CN115270535A - Oil-gas migration aggregation numerical simulation method and system based on component equation - Google Patents

Oil-gas migration aggregation numerical simulation method and system based on component equation Download PDF

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CN115270535A
CN115270535A CN202110477270.1A CN202110477270A CN115270535A CN 115270535 A CN115270535 A CN 115270535A CN 202110477270 A CN202110477270 A CN 202110477270A CN 115270535 A CN115270535 A CN 115270535A
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盛秀杰
金之钧
解国军
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China Petroleum and Chemical Corp
Sinopec Exploration and Production Research Institute
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Abstract

The invention discloses an oil-gas migration aggregation numerical simulation method and system based on a component equation. The method comprises the following steps: establishing a basic equation and an auxiliary equation, wherein the basic equation is a partial differential equation system based on component mass balance and comprises an accumulation term, a Darcy seepage term, a compaction term and a source and sink term; discretizing the partial differential equation set by adopting a finite volume method to obtain a finite volume equation; carrying out full implicit solution on the finite volume equation to obtain main unknown quantity of a partial differential equation set; obtaining the rest unknowns of the partial differential equation set based on the auxiliary equation according to the obtained main unknowns; and carrying out numerical simulation of oil-gas migration accumulation according to the solved partial differential equation set. The system comprises the following steps: the method is implemented when a processor executes a computer program stored in a memory. According to the method, the problem that hydrocarbons with variable component contents in basin evolution cannot be accurately simulated by the existing Darcy seepage-based oil-gas migration aggregation numerical simulation method can be solved.

Description

Oil-gas migration aggregation numerical simulation method and system based on component equation
Technical Field
The invention belongs to the technical field of numerical simulation, and particularly relates to an oil-gas migration aggregation numerical simulation method and system based on a component equation.
Background
The oil and gas migration and accumulation analysis is important content in petroleum geological research, and the numerical simulation of the oil and gas migration and accumulation is an important component in basin simulation research and can be used for predicting the accumulation place and accumulation amount of oil and gas. In the existing basin simulation, the adopted oil-gas migration and accumulation numerical simulation method mainly comprises three methods, namely a streamline method, an invasion Yu-seepage method and a Darcy seepage equation solution method.
Among them, the streamline method is the simplest and fastest calculation method, and is generally used for rapid screening and evaluation. The flow line method is typically applied to highly permeable reservoirs or to sparse layers. In application, a permeability threshold value is usually set to distinguish the hydrophobic layer from the low-permeability layer or directly defined manually to give the hydrophobic layer and the low-permeability layer. When oil and gas enters a high permeable layer, buoyancy is considered as a driving force, and the oil and gas vertically moves to the next overlying rock unit until encountering a capillary and entering a low permeable layer with higher pressure, and preventing further movement. The flow line method does not take into account time or flow rate.
The invasion Yu-seepage method simulates migration of underground oil gas by drawing a breakthrough capillary pressure distribution diagram of each model grid body. Although the invasive Yu-ooze method is not a physically accurate numerical simulation method, the migration type generated by the method is well matched with the experiment, satisfactory results can be given to various geological scenes, and the numerical method is simple and easy to program. In addition, the invasion Yu-Permeability method adopts the same treatment mode for the reservoir and the non-reservoir, so that the migration of oil and gas in low permeability rock can be simulated.
Because the flow line method and the invasion Yu-osmotic method adopt models based on static force, the flow line method and the invasion Yu-osmotic method have no concept of time or flow rate and are irrelevant to parameters such as viscosity, permeability and the like. Meanwhile, the migration process and the gathering process of oil and gas are separately processed by a streamline method and an invasive percolation method, the saturation of the oil and gas in a grid body is usually given a fixed value, and therefore the distribution of the oil saturation of a reservoir cannot be accurately simulated by the two methods. In addition, neither of these methods addresses the process of oil and gas transport or drainage in the source rock.
The Darcy's equation solution to seepage can handle the rock permeability of wide range in nature in basin simulation. The computation time of the darcy's equation solver increases rapidly as the number of simulated grids increases, and therefore, lower precision grids are typically used. The Darcy seepage equation solution is the only method capable of simulating the migration and aggregation rate of real oil gas in the three methods, can simulate abnormal pressure, is the only method capable of simulating the formation and development of dynamic gas reservoirs such as deep basin gas and the like, and supports the downward migration of the oil gas. Therefore, the darcy seepage equation solution is unique and irreplaceable.
In basin simulation, there are many methods for realizing the Darcy seepage-based oil and gas migration aggregation numerical simulation, for example, the Petrommod basin simulation software adopts a finite element-based solving method, and more simulation techniques based on a finite volume method (Wendebourg & Harbaugh,1997; yuanyike and Hanyuga, 2008; shiguanren, et al, 2010; guo-autumn, et al, 2015), in which the first two documents solve the oil-water two-phase problem, and the last two documents solve the black oil model.
Due to the diversity of the phase states in which hydrocarbons exist in basins, and the large variation of hydrocarbon composition due to the varying degrees of thermal evolution, numerical simulations of darcy's percolation solutions based on component conservation become necessary. Multicomponent Darcy's percolation solutions are more commonly found in reservoir simulations, and are typically solved using partial differential equations based on the molar conservation of the components, and based on the molar ratios of the components as the basis variables (Langmuin, chenthon, 1990; zhanglin et al, 1991; yerengen, wu Rehong, 2000; zhanglin et al, 2002 Chen, 2007.
In basin simulation, various types of basins can be met, and the burial process of a stratum from shallow to deep is simulated, so that generated hydrocarbon components are evolved from heavy hydrocarbon components mainly to light hydrocarbon components mainly along with the gradual increase of the depth of source rocks, and the generated hydrocarbons are subjected to thermal cracking of the hydrocarbons along with the increase of the temperature of the stratum, so that the component content change of the hydrocarbons in the whole basin simulation process is usually very large, and an oil-water or gas-water two-phase model or a black oil model which is usually used for describing a single oil-gas phase and is used for oil reservoir simulation cannot meet the requirements of the existing basin simulation on various conditions that two oil-gas phases exist simultaneously or the phase changes in the evolution process, and therefore, a numerical simulation model capable of processing the hydrocarbon components and the phase changes is urgently needed.
Disclosure of Invention
The invention aims to solve the problem that the existing oil-gas migration and aggregation numerical simulation method based on Darcy seepage cannot accurately simulate hydrocarbons with variable component contents in basin evolution.
In order to achieve the purpose, the invention provides an oil-gas migration aggregation numerical simulation method and system based on a component equation.
According to a first aspect of the invention, a component equation-based oil and gas migration and accumulation numerical simulation method is provided, and comprises the following steps:
establishing a basic equation and an auxiliary equation, wherein the basic equation is a partial differential equation set based on component mass balance, the partial differential equation set comprises an accumulation term, a Darcy seepage term, a compaction term and a source sink term, and the auxiliary equation comprises a phase balance equation, a saturation constraint equation, a capillary pressure equation and a mass fraction constraint equation;
discretizing the partial differential equation set by adopting a finite volume method to obtain a finite volume equation;
carrying out full implicit solution on the finite volume equation to obtain main unknown quantities of the partial differential equation set;
acquiring the rest unknowns of the partial differential equation set based on the auxiliary equation according to the acquired main unknowns;
and carrying out numerical simulation of oil-gas migration accumulation according to the solved partial differential equation set.
Preferably, the expression of the partial differential equation system based on component mass balance is as follows:
Figure BDA0003047574060000041
in the above formula, L =1, \ 8230, N-1 is a hydrocarbon component, and L = N is a water component;
Figure BDA0003047574060000042
as gradient operator, uo、uwAnd ugOil overpressure, water overpressure, and gas overpressure, respectively, phi is the effective porosity of the rock, So、SwAnd SgRespectively oil saturation, water saturation, gas saturation, ulIn a calm rock potential, kro、krwAnd krgThe 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, rhoo、ρwAnd ρgThe density of the oil phase fluid, the density of the water phase fluid and the density of the gas phase fluid, mu, respectivelyo、μwAnd mugThe viscosity of the oil phase fluid, the viscosity of the water phase fluid and the viscosity of the gas phase fluid, qwIs the source-sink intensity of water, qLRepresenting the source-sink strength, σ, of the hydrocarbon componenteEffective stress, CLwIs the mass fraction of the component L in the water phase, CLoIs the mass fraction of component L in the oil phase, CLgIs the mass fraction of component L in the gas phase.
Preferably, the expression of the phase equilibrium equation is:
Figure BDA0003047574060000043
Figure BDA0003047574060000044
in the above formula, KLgoIs the equilibrium constant, K, of the component L between the gas phase and the oil phaseLgwF (x) is a function of pressure, temperature and component content, as is the equilibrium constant of component L between the gas phase and the water phase.
Preferably, the expression of the saturation constraint equation is:
So+Sw+Sg＝1 (4)。
preferably, the expression of the capillary pressure equation is:
uo-uw＝Pco(Sw)+Pwstatic-Postatic (5)
ug-uo＝Pcg(So)+Postatic-Pgstatic (6)
in the above formula, Pwstatic、PostaticAnd PgstaticRespectively hydrostatic, hydrostatic and hydrostatic pressure, Pco(Sw) Capillary pressure, P, to which the oil phase is subjectedcg(So) The capillary pressure to which the gas phase is subjected.
Preferably, the expression of the mass fraction constraint equation is:
Figure BDA0003047574060000051
in the above formula, o represents an oil phase, g represents a gas phase, and w represents an aqueous phase.
Preferably, the expression of the finite volume equation is:
Figure BDA0003047574060000052
in the above formula, Di，j，kAnd (3) representing the control volume of the grid unit with the coordinate (i, j, k) of the central point of the target calculation region.
Preferably, the fully implicit solving of the finite volume equation is specifically as follows:
the implicit iteration format of the finite volume equation is:
Figure BDA0003047574060000061
in the above formula, Vi,j,kIs the volume of the grid cell with center point coordinates (i, j, k), tn+1And tnBoth are time steps, l and l +1 are iteration times.
Preferably, all unknowns of the system of partial differential equations comprise overpressure of the fluid, saturation of the fluid, and mass fraction of components in the phase;
the primary unknowns include overpressure of the water and hydrocarbon component mass.
According to a second aspect of the present invention, there is provided a component equation-based hydrocarbon migration aggregation numerical simulation system, which comprises a processor and a memory, wherein the processor implements any one of the above-mentioned hydrocarbon migration aggregation numerical simulation methods when executing a computer program stored in the memory.
The invention relates to an oil-gas migration aggregation numerical simulation method based on component equations, which comprises the steps of firstly establishing a partial differential equation set and an auxiliary equation based on component mass balance for simulating oil-gas migration aggregation; secondly, discretizing the partial differential equation set by adopting a finite volume method to obtain a finite volume equation; carrying out full-implicit solution on the finite volume equation again to obtain main unknown quantity of the partial differential equation set; acquiring the other unknowns of the partial differential equation set based on the secondary equation according to the acquired main unknowns; and finally, carrying out numerical simulation of oil-gas migration aggregation according to the solved partial differential equation set.
The invention has the beneficial effects that:
1. the existing oil-gas migration and aggregation numerical simulation method based on Darcy seepage adopts a solution based on a two-phase flow or black oil model equation, so that the geological reality that the oil-gas phase state is changeable and the component composition difference is possibly huge under the actual geological condition cannot be completely described. The oil-gas migration aggregation numerical simulation method based on the component equation adopts a multi-component solution, so that the characteristic of various hydrocarbon composition changes in basin evolution can be accurately simulated.
2. At present, the establishment and the numerical solution of the multi-component mathematical model are both established on the basis of component molar conservation and solution by taking a component molar ratio as a basic variable, and the oil-gas migration aggregation numerical simulation method based on the component equation adapts to the actual geological situation in basin simulation, adopts the mathematical model based on grid body component mass balance, and solves by taking the grid body component mass as the basic variable, so that the solution result is directly reflected to the oil-gas mass distribution of a grid unit.
The component equation-based oil-gas migration and accumulation numerical simulation system and the component equation-based oil-gas migration and accumulation numerical simulation method belong to a general inventive concept, so the system and the method have the same beneficial effects as the component equation-based oil-gas migration and accumulation numerical simulation method, and are not repeated herein.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
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The above and other objects, features and advantages of the present invention will become more apparent by describing in more detail exemplary embodiments thereof with reference to the attached drawings, in which like reference numerals generally represent like parts throughout.
FIG. 1 shows a flow chart of an implementation of a component equation based hydrocarbon migration aggregation numerical simulation method according to embodiment 1 of the present disclosure;
fig. 2 shows a schematic view of a typical hexahedral cell according to embodiment 1 of the present invention;
fig. 3 shows a geological map of a slope region in a Tarim basin tower according to embodiment 1 of the present invention, wherein the region outlined by the small boxes is the region simulated by specific example 1;
FIG. 4 shows oil saturation profiles of middle and lower martial arts in two different periods according to example 1 of the present invention, wherein the left graph is the oil saturation profile of the middle and lower martial arts in 224 million years, and the right graph is the oil saturation profile of the middle and lower martial arts in 206 million years;
fig. 5 shows the oil saturation profiles of the hypothalamic wurtzitic formation and the middle hypothalamic formation at 433 million years according to example 1 of the present invention, wherein the left graph is the oil saturation profile of the hypothalamic wurtzitic formation at 433 million years, and the right graph is the oil saturation profile of the middle hypothalamic formation at 433 million years.
Detailed Description
Preferred embodiments of the present invention will be described in more detail below. While the following describes preferred embodiments of the present invention, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
Example 1: the component equation-based oil and gas migration and accumulation numerical simulation method is a finite volume method solving method of a three-dimensional three-phase multi-component partial differential equation based on a Darcy seepage model, and can be used for processing oil and gas migration and accumulation in a complex geological scene. The geological scene may be a conceptualized geologic volume, an oil and gas system, or a basin.
In the oil and gas migration and accumulation numerical simulation method based on the component equation, a partial differential equation set for simulating oil and gas migration and accumulation is obtained based on the mass conservation of the components and comprises an accumulation term, a Darcy seepage term, a compaction term and a source and sink term. The auxiliary equations considered simultaneously are a phase equilibrium equation, a saturation constraint equation, a capillary pressure equation and a mass fraction constraint equation. The variables to be solved for by the system of partial differential equations include the overpressure of the fluid, the saturation of the fluid, and the mass fractions of the components in the phases. The oil and gas migration aggregation numerical simulation method based on the component equations discretizes the partial differential equation set by a finite volume method. Since conservation of integration is satisfied for any set of control volumes, the entire calculation region is also conserved. The embodiment of the invention provides a finite volume method discrete process and a result of each item of an equation.
Because basin simulation generally involves a numerical simulation process with a large time scale and has high requirements on the stability of the simulation process, the embodiment of the invention provides a fully implicit solution of a finite volume equation. In a specific solving process, the main unknown variables are the overpressure of water and the mass of the hydrocarbon component, and the other variables are solved for by a functional relationship with pressure, temperature and the mass of the hydrocarbon component. These functions can be functionally formed by solving the functions for mass and mass fraction relationships, auxiliary equations, and other parameters such as density, viscosity, etc. of the phases.
FIG. 1 shows a flow chart of an implementation of a component equation-based oil and gas migration aggregation numerical simulation method according to an embodiment of the present invention. Referring to fig. 1, the oil and gas migration aggregation numerical simulation method based on the component equation of the embodiment of the invention comprises the following steps:
s100, establishing a basic equation and an auxiliary equation, wherein the basic equation is a partial differential equation set based on component mass balance, the partial differential equation set comprises an accumulation item, a Darcy seepage item, a compaction item and a source sink item, and the auxiliary equation comprises a phase balance equation, a saturation constraint equation, a capillary pressure equation and a mass fraction constraint equation;
s200, discretizing the partial differential equation set by adopting a finite volume method to obtain a finite volume equation;
step S300, carrying out full implicit solution on the finite volume equation to obtain main unknown quantity of the partial differential equation set;
s400, acquiring the rest unknowns of the partial differential equation set based on the auxiliary equation according to the acquired main unknowns;
and S500, carrying out numerical simulation of oil-gas migration aggregation according to the solved partial differential equation set.
Further, in step S100 of the embodiment of the present invention, the expression of the partial differential equation system based on the component mass balance is:
Figure BDA0003047574060000091
Figure BDA0003047574060000101
in the above formula, L =1, \ 8230, N-1 is a hydrocarbon component, and L = N is a water component;
Figure BDA0003047574060000102
as gradient operator, uo、uwAnd ugRespectively oil overpressure, water overpressure, and gas overpressure, [ Pa](ii) a Phi is the effective porosity of the rock, and is dimensionless; so、SwAnd SgOil saturation, water saturation and gas saturation are adopted respectively, and no dimension is adopted; u. ulIs a static rock potential, is dimensionless and is equal to static rock pressure-hydrostatic pressure; k is a radical ofro、krwAnd krgThe relative permeability of the oil phase fluid, the relative permeability of the water phase fluid and the relative permeability of the gas phase fluid are dimensionless; k is the absolute permeability of the rock, [ m ]2]；ρo、ρwAnd ρgDensity of oil phase fluid, density of water phase fluid anddensity of gas phase fluid, [ kg/m ]3]；μo、μwAnd mugThe viscosity of the oil phase fluid, the viscosity of the water phase fluid, and the viscosity of the gas phase fluid, [ pascal. Sec., pa.s ], respectively]；qwThe strength of the water source and sink, [ kg/(s.m ]3)]；qLRepresents the sink-source strength of the hydrocarbon component, [ kg/(s.m ]3)]；σeEffective stress, equal to ul-uw；CLwIs the mass fraction of the component L in the water phase, CLoIs the mass fraction of the component L in the oil phase, CLgIs the mass fraction of component L in the gas phase.
Still further, in step S100 of the embodiment of the present invention, the expression of the phase equilibrium equation is:
Figure BDA0003047574060000103
Figure BDA0003047574060000104
in the above formula, KLgoIs the equilibrium constant, K, of the component L between the gas phase and the oil phaseLgwF (x) is a function of pressure, temperature and component content, as is the equilibrium constant of component L between the gas phase and the water phase.
Between each two phases there is an equilibrium constant for each component which is a function of pressure, temperature and component content.
Still further, in step S100 of the embodiment of the present invention, an expression of the saturation constraint equation is:
So+Sw+Sg＝1 (4)。
still further, in step S100 of the embodiment of the present invention, the expression of the capillary pressure equation is:
uo-uw＝Pco(Sw)+Pwstatic-Postatic (5)
ug-uo＝Pcg(So)+Postatic-Pgstatic (6)
in the above formula, Pwstatic、PostaticAnd PgstaticRespectively hydrostatic, hydrostatic and hydrostatic pressure, Pco(Sw) Capillary pressure, P, to which the oil phase is subjectedcg(So) The capillary pressure of the gas phase.
Still further, in step S100 of the embodiment of the present invention, an expression of the quality fraction constraint equation is as follows:
Figure BDA0003047574060000111
in the above formula, o represents an oil phase, g represents a gas phase, and w represents an aqueous phase.
Still further, 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 one control volume around each grid point; and integrating the partial differential equation set to be solved based on the component mass balance into each control volume, and obtaining a set of discrete equations, wherein the unknown number is the value of the dependent variable on the grid point. In order to integrate the control volume, the law of the change of the assumed value between the grid points, i.e. the piecewise distribution characteristic of the assumed value, must be known.
Considering the case of a hexahedral control volume, the investigation region is subdivided into hexahedral cells as shown in fig. 2, for the cell (i, j, k) the volume (D) is controlled at (i, j, k)i，j，k) And integrating the partial differential equation set, and unfolding and sorting to obtain:
Figure BDA0003047574060000112
the following items are given for the control body unit of the internal node, respectively:
cumulative term (i.e. stored variance):
Figure BDA0003047574060000121
Figure BDA0003047574060000122
Figure BDA0003047574060000123
cell boundary inflow term (i.e., darcy seepage term):
Figure BDA0003047574060000124
Figure BDA0003047574060000125
Figure BDA0003047574060000126
Figure BDA0003047574060000131
wherein, the first and the second end of the pipe are connected with each other,
Figure BDA0003047574060000132
Figure BDA0003047574060000133
Figure BDA0003047574060000134
a compaction term:
Figure BDA0003047574060000135
and (4) source and sink items:
Figure BDA0003047574060000136
recording:
Figure BDA0003047574060000137
obtaining:
Figure BDA0003047574060000141
recording:
Figure BDA0003047574060000151
Figure BDA0003047574060000152
ΔxU＝Ui+1-Ui，ΔxTXΔxUi＝Ti+1/2(Ui+1—Ui)+Ti-1/2(Ui-1-Ui)，ΔyU＝Uj+1-Uj，ΔyTYΔyUj＝Tj+1/2(Uj+1-Uj)+Tj-1/2(Uj-1-Uj)ΔzU＝Uk+1-Uk，ΔzTZΔzUk＝Tk+1/2(Uk+1-Uk)+Tk-1/2(Uk-1-Uk)ΔTΔU＝ΔxTXΔxU+ΔyTYΔyU+ΔzTZΔzU
Figure BDA0003047574060000153
and
Figure BDA0003047574060000154
the resulting equation (18) is in shorthand form:
Figure BDA0003047574060000155
still further, step S300 of the present embodiment is a fully implicit solution of the finite volume equation. For any slave tnTo tn+1When the total implicit iteration is used for solving, setting an arbitrary variable U, and defining the difference value of U between two iterations l and l +1 as follows:
Figure BDA0003047574060000156
namely, it is
Figure BDA0003047574060000157
Also, when l =0, U0＝UnAfter multiple iterations, when | Ul+1-UlIf | < ε, Un+1＝Ul+1. Where epsilon is the given accuracy requirement. The iterative format can be written as:
Figure BDA0003047574060000158
the implicit iterative format of the finite volume equation that expands the flow term and the cumulative term is as follows:
Figure BDA0003047574060000161
by using implicit functional relationships, get relationships about
Figure BDA0003047574060000162
Figure BDA0003047574060000163
And
Figure BDA0003047574060000164
and
Figure BDA0003047574060000165
the functional relationship of (a). M in this caserThe mass of each component in the lattice. Through a series of simplified processes, a simplified set of equations can be obtained:
Figure BDA0003047574060000166
specific calculation of matrix elements of the equation set:
some terms of the above equation related to the difference need to be expanded, including the coefficients of the unknown terms at the left end and the R4 of the terms at the right endLi,j,k、R5Li,j,k、R7i,j,k、R8i,j,kThe values relating to the 6 nodes around (i, j, k) need to be sorted out. Of particular note are three situations:
(1) for the node (i, j, k), the part related to the storage quantity and the compaction term is the right end term of the coefficient and the corresponding part for directly calculating the unknown number at the node;
(2) if the expression relates to the node (i, j, k) and the 6 nodes around the node (i, j, k), then the coefficients of 7 point unknowns or the right-end terms of 7 points are calculated simultaneously;
(3) if the expression relates to the value at 1/2 between the node (i, j, k) and the 6 nodes around it, then the right end term of 7 points or 6 points is also calculated at the same time; the specific situation varies according to the algorithm. If the upstream method is used, 7 points may be involved, and if simply replaced by another method, only 6 points may be involved.
Formation of the overall matrix:
in the above equation, an unknown quantity is defined at 1/2For p and S at 1/2wThe value of (1) adopts the principle of upstream weight. In the present equation, the quantities to be solved are respectively
Figure BDA0003047574060000171
(r =1,2,3, \8230;, N-1), and thus there are N total equations to be solved for conservation of component mass, the overall matrix is formed as follows:
(1) The nodes are as per k =1,nz; j =1,ny; i =1,nx in a cyclic order;
(2) For a given (i, j, k), the components are listed individually under component numbers 1,2, \8230;, N-1 (assuming component N is a water component); the number of discrete equations is then (N-1). Times.nx.ny. Times.nz.
An overall matrix equation constructed in accordance with the above method. Matrix solution adopts LU decomposition method.
The effect of the oil-gas migration aggregation numerical simulation method based on the component equation in the embodiment of the invention is described based on two specific examples as follows:
(1) Simulating oil and gas migration and accumulation in a small range of a Tarim basin:
a small area of the sloped region in the tower of the tali basin was selected for simulation (small boxed part in fig. 3). There are two sets of source rocks in this area, namely the middle-lower frigid system and the middle-lower Ordovician system. Hydrocarbon generation model A four-component hydrocarbon model from Behar et al (1997) was used, with four components C1, C2-C5, C6-C14 and C15+, respectively. And simulating the phase state of the oil gas by flash evaporation calculation. Through simulation of the burial history, the thermal history and the hydrocarbon generation and discharge history, the amount of four components discharged from the source rock is used as a source item to enter a numerical simulation model for oil and gas gathering simulation, and overpressure in the simulation comes from overpressure simulation of the burial history in basin simulation. Fig. 4 shows the distribution of oil saturation of the middle-lower fringed strata obtained after simulation at two different moments.
(2) Simulating oil and gas migration and accumulation in the whole Tarim basin range:
the entire Tarim basin was selected for simulation. The whole basin range also adopts two sets of source rocks of middle and lower frigidity and middle and lower Orotan systems, and the hydrocarbon generation model adopts a four-component hydrocarbon model of Behar et al (1997), wherein the four components are respectively C1, C2-C5, C6-C14 and C15+. And simulating the oil-gas phase state by adopting flash evaporation calculation. Through simulation of the burial history, the thermal history and the hydrocarbon generation and discharge history, the amount of four components discharged from the source rock is used as a source item to enter a numerical simulation model for oil and gas gathering simulation, and overpressure in the simulation comes from overpressure simulation of the burial history in basin simulation. Fig. 5 shows the oil saturation distribution of the middle-lower han wushu strata and the middle-lower aodong system strata obtained after the simulation in 433 million years.
The embodiment of the invention provides a numerical simulation method of three-phase multi-component Darcy seepage. In view of the characteristic that the oil and gas components in the basin simulation are usually expressed by mass in grid units at present, the method of the embodiment of the invention takes the component mass rather than the molar ratio as a basic variable, and then carries out the fully-implicit discrete solution based on the finite volume method. The embodiment of the invention provides a numerical solution method of partial differential equations, which comprises an accumulation term, a Darcy seepage term, a compaction term and a source-sink term and is suitable for basin simulation. The embodiment of the invention adopts a finite volume method to carry out discretization and carries out full implicit solution. The main unknowns in the solution are the overpressure of water and the mass of the hydrocarbon component, and other variables and parameters are solved through the relation between the parameters and the temperature, the pressure and the mass of the component, so that the aim of solving the whole differential equation set is fulfilled.
Example 2: on the basis of the oil and gas migration and accumulation numerical simulation method based on the component equation provided in the embodiment 1, the embodiment of the invention correspondingly provides an oil and gas migration and accumulation numerical simulation system based on the component equation, which comprises a processor and a memory, wherein the processor realizes the oil and gas migration and accumulation numerical simulation method based on the component equation in the embodiment 1 when executing the computer program stored in the memory.
The component equation-based oil-gas migration and accumulation numerical simulation system in the embodiment of the invention has the same beneficial effects as the component equation-based oil-gas migration and accumulation numerical simulation method in the embodiment 1, and is not repeated here for avoiding repetition.
Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.

Claims (10)

1. The oil-gas migration aggregation numerical simulation method based on the component equation is characterized by comprising the following steps of:
establishing a basic equation and an auxiliary equation, wherein the basic equation is a partial differential equation set based on component mass balance, the partial differential equation set comprises an accumulation term, a Darcy seepage term, a compaction term and a source sink term, and the auxiliary equation comprises a phase balance equation, a saturation constraint equation, a capillary pressure equation and a mass fraction constraint equation;
discretizing the partial differential equation set by adopting a finite volume method to obtain a finite volume equation;
performing full-implicit solution on the finite volume equation to obtain main unknowns of the partial differential equation set;
acquiring the rest unknowns of the partial differential equation set based on the auxiliary equation according to the acquired main unknowns;
and carrying out numerical simulation of oil-gas migration aggregation according to the solved partial differential equation set.
2. The hydrocarbon migration aggregation numerical simulation method of claim 1, wherein the expression of the partial differential equation set based on component mass balance is:
Figure FDA0003047574050000011
in the above formula, L =1, \ 8230, N-1 is a hydrocarbon component, and L = N is a water component;
Figure FDA0003047574050000021
as gradient operator, uo、uwAnd ugOil overpressure, water overpressure and gas overpressure, respectively, phi is the effective porosity of the rock, So、SwAnd SgAre respectively oil saturation, water saturation, gas saturation, ulIn a calm rock potential, kro、krwAnd krgThe 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, po、pwAnd ρgThe density of the oil phase fluid, the density of the water phase fluid and the density of the gas phase fluid, mu, respectivelyo、μwAnd mugThe viscosity of the oil phase fluid, the viscosity of the water phase fluid and the viscosity of the gas phase fluid, qwIs the source-sink intensity of water, qLRepresents the source-sink strength, σ, of the hydrocarbon componenteEffective stress, CLwIs the mass fraction of the component L in the water phase, CLoIs the mass fraction of component L in the oil phase, CLgIs the mass fraction of component L in the gas phase.
3. The hydrocarbon migration aggregation numerical simulation method of claim 2, wherein the expression of the phase equilibrium equation is:
Figure FDA0003047574050000022
Figure FDA0003047574050000023
in the above formula, KLgoIs the equilibrium constant, K, of the component L between the gas phase and the oil phaseLgwF (x) is a function of pressure, temperature and component content, as is the equilibrium constant of component L between the gas phase and the water phase.
4. The hydrocarbon migration aggregation numerical simulation method of claim 3, wherein the expression of the saturation constraint equation is:
So+Sw+Sg＝1 (4)。
5. the hydrocarbon migration and accumulation numerical simulation method of claim 4, wherein the expression of the capillary pressure equation is:
uo-uw＝Pco(Sw)+Pwstatic-Postatic (5)
ug-uo＝Pcg(So)+Postatic-Pgstatic (6)
in the above formula, Pwstatic、PostaticAnd PgstaticRespectively hydrostatic, hydrostatic and hydrostatic pressure, Pco(Sw) Capillary pressure, P, to which the oil phase is subjectedcg(So) The capillary pressure to which the gas phase is subjected.
6. The hydrocarbon migration aggregation numerical simulation method of claim 5, wherein the expression of the mass fraction constraint equation is:
Figure FDA0003047574050000031
in the above formula, o represents an oil phase, g represents a gas phase, and w represents an aqueous phase.
7. The hydrocarbon migration accumulation numerical simulation method of claim 6, wherein the finite volume equation has the expression:
Figure FDA0003047574050000032
in the above formula, Di，j，kAnd (3) representing the control volume of the grid unit with the coordinate of the central point of the target calculation region being (i, j, k).
8. The hydrocarbon migration and accumulation numerical simulation method of claim 7, wherein said fully implicit solving of said finite volume equation is specifically:
the implicit iteration format of the finite volume equation is:
Figure FDA0003047574050000033
in the above formula, Vi，j，kIs the volume of the grid cell with center point coordinates (i, j, k), tn+1And tnBoth time steps, l and l +1 are the number of iterations.
9. The hydrocarbon migration accumulation numerical simulation method of claim 8 wherein all unknowns of the system of partial differential equations comprise overpressure of the fluid, saturation of the fluid, and component mass fractions in the phases;
the primary unknowns include overpressure of water and hydrocarbon component mass.
10. A hydrocarbon migration accumulation numerical simulation system based on a compositional equation, comprising a processor and a memory, the processor implementing the hydrocarbon migration accumulation numerical simulation method of any one of claims 1-9 when executing a computer program stored in the memory.
CN202110477270.1A 2021-04-29 2021-04-29 Oil-gas migration aggregation numerical simulation method and system based on component equation Pending CN115270535A (en)

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