A simulation method and system for vertical well seepage of composite carbonate rock oil reservoir

Abstract

The application discloses a simulation method and system for vertical well seepage of composite carbonate rock oil reservoirs, constructs inner and outer zone seepage continuity equations, inner and outer boundary conditions and initial conditions of fracture systems, cave systems and matrix systems in the inner and outer zones, and obtains a vertical well seepage model of the composite triple medium oil reservoir by using methods such as source functions, Laplace transform, perturbation transform and linear superposition principles of partial differential equations, so as to provide a theoretical basis for vertical well testing analysis of the composite oil reservoir.

Description

Technical Field

[0001] The present invention relates to the field of oil and gas reservoir development in petroleum and natural gas engineering, and in particular to a method and system for simulating seepage in vertical wells of composite carbonate reservoirs. Background Art

[0002] Carbonate reservoirs are widely distributed worldwide. A typical fracture-vuggy reservoir is composed of large, well-connected fractures, a low-permeability rock matrix, and numerous pores. Carbonate reservoirs are susceptible to mud contamination during drilling and development, and therefore are often acidized before production. After acidization, reservoir properties near the wellbore are improved while those far from the wellbore remain unchanged. Such reservoirs are commonly referred to as composite reservoirs. The seepage patterns in composite carbonate reservoirs are complex, and simulating the seepage of fluids in these reservoirs has become a challenging problem for petroleum professionals both domestically and internationally.

[0003] Existing reservoir fluid models can be divided into two categories: continuous medium models and discrete medium models.

[0004] In 1960, Barenblatt and other researchers established a continuous medium flow model for fractured reservoirs. In 1963, Warren and Root, building on Barenblatt's work, further clarified the concept and related theories of dual-medium flow. The continuum model assumes that the smallest physical entity constituting a fluid is a fluid particle, and that the fluid is composed of an infinite number of fluid particles in a continuous stream, with no gaps between them. This model is suitable for reservoirs with relatively small fractures and cavities. However, the flow patterns in composite carbonate reservoirs are more complex, with larger fractures and cavities and greater heterogeneity.

[0005] Discrete medium models often display large caves, describing fluid motion within caves using the Navier-Stokes (NS) equations and fluid flow within porous media using Darcy flow. The difficulty of discrete medium models lies in how to handle the coupled flow of fluids at the cave-porous medium interface. Currently, there are two main approaches in the literature: the single-domain approach (SDA) established by Brinkman in 1947, and the two-domain approach (TDA) established by Beavers and Joseph in 1967. Continuous medium models are suitable for reservoirs with weak heterogeneity and are also unsuitable for simulating the permeability of composite carbonate reservoirs. Summary of the Invention

[0006] In response to the problems existing in the prior art, the present invention provides a simulation method for seepage of vertical wells in composite carbonate reservoirs, which realizes the seepage simulation of fluids in carbonate reservoirs and provides a theoretical basis for well testing analysis of vertical wells in composite carbonate reservoirs.

[0007] The present invention is achieved through the following technical solutions:

[0008] A method for simulating seepage in a vertical well of a composite carbonate reservoir comprises the following steps:

[0009] Step 1: Based on the relationship between the cumulative produced liquid volume and the instantaneous flow rate of the triple medium reservoir, the inner boundary conditions of the point source function of the composite triple medium reservoir are established;

[0010] Step 2: Based on the assumptions of the composite triple-medium reservoir model and the inner boundary conditions of the point source function, the nonlinear continuity equations of the inner and outer zone seepage of the inner and outer zone fracture system, the cave system, and the matrix system are established;

[0011] Step 3: Based on the dimensionless parameters, the nonlinear continuity equations of the inner and outer zones are dimensionless and simplified to obtain simplified nonlinear continuity equations of the inner and outer zones;

[0012] Step 4, transforming the simplified nonlinear continuity equation of seepage in the inner and outer zones into the linear equation of seepage in the inner and outer zones;

[0013] Step 5: Based on the linear equations of seepage in the inner and outer zones and the principle of linear superposition, and taking the continuity condition at the interface between the inner and outer zones as a basis, determine the general solution of the point source function of the composite triple medium reservoir;

[0014] Step 6: Taking the equal pressure and flow rate at the interface between the inner and outer zones as conditions, determine the unknowns in the general solution of the point source function of the composite triple medium reservoir according to the nonlinear continuity equation of the seepage between the inner and outer zones;

[0015] Step 7: Substitute the unknowns into the general solution of the point source function of the composite triple-medium reservoir and integrate it along the Z-axis to obtain the vertical well seepage model of the composite triple-medium reservoir. Based on this model, the vertical well seepage law of the composite carbonate rock is analyzed.

[0016] Preferably, the relationship between the cumulative output liquid volume and the instantaneous flow rate in step 1 is as follows:

[0017]

[0018] The flow rate of the formation fluid near the point source into the point source is equal to the cumulative output fluid volume According to the relationship between the cumulative output liquid volume and the instantaneous flow rate, the flow rate of the inflow point source and the cumulative output liquid volume are established. By simplifying the equivalent equation, we can obtain the inner boundary conditions of the point source function of the composite triple medium reservoir, as follows:

[0019]

[0020] Where r is the reservoir radius, k is the permeability, μ is the viscosity, Δp is the pressure difference, and f is the fracture.

[0021] Preferably, the assumptions of the composite triple-medium reservoir model in step 2 are as follows:

[0022] a. The reservoir consists of a matrix system, inner and outer zone fracture systems, and a cave system. Pseudo-steady-state crossflow occurs between the matrix system and the cave system toward the fracture system, but crossflow does not occur between the matrix system and the cave system.

[0023] b. The matrix system and cave system are the main storage spaces, and the inner and outer zone fracture systems are the main flow channels; all oil well production comes from the inflow of the inner and outer zone fracture systems;

[0024] c. Considering the permeability sensitivity of the natural inner and outer zone fracture system, assuming that the stress sensitivity coefficients of the inner and outer zones are equal, and the permeabilities of the matrix system and the cave system are constant;

[0025] d. The initial reservoir pressure is pi, and the temperature remains constant during production;

[0026] f. The continuity condition is met at the interface between the inner and outer areas.

[0027] Preferably, the nonlinear linear equations of the inner and outer zone seepage are as follows:

[0028] Nonlinear continuity equation for inner zone seepage

[0029]

[0030] The nonlinear continuity equation of the external seepage flow is as follows:

[0031]

[0032] Where k is permeability, f is fracture, r is reservoir radius, Δp is pressure difference, μ is viscosity, φ is porosity, c is compressibility, m is matrix system, v is cave system, t is time, and x, y, z are coordinate locations.

[0033] Preferably, in step 4, the simplified inner and outer zone seepage nonlinear continuity equation is transformed into the inner and outer zone seepage linear equation by using perturbation transformation, and then the inner and outer zone seepage linear equation is simplified by using the 0th order perturbation solution to obtain the simplified inner and outer zone seepage linear equation.

[0034] Preferably, in step 5, the general solution of the composite triple medium reservoir point source function is expressed as follows:

[0035]

[0036] Where ψ is pressure, q is flow rate, μ is viscosity, k is permeability, f is fracture, L is reference length, h is height, and D is dimensionless; K0 and I0 are Bessel functions, r is reservoir radius, s is Laplace variable, and w is wellbore.

[0037] Preferably, in step 6, the unknowns of the general solution of the composite triple medium reservoir point source function include A and Bn;

[0038]

[0039]

[0040] Where K0 and I0 are Bessel functions; r is the reservoir radius, in is the boundary of the inner and outer regions, D is dimensionless; and s is the Laplace variable.

[0041] Preferably, in step 7, the vertical well seepage model of the composite triple medium reservoir is expressed as follows:

[0042]

[0043] Where ψ is pressure, q is flow rate, μ is viscosity, k is permeability, f is fracture, L is reference length, h is height, D is dimensionless, K0 and I0 are Bessel functions, r is reservoir radius, s is Laplace variable, and w is wellbore.

[0044] Preferably, in step 7, the method for analyzing the seepage law of composite carbonate vertical wells according to the composite triple-medium reservoir vertical well seepage model is as follows:

[0045] Stehfest numerical inversion is used to transform the Laplace space solution of the vertical well seepage model in a composite triple-medium reservoir into a time-space solution. The result is substituted into the perturbation transformation equation to obtain the bottomhole pressure considering the influence of stress sensitivity. The bottomhole pressure and time are plotted in a double logarithmic coordinate system to obtain a well test curve, which is used to analyze the seepage law of vertical wells in composite carbonate rocks.

[0046] A composite carbonate reservoir vertical well seepage simulation system is provided. When the simulation system is running, the composite carbonate reservoir vertical well seepage simulation method is executed.

[0047] Compared with the prior art, the present invention has the following beneficial technical effects:

[0048] The present invention provides a simulation method for vertical well seepage in a composite carbonate reservoir, which establishes the inner boundary conditions of a point source function of a composite ternary medium reservoir; based on the assumptions of the composite ternary medium reservoir model and the inner boundary conditions of the point source function, the inner and outer zone seepage continuity equations of the inner and outer zone fracture systems, cave systems and matrix systems are established, and the vertical well seepage model of the composite ternary medium reservoir is determined by using methods such as source function, Laplace transform, perturbation transform and linear superposition principle of partial differential equations, thereby overcoming the shortcomings that the continuous medium model is applicable to reservoirs with weak heterogeneity and the discrete medium model is more applicable to reservoirs with larger geometric sizes of fractures and caves and stronger heterogeneity. In addition, the method is based on the basic theory of source function, which expands the application scope of the original source function in the field of carbonate composite reservoir seepage simulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is a flow chart of the simulation method for vertical well seepage in composite carbonate reservoirs of the present invention.

[0050] Figure 2 This is a schematic diagram of point source local seepage in an infinite triple medium reservoir according to the present invention.

[0051] Figure 3 This is a map of the composite carbonate reservoir of the present invention. DETAILED DESCRIPTION

[0052] The present invention will be further described in detail below with reference to the accompanying drawings, which are intended to explain rather than limit the present invention.

[0053] A method for simulating seepage in a vertical well of a composite carbonate reservoir comprises the following steps:

[0054] Step 1: Establish the internal boundary conditions of the point source function of the reservoir based on the relationship between the cumulative produced liquid volume and the instantaneous flow rate of the reservoir;

[0055] Assume that there is a point source in the triple medium reservoir. This point is infinitely small in the reservoir scale but large enough in the microscopic scale. At t = 0, the cumulative output of this point is The flow rate of the liquid is large or small. The production of the liquid causes the flow of the fluid near the point. The local seepage of the infinite triple medium reservoir is as follows: Figure 2 shown.

[0056] Assuming that the flow rate out of the point source at t = 0 is q(t), the cumulative output liquid volume is The relationship between it and the instantaneous flow rate q(t) is:

[0057]

[0058] The flow rate of the formation fluid near the point source into the point source is equal to the cumulative fluid production Flow rate into point source and cumulative output liquid volume The equivalent equation is as follows:

[0059]

[0060] Where r is the reservoir radius, m; k is the permeability, m 2 ; μ is viscosity, mPa·s; Δp is pressure difference; f is crack; t is time.

[0061] The equivalent equation is simplified according to the properties of the function to obtain the internal boundary conditions of the point source function, as shown in Formula 3.

[0062]

[0063] Step 2: Establish a composite reservoir mathematical model based on the internal boundary conditions of the point source function, which specifically includes the following steps:

[0064] S1. Assumptions of the composite reservoir mathematical model are as follows:

[0065] a. The reservoir consists of a matrix system, inner and outer zone fracture systems, and a cave system. Pseudo-steady-state crossflow occurs between the matrix and cave systems toward the fracture system, but not between the matrix and cave systems.

[0066] b. The matrix and cave systems are the primary storage spaces, while the inner and outer fracture systems are the primary flow channels. All well production comes from the inflow of the inner and outer fracture systems.

[0067] c. Consider the permeability sensitivity of the natural inner and outer fracture systems. Assume that the stress sensitivity coefficients of the inner and outer zones are equal, and the permeabilities of the matrix system and the cave system are constant.

[0068] d. The initial pressure of the reservoir is pi, and the temperature remains constant during the production process.

[0069] f. The continuity condition is met at the interface between the inner and outer areas.

[0070] S2. Establish the nonlinear continuity equations for the inner and outer zone seepage of the inner and outer zone fracture system, the cave system, and the matrix system, as well as the boundary conditions and initial conditions of the inner and outer zones. The details are as follows:

[0071] The nonlinear continuity equation of the inner zone seepage is shown in formula (4):

[0072]

[0073] Where φ is the porosity; c is the compressibility, Pa -1 ; m is the matrix system; v is the cave system; t is time, x, y, z are coordinate positioning.

[0074] The nonlinear continuity equation of the external seepage is shown in formula (5):

[0075]

[0076] The initial conditions of the inner and outer regions are:

[0077] Δp f,j (x, y, z, t = 0) = Δp m,j (x, y, z, t = 0) = Δp v,j (x,y,z,t=0)=0 (j=1,2)(6)

[0078] Three different outer boundary conditions are considered: infinite outer boundary, closed outer boundary and constant pressure outer boundary.

[0079]

[0080] The boundary conditions within the point source are:

[0081]

[0082] Where L is the reference length, m; D is dimensionless; q is the flow rate, m 3 / s.

[0083] Considering the stress sensitivity of the natural fracture system, the permeability of the natural fractures in the inner and outer zones can be expressed as:

[0084] The permeability of natural fractures in the inner area is as follows:

[0085]

[0086] Among them, i is the initial value; α is the stress sensitivity coefficient; p is the pressure, pa.

[0087] The permeability of natural fractures in the outer area is as follows:

[0088]

[0089] S3. Based on the introduced dimensionless parameters, the nonlinear continuity equations of the inner and outer zones are dimensionless and simplified to obtain the simplified nonlinear continuity equations of the inner and outer zones.

[0090] The dimensionless parameters are introduced as follows:

[0091]

[0092]

[0093]

[0094]

[0095]

[0096] Where μ is the viscosity, mPa·s; L is the reference length, m; D is dimensionless; ω is the storage rate; V is the volume; σ is the shape coefficient; and λ is the cross-flow coefficient.

[0097] The nonlinear continuity equations of the inner and outer zones are dimensionless based on dimensionless parameters, and the simplified nonlinear continuity equations of the inner and outer zones are obtained.

[0098] The simplified dimensionless equation of nonlinear continuity of inner zone seepage is as follows:

[0099]

[0100] The simplified dimensionless equation of nonlinear continuity of external seepage is as follows:

[0101]

[0102] Where:

[0103]

[0104] Among them, V is the volume; z is the coordinate location; i is the initial value.

[0105] The simplified nonlinear continuity equation (11) of the inner zone seepage is simplified quadratically as follows:

[0106]

[0107] Where s is the Laplace variable.

[0108] Where: The simplified nonlinear continuity equation (12) of the external seepage flow is simplified twice as follows:

[0109]

[0110] Where:

[0111]

[0112] S4. The finally simplified nonlinear continuity equations of the inner and outer zones are transformed into linear equations of the inner and outer zones and simplified.

[0113] The seepage continuity equation of the inner and outer zones after quadratic simplification is a nonlinear partial differential equation, which is linearized through perturbation transformation and transformed through the following equation:

[0114]

[0115] Where p is pressure, Pa; ψ is pressure, Pa.

[0116] The 0th-order perturbation solution is used to simplify the linear equations of seepage in the inner and outer zones, and the simplified linear equations of seepage in the inner and outer zones are obtained.

[0117] Since the permeability modulus is often small, the 0th order perturbation solution fully meets the needs of engineering calculations. The 0th order perturbation solution is substituted into the seepage continuity equations of the inner and outer zones respectively and simplified to obtain:

[0118] The simplified linear equation of seepage in the inner zone;

[0119]

[0120] The simplified linear equation of seepage in the outer zone;

[0121]

[0122] The continuity condition at the interface between the inner and outer zones is:

[0123] Equal interface pressure

[0124] Where in is the boundary between the inner and outer regions.

[0125] Equal interface flow

[0126] If the upper and lower boundaries of the reservoir are closed:

[0127]

[0128] S5. The linear equation for the inner zone seepage is a linear equation. Therefore, according to the superposition property of linear partial differential equations, the general solution of the linear equation for the inner zone seepage can be written as:

[0129]

[0130] in, To satisfy the solution of the inner zone seepage equation, inner boundary conditions, initial boundary conditions, upper and lower boundary conditions and infinite outer boundary conditions; It is a solution that satisfies the inner zone seepage equation, upper and lower boundary conditions, and outer boundary conditions, and the contribution of this solution to the oil well production is 0.

[0131] The solution that satisfies the linear equation of seepage in the inner zone, the inner boundary conditions, the initial boundary conditions, the upper and lower boundary conditions, the infinite outer boundary conditions, and the infinite outer boundary The expression is as follows:

[0132]

[0133] Where K0 is the Bessel function; s is the Laplace variable; z is the coordinate location; and w is the wellbore.

[0134] The solution that satisfies the linear equation of seepage in the inner zone and the continuity condition at the interface between the inner and outer zones The expression is as follows:

[0135]

[0136] Among them, I0 is the Bessel function; s is the Laplace variable; z is the coordinate location.

[0137] Where,

[0138] The general solution of the dimensionless seepage linear equation in the inner area is as follows:

[0139]

[0140] The general solution of the dimensionless seepage linear equation in the inner zone is the solution of the point source function of the composite triple-medium reservoir.

[0141] S6. Using the interface continuity conditions of the inner and outer zones, which include equal interface pressure and equal interface flow, and combining the linear seepage equations of the inner and outer zones, the unknowns A and Bn in the solution of the point source function of the triple medium reservoir are solved.

[0142] According to the linear equation of seepage in the inner and outer zones and the pressure equalization condition at the interface, the following pressure equation can be obtained:

[0143]

[0144] According to the linear equation of seepage in the inner and outer zones and the condition of equal flow at the interface, the following flow equation can be obtained:

[0145]

[0146] In order for the pressure equation and flow equation to be valid, the corresponding parts need to be equal one by one, and the following four equations are obtained:

[0147]

[0148]

[0149]

[0150]

[0151] Dividing (27) and (28) to simplify, we can get:

[0152]

[0153] Dividing (29) and (30) to simplify, we can get:

[0154]

[0155] S7. Integrating the general solution of the dimensionless flow equation for the inner zone along the z-axis yields the seepage equation for vertical wells in composite reservoirs. Integrating along the x-axis yields the seepage equation for horizontal wells in composite reservoirs. Integrating along the x-axis first and then along the z-axis yields the seepage equation for fractured wells. This paper focuses on the vertical well seepage model for composite triple-medium reservoirs. Therefore, substituting the unknowns A and Bn into the solution of the point source function for the composite triple-medium reservoir and integrating along the z-axis yields the vertical well seepage model as follows:

[0156]

[0157] Define dimensionless variables For vertical wells, Q = qh w , L=h, then the above formula is simplified to:

[0158]

[0159] The Laplace space solution of Equation (34) is transformed into a time-space solution using Stehfest numerical inversion, and the result is substituted into Equation (15) to obtain the bottom hole pressure considering the influence of stress sensitivity. The bottom hole pressure and time are plotted in a double logarithmic coordinate system to obtain a well test curve, which is used to analyze the seepage law of composite carbonate vertical wells. Figure 3 This is a map of composite carbonate reservoirs.

[0160] The present invention also provides a simulation system for vertical well seepage in a composite carbonate reservoir, comprising the following steps:

[0161] The internal boundary condition module is used to establish the internal boundary conditions of the point source function of the composite triple medium reservoir based on the relationship between the cumulative produced liquid volume and the instantaneous flow rate of the triple medium reservoir;

[0162] The seepage equation establishment module is used to establish the nonlinear continuity equations of the inner and outer zone seepage of the inner and outer zone fracture system, cave system and matrix system based on the assumptions of the composite triple-medium reservoir model and the inner boundary conditions of the point source function;

[0163] A dimensionless module is used to dimensionlessly simplify the nonlinear continuity equations of the inner and outer zones based on dimensionless parameters to obtain simplified nonlinear continuity equations of the inner and outer zones;

[0164] A linear transformation module is used to transform the simplified nonlinear continuity equations of the inner and outer zones into linear equations of the inner and outer zones;

[0165] The general solution module is used to determine the general solution of the point source function of the composite triple medium reservoir based on the linear seepage equation of the inner and outer zones, combined with the principle of linear superposition, and based on the continuity condition at the interface between the inner and outer zones;

[0166] The unknown number module is used to determine the unknown numbers in the general solution of the point source function of the composite triple medium reservoir based on the nonlinear continuity equation of the seepage flow in the inner and outer zones, taking the equal pressure and flow rate at the interface between the inner and outer zones as conditions;

[0167] The analysis module is used to substitute unknown numbers into the general solution of the point source function of the composite triple-medium reservoir and integrate it in the Z-axis direction to obtain the vertical well seepage model of the composite triple-medium reservoir. Based on this model, the seepage law of the composite carbonate vertical well is analyzed.

[0168] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for simulating seepage in a vertical well of a composite carbonate reservoir, characterized in that: The following steps are involved: Step 1: Based on the relationship between the cumulative produced liquid volume and the instantaneous flow rate of the triple medium reservoir, the inner boundary conditions of the point source function of the composite triple medium reservoir are established; The relationship between the cumulative output liquid volume and the instantaneous flow rate is as follows: The flow rate of the formation fluid near the point source into the point source is equal to the cumulative output fluid volume According to the relationship between the cumulative output liquid volume and the instantaneous flow rate, the flow rate of the inflow point source and the cumulative output liquid volume are established. By simplifying the equivalent equation, we can obtain the inner boundary conditions of the point source function of the composite triple medium reservoir, as follows: in, is the reservoir radius, is the permeability, is the viscosity, Δp is the pressure difference, For cracks; Step 2: Based on the assumptions of the composite triple-medium reservoir model and the inner boundary conditions of the point source function, the nonlinear continuity equations of the inner and outer zone seepage of the inner and outer zone fracture system, the cave system, and the matrix system are established; Step 3: Based on the dimensionless parameters, the nonlinear continuity equations of the inner and outer zones are dimensionless and simplified to obtain simplified nonlinear continuity equations of the inner and outer zones; Step 4, transforming the simplified nonlinear continuity equation of seepage in the inner and outer zones into the linear equation of seepage in the inner and outer zones; Step 5: Based on the linear equations of seepage in the inner and outer zones and the principle of linear superposition, and taking the continuity condition at the interface between the inner and outer zones as a basis, determine the general solution of the point source function of the composite triple medium reservoir; Step 6: Taking the equal pressure and flow rate at the interface between the inner and outer zones as conditions, determine the unknowns in the general solution of the point source function of the composite triple medium reservoir according to the linear equation of seepage between the inner and outer zones; Step 7: Substitute the unknowns into the general solution of the point source function of the composite triple-medium reservoir and integrate it along the Z-axis to obtain the vertical well seepage model of the composite triple-medium reservoir. Based on this model, the vertical well seepage law of the composite carbonate rock is analyzed.

2. The method for simulating seepage in a vertical well of a composite carbonate reservoir according to claim 1, characterized in that: The assumptions of the composite triple-medium reservoir model described in step 2 are as follows: a. The reservoir consists of a matrix system, inner and outer zone fracture systems, and a cave system. Pseudo-steady-state crossflow occurs between the matrix system and the cave system toward the fracture system, but crossflow does not occur between the matrix system and the cave system. b. The matrix system and cave system are the main storage spaces, and the inner and outer zone fracture systems are the main flow channels; all oil well production comes from the inflow of the inner and outer zone fracture systems; c. Considering the permeability sensitivity of the natural inner and outer zone fracture system, assuming that the stress sensitivity coefficients of the inner and outer zones are equal, and the permeabilities of the matrix system and the cave system are constant; d. The initial reservoir pressure is pi, and the temperature remains constant during production; f. The continuity condition is met at the interface between the inner and outer areas.

3. The method for simulating vertical well seepage in a composite carbonate reservoir according to claim 1, wherein: The nonlinear continuity equation of the inner and outer zone seepage is as follows: Nonlinear continuity equation for inner zone seepage The nonlinear continuity equation of the external seepage flow is as follows: in, is the permeability, For cracks, is the reservoir radius, Δp is the pressure difference, is the viscosity, is the porosity, is the compression coefficient, For the matrix system, It is a cave system. For time, For coordinate positioning.

4. The method for simulating seepage in a vertical well of a composite carbonate reservoir according to claim 1, wherein: In step 4, the simplified nonlinear continuity equations of the inner and outer zones are transformed into linear equations of the inner and outer zones using perturbation transformation, and then the linear equations of the inner and outer zones are simplified using the 0th-order perturbation solution to obtain simplified linear equations of the inner and outer zones.

5. The method for simulating seepage in a vertical well of a composite carbonate reservoir according to claim 1, characterized in that: In step 5, the general solution of the composite triple medium reservoir point source function is expressed as follows: in, For pressure, For traffic, is the viscosity, is the permeability, For cracks, is the reference length, is the height, is a dimensionless parameter; and is the Bessel function, is the reservoir radius, is the Laplace variable, For the wellbore.

6. The method for simulating seepage in a vertical well of a composite carbonate reservoir according to claim 1, characterized in that: In step 6, the unknowns of the general solution of the composite triple medium reservoir point source function include A and B n ; in, , is the Bessel function; is the reservoir radius, is the boundary between the inner and outer regions, is a dimensionless parameter; is the Laplace variable.

7. The method for simulating seepage in a vertical well of a composite carbonate reservoir according to claim 1, characterized in that: In step 7, the vertical well seepage model of the composite triple medium reservoir is expressed as follows: in, For pressure, For traffic, is the viscosity, is the permeability, For cracks, is the reference length, is the height, is a dimensionless parameter, and is the Bessel function, is the reservoir radius, is the Laplace variable, For the wellbore.

8. The method for simulating seepage in a vertical well of a composite carbonate reservoir according to claim 1, characterized in that: In step 7, the method for analyzing the seepage law of composite carbonate vertical wells based on the composite triple-medium reservoir vertical well seepage model is as follows: Stehfest numerical inversion is used to transform the Laplace space solution of the vertical well seepage model in a composite triple-medium reservoir into a time-space solution. The result is substituted into the perturbation transformation equation to obtain the bottomhole pressure considering the influence of stress sensitivity. The bottomhole pressure and time are plotted in a double logarithmic coordinate system to obtain a well test curve, which is used to analyze the seepage law of vertical wells in composite carbonate rocks.

9. A simulation system for vertical well seepage in composite carbonate reservoirs, characterized in that: When the simulation system is running, the simulation method for vertical well seepage in a composite carbonate reservoir according to any one of claims 1 to 8 is executed.

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