Numerical Simulation Method and System for Oil and Gas Migration and Accumulation Based on Component Equations

Abstract

The present invention discloses a numerical simulation method and system for hydrocarbon migration and accumulation based on component equations. The method includes: establishing a basic equation and an auxiliary equation, where the basic equation is a system of partial differential equations based on component mass balance, including an accumulation term, a Darcy seepage term, a compaction term, and a source-sink term; discretizing the system of partial differential equations using the finite volume method to obtain a finite volume equation; performing a fully implicit solution to the finite volume equation to obtain the main unknowns of the system of partial differential equations; obtaining the remaining unknowns of the system of partial differential equations based on the auxiliary equation according to the obtained main unknowns; and performing numerical simulation of hydrocarbon migration and accumulation based on the solved system of partial differential equations. The system: when a processor executes a computer program stored in a memory, the method is implemented. According to the present invention, it is possible to solve the problem that the existing numerical simulation method for hydrocarbon migration and accumulation based on Darcy seepage cannot accurately simulate hydrocarbons with variable component contents during basin evolution.

Description

Technical Field

[0001] The present invention belongs to the technical field of numerical simulation, and more specifically, relates to a numerical simulation method and system for oil and gas migration and accumulation based on a component equation. Background Art

[0002] Analysis of oil and gas migration and accumulation is an important part of petroleum geology research, and numerical simulation of oil and gas migration and accumulation is an important component of basin simulation research, which can be used to predict the accumulation sites and accumulation amounts of oil and gas. In existing basin simulations, the numerical simulation methods for oil and gas migration and accumulation mainly include three methods: the streamline method, the invasion percolation method, and the method for solving the Darcy flow equation.

[0003] Among them, the streamline method is the simplest and fastest calculation method, and is usually used for rapid screening and evaluation. The streamline method is typically applied to high-permeability reservoirs or conduits. When applying it, the permeability threshold value is usually set to distinguish the conduit layer from the low-permeability layer or the conduit layer and the low-permeability layer is directly defined manually. When oil and gas enter the high-permeability layer, buoyancy is considered as the driving force, and the oil and gas vertically migrate to the next overlying rock unit until they encounter the capillary entry pressure of the higher low-permeability layer, which prevents their further movement. The streamline method does not consider time or flow rate.

[0004] The invasion percolation method simulates the underground oil and gas migration by drawing the breakthrough capillary pressure distribution map of each model grid body. Although the invasion percolation method is not a physically accurate numerical simulation method, the migration types generated by it are in good agreement with the experiments, can give satisfactory results for various geological scenarios, and the numerical method is simple and easy to program. In addition, the invasion percolation method treats the reservoir and non-reservoir in the same way, so it can also simulate the migration of oil and gas in low-permeability lithologies.

[0005] Since both the streamline method and the invasion percolation method adopt static-based models, there is no concept of time or flow rate in both the streamline method and the invasion percolation method, and they are independent of parameters such as viscosity and permeability. At the same time, both the streamline method and the invasion percolation method separately process the migration process and the accumulation process of oil and gas, and the saturation of oil and gas in the grid body usually gives a fixed value, so these two methods cannot accurately simulate the distribution of oil saturation in the reservoir. In addition, these two methods cannot handle the migration, accumulation or discharge process of oil and gas in the source rock.

[0006] The solution method of Darcy's seepage equation can handle a wide range of rock permeabilities in nature in basin simulation. The calculation time of the solution method of Darcy's seepage equation increases rapidly with the increase of the simulation grid number. Therefore, grids with relatively low precision are usually used. The solution method of Darcy's seepage equation is the only method among the three that can simulate the real oil and gas migration and accumulation rates, can simulate abnormal pressures, and is also the only method to simulate the formation and development of dynamic gas reservoirs such as deep basin gas, and supports the downward migration of oil and gas. Therefore, the solution method of Darcy's seepage equation has uniqueness and irreplaceability.

[0007] In basin simulation, there are many implementation methods for numerical simulation of oil and gas migration and accumulation based on Darcy's seepage. For example, the PetroMod basin simulation software adopts a solution method based on finite elements, and more are simulation techniques based on the finite volume method (Wendebourg & Harbaugh, 1997; Yuan Yirang & Han Yuji, 2008; Shi Guangren et al., 2010; Guo Qiulin et al., 2015). In the finite volume solution method, the first two literatures solve the problems of oil and water two-phase, and the last two literatures solve the black oil model.

[0008] Due to the diversity of the phases in which hydrocarbons exist in the basin, and because the oil and gas components vary greatly due to different degrees of thermal evolution, it is very necessary to conduct numerical simulation of Darcy's seepage solution based on component conservation. The solution of multi-component Darcy's seepage is more commonly seen in reservoir simulation. Usually, partial differential equations based on component molar conservation are adopted, and the solution is carried out based on the molar ratio of components as the basic variable (Lang Zhaoxin, Cheng Linsong, 1990; Zhang Maolin et al., 1991; Ye Jigen, Wu Xianghong, 2000; Zhang Maolin et al., 2002; Chen, 2007).

[0009] In basin simulation, various types of basins will be encountered, and the burial process of the simulated strata is from shallow to deep. Therefore, the generated hydrocarbon components gradually evolve from being mainly heavy hydrocarbon components to being mainly light hydrocarbon components as the source rock depth gradually increases. At the same time, the generated hydrocarbons will also undergo thermal cracking of hydrocarbons with the increase of formation temperature. Therefore, the change of hydrocarbon component content is usually very large during the whole basin simulation process. The oil-water or gas-water two-phase models or black oil models used for reservoir simulation, which are usually used to describe a single oil and gas phase, cannot meet the requirements of existing basin simulation for simulating various situations where two oil and gas phases coexist or the phase changes during the evolution process. Therefore, there is an urgent need for a numerical simulation model that can handle hydrocarbon component and phase changes. Summary of the Invention

[0010] The object of the present invention is to solve the problem that the existing numerical simulation methods of oil and gas migration and accumulation based on Darcy's seepage cannot accurately simulate hydrocarbons with variable component contents during basin evolution.

[0011] To achieve the above object, the present invention provides a numerical simulation method and system for oil and gas migration and accumulation based on component equations.

[0012] According to a first aspect of the present invention, there is provided a numerical simulation method for oil and gas migration and accumulation based on component equations, and the numerical simulation method for oil and gas migration and accumulation based on component equations includes the following steps:

[0013] Establish a basic equation and an auxiliary equation, where the basic equation is a partial differential equation system based on component mass balance, the partial differential equation system includes an accumulation term, a Darcy flow term, a compaction term, and a source-sink term, and the auxiliary equation includes a phase equilibrium equation, a saturation constraint equation, a capillary pressure equation, and a mass fraction constraint equation;

[0014] Discretize the partial differential equation system by using the finite volume method to obtain a finite volume equation;

[0015] Perform a fully implicit solution to the finite volume equation to obtain the main unknowns of the partial differential equation system;

[0016] Based on the obtained main unknowns, obtain the remaining unknowns of the partial differential equation system based on the auxiliary equation;

[0017] Perform a numerical simulation of oil and gas migration and accumulation according to the solved partial differential equation system.

[0018] Preferably, the expression of the partial differential equation system based on component mass balance is:

[0019]

[0020] In the above formula, let L = 1,..., N - 1 be hydrocarbon components, and L = N be water component;

[0021] is the gradient operator, u o , u w and u g are the oil overpressure, water overpressure, and gas overpressure respectively, φ is the effective porosity of the rock, S o , S w and S g are the oil saturation, water saturation, and gas saturation respectively, u l is the static rock potential, k ro , k rw and k rg are the relative permeability of the oil-phase fluid, the relative permeability of the water-phase fluid, and the relative permeability of the gas-phase fluid respectively, k is the absolute permeability of the rock, ρ o , ρ w and ρ g are the density of the oil-phase fluid, the density of the water-phase fluid, and the density of the gas-phase fluid respectively, μo , μ w and μ g are the viscosities of the oil - phase fluid, water - phase fluid, and gas - phase fluid respectively, q w is the source - sink intensity of water, q L represents the source - sink intensity of hydrocarbon components, σ e is the effective stress, C Lw is the mass fraction of component L in the water phase, C Lo is the mass fraction of component L in the oil phase, C Lg is the mass fraction of component L in the gas phase.

[0022] Preferably, the expression of the phase equilibrium equation is:

[0023]

[0024]

[0025] In the above formula, K Lgo is the equilibrium constant of component L between the gas phase and the oil phase, K Lgw is the equilibrium constant of component L between the gas phase and the water phase, and f(x) is a function of pressure, temperature, and component content.

[0026] Preferably, the expression of the saturation constraint equation is:

[0027] S o + S w + S g = 1 (4).

[0028] Preferably, the expression of the capillary pressure equation is:

[0029] u o - u w = P co (S w ) + P wstatic - P ostatic (5)

[0030] u g - u o = P cg (S o ) + P ostatic - P gstatic (6)

[0031] In the above formula, P wstatic , P ostatic and P gstatic are the hydrostatic pressure, static oil pressure, and static gas pressure respectively, P co (S w ) is the capillary pressure exerted on the oil phase, Pcg (S o ) is the capillary pressure received by the gas phase.

[0032] Preferably, the expression of the mass fraction constraint equation is:

[0033]

[0034] In the above formula, o represents the oil phase, g represents the gas phase, and w represents the water phase.

[0035] Preferably, the expression of the finite volume equation is:

[0036]

[0037] In the above formula, D i，j，k represents the control volume of the grid cell with the center point coordinates of (i, j, k) in the target calculation area.

[0038] Preferably, the full implicit solution of the finite volume equation is as follows:

[0039] The implicit iteration format of the finite volume equation is:

[0040]

[0041] In the above formula, V i,j,k is the volume of the grid cell with the center point coordinates of (i, j, k), t n+1 and t n are both time steps, and l and l + 1 are both iteration times.

[0042] Preferably, all unknowns of the partial differential equation system include the overpressure of the fluid, the saturation of the fluid, and the component mass fraction in the phase;

[0043] The main unknowns include the overpressure of water and the mass of hydrocarbon components.

[0044] According to the second aspect of the present invention, a numerical simulation system for oil and gas migration and accumulation based on a component equation is provided. The numerical simulation system for oil and gas migration and accumulation based on a component equation includes a processor and a memory. When the processor executes the computer program stored in the memory, the above-mentioned any oil and gas migration and accumulation numerical simulation method is implemented.

[0045] The numerical simulation method for oil and gas migration and accumulation based on component equations of the present invention first establishes a partial differential equation set and auxiliary equations based on component mass balance for simulating oil and gas migration and accumulation; secondly, discretizes the partial differential equation set by using the finite volume method to obtain finite volume equations; thirdly, performs fully implicit solution on the finite volume equations to obtain the main unknowns of the partial differential equation set; fourthly, based on the obtained main unknowns, obtains the remaining unknowns of the partial differential equation set based on the auxiliary equations; finally, performs numerical simulation of oil and gas migration and accumulation according to the solved partial differential equation set.

[0046] The beneficial effects of the present invention are as follows:

[0047] 1. Existing numerical simulation methods for oil and gas migration and accumulation based on Darcy flow all adopt two-phase flow or solutions based on black oil model equations. Therefore, they cannot fully describe the geological reality where the oil and gas phases vary greatly and the component compositions may be very different under actual geological conditions. However, the numerical simulation method for oil and gas migration and accumulation based on component equations of the present invention adopts a multi-component solution, so it can accurately simulate the characteristics of diverse hydrocarbon compositions during basin evolution.

[0048] 2. Currently, the establishment and numerical solution of multi-component mathematical models are all based on component molar conservation and solved with component molar ratios as basic variables. However, the numerical simulation method for oil and gas migration and accumulation based on component equations of the present invention adapts to the actual geological situation in basin simulation, adopts a mathematical model based on component mass balance in grid blocks, and solves with the component mass in grid blocks as the basic variable. Therefore, the solution results directly reflect the oil and gas mass distribution in grid cells.

[0049] The numerical simulation system for oil and gas migration and accumulation based on component equations of the present invention belongs to the same general inventive concept as the above-mentioned numerical simulation method for oil and gas migration and accumulation based on component equations. Therefore, it has the same beneficial effects as the above-mentioned numerical simulation method for oil and gas migration and accumulation based on component equations, and will not be elaborated here.

[0050] Other features and advantages of the present invention will be described in detail in the following specific implementation part. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] By describing the exemplary embodiments of the present invention in more detail in conjunction with the drawings, the above-mentioned and other objects, features, and advantages of the present invention will become more obvious. Among them, in the exemplary embodiments of the present invention, the same reference numerals generally represent the same components.

[0052] Figure 1 Shows a flowchart of the implementation of the numerical simulation method for oil and gas migration and accumulation based on component equations according to Embodiment 1 of the present invention;

[0053] Figure 2 A schematic diagram of a typical hexahedral unit according to Embodiment 1 of the present invention is shown;

[0054] Figure 3 A geological map of the Tazhong slope area in the Tarim Basin according to Embodiment 1 of the present invention is shown, wherein the area outlined by the small square is the area simulated in Specific Example 1;

[0055] Figure 4 An oil saturation distribution map of the Middle-Lower Cambrian strata at two different times according to Embodiment 1 of the present invention is shown, wherein the left figure is the oil saturation distribution map of the Middle-Lower Cambrian strata at 224 million years, and the right figure is the oil saturation distribution map of the Middle-Lower Cambrian strata at 206 million years;

[0056] Figure 5 An oil saturation distribution map of the Lower Cambrian strata and the Middle-Lower Ordovician strata at 433 million years according to Embodiment 1 of the present invention is shown, wherein the left figure is the oil saturation distribution map of the Lower Cambrian strata at 433 million years, and the right figure is the oil saturation distribution map of the Middle-Lower Ordovician strata at 433 million years. Detailed implementation manners

[0057] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0058] Embodiment 1: The numerical simulation method for oil and gas migration and accumulation based on the component equation in the embodiments of the present invention is a finite volume method for solving a three-dimensional three-phase multi-component partial differential equation based on the Darcy seepage model, which can handle oil and gas migration and accumulation in complex geological scenarios. The geological scenario here can be a conceptualized geological body, an oil and gas system or a basin.

[0059] In the numerical simulation method for oil and gas migration and accumulation based on component equations according to the embodiments of the present invention, the partial differential equation system for simulating oil and gas migration and accumulation is obtained based on the mass conservation of components, and includes an accumulation term, a Darcy flow term, a compaction term, and a source-sink term. The auxiliary equations considered simultaneously include a phase equilibrium equation, a saturation constraint equation, a capillary pressure equation, and a mass fraction constraint equation. The variables to be solved in the partial differential equation system include the overpressure of the fluid, the saturation of the fluid, and the component mass fraction in the phase. The numerical simulation method for oil and gas migration and accumulation based on component equations according to the embodiments of the present invention discretizes the partial differential equation system by the finite volume method. Since integral conservation is satisfied for any set of control volumes, the entire computational domain also satisfies conservation. The embodiments of the present invention give the discretization process and results of each term of the equation by the finite volume method.

[0060] Since basin simulation usually involves a numerical simulation process with a large time scale and has high requirements for the stability of the simulation process, therefore, the fully implicit solution method of the finite volume equation is given in the embodiments of the present invention. In the specific solution process, the main unknown variables are the overpressure of water and the mass of hydrocarbon components, and other variables are solved through functional relationships with pressure, temperature, and the mass of hydrocarbon components. These functions can be formed through mass and mass fraction relationships, auxiliary equations, and other parameter solution functions such as the density and viscosity of the phase state.

[0061] Figure 1 The implementation flowchart of the numerical simulation method for oil and gas migration and accumulation based on component equations according to the embodiments of the present invention is shown. Referring to Figure 1 , the numerical simulation method for oil and gas migration and accumulation based on component equations according to the embodiments of the present invention includes the following steps:

[0062] Step S100, establish a basic equation and an auxiliary equation, where the basic equation is a partial differential equation system based on component mass balance, the partial differential equation system includes an accumulation term, a Darcy flow term, a compaction term, and a source-sink term, and the auxiliary equation includes a phase equilibrium equation, a saturation constraint equation, a capillary pressure equation, and a mass fraction constraint equation;

[0063] Step S200, discretize the partial differential equation system by the finite volume method to obtain a finite volume equation;

[0064] Step S300, perform a fully implicit solution on the finite volume equation to obtain the main unknowns of the partial differential equation system;

[0065] Step S400, based on the obtained main unknowns, and based on the auxiliary equation, obtain the remaining unknowns of the partial differential equation system;

[0066] Step S500, perform a numerical simulation of oil and gas migration and accumulation according to the solved partial differential equation system.

[0067] Further, in step S100 of the embodiment of the present invention, the expression of the partial differential equation group based on component mass balance is as follows:

[0068]

[0069] In the above formula, let L = 1,..., N - 1 be hydrocarbon components, and L = N be the water component;

[0070] is the gradient operator, u o , u w and u g are the oil overpressure, water overpressure and gas overpressure respectively, [Pa]; φ is the effective porosity of the rock, dimensionless; S o , S w and S g are the oil saturation, water saturation and gas saturation respectively, dimensionless; u l is the static rock potential, dimensionless, equal to the static rock pressure - hydrostatic pressure; k ro , k rw and k rg are the relative permeability of the oil-phase fluid, the relative permeability of the water-phase fluid and the relative permeability of the gas-phase fluid respectively, dimensionless; k is the absolute permeability of the rock, [m 2 ; ρ o , ρ w and ρ g are the density of the oil-phase fluid, the density of the water-phase fluid and the density of the gas-phase fluid respectively, [kg / m 3 ; μ o , μ w and μ g are the viscosity of the oil-phase fluid, the viscosity of the water-phase fluid and the viscosity of the gas-phase fluid respectively, [Pascal.second, Pa.s]; q w is the source-sink intensity of water, [kg / (s.m 3 )]; q L represents the source-sink intensity of hydrocarbon components, [kg / (s.m 3 )]; σ e is the effective stress, equal to u l -u w ; C Lw is the mass fraction of component L in the water phase, C Lo is the mass fraction of component L in the oil phase, C Lg is the mass fraction of component L in the gas phase.

[0071] Still further, in step S100 of the embodiment of the present invention, the expression of the phase equilibrium equation is as follows:

[0072]

[0073]

[0074] In the above formula, K Lgo is the equilibrium constant of component L between the gas phase and the oil phase, and K Lgw is the equilibrium constant of component L between the gas phase and the water phase. f(x) is a function of pressure, temperature, and component content.

[0075] Between every two phases, there is an equilibrium constant for each component, and this equilibrium constant is a function of pressure, temperature, and component content.

[0076] Furthermore, in step S100 of the embodiment of the present invention, the expression of the saturation constraint equation is:

[0077] S o +S w +S g = 1 (4).

[0078] Furthermore, in step S100 of the embodiment of the present invention, the expression of the capillary pressure equation is:

[0079] u o -u w = P co (S w )+P wstatic -P ostatic (5)

[0080] u g -u o = P cg (S o )+P ostatic -P gstatic (6)

[0081] In the above formula, P wstatic , P ostatic and P gstatic are the hydrostatic pressure, the static oil pressure, and the static gas pressure respectively. P co (S w ) is the capillary pressure exerted on the oil phase, and P cg (S o ) is the capillary pressure exerted on the gas phase.

[0082] Furthermore, in step S100 of the embodiment of the present invention, the expression of the mass fraction constraint equation is:

[0083]

[0084] In the above formula, o represents the oil phase, g represents the gas phase, and w represents the water phase.

[0085] Furthermore, step S200 of the embodiment of the present invention is to establish a finite volume equation. The basic idea of ​​the finite volume method is to divide the calculation area into a series of non-repeating control volumes, and to have a control volume around each grid point; the partial differential equations to be solved based on the mass balance of the components are integrated for each control volume, and a set of discrete equations is obtained, in which the unknowns are the values ​​of the dependent variables at the grid points. In order to find the integral of the control volume, it is necessary to know the variation law of the assumed value between the grid points, that is, the segmented distribution characteristics of the assumed value.

[0086] Considering the case where the control volume is a hexahedron, the study area is divided into Figure 2 The hexahedral element shown in the figure has a control volume (D i，j，k ), integrate the partial differential equations and expand them to obtain:

[0087]

[0088] The following are the control volume elements for the internal nodes:

[0089] Cumulative items (i.e. stored changes):

[0090]

[0091]

[0092]

[0093] Unit boundary inflow term (i.e. Darcy seepage term):

[0094]

[0095]

[0096]

[0097] in,

[0098]

[0099]

[0100]

[0101] Compacted items:

[0102]

[0103] Source and sink items:

[0104]

[0105] Note:

[0106]

[0107] Obtain:

[0108]

[0109] Note:

[0110] Δ x U = U i+1 -U i , Δ x TXΔ x U i = T i+1 / 2 (U i+1 —U i ) + T i-1 / 2 (U i-1 -U i ), Δ y U = U j+1 -U j , Δ y TYΔ y U j = T j+1 / 2 (U j+1 -U j ) + T j-1 / 2 (U j-1 -U j )Δ z U = U k+1 -U k , Δ z TZΔ z U k = T k+1 / 2 (U k+1 -U k ) + T k-1 / 2 (U k- 1 - U k )ΔTΔU = Δ x TXΔ x U + Δ y TYΔ y U + Δ z TZΔ z U And

[0111] The simplified form of the obtained equation (18):

[0112]

[0113] Furthermore, step S300 of the embodiment of the present invention is the fully implicit solution of the finite volume equation. For any time step from t n to t n+1 When solving by fully implicit iteration, for any variable U, the difference in U between two iterations l and l + 1 is defined as:

[0114]

[0115] That is

[0116]

[0117] Moreover, when l = 0, U 0 = U n , after multiple iterations, when |U l+1 - U l | < ε, U n+1 = U l+1 . Where ε is the given accuracy requirement. Then the iteration format can be written as:

[0118]

[0119] The implicit iteration format of the finite volume equation with the convective term and the accumulation term expanded is as follows:

[0120]

[0121] Using the implicit function relationship, the functional relationship between and and is obtained. Here, M r is the mass of each component in the grid body. Through a series of simplification processes, a simplified system of equations can be obtained:

[0122]

[0123] Specific calculation of the matrix elements of the system of equations:

[0124] Some terms related to the difference in the above equations need to be expanded, including the coefficients of the unknown terms on the left end and R4 Li,j,k , R5 Li,j,k , R7 i,j,k , R8 i,j,k on the right end, which involve the values of 6 nodes around (i, j, k) and need to be expanded and sorted out. It should be particularly noted that there are three cases:

[0125] ①For the node (i, j, k), the part related to the storage quantity and the compaction term directly calculates the coefficient of the unknown at this node and the corresponding part of the right-hand side term.

[0126] ②For the part related to the convection term, if the expression involves the node (i, j, k) and its six surrounding nodes, the coefficients of the unknowns at seven points or the right-hand side terms at seven points are calculated simultaneously at this time.

[0127] ③For the part related to the convection term, if the expression involves the value at the 1 / 2 position between the node (i, j, k) and its six surrounding nodes, the right-hand side terms at seven points or six points are also calculated simultaneously at this time; the specific situation varies according to different algorithms. If the upstream weight method is adopted, it may involve seven points, and if other methods are simply used instead, it may only involve six points.

[0128] Formation of the overall matrix:

[0129] In the above equations, there are unknowns defined at the 1 / 2 position. For p and S at the 1 / 2 position, w the upstream weight principle is adopted for their values. In the current equations, the quantities to be solved are respectively (r = 1, 2, 3,..., N - 1), so there are a total of N quantities to be solved. For the component mass conservation equation, the overall matrix is formed as follows:

[0130] (1) The nodes are arranged in the cyclic order of k = 1, nz; j = 1, ny; i = 1, nx.

[0131] (2) For the given (i, j, k), each component is listed separately according to the component numbers 1, 2,..., N - 1 (assuming component N is the water component); thus, the number of discrete equations is (N - 1) × nx × ny × nz.

[0132] The overall matrix equation is formed according to the above method. The matrix is solved using the LU decomposition method.

[0133] The following is based on two specific examples to illustrate the effect of the numerical simulation method for oil and gas migration and accumulation based on the component equation in the embodiment of the present invention:

[0134] (1) Simulation of oil and gas migration and accumulation in a small area of the Tarim Basin:

[0135] Select a small area in the Tazhong slope area of the Tarim Basin for simulation ( Figure 3The part within the small and medium-sized square boxes). There are two sets of source rocks in this area, namely the middle-lower Cambrian and the middle-lower Ordovician. The hydrocarbon generation model uses the four-component hydrocarbon generation model of Behar et al. (1997), and the four components are C1, C2-C5, C6-C14, and C15+. The phase state of oil and gas is simulated using flash calculation. Through the simulation of burial history, thermal history, and hydrocarbon generation and expulsion history, the amounts of the four components expelled from the source rocks enter the numerical simulation model as source terms for oil and gas migration and accumulation simulation. The overpressure in the simulation comes from the overpressure simulation of the burial history in basin simulation. Figure 4 It is the distribution of oil saturation in the middle-lower Cambrian strata at two different times obtained after simulation.

[0136] (2) Simulation of oil and gas migration and accumulation within the entire Tarim Basin:

[0137] The entire Tarim Basin is selected for simulation. The middle-lower Cambrian and the middle-lower Ordovician are also used as the two sets of source rocks in the whole basin. The hydrocarbon generation model uses the four-component hydrocarbon generation model of Behar et al. (1997), and the four components are C1, C2-C5, C6-C14, and C15+. The phase state of oil and gas is simulated using flash calculation. Through the simulation of burial history, thermal history, and hydrocarbon generation and expulsion history, the amounts of the four components expelled from the source rocks enter the numerical simulation model as source terms for oil and gas migration and accumulation simulation. The overpressure in the simulation comes from the overpressure simulation of the burial history in basin simulation. Figure 5 It is the distribution of oil saturation in the middle-lower Cambrian strata and the middle-lower Ordovician strata at 433 million years obtained after simulation.

[0138] The embodiment of the present invention proposes a numerical simulation method for three-phase multi-component Darcy flow. In view of the current characteristic that oil and gas components are usually expressed in mass in grid cells in basin simulation, the method of the embodiment of the present invention uses component mass rather than molar ratio as the basic variable, and then performs fully implicit discrete solution based on the finite volume method. The embodiment of the present invention proposes a numerical solution method for partial differential equations applicable to basin simulation that includes a cumulative term, a Darcy flow term, a compaction term, and a source-sink term. The embodiment of the present invention uses the finite volume method for discretization and performs fully implicit solution. The main unknowns in the solution are the overpressure of water and the mass of hydrocarbon components, and other variables and parameters are solved through their relationships with temperature, pressure, and component mass, so as to achieve the purpose of solving the entire differential equation system.

[0139] Embodiment 2: Based on the numerical simulation method for oil and gas migration and accumulation based on the component equation proposed in Embodiment 1, the embodiment of the present invention correspondingly proposes a numerical simulation system for oil and gas migration and accumulation based on the component equation. The system includes a processor and a memory. When the processor executes the computer program stored in the memory, it implements the numerical simulation method for oil and gas migration and accumulation based on the component equation as described in Embodiment 1.

[0140] The numerical simulation system for oil and gas migration and accumulation based on the component equation in the embodiment of the present invention has the same beneficial effects as the numerical simulation method for oil and gas migration and accumulation based on the component equation described in Embodiment 1. To avoid repetition, it will not be elaborated here.

[0141] The embodiments of the present invention have been described above. The above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations are obvious to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A numerical simulation method for hydrocarbon migration and accumulation based on component equations, characterized in that, Comprising: Establishing a basic equation and auxiliary equations, where the basic equation is a system of partial differential equations based on component mass balance, the system of partial differential equations includes an accumulation term, a Darcy flow term, a compaction term, and a source-sink term, and the auxiliary equations include a phase equilibrium equation, a saturation constraint equation, a capillary pressure equation, and a mass fraction constraint equation; Discretizing the system of partial differential equations by using the finite volume method to obtain a finite volume equation; Performing a fully implicit solution to the finite volume equation to obtain the main unknowns of the system of partial differential equations, where the main unknowns include the overpressure of water and the mass of hydrocarbon components; Based on the obtained main unknowns, obtaining the remaining unknowns of the system of partial differential equations based on the auxiliary equations; Performing a numerical simulation of hydrocarbon migration and accumulation according to the solved system of partial differential equations; Wherein, the expression of the system of partial differential equations based on component mass balance is: In the above formula, let L = 1, …, N - 1 be hydrocarbon components, and L = N be the water component; is the gradient operator, u o , u w and u g are the oil overpressure, water overpressure and gas overpressure respectively, φ is the effective porosity of the rock, S o , S w and S g are the oil saturation, water saturation and gas saturation respectively, u l is the static rock potential, k ro , k rw and k rg are the relative permeability of the oil-phase fluid, the relative permeability of the water-phase fluid and the relative permeability of the gas-phase fluid respectively, k is the absolute permeability of the rock, ρ o , ρ w and ρ g are the density of the oil-phase fluid, the density of the water-phase fluid and the density of the gas-phase fluid respectively, μ o , μ w and μ g are the viscosity of the oil-phase fluid, the viscosity of the water-phase fluid and the viscosity of the gas-phase fluid respectively, q w is the source-sink strength of water, q L represents the source-sink strength of hydrocarbon components, σ e is the effective stress, C Lw is the mass fraction of component L in the water phase, C Lo is the mass fraction of component L in the oil phase, C Lg is the mass fraction of component L in the gas phase.

2. The numerical simulation method for hydrocarbon migration and accumulation according to claim 1, characterized in that, The expression of the phase equilibrium equation is: In the above formula, K Lgo is the equilibrium constant of component L between the gas phase and the oil phase, and K Lgw is the equilibrium constant of component L between the gas phase and the water phase. f(x) is a function of pressure, temperature, and component content.

3. The numerical simulation method for hydrocarbon migration and accumulation according to claim 2, characterized in that, The expression of the saturation constraint equation is: S o +S w +S g = 1 (4).

4. The numerical simulation method for hydrocarbon migration and accumulation according to claim 3, characterized in that, The expression of the capillary pressure equation is: u o -u w =P co (S w )+P wstatic -P ostatic (5)u g -u o =P cg (S o )+P ostatic -P gstatic (6) In the above formula, P wstatic , p ostatic and P gstatic are the hydrostatic pressure, the static oil pressure and the static gas pressure respectively, and P co (S w ) is the capillary pressure received by the oil phase, and P cg (S o ) is the capillary pressure received by the gas phase.

5. The numerical simulation method for hydrocarbon migration and accumulation according to claim 4, characterized in that, The expression of the mass fraction constraint equation is: In the above formula, o represents the oil phase, g represents the gas phase, and w represents the water phase.

6. The numerical simulation method for hydrocarbon migration and accumulation according to claim 5, characterized in that, The expression of the finite volume equation is: In the above formula, D i,j,k represents the control volume of the grid cell with the center point coordinates of (i, j, k) in the target calculation area.

7. The numerical simulation method for hydrocarbon migration and accumulation according to claim 6, characterized in that, The performing a fully implicit solution to the finite volume equation specifically is: The implicit iteration format of the finite volume equation is: In the above formula, V i,j,k is the volume of the grid cell with the center point coordinates (i, j, k), t n+1 and t n are both time steps, and l and l + 1 are both the number of iterations.

8. The numerical simulation method for hydrocarbon migration and accumulation according to claim 7, characterized in that, All the unknowns of the system of partial differential equations include the overpressure of the fluid, the saturation of the fluid, and the mass fraction of components in the phase.

9. A numerical simulation system for oil and gas migration and accumulation based on component equations, characterized in that, Including a processor and a memory, when the processor executes the computer program stored in the memory, it implements the numerical simulation method of hydrocarbon migration and accumulation according to any one of claims 1 - 8.

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