CN116663370B - Fluid-solid coupling numerical simulation method for deep fracture-cavity type carbonate reservoir - Google Patents
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- 238000000034 method Methods 0.000 title claims abstract description 55
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 title claims abstract description 36
- 230000008878 coupling Effects 0.000 title claims abstract description 33
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- 230000035699 permeability Effects 0.000 claims description 23
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 21
- 239000004215 Carbon black (E152) Substances 0.000 claims description 9
- 229930195733 hydrocarbon Natural products 0.000 claims description 9
- 150000002430 hydrocarbons Chemical class 0.000 claims description 9
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- 230000009286 beneficial effect Effects 0.000 abstract 1
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- 238000007596 consolidation process Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 230000005501 phase interface Effects 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
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Abstract
The invention discloses a fluid-solid coupling numerical simulation method for a deep fracture-cavity type carbonate reservoir, which comprises the following steps of: s1: calculating grid geometric information and connection information of matrixes, cracks and karst cave according to a fracture-cave type carbonate reservoir geological model provided by an oilfield site and by combining a discrete fracture-cave model; s2: establishing a fluid-solid coupling mathematical model and a numerical solution format of a deep fracture-cavity type carbonate reservoir; s3: and carrying out fracture-cavity type carbonate reservoir numerical simulation according to the reservoir grid geometric information and the reservoir and fluid attribute parameters. The beneficial effects of the invention are as follows: by considering the factors such as multiphase multicomponent seepage in the matrix and the cracks, multiphase free flow in the karst cave, elastoplastic deformation of the matrix, nonlinear deformation of the cracks, deformation of the karst cave and the like, the development process and production dynamics of the deep fracture-cave type carbonate reservoir can be accurately simulated and predicted through the method.
Description
Technical Field
The invention relates to the technical field of carbonate oil gas development, in particular to a fluid-solid coupling numerical simulation method for a deep fracture-cavity type carbonate oil reservoir.
Background
The oil and gas resources of the western carbonate reservoirs in China are rich, wherein the fracture-cavity accounts for about 2/3, and the method is a realistic field of increasing the storage and the production. Unlike conventional reservoirs, fracture-cavity reservoirs have tremendous differences from reservoir space to flow law, first: fracture-cavity type oil reservoir reservoirs are generally buried extremely deeply, more than 5000m and deep or ultra-deep, and are in a high-temperature, high-pressure and high-stress 'three-high' environment; second,: the oil-gas phase state is complex in the environment of three highs, and the rock deformation is transformed from elasticity to elastoplasticity; third,: the fracture-cavity type oil reservoir has various reservoir space types, not only comprises cracks and dissolved pores, but also has karst cavities with different space scales, and is a complicated seepage-free flow coupling flow mode in flow.
At present, conventional oil and gas reservoir flow numerical simulation technology is relatively mature, and a plurality of commercial software is formed, but a numerical simulation theory and a method of a comprehensive system are not formed for a fracture-cavity type oil reservoir. Firstly, aiming at a complex fracture-karst cave structure and a seepage-free flow coupling flow mode existing in a fracture-vug type oil reservoir, a conventional simulation technology is basically described by adopting local grid encryption and a high-speed non-Darcy model, but the high-speed non-Darcy model cannot accurately represent the free flow characteristics of multiphase fluid in the karst cave, the local grid encryption can cause extremely large calculated grid quantity, and complex fracture morphology cannot be processed efficiently; in addition, the conventional oil reservoir numerical simulation technology generally adopts a compression coefficient to represent deformation effect in the oil reservoir development process, and the oil reservoir deformation is considered to be only related to fluid pressure change, so that the influence of ground stress is ignored, but for a fracture-cavity type oil reservoir with strong stress sensitivity under deep high-stress conditions, the influence of elastoplastic deformation of a matrix reservoir and the mechanical deformation effect of a fracture-karst cavity is obvious, and the accuracy of numerical simulation is seriously influenced by neglecting or weakening the effect. Therefore, in order to develop the deep fracture-cavity type carbonate reservoir, through long-term research of the inventor, a fluid-solid coupling numerical simulation method for the deep fracture-cavity type carbonate reservoir is invented.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a fluid-solid coupling numerical simulation method for a deep fracture-cavity type carbonate reservoir.
The aim of the invention is achieved by the following technical scheme: a fluid-solid coupling numerical simulation method for a deep fracture-cavity type carbonate reservoir comprises the following steps:
s1: calculating grid geometric information and connection information of matrixes, cracks and karst cave according to a fracture-cave type carbonate reservoir geological model provided by an oilfield site and by combining a discrete fracture-cave model;
s2: establishing a fluid-solid coupling mathematical model and a numerical solution format of a deep fracture-cavity type carbonate reservoir;
s3: and carrying out fracture-cavity type carbonate reservoir numerical simulation according to the reservoir grid geometric information and the reservoir and fluid attribute parameters.
Preferably, in step S1, the method further includes the steps of:
s1.1: calculating the center coordinates and the grid volume of each grid according to a corner grid geological model of a fracture-cavity oil reservoir provided by an oilfield site, and identifying matrixes and karst cavity grids based on grid attribute numbers;
s1.2: according to a three-dimensional complex fracture structure provided by an oilfield site, performing grid subdivision by adopting unstructured grids, and calculating the central coordinate and unit volume of each fracture grid;
s1.3: combining grids in each karst cave region to form a new karst cave grid;
s1.4: identifying and establishing connection relations between the matrix grids and between the matrix and the karst cave grids according to node information of the matrix and the karst cave grids; identifying and establishing a connection relation among the crack grids according to node information of the crack grids; based on the central coordinates of the crack grids, identifying the matrix grids where the crack grids are located, and establishing a connection relationship between the crack-matrix grids and the crack-karst cave grids by combining the connection relationship between the matrix and the karst cave grids.
Preferably, in step 1.3, the coordinates of the new karst cave grid are obtained by weighting the coordinates of the grid in the karst cave region by a volume obtained by summing the volumes of the grids in the karst cave region.
Preferably, in step S2, the method further includes the steps of:
s2.1: establishing a multi-phase multi-component seepage mathematical model of the deep fracture-cavity type carbonate reservoir;
s2.2: establishing an elastoplastic mechanical model of the deep fracture-cavity oil reservoir;
s2.3: establishing a fluid-solid coupling constitutive relation;
s2.4: performing numerical discrete on the seepage mathematical model by a finite volume method, and performing full implicit solving by adopting a Newton iteration method;
s2.5: performing numerical discrete on the mechanical model by a finite element method, solving and updating plastic deformation by adopting a rollback mapping method, and solving the mechanical model by adopting a Newton iteration method;
s2.6: and solving fluid-solid coupling through a fixed stress splitting iteration method.
Preferably, in step S2.1, a model is built by a mass conservation equation of hydrocarbon and water components in the matrix, the fracture and the karst cave, a motion equation of three phases of oil, gas and water in the matrix and the fracture, a multiphase fluid instantaneous gravity difference model in the karst cave, an auxiliary equation and a seepage boundary condition, wherein the mass conservation equation of hydrocarbon and water components in the matrix, the fracture and the karst cave is as follows:
；
；
wherein, subscripts o, g and w respectively represent three phases of oil, gas and water,representing hydrocarbonsiThe mole fraction of the components in the oil phase,representing hydrocarbonsiMole fraction of the components in the gas phase, +.>For molar density, +.>Is of saturation degree>Representing reservoir porosity, +.>Representing hydrocarbonsiThe source and sink items of the components, < >>Representing the source sink of the water component,
the motion equation of the three phases of oil, gas and water in the matrix and the crack is as follows:
；
；
wherein ,for seepage velocity, +.>Is viscosity; />For relative permeability, ++>Indicating the depth of the reservoir,
the auxiliary equation is:
；
；
；
；
；
wherein ,for component number, & gt>For the phase pressure +.>Capillary force representing moisture->Representing the capillary force of the oil and gas,
the seepage boundary conditions are as follows:
；
wherein ,is the pressure value on the fixed pressure boundary; />Unit normal vector for closed boundary; />Is a Dirichlet boundary; />Is a Neumann boundary.
Preferably, in step 2.2, the deep fracture-cavity oil reservoir elastoplastic model is established through a mechanical equilibrium equation, an incremental stress-strain constitutive equation, a plastic yield criterion, a flow criterion and mechanical boundary conditions, wherein the mechanical equilibrium equation is as follows:
；
wherein ,is the total stress tensor; />In the form of a volumetric force,
the incremental stress-strain constitutive equation is:
；
wherein ,is elastic rigidity matrix>Representing the elastic strain tensor->Is the Biot coefficient; />Is the total fluid pressure; />Is a unit tensor;
the plastic yield criterion is:
；
wherein ,a second invariant to stress bias; />A first invariant which is a stress tensor; /> and />As a parameter of the intensity of the light,
the plastic flow criteria were:
；
wherein ,representing the plastic strain tensor->In the form of a plastic multiplier, the plastic multiplier,
the mechanical boundary conditions are as follows:
；
；
；
；
wherein ,for locating the displacement value on the displacement boundary +.>For the load value at the fixed load boundary +.>Is a unit normal vector on a fixed load boundary, +.>Is the unit normal vector on the crack face, +.>Biot coefficient for cleavage, < >>Biot pressure for cleavage, +.>For crack border +.>Is a unit normal vector on the karst cave boundary; />Is the karst cave boundary.
Preferably, in step S2.3, a fluid-solid coupling constitutive relation is established through a matrix porosity and permeability constitutive relation, a fracture porosity and permeability constitutive relation and a karst cave volume updating formula, where the matrix porosity and permeability constitutive relation is:
；
；
wherein the subscriptFor matrix, subscript 0 indicates initial state, ++>For true porosity, the true porosity is related to reservoir porosity as follows:
；
wherein ,、/>the volume strain and the average stress are indicated respectively,Kfor the bulk modulus of the material,
the constitutive relation of the porosity and the permeability of the crack is as follows:
；
；
；
；
wherein ,findicating that the crack is to be formed,is the crack closing amount; />Maximum allowable closing amount of the crack; />Is a normal stress acting on the fracture surface; />Initial stiffness for the fracture;dis the opening degree of the crack, the opening degree of the crack is the opening degree of the crack,
the karst cave grid is cut into a plurality of sub-grids, the deformed sub-grid volumes are calculated and summed, and the karst cave volumes are updated according to the following updating formula:
；
wherein ,is the karst cave volume; />The number of subunits formed after cutting the karst cave units; />To the post-cutting firstiThe volume of the subunit.
Preferably, in step S2.4, when fluid flows from the karst cave to other mediums, the phase of the karst cave is defined as follows:
；
wherein , and />And respectively representing the saturation corresponding to the upper and lower boundaries of other medium grids connected with the karst cave.
Preferably, in step S3, the method further includes the steps of:
s3.1: generating input information required by reservoir numerical simulation by combining the grid geometric information and the connection information through the matrix, the porosity, the permeability, the relative permeability curve, the capillary force curve of the crack, the Young modulus, the Poisson ratio and the hardening curve of the matrix, the initial rigidity, the maximum allowable closing amount of the crack and the phase state parameters of reservoir fluid;
s3.2: carrying out oil reservoir numerical simulation through the numerical discrete format and the solving flow in the step S2;
s3.3: and outputting the simulation results of the oil reservoir pressure, saturation distribution and oil and water yield curves.
The invention has the following advantages: according to the method, the development process and production dynamics of the deep fracture-cavity type carbonate reservoir can be accurately simulated and predicted by considering the factors such as multiphase multicomponent seepage in the matrix and the fracture, multiphase free flow in the karst cavity, elastoplastic deformation of the matrix, nonlinear deformation of the fracture, deformation of the karst cavity and the like.
Drawings
FIG. 1 is a schematic illustration of a non-structural meshing of a three-dimensional complex fracture structure;
FIG. 2 is a schematic diagram of karst cave grid consolidation;
FIG. 3 is a schematic view of karst cave mesh cutting when updating the karst cave mesh volume;
FIG. 4 is a schematic diagram of a gravity differential model of a karst cave multiphase fluid;
fig. 5 is a flow chart of a fixed stress split iterative coupling solution.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the invention, as presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, based on the embodiments of the invention, which are apparent to those of ordinary skill in the art without inventive faculty, are intended to be within the scope of the invention.
In addition, the embodiments of the present invention and the features of the embodiments may be combined with each other without collision.
It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.
In this embodiment, a method for simulating fluid-solid coupling values of a deep fracture-cavity carbonate reservoir includes the following steps:
s1: calculating grid geometric information and connection information of matrixes, cracks and karst cave according to a fracture-cave type carbonate reservoir geological model provided by an oilfield site and by combining a discrete fracture-cave model;
s2: establishing a fluid-solid coupling mathematical model and a numerical solution format of a deep fracture-cavity type carbonate reservoir;
s3: and carrying out fracture-cavity type carbonate reservoir numerical simulation according to the reservoir grid geometric information and the reservoir and fluid attribute parameters. By considering the factors such as multiphase multicomponent seepage in the matrix and the cracks, multiphase free flow in the karst cave, elastoplastic deformation of the matrix, nonlinear deformation of the cracks, deformation of the karst cave and the like, the development process and production dynamics of the deep fracture-cave type carbonate reservoir can be accurately simulated and predicted through the method.
Further, in step S1, the method further includes the following steps:
s1.1: calculating the center coordinates and the grid volume of each grid according to a corner grid geological model of a fracture-cavity oil reservoir provided by an oilfield site, and identifying matrixes and karst cavity grids based on grid attribute numbers;
s1.2: according to the three-dimensional complex fracture structure provided by the oilfield site, adopting an unstructured grid to conduct grid subdivision, as shown in fig. 1, and calculating the central coordinate and unit volume of each fracture grid;
as shown in fig. 2, S1.3: combining grids in each karst cave region to form a new karst cave grid; preferably, in step 1.3, the coordinates of the new karst cave grid are obtained by weighting the coordinates of the grid in the karst cave region by a volume obtained by summing the volumes of the grids in the karst cave region.
S1.4: identifying and establishing connection relations between the matrix grids and between the matrix and the karst cave grids according to node information of the matrix and the karst cave grids; identifying and establishing a connection relation among the crack grids according to node information of the crack grids; based on the central coordinates of the crack grids, identifying the matrix grids where the crack grids are located, and establishing a connection relationship between the crack-matrix grids and the crack-karst cave grids by combining the connection relationship between the matrix and the karst cave grids.
In this embodiment, in step S2, the following steps are further included:
s2.1: establishing a multi-phase multi-component seepage mathematical model of the deep fracture-cavity type carbonate reservoir; further, in step S2.1, a model is built by a mass conservation equation of hydrocarbon and water components in the matrix, the fracture and the karst cave, a motion equation of three phases of oil, gas and water in the matrix and the fracture, an instantaneous gravity difference model of multiphase fluid in the karst cave, an auxiliary equation and a seepage boundary condition, wherein the mass conservation equation of hydrocarbon and water components in the matrix, the fracture and the karst cave is as follows:
；
；
wherein, subscripts o, g and w respectively represent three phases of oil, gas and water,representing hydrocarbonsiThe mole fraction of the components in the oil phase,representing hydrocarbonsiMole fraction of the components in the gas phase, +.>For molar density, +.>Is of saturation degree>Representing reservoir porosity, +.>Representing hydrocarbonsiThe source and sink items of the components, < >>Representing the source sink of the water component,
the motion equation of the three phases of oil, gas and water in the matrix and the crack is as follows:
；
；
wherein ,for seepage velocity, +.>Is viscosity; />For relative permeability, ++>Indicating the depth of the reservoir,
the auxiliary equation is:
；
；
；
；
；
wherein ,for component number, & gt>For the phase pressure +.>Capillary force representing moisture->Representing the capillary force of the oil and gas,
the seepage boundary conditions are as follows:
；
wherein ,is the pressure value on the fixed pressure boundary; />Unit normal vector for closed boundary; />Is a Dirichlet boundary; />Is a Neumann boundary.
S2.2: establishing an elastoplastic mechanical model of the deep fracture-cavity oil reservoir; in step 2.2, a deep fracture-cavity oil reservoir elastoplastic model is built by a mechanical equilibrium equation, an incremental stress-strain constitutive equation, a plastic yield criterion, a flow criterion and mechanical boundary conditions, wherein the mechanical equilibrium equation is as follows:
；
wherein ,is the total stress tensor; />In the form of a volumetric force,
the incremental stress-strain constitutive equation is:
；
wherein ,is elastic rigidity matrix>Representing the elastic strain tensor->Is the Biot coefficient; />Is the total fluid pressure; />Is a unit tensor;
the plastic yield criterion is:
；
wherein ,a second invariant to stress bias; />A first invariant which is a stress tensor; /> and />As a parameter of the intensity of the light,
the plastic flow criteria were:
；
wherein ,representing the plastic strain tensor->In the form of a plastic multiplier, the plastic multiplier,
the mechanical boundary conditions are as follows:
；
；
；
；
wherein ,for locating the displacement value on the displacement boundary +.>For the load value at the fixed load boundary +.>Is a unit normal vector on a fixed load boundary, +.>Is the unit normal vector on the crack face, +.>Biot coefficient for cleavage, < >>Biot pressure for cleavage, +.>For crack border +.>Is a unit normal vector on the karst cave boundary; />Is the karst cave boundary.
S2.3: establishing a fluid-solid coupling constitutive relation; in this embodiment, in step S2.3, a fluid-solid coupling constitutive relation is established through a matrix porosity and permeability constitutive relation, a fracture porosity and permeability constitutive relation and a karst cave volume update formula, where the matrix porosity and permeability constitutive relation is:
；
；
wherein the subscriptFor matrix, subscript 0 indicates initial state, ++>For true porosity, the true porosity is related to reservoir porosity as follows:
；
wherein ,、/>the volume strain and the average stress are indicated respectively,Kfor the bulk modulus of the material,
the constitutive relation of the porosity and the permeability of the crack is as follows:
；
；
；
；
wherein ,findicating that the crack is to be formed,is the crack closing amount; />Maximum allowable closing amount of the crack; />Is a normal stress acting on the fracture surface; />Initial stiffness for the fracture;dis the opening degree of the crack, the opening degree of the crack is the opening degree of the crack,
as shown in fig. 3, by cutting the karst cave grid into a plurality of sub-grids, calculating and summing the deformed sub-grid volumes, updating the karst cave volume, the update formula of which is as follows:
；
wherein ,is the karst cave volume; />The number of subunits formed after cutting the karst cave units; />To the post-cutting firstiThe volume of the subunit.
S2.4: performing numerical discrete on the seepage mathematical model by a finite volume method, and performing full implicit solving by adopting a Newton iteration method; further, as shown in fig. 4, in step S2.4, the flow in the karst cave is described by using a multiphase fluid instantaneous gravity difference model, and when the fluid flows from the karst cave to other mediums, the flow condition is related to the phase interface position in the karst cave, and the phase permeability of the karst cave is defined as follows:
；
wherein , and />And respectively representing the saturation corresponding to the upper and lower boundaries of other medium grids connected with the karst cave.
S2.5: performing numerical discrete on the mechanical model by a finite element method, solving and updating plastic deformation by adopting a rollback mapping method, and solving the mechanical model by adopting a Newton iteration method;
as shown in fig. 5, S2.6: and solving fluid-solid coupling through a fixed stress splitting iteration method. Specifically, firstly, solving a seepage mathematical model under the condition of unchanged average stress; solving a mechanical model based on the pressure and saturation results obtained by the seepage solution; updating the porosity and permeability of the matrix and the crack and the volume of the karst cave according to the fluid-solid coupling constitutive relation; checking whether the flow field or the displacement field is stable, if so, performing iterative coupling convergence, entering the next time step, and if not, continuing iteration.
In this embodiment, in step S3, the following steps are further included:
s3.1: generating input information required by reservoir numerical simulation by combining the grid geometric information and the connection information through the matrix, the porosity, the permeability, the relative permeability curve, the capillary force curve of the crack, the Young modulus, the Poisson ratio and the hardening curve of the matrix, the initial rigidity, the maximum allowable closing amount of the crack and the phase state parameters of reservoir fluid;
s3.2: carrying out oil reservoir numerical simulation through the numerical discrete format and the solving flow in the step S2;
s3.3: and outputting the simulation results of the oil reservoir pressure, saturation distribution and oil and water yield curves.
Although the present invention has been described with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments described, or equivalents may be substituted for elements thereof, and any modifications, equivalents, improvements and changes may be made without departing from the spirit and principles of the present invention.
Claims (7)
1. A fluid-solid coupling numerical simulation method for a deep fracture-cavity type carbonate reservoir is characterized by comprising the following steps of: the method comprises the following steps:
s1: calculating grid geometric information and connection information of matrixes, cracks and karst cave according to a fracture-cave type carbonate reservoir geological model provided by an oilfield site and by combining a discrete fracture-cave model;
s2: establishing a fluid-solid coupling mathematical model and a numerical solution format of a deep fracture-cavity type carbonate reservoir;
s3: carrying out fracture-cavity type carbonate reservoir numerical simulation according to the reservoir grid geometric information and reservoir and fluid attribute parameters;
in the step S2, the method further includes the following steps:
s2.1: establishing a multi-phase multi-component seepage mathematical model of the deep fracture-cavity type carbonate reservoir;
s2.2: establishing an elastoplastic mechanical model of the deep fracture-cavity oil reservoir;
s2.3: establishing a fluid-solid coupling constitutive relation;
s2.4: performing numerical discrete on the seepage mathematical model by a finite volume method, and performing full implicit solving by adopting a Newton iteration method;
s2.5: performing numerical discrete on the mechanical model by a finite element method, solving and updating plastic deformation by adopting a rollback mapping method, and solving the mechanical model by adopting a Newton iteration method;
s2.6: solving fluid-solid coupling through a fixed stress splitting iteration method;
in the step 2.2, a deep fracture-cavity oil reservoir elastoplastic model is established through a mechanical balance equation, an incremental stress-strain constitutive equation, a plastic yield criterion, a flow criterion and mechanical boundary conditions, wherein the mechanical balance equation is as follows:
wherein σ is the total stress tensor; b is the volume force of the force,
the incremental stress-strain constitutive equation is:
dσ＝C:dε e -abp t I；
wherein C is an elastic stiffness matrix epsilon e Representing the elastic strain tensor, a being the Biot coefficient; p is p t Is the total fluid pressure; i is a unit tensor;
the plastic yield criterion is:
wherein ,J2 A second invariant to stress bias; i 1 A first invariant which is a stress tensor; η and ζ are the intensity parameters,
the plastic flow criteria were:
wherein ,εp Represents the plastic strain tensor, dγ is the plastic multiplier,
the mechanical boundary conditions are as follows:
σ n ＝n f ·(σ+a f p f I)·n f on Γ f ；
σ·n v ＝-p t I·n v on Γ v ；
wherein ,for locating the displacement value on the displacement boundary +.>To determine the load value at the load boundary, n r For unit normal vector at fixed load boundary, n f Is a unit normal vector on the fracture surface, a f Is a crackBiot coefficient, p f Biot pressure, Γ, for a crack f Is a crack boundary Γ D For Dirichlet boundary Γ N For Neumann boundary, n v Is a unit normal vector on the karst cave boundary; Γ -shaped structure v Is the karst cave boundary.
2. The method for simulating fluid-solid coupling numerical simulation of a deep fracture-cavity carbonate reservoir according to claim 1, wherein the method is characterized by comprising the following steps of: the step S1 further includes the following steps:
s1.1: calculating the center coordinates and the grid volume of each grid according to a corner grid geological model of a fracture-cavity oil reservoir provided by an oilfield site, and identifying matrixes and karst cavity grids based on grid attribute numbers;
s1.2: according to a three-dimensional complex fracture structure provided by an oilfield site, performing grid subdivision by adopting unstructured grids, and calculating the central coordinate and unit volume of each fracture grid;
s1.3: combining grids in each karst cave region to form a new karst cave grid;
s1.4: identifying and establishing connection relations between the matrix grids and between the matrix and the karst cave grids according to node information of the matrix and the karst cave grids; identifying and establishing a connection relation among the crack grids according to node information of the crack grids; based on the central coordinates of the crack grids, identifying the matrix grids where the crack grids are located, and establishing a connection relationship between the crack-matrix grids and the crack-karst cave grids by combining the connection relationship between the matrix and the karst cave grids.
3. The method for simulating fluid-solid coupling numerical simulation of a deep fracture-cavity carbonate reservoir according to claim 2, wherein the method is characterized by comprising the following steps of: in the step S1.3, the coordinates of the new karst cave grid are obtained by weighting the coordinates of the grid in the karst cave region by a volume, and the volume is obtained by summing the volumes of the grids in the karst cave region.
4. The method for simulating fluid-solid coupling values of a deep fracture-cavity carbonate reservoir according to claim 3, wherein the method comprises the following steps of: in the step S2.1, a model is built through a mass conservation equation of hydrocarbon and water components in a matrix, a crack and a karst cave, a motion equation of three phases of oil, gas and water in the matrix and the crack, a multiphase fluid instant gravity difference model in the karst cave, an auxiliary equation and a seepage boundary condition, wherein the mass conservation equation of the hydrocarbon and water components in the matrix, the crack and the karst cave is as follows:
wherein subscripts o, g and w respectively represent oil, gas and water phases, x i Represents the mole fraction of the hydrocarbon i component in the oil phase, y i Represents the mole fraction of the hydrocarbon i component in the gas phase, ρ is the molar density, S is the saturation, φ represents the reservoir porosity, q i Source sink term, q, representing hydrocarbon i component w Representing the source sink of the water component,
the motion equation of the three phases of oil, gas and water in the matrix and the crack is as follows:
ψ β ＝ρ β -ρ g D；
wherein v is the seepage velocity and μ is the viscosity; k (k) r For relative permeability, D represents reservoir depth,
the auxiliary equation is:
S o +S g +S w ＝1；
p w ＝p g -p cwg (S w )；
p o ＝p g -p cog (S w ,S o )；
wherein ,Nc Is the component number, p is the phase pressure, p cwg Capillary force, p, representing moisture cog Representing the capillary force of the oil and gas,
the seepage boundary conditions are as follows:
v β ·n＝0 on Γ N ；
wherein ,is the pressure value on the fixed pressure boundary; n is a unit normal vector of the closed boundary; Γ -shaped structure D Is a Dirichlet boundary; Γ -shaped structure N Is a Neumann boundary.
5. The method for simulating fluid-solid coupling values of a deep fracture-cavity carbonate reservoir according to claim 4, wherein the method comprises the following steps of: in the step S2.3, a fluid-solid coupling constitutive relation is established through a matrix porosity and permeability constitutive relation, a crack porosity and permeability constitutive relation and a karst cave volume updating formula, wherein the matrix porosity and permeability constitutive relation is as follows:
wherein the subscript m isMatrix, subscript 0 indicates initial state, φ * For true porosity, the true porosity is related to reservoir porosity as follows:
φ＝φ * (1+ε v )；
wherein ,εv 、σ v Respectively representing the volume strain and the average stress, K is the volume modulus,
the constitutive relation of the porosity and the permeability of the crack is as follows:
d＝d 0 -ζ；
wherein f represents a crack, and ζ represents a crack closing amount; zeta type max Maximum allowable closing amount of the crack; sigma (sigma) n Is a normal stress acting on the fracture surface; k (k) ni Initial stiffness for the fracture; d is the opening degree of the crack, and the opening degree of the crack is equal to d,
the karst cave grid is cut into a plurality of sub-grids, the deformed sub-grid volumes are calculated and summed, and the karst cave volumes are updated according to the following updating formula:
wherein ,Vv Is the karst cave volume; n is n v The number of subunits formed after cutting the karst cave units; v (V) v,i Is the volume of the ith subunit after cutting.
6. The method for simulating fluid-solid coupling values of a deep fracture-cavity carbonate reservoir according to claim 5, wherein the method is characterized by comprising the following steps of: in the step S2.4, when the fluid flows from the karst cave to other mediums, the phase of the karst cave is defined as follows:
k rw ＝0(g-0)；
k ro ＝0,k rw ＝1(w)；
wherein ,Su and Sd And respectively representing the saturation corresponding to the upper and lower boundaries of other medium grids connected with the karst cave.
7. The method for simulating fluid-solid coupling values of a deep fracture-cavity carbonate reservoir according to claim 6, wherein the method is characterized by comprising the following steps of: in the step S3, the method further includes the following steps:
s3.1: generating input information required by reservoir numerical simulation by combining the grid geometric information and the connection information through the matrix, the porosity, the permeability, the relative permeability curve, the capillary force curve of the crack, the Young modulus, the Poisson ratio and the hardening curve of the matrix, the initial rigidity, the maximum allowable closing amount of the crack and the phase state parameters of reservoir fluid;
s3.2: carrying out oil reservoir numerical simulation through the numerical discrete format and the solving flow in the step S2;
s3.3: and outputting the simulation results of the oil reservoir pressure, saturation distribution and oil and water yield curves.
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