the pressures of grid i and grid j respectively; t represents time.

[0035] A further optimization solution is that the flow exchange between the grid i and the adjacent grid j satisfies the following conditions:

[0036]

[0037] in, represents the Hamilton operator; C t Indicates the compressibility coefficient of the fluid; φ c0 represents the initial porosity; p i represents the integrated pressure of grid i; V bi represents the volume of grid i; t represents time.

[0038] A further optimization scheme is to obtain the single-phase flow and pressure diffusion equations in the grid i according to the law of conservation of mass, including the following method:

[0039] The single-phase flow and pressure diffusion equations are:

[0040]

[0041] After considering the sink-source term Ql of the actual production injection and production fluids, the single-phase flow and pressure diffusion equations of each grid are:

[0042]

[0043] ω=φ c0i V bi C t ;

[0044] Where j represents the grid adjacent to grid i; Δp ij represents the pressure difference between grid i and grid j; φ c0i is the initial porosity of grid i; Δt is the simulation time step; Δp i is the change in pressure of grid i within Δt.

[0045] A further optimization scheme is to obtain the actual fluid and actual formation pressure, and adjust the reservoir single-phase flow and pressure diffusion model according to the actual fluid and actual formation pressure; including the following method:

[0046] Obtain the actual fluid. When the actual fluid is light oil, adjust the fluid viscosity in the reservoir single-phase flow and pressure diffusion model to: μ s =μ o , μ o is the viscosity of light oil;

[0047] When the actual fluid is heavy oil, a pressure threshold Pe is preset. When the actual formation pressure is greater than the pressure threshold Pe, the fluid viscosity μ in the reservoir single-phase flow and pressure diffusion model is adjusted. s for:

[0048]

[0049] Among them, μ c is the initial viscosity of heavy oil; δ 12 is the fluid viscosity μ s =μ c Shear stress at / 2, unit: Pa -1 ;α represents the empirical constant related to the shear rheology of heavy oil;

[0050] When the actual formation pressure is less than or equal to the pressure threshold Pe, the fluid viscosity μ in the reservoir single-phase flow and pressure diffusion model is adjusted. s for:

[0051]

[0052] Where μ c is the initial viscosity of heavy oil; r eff is the effective radius of the fluid in the critical path, and its value is r cij ·φ cij ; r cij is the critical radius between grids i and j; φ cij represents the effective porosity between adjacent grids i and j.

[0053] A further optimization scheme is to transform the adjusted single-phase flow and pressure diffusion model into a nonlinear algebraic equation system based on the finite difference method, and solve the flow rate of the single-phase fluid in each grid; including the following method:

[0054] The sink-source term Q of injected and produced fluids in actual production l The right side of the single-phase flow and pressure diffusion model is differentiated to obtain the differential equation:

[0055]

[0056] Where p i n+1 、p i n are the pressure values ​​of grid i at the next moment and the current moment respectively.

[0057] Traverse all grids according to the difference equation and construct the matrix equation:

[0058]

[0059] Solving the matrix equation based on the conjugate gradient method to obtain the fluid pressure;

[0060] Based on the conductivity and fluid pressure of each grid, the flow rate of the single-phase fluid in each grid is obtained.

[0061] This solution also provides a single-phase seepage model construction system based on critical path seepage, which is used to implement the above-mentioned single-phase seepage model construction method based on critical path seepage; the system includes:

[0062] The first model building module is used to establish a critical radius model based on nuclear magnetic logging technology and critical theory;

[0063] A second model building module is used to establish a reservoir single-phase flow and pressure diffusion model based on the critical radius model and the mass conservation equation;

[0064] an adjustment module, configured to obtain actual formation pressure data and adjust the reservoir single-phase flow and pressure diffusion model according to the actual formation pressure data;

[0065] The solving module is used to transform the adjusted single-phase flow and pressure diffusion model into a nonlinear algebraic equation system based on the finite difference method, and solve the flow rate of the single-phase fluid in each grid.

[0066] The present solution also provides a computer-readable medium having a computer program stored thereon, and the computer program is executed by a processor to implement the above-mentioned method for constructing a single-phase seepage model based on critical path seepage.

[0067] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0068] The present invention provides a method, system and medium for constructing a single-phase seepage model based on critical path seepage. For oil and gas reservoirs where the viscosity of heavy oil layers and light oil layers changes greatly with formation pressure, the method is improved on the basis of traditional single-phase seepage model construction technology. On the one hand, a critical radius model is established based on nuclear magnetic resonance logging technology and critical theory, and a single-phase flow and pressure diffusion model of the reservoir is established according to the critical radius model and the mass conservation equation, thereby improving the modeling rate. On the other hand, this solution also adjusts the single-phase flow and pressure diffusion model of the reservoir according to the actual fluid and actual formation pressure. In the process of the viscosity of the heavy oil layer and light oil layer changing with formation pressure, it is timely adjusted to an adaptive single-phase flow and pressure diffusion model of the reservoir, thereby improving the modeling rate and accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the examples. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be considered as limiting the scope. A person of ordinary skill in the art can also derive other relevant drawings based on these drawings without inventive effort. In the drawings:

[0070] Figure 1 A flow chart of the method for constructing a single-phase seepage model based on critical path seepage;

[0071] Figure 2 Schematic diagram of mass conservation of fluid flow exchange within a grid element;

[0072] Figure 3 Top view of injected oil flowing in the reservoir;

[0073] Figure 4 Top view of the flow of injected Ellis non-Newtonian fluid in the reservoir;

[0074] Figure 5 Top view of the flow of injected Bingham non-Newtonian fluid in the reservoir. DETAILED DESCRIPTION

[0075] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with examples and drawings. The exemplary embodiments of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0076] Example 1

[0077] This embodiment provides a method for constructing a single-phase seepage model based on critical path seepage, such as Figure 1 As shown, including:

[0078] Step 1: Establish a critical radius model based on nuclear magnetic logging technology and critical theory; this step specifically includes the following methods:

[0079] Construct a well location grid model and calculate the permeability and porosity of each grid;

[0080] Based on the critical path seepage theory, the actual rock pore throat characteristics and seepage channel characteristics are considered in the well location grid model to construct a critical radius model. The critical radius model includes:

[0081] The critical radius r between grids i and j cij for:

[0082]

[0083] Among them, φ ij represents the porosity between adjacent grids i and j; k ij represents the permeability between adjacent grids i and j; τ is the tortuosity; σ / <r>is the rock pore throat variation coefficient, where σ represents the standard deviation of the pore throat radius distribution curve, <r>is the mean value; z represents the rock pore throat coordination number;

[0084] The volume flow rate q between grid i and grid j is expressed based on the critical radius model ij :

[0085]

[0086] Δp ij =(p i -p j )=(p oi -p oj +ρgZ i -ρgZ j )

[0087] Among them, κ ij is the conductivity of the critical path between grid i and grid j; B s is the volume coefficient of the single-phase fluid; μ s is the fluid viscosity; p i represents the integrated pressure of grid i, p i =p oi +ρgZ i , p oi is the pore pressure of grid i, ρgZ i is the gravity of the fluid in grid i, ρ is the fluid density, g is the acceleration due to gravity; p j represents the integrated pressure at grid j, p j =p oj +ρgZ j , p oj is the pore pressure of grid j, ρgZ j is the gravity of the fluid in grid j; Z i is the vertical height of grid i; Z j is the vertical height of grid j; l ij is the distance between the center points of grid i and grid j; Δp ij represents the pressure difference between grid i and grid j, r cij is the critical radius between grids i and j; τ is the tortuosity; φ cij represents the effective porosity between adjacent grids i and j.

[0088] Step 2: Establishing a reservoir single-phase flow and pressure diffusion model based on the critical radius model and mass conservation equation; this step specifically includes the following methods:

[0089] S21, obtain the grid element of the critical radius model, and express the fluid seepage velocity in three dimensions based on the grid element:

[0090]

[0091] Among them, v x , v y , v z are the components of the seepage velocity in the x-axis direction, y-axis direction, and z-axis direction respectively; l x , l y , l z are the lengths of the grid edge of the grid element in the x-axis direction, y-axis direction, and z-axis direction respectively; The conductivity gradient of the critical path between grid i and grid j is expressed as

[0092] S22, according to the law of conservation of mass, in unit time, the mass of fluid flowing into the grid element - the mass of fluid flowing out of the element = the change in the mass of fluid in the element, such as Figure 2 As shown; the mass flow rate on each side of the grid element is replaced by the mass of the center point of its side; based on the law of conservation of mass and fluid seepage velocity, the fluid mass flow rate is expressed in three dimensions:

[0093]

[0094] Among them, the center coordinates of the microelement of grid i are (x i ,y i ,z i );Δl x , Δl y , Δl z are the lengths of the sides of the microelement in the x, y, and z directions respectively; ρ is the density of the single-phase fluid; v x 、v y 、v z are the flow velocities of the single-phase fluid in the x, y, and z directions respectively; Δx, Δy, and Δz are the distances that the single-phase fluid flows in the x, y, and z directions of the microelement respectively;

[0095] S23, since the reservoir rock and the fluid inside the rock pore throat are both compressible, it is necessary to consider the state of the porous medium and the state of the elastic liquid, construct the state equation of the grid micro-element, and determine the change of the fluid mass flow rate in the grid micro-element based on the state equation;

[0096] The state equation of the grid element is:

[0097] φ c =φ c0 [1+C φc (p-p0)]

[0098] ρ=ρ0[1+C ρ (p-p0)]

[0099] Where, φ c is the pressure p of grid i and grid j. i and p j The arithmetic mean of p = (p i +p j ) / 2 variable porosity, dimensionless; φ c0 is the average effective porosity of grid i and grid j under the initial pressure, and its value is φ at the initial moment cij value, dimensionless; ρ is the density value that changes with pressure p, unit kg / m 3 ; ρ0 is the density at the initial pressure, kg / m 3 ; C φc0 and C ρ are the compressibility coefficients of porosity and density, respectively, in Pa -1 ; p0 is the initial state pressure value (its value is the initial pressure p of grid i and grid j i0 and p j0 The arithmetic mean of p0=(p i0 +p j0 ) / 2), unit: Pa.

[0100] Multiplying the two equations of state gives:

[0101] φ c ρ=φ c0 ρ0+φ c0 ρ0(C φc +C ρ )(p-p0)+φ c0 ρ0C φc C ρ (p-p0) 2

[0102] Let C t =C φc +C ρ , due to C φc and C ρ are all very small constants, so C is omitted in formula (27) φc ·C ρ Then we get:

[0103] φ c ρ=φ c0 ρ0+φ c0 ρ0(C φc +C ρ )(p-p0)=φ c0 ρ0+φ c0 ρ0C t (p-p0)

[0104] The change of fluid mass flow rate in the grid element is:

[0105]

[0106] Among them, φ c Indicates the porosity that changes with the average pressure p, p = (p i +p j ) / 2), p i and p j are the pressures of grid i and grid j respectively; t represents time.

[0107] According to the law of conservation of matter:

[0108]

[0109] Divide both sides of the above equation by Δl x Δl y Δl z ,get:

[0110]

[0111] Let Δx→0, Δy→0, Δz→0, and we get Formula 1:

[0112]

[0113] Taking the derivative of formula 1 with respect to time, we can get formula 2:

[0114] The left side of formula 2 is related to the seepage velocity in the x direction in formula 3:

[0115]

[0116] Similarly, we can get Formula 4 and Formula 5 in the y and z directions:

[0117]

[0118] Formula 1 to Formula 5 are solved together to obtain Formula 6:

[0119]

[0120] Formula 6 can be written as follows:

[0121]

[0122] in is the Hamilton operator. Replace the linear velocity with the volume flow rate (consider the model volume grid V bi (m 3 , V bi =l ij 3 )) Then, the flow exchange between grid i and any adjacent grid j satisfies:

[0123]

[0124] in, represents the Hamilton operator; C t Indicates the compressibility coefficient of the fluid; φ c0 represents the initial porosity; p i represents the integrated pressure of grid i; V bi represents the volume of grid i; t represents time.

[0125] S25, in the established reservoir model, each grid i is connected to six adjacent grids j, and the inflow and outflow mass flows in any grid satisfy the mass conservation law. Finally, in grid i, according to the mass conservation law, a single-phase flow and pressure diffusion equation is obtained. This step specifically includes the following method:

[0126] The single-phase flow and pressure diffusion equations are:

[0127]

[0128] After considering the sink-source term Ql of the actual production injection and production fluids, the single-phase flow and pressure diffusion equations of each grid are:

[0129]

[0130] ω=φ c0i V bi C t ;

[0131] Where j represents the grid adjacent to grid i; Δp ij represents the pressure difference between grid i and grid j; φ c0i is the initial porosity of grid i; Δt is the simulation time step; Δp i is the change in pressure of grid i within Δt.

[0132] Step 3: Obtaining actual fluid and actual formation pressure, and adjusting the reservoir single-phase flow and pressure diffusion model according to the actual fluid and actual formation pressure; this step specifically includes the following methods:

[0133] Obtain the actual fluid. When the actual fluid is light oil, adjust the fluid viscosity in the reservoir single-phase flow and pressure diffusion model to: μ s =μ o , μ o is the viscosity of light oil;

[0134] When the actual fluid is heavy oil, a pressure threshold Pe is preset. When the actual formation pressure is greater than the pressure threshold Pe, the fluid viscosity μ in the reservoir single-phase flow and pressure diffusion model is adjusted. s for:

[0135]

[0136] Among them, μ c is the initial viscosity of heavy oil; δ 12 is the fluid viscosity μ s =μ c Shear stress at / 2, unit: Pa -1 ; α is an empirical constant related to the shear rheology of the fluid; τ is the tortuosity;

[0137] When the actual formation pressure is less than or equal to the pressure threshold Pe, the fluid viscosity μ in the reservoir single-phase flow and pressure diffusion model is adjusted. s for:

[0138]

[0139] Where μ c is the initial viscosity of heavy oil; r eff is the effective radius of the fluid in the critical path, and its value is r cij ·φ cij ; r cij is the critical radius between grids i and j; φ cij represents the effective porosity between adjacent grids i and j.

[0140] Step 4: Based on the finite difference method, the adjusted single-phase flow and pressure diffusion model is transformed into a nonlinear algebraic equation system, and the flow rate of the single-phase fluid in each grid is obtained by solving it;

[0141] This step specifically includes the following methods:

[0142] S41, the sink-source term Q for injected and produced fluids in actual production l The right side of the single-phase flow and pressure diffusion model is differentiated to obtain the differential equation:

[0143]

[0144] Where p i n+1 、p i n are the pressure values ​​of grid i at the next moment and the current moment respectively.

[0145] S42, traverse all grids according to the difference equation and construct the matrix equation:

[0146]

[0147] That is, Ap=B, where A is a symmetric, positive definite, diagonally occupied sparse matrix, and the elements in the sparse matrix are expressed as:

[0148] 1) Off-diagonal element A ij =κ ij ;

[0149] 2) Diagonal elements

[0150] p is the vector consisting of the pressure at each node B is the vector [B] n =[B1,B2,B3,…B N ] T , and any element B in vector B i Expressed as: N is the total number of grids;

[0151] S43, solving the matrix equation based on the conjugate gradient method to obtain the fluid pressure;

[0152] S44, based on the conductivity and fluid pressure of each grid, the flow rate of the single-phase fluid in each grid is obtained.

[0153] In this embodiment, the above method is used to obtain the top view of the flow of oil, Ellis non-Newtonian fluid and Bingham non-Newtonian fluid from the injection well to the oil reservoir, as shown in FIG. Figure 3-5 As shown, different colors represent different saturations of the single-phase fluid.

[0154] Example 2

[0155] This embodiment provides a system for constructing a single-phase seepage model based on critical path seepage, which is used to implement the method for constructing a single-phase seepage model based on critical path seepage in Example 1; the system includes:

[0156] The first model building module is used to establish a critical radius model based on nuclear magnetic logging technology and critical theory;

[0157] A second model building module is used to establish a reservoir single-phase flow and pressure diffusion model based on the critical radius model and the mass conservation equation;

[0158] an adjustment module, configured to obtain actual formation pressure data and adjust the reservoir single-phase flow and pressure diffusion model according to the actual formation pressure data;

[0159] The solving module is used to transform the adjusted single-phase flow and pressure diffusion model into a nonlinear algebraic equation system based on the finite difference method, and solve the flow rate of the single-phase fluid in each grid.

[0160] Example 3

[0161] This embodiment provides a computer-readable medium having a computer program stored thereon, wherein the computer program is executed by a processor to implement the method for constructing a single-phase seepage model based on critical path seepage as described in Example 1.

[0162] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method 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 in the scope of protection of the present invention.< / r> < / r> < / r> < / r>

Claims

1. A method for constructing a single-phase seepage model based on critical path seepage, characterized in that: include: A critical radius model is established based on nuclear magnetic logging technology and critical theory. The specific method includes: constructing a well location grid model and calculating the permeability and porosity of each grid; Based on the critical path seepage theory, the actual rock pore throat characteristics and seepage channel characteristics are considered in the well location grid model to construct a critical radius model; the critical radius model includes: the critical radius r between grids i and j cij for: Among them, φ ij represents the porosity between adjacent grids i and j; k ij represents the permeability between adjacent grids i and j; σ / <r>is the rock pore throat variation coefficient, where σ represents the standard deviation of the pore throat radius distribution curve, <r> is the mean value; z represents the rock pore throat coordination number;< / r> < / r> The volume flow rate q between grid i and grid j is expressed based on the critical radius model ij : Among them, κ ij is the conductivity of the critical path between grid i and grid j; B s is the volume coefficient of the single-phase fluid; μ s is the fluid viscosity; p i =p oi +ρgZ i ;p oi is the pore pressure of grid i; p i represents the integrated pressure at grid i, ρgZ i is the gravity of the fluid in grid i, ρ is the fluid density, g is the acceleration due to gravity; p j represents the integrated pressure at grid j, p j =p oj +ρgZ j , p oj is the pore pressure of grid j, ρgZ j is the gravity of the fluid in grid j; Z i is the vertical height of grid i; Z j is the vertical height of grid j; l ij is the distance between the center points of grid i and grid j; Δp ij represents the pressure difference between grid i and grid j, r cij is the critical radius between grids i and j; τ is the tortuosity; φ cij represents the effective porosity between adjacent grids i and j; Establishing a reservoir single-phase flow and pressure diffusion model based on the critical radius model and mass conservation equation; Acquiring actual fluid and actual formation pressure, and adjusting the reservoir single-phase flow and pressure diffusion model according to the actual fluid and actual formation pressure; Based on the finite difference method, the adjusted single-phase flow and pressure diffusion model is transformed into a set of nonlinear algebraic equations, and the flow rate of the single-phase fluid in each grid is obtained by solving them.

2. The method for constructing a single-phase seepage model based on critical path seepage according to claim 1, characterized in that: Establishing a reservoir single-phase flow and pressure diffusion model based on the critical radius model and mass conservation equation; Includes methods: S21, obtain the grid element of the critical radius model, and express the fluid seepage velocity in three dimensions based on the grid element: Among them, v x , v y , v z are the components of the seepage velocity in the x-axis direction, y-axis direction, and z-axis direction respectively; l x , l y , l z are the lengths of the grid edge of the grid element in the x-axis direction, y-axis direction, and z-axis direction respectively; The conductivity gradient of the critical path between grid i and grid j is expressed as p represents the average pressure; S22, based on the law of conservation of mass and fluid seepage velocity, expresses the fluid mass flow rate of any grid i in three dimensions: Among them, the center coordinates of the microelement of grid i are (x i ,y i ,z i );Δl x , Δl y , Δl z are the lengths of the sides of the microelement in the x, y, and z directions respectively; ρ is the density of the single-phase fluid; v x 、v y 、v z are the flow velocities of the single-phase fluid in the x, y, and z directions respectively; Δx, Δy, and Δz are the distances that the single-phase fluid flows in the x, y, and z directions of the microelement respectively; S23, considering the state of the porous medium and the state of the elastic liquid, constructing a state equation of the grid element, and determining the change of the fluid mass flow rate in the grid element according to the state equation; S24, converting the mass flow rate and its change of the fluid in the grid micro-element into volume flow rate, and obtaining the flow exchange satisfaction between grid i and adjacent grid j; S25, finally, in grid i, according to the law of conservation of mass, the single-phase flow and pressure diffusion equations are obtained.

3. The method for constructing a single-phase seepage model based on critical path seepage according to claim 2, characterized in that: The change of the fluid mass flow rate in the grid micro-element includes: Among them, φ c Indicates the porosity that changes with the average pressure p, p = (p i +p j ) / 2, p i and p j are the pressures of grid i and grid j respectively; t represents time.

4. The method for constructing a single-phase seepage model based on critical path seepage according to claim 2, characterized in that: The flow exchange between the grid i and the adjacent grid j satisfies the following conditions: Where, ▽ represents Hamilton operator; C t Indicates the compressibility coefficient of the fluid; φ c0 represents the initial porosity; p i represents the integrated pressure of grid i; V bi represents the volume of grid i; t represents time.

5. The method for constructing a single-phase seepage model based on critical path seepage according to claim 4, characterized in that: Finally, in the grid i, according to the law of conservation of mass, the single-phase flow and pressure diffusion equations are obtained; Includes methods: The single-phase flow and pressure diffusion equations are: Introducing the sink-source term Q of the actual production injection and production fluid l After that, the single-phase flow and pressure diffusion equations of each grid are: Where j represents the grid adjacent to grid i; Δp ij represents the pressure difference between grid i and grid j; φ c0i is the initial porosity of grid i; Δt is the simulation time step; Δp i is the change in pressure of grid i within Δt.

6. The method for constructing a single-phase seepage model based on critical path seepage according to claim 5, characterized in that: The actual fluid and actual formation pressure are obtained, and the reservoir single-phase flow and pressure diffusion model is adjusted according to the actual fluid and actual formation pressure; Includes methods: Obtain the actual fluid. When the actual fluid is light oil, adjust the fluid viscosity in the reservoir single-phase flow and pressure diffusion model to: μ s =μ o , μ o is the viscosity of light oil; When the actual fluid is heavy oil, a pressure threshold Pe is preset. When the actual formation pressure is greater than the pressure threshold Pe, the fluid viscosity μ in the reservoir single-phase flow and pressure diffusion model is adjusted. s for: Among them, μ c is the initial viscosity of heavy oil; δ 1 / 2 is the fluid viscosity μ s =μ c / 2; α represents the empirical constant related to the shear rheology of heavy oil; When the actual formation pressure is less than or equal to the pressure threshold Pe, the fluid viscosity μ in the reservoir single-phase flow and pressure diffusion model is adjusted. s for: Where μ c is the initial viscosity of heavy oil; r eff is the effective radius of the fluid in the critical path, and its value is r cij ·φ cij ; r cij is the critical radius between grids i and j; φ cij represents the effective porosity between adjacent grids i and j.

7. The method for constructing a single-phase seepage model based on critical path seepage according to claim 5, characterized in that: The adjusted single-phase flow and pressure diffusion model is converted into a nonlinear algebraic equation system based on the finite difference method, and the flow rate of the single-phase fluid in each grid is obtained by solving the equation; including method: The sink-source term Q of injected and produced fluids in actual production l The right side of the single-phase flow and pressure diffusion model is differentiated to obtain the differential equation: Where p i n+1 、p i n are the pressure values ​​of grid i at the next moment and the current moment respectively; Traverse all grids according to the difference equation and construct the matrix equation: Solving the matrix equation based on the conjugate gradient method to obtain the fluid pressure; Based on the conductivity and fluid pressure of each grid, the flow rate of the single-phase fluid in each grid is obtained.

8. A single-phase seepage model construction system based on critical path seepage, characterized in that: A method for constructing a single-phase seepage model based on critical path seepage according to any one of claims 1 to 7; the system comprises: The first model building module is used to establish a critical radius model based on nuclear magnetic logging technology and critical theory; A second model building module is used to establish a reservoir single-phase flow and pressure diffusion model based on the critical radius model and the mass conservation equation; an adjustment module, configured to obtain actual formation pressure data and adjust the reservoir single-phase flow and pressure diffusion model according to the actual formation pressure data; The solving module is used to transform the adjusted single-phase flow and pressure diffusion model into a nonlinear algebraic equation system based on the finite difference method, and solve the flow rate of the single-phase fluid in each grid.

9. A computer-readable medium having a computer program stored thereon, characterized in that: The computer program is executed by a processor to implement the method for constructing a single-phase seepage model based on critical path seepage as described in any one of claims 1 to 7.

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