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

Abstract

The invention discloses a single-phase seepage model construction method and system based on critical path seepage and a medium. Relates to the technical field of reservoir simulation. The method is improved on the basis of a traditional single-phase seepage model construction technology for oil and gas reservoirs with large viscosity changes of heavy oil layers and light oil layers along with formation pressure, and on one hand, a critical radius model is established based on a nuclear magnetic logging technology and a critical theory; an oil reservoir single-phase flow and pressure diffusion model is established according to the critical radius model and the mass conservation equation, and the modeling rate is increased; and on the other hand, according to the scheme, the oil reservoir single-phase flow and pressure diffusion model is adjusted according to the actual fluid and the actual formation pressure, in the viscous change process of the heavy oil layer and the light oil layer along with the formation pressure, the adaptive oil reservoir single-phase flow and pressure diffusion model is adjusted in time, and the modeling speed and precision are improved.

Description

Technical Field

[0001] The invention relates to the technical field of 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 become mature. Most researchers use numerical simulation methods to reduce development costs, and formulate reasonable development plans and provide scientific guidance based on simulation results. The numerical simulation method of reservoirs refers to the use of 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 the numerical simulation method of reservoirs is to use a set of partial differential equations to describe the state of reservoir exploitation, and obtain changes in development indicators through computer numerical solutions. The numerical simulation method of reservoirs can take into account the impact of factors such as reservoir geometry, heterogeneity, changes in rock and fluid properties, well network mode and production on dynamics. It is the method that considers the most factors in reservoir dynamic research so far, and has become one of the important means of reservoir development research. The main feature of the numerical simulation method is to analyze and predict development dynamics by simulating and analyzing the fluid and energy distribution in 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. The conventional single-phase seepage model is independent of the heavy oil layer model and the light oil layer model. 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 precision defects; the purpose of the present invention is to provide a single-phase seepage model construction method, system and medium 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 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, thereby improving the modeling rate; on the other hand, the scheme also adjusts the single-phase flow and pressure diffusion model of the reservoir according to the actual fluid and the 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 precision.

[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] A single-phase flow and pressure diffusion model of an oil reservoir is established based on the critical radius model and the 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, 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 the actual formation pressure, and in the process of the viscosity of the heavy oil layer and the 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, thereby improving 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 method:

[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, and τ is the tortuosity;

[0018] Based on the critical radius model, the volume flow rate q between grid i and grid j is expressed as 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 gravitational acceleration; 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 single-phase flow and pressure diffusion model of the reservoir based on the critical radius model and the mass conservation equation; including methods:

[0023] S21, obtain the grid micro-element of the critical radius model, and express the fluid seepage velocity in three dimensions based on the grid micro-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 edges of the grid microelement 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] The center coordinates of the microelement of grid i are (x i ,y i , z i );Δl x , Δl y , Δl z are the side lengths 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 micro-element, and determining the change of the fluid mass flow rate in the grid micro-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 the volume flow rate, and obtaining the flow exchange satisfaction between the grid i and the 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 scheme is that the flow exchange between the grid i and the adjacent grid j satisfies, including:

[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 that, finally, in the grid i, according to the law of conservation of mass, a single-phase flow and pressure diffusion equation is obtained; including the 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 fluid, 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 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; including the method:

[0046] Get 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] In the formula, 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 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 of the single-phase fluid in each grid is obtained by solving the equation; including the method:

[0054] The sink-source term Q of the 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] In the formula, 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] The present 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, used for acquiring actual formation pressure data and adjusting the reservoir single-phase flow and pressure diffusion model according to the actual formation pressure data;

[0065] The solution module is used to transform the adjusted single-phase flow and pressure diffusion model into a nonlinear algebraic equation group based on the finite difference method, and solve the flow 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 whose viscosity of heavy oil layers and light oil layers varies 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, the scheme also adjusts the single-phase flow and pressure diffusion model of the reservoir according to the actual fluid and actual formation pressure, and timely adjusts it to an adaptive single-phase flow and pressure diffusion model of the reservoir during the process of viscosity change of the heavy oil layer and the light oil layer with formation pressure, 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 embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0070] Figure 1 A schematic diagram of the process of constructing a single-phase seepage model based on critical path seepage;

[0071] Figure 2 This is a schematic diagram of mass conservation of fluid flow exchange within a grid microelement;

[0072] Figure 3 A top view of the flow of injected oil in the reservoir;

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

[0074] Figure 5 Top view of the flow of a Bingham non-Newtonian fluid injected into a 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 embodiments and drawings. The exemplary embodiments of the present invention and their description 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] Based on the critical radius model, the volume flow rate q between grid i and grid j is expressed as 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 gravitational acceleration; 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 single-phase flow and pressure diffusion model of the reservoir based on the critical radius model and the mass conservation equation; this step specifically includes the following methods:

[0089] S21, obtain the grid micro-element of the critical radius model, and express the fluid seepage velocity in three dimensions based on the grid micro-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 edges of the grid microelement 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 micro-element minus the mass of fluid flowing out of the unit = the change in the mass of fluid in the unit, such as Figure 2 As shown; the mass flow rate on each side of the grid microelement 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] The center coordinates of the microelement of grid i are (x i ,y i ,z i );Δl x , Δl y , Δl z are the side lengths 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 according to the state equation;

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

[0097] φ c =φ c0 [1+C φc (p-p0)]

[0098] ρ=ρ0[1+C ρ (p-p0)]

[0099] In the formula, φ c is the pressure p of grid i and grid j. i and p j The arithmetic mean of 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, in Pa -1 ; p0 is the initial 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 the state equation 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 microelement 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 formula 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 )) After that, 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 6 adjacent grids j, and the inflow and outflow mass flow in any grid satisfies the law of conservation of mass. Finally, in grid i, according to the law of conservation of mass, 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 fluid, 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 the actual fluid and the actual formation pressure, and adjusting the reservoir single-phase flow and pressure diffusion model according to the actual fluid and the actual formation pressure; this step specifically includes the following methods:

[0133] Get 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] In the formula, 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 and source term Q of the 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] In the formula, 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) Non-diagonal elements A ij =κ ij ;

[0149] 2) Diagonal elements

[0150] p is the vector consisting of the pressures at each node B is the vector [B] n =[B1,B2,B3,…B N ] T , and any element B in vector B i It is 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 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 single-phase seepage model construction system based on critical path seepage, which is used to implement the single-phase seepage model construction method 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, used for acquiring actual formation pressure data and adjusting the reservoir single-phase flow and pressure diffusion model according to the actual formation pressure data;

[0159] The solution module is used to transform the adjusted single-phase flow and pressure diffusion model into a nonlinear algebraic equation group based on the finite difference method, and solve the flow 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: Establish a critical radius model based on nuclear magnetic logging technology and critical theory; A single-phase flow and pressure diffusion model of an oil reservoir is established based on the critical radius model and the 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: The method of establishing a critical radius model based on nuclear magnetic logging technology and critical theory includes: Construct a well location grid model and calculate 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; 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;< / r> < / r> Based on the critical radius model, the volume flow rate q between grid i and grid j is expressed as ij : Δp ij =(p i -p j )=(p oi -p oj +ρgZ i -ρgZ j ) 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 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 gravitational acceleration; 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.

3. The method for constructing a single-phase seepage model based on critical path seepage according to claim 2, characterized in that: A single-phase flow and pressure diffusion model of the reservoir is established based on the critical radius model and the mass conservation equation; Included methods: S21, obtain the grid micro-element of the critical radius model, and express the fluid seepage velocity in three dimensions based on the grid micro-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 edges of the grid microelement 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 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: The center coordinates of the microelement of grid i are (x i ,y i ,z i );Δl x , Δl y , Δl z are the side lengths 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 micro-element, and determining the change of the fluid mass flow rate in the grid micro-element according to the state equation; S24, converting the mass flow rate and its change of the fluid in the grid micro-element into the volume flow rate, and obtaining the flow exchange satisfaction between the grid i and the 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.

4. The method for constructing a single-phase seepage model based on critical path seepage according to claim 3, 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.

5. The method for constructing a single-phase seepage model based on critical path seepage according to claim 3, characterized in that: The traffic exchange between the grid i and the adjacent grid j satisfies, including: 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.

6. The method for constructing a single-phase seepage model based on critical path seepage according to claim 5, 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; Included methods: The single-phase flow and pressure diffusion equations are: Introducing the sink-source term Q of the actual production injected and produced fluids l After that, the single-phase flow and pressure diffusion equations of each grid are: ω=φ c0i V bi C t ; 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.

7. The method for constructing a single-phase seepage model based on critical path seepage according to claim 6, characterized in that: The actual fluid and the actual formation pressure are obtained, and the reservoir single-phase flow and pressure diffusion model is adjusted according to the actual fluid and the actual formation pressure; Included methods: Get 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: In the formula, 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.

8. The method for constructing a single-phase seepage model based on critical path seepage according to claim 6, characterized in that: The adjusted single-phase flow and pressure diffusion model is converted into a nonlinear algebraic equation group 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 the 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: In the formula, 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.

9. 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 8; 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, used for acquiring actual formation pressure data and adjusting the reservoir single-phase flow and pressure diffusion model according to the actual formation pressure data; The solution module is used to transform the adjusted single-phase flow and pressure diffusion model into a nonlinear algebraic equation group based on the finite difference method, and solve the flow of the single-phase fluid in each grid.

10. 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 8.

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