CN104533370B - Pressure break horizontal well oil reservoir, crack, pit shaft coupled model method - Google Patents

Abstract

The invention provides a kind of pressure break horizontal well oil reservoir, crack, pit shaft coupled model method, comprise the following steps：Obtain the |input paramete of capability forecasting numerical simulation；The crack that |input paramete input is pre-build, the coupling model coupled between oil reservoir and pit shaft three；Fully implicit scheme is carried out to the coupling model solves the numerical simulation result for obtaining fractured horizontal well's productivity prediction.The present invention for |input paramete, has carried out fully implicit scheme using N R alternative manners to coupling model on the basis of the coupling model of the complete Fractured Reservoir pit shaft coupling for pre-building, it is achieved thereby that to solving while oil reservoir, crack, wellbore parameters.The present invention take into account the coupled relation between oil reservoir, crack, pit shaft, oil reservoir and crack are considered not only, flow between the flow being additionally contemplates that between reservoir fractures and crack pit shaft, so that its well capacity prediction Numerical-Mode result for obtaining more is coincide with pressure break horizontal well practical situation.

Description

Full-coupling simulation method for oil deposit, crack and shaft of fractured horizontal well

Technical Field

The invention relates to the technical field of geological exploration numerical simulation, in particular to a full-coupling simulation method for oil reservoirs, cracks and mineshafts of fractured horizontal wells.

Background

Since the 90 s of the 20 th century, horizontal well technology has been widely used in the development of oil and gas fields. The horizontal well increases the contact area between the well and an oil reservoir, improves the oil and gas yield and the ultimate recovery ratio, and solves the problem that some vertical wells cannot effectively solve due to the development of the horizontal well technology. However, for a low-permeability oil reservoir, the single-well productivity is still very low by relying on the development of a horizontal well, which is determined by the characteristics of the low-permeability oil reservoir, because of low permeability, large seepage resistance and poor connectivity, the horizontal well is required to be utilized to perform fracturing transformation on the low-permeability oil reservoir to further increase the yield and the final recovery ratio, and a plurality of cracks are usually required to be pressed open to increase seepage channels. Particularly for thin interbed low-permeability oil reservoirs, a good effect cannot be achieved by using vertical well fracturing, a plurality of oil layers can be communicated by using a horizontal well staged fracturing technology, the productivity can reach three times that of a vertical well, and the decreasing speed of the productivity is obviously lower than that of the vertical well.

However, the fracturing cost of the horizontal well is high, and whether the horizontal well is fractured or not needs to be evaluated economically in addition to considering oil reservoir conditions and technical conditions, so that the productivity after the horizontal well is fractured needs to be accurately predicted. The productivity prediction and economic evaluation are carried out on the fractured horizontal well, on one hand, the scientificity of fracturing decision can be improved, the economic benefit is maximized, and on the other hand, reliable basis is provided for optimizing fracturing process parameters of the horizontal well and the like.

At present, the prior art methods for predicting the yield of a fractured horizontal well mainly comprise two methods: numerical simulation method and analytical model method. The form of the analytic model is simple, the required parameters are few during calculation, the calculation amount is small, and the horizontal well productivity obtained through calculation can be used as a reference during horizontal well screening. However, the analytical model requires more assumed conditions, and usually only results under single-phase flow and stable conditions can be obtained, which is greatly different from the actual production situation, whereas the numerical simulation method can consider multiphase flow and predict the production dynamics of fractured horizontal wells, and consider more comprehensive factors, including the heterogeneity of the oil reservoir.

The numerical simulation method can more accurately simulate the production dynamics of the fractured horizontal well, parameters such as oil production, liquid production, water content, accumulated oil production, accumulated liquid production, formation pressure and the like calculated by the numerical simulation method change along with the change of time and are dynamic results, and the accuracy of the numerical simulation method is higher than that of an analytic model method. The numerical simulation method can be divided into two types, one is to regard the oil reservoir and the crack as the same seepage system, and the other is to respectively establish the seepage systems of the oil reservoir and the crack. The permeability of a fracture formed underground by hydraulic fracturing is far larger than that of a stratum, the width of the fracture is small and is generally only 0.002-0.005m, in actual calculation, if the fracture and the stratum are regarded as the same seepage system, the fracture is independently used as a row of grids in grid division, the fracture grids need to be arranged to enable the width of the fracture grids to be small and the permeability to be large, in order to guarantee convergence and stability of calculation, the width of an oil reservoir grid close to the wall surface of the fracture needs to be small, an oil reservoir grid system with the size gradually increasing from the wall surface of the fracture to the outer grid surface is formed, and meanwhile, the time step length of calculation needs to be small. The small time step and the small size of the grid inevitably increase the total time and the total number of grids, thereby increasing the calculation and memory occupation and the calculation time. Currently, some scholars research a second type of treatment method, respectively establish seepage models in a stratum and a fracture and a flow model in a horizontal shaft aiming at a fractured horizontal well, and solve the seepage models by using an oil reservoir numerical simulation method. However, for the solution of the model, actually, a seepage equation in the formation, a seepage equation in the fracture and a pressure drop equation in the shaft are respectively solved, and the calculation is finished by repeatedly calculating until the difference value of the horizontal well yield calculated twice is within a certain error range. Therefore, from the process of processing and solving the numerical model, the existing model does not realize the real coupling among the oil deposit, the crack and the shaft, and can not realize the simultaneous calculation of the pressure, the saturation and other parameters in the oil deposit, the crack and the shaft.

Therefore, the existing fractured horizontal well oil reservoir, fracture and shaft full-coupling simulation methods solve the parameters of the fracture, oil reservoir and shaft respectively, but do not solve the parameters simultaneously, so that the coupling among the oil reservoir, the fracture and the shaft is difficult to realize, and the obtained simulation result is difficult to be matched with the actual condition of the fractured horizontal well.

Disclosure of Invention

The invention aims to provide a fractured horizontal well oil reservoir, crack and shaft fully-coupled simulation method to achieve the effect that the obtained well productivity prediction numerical model result can be more consistent with the actual condition of a fractured horizontal well.

In order to achieve the aim, the invention provides a full-coupling simulation method for oil reservoirs, cracks and mineshafts of fractured horizontal wells, which comprises the following steps:

acquiring input parameters of capacity prediction numerical simulation;

inputting the input parameters into a coupling model which is established in advance and is coupled among the crack, the oil reservoir and the shaft;

and carrying out fully-implicit differential solution on the coupling model to obtain a numerical simulation result of the fracturing horizontal well productivity prediction.

The invention discloses a full-coupling simulation method for an oil reservoir, a crack and a shaft of a fractured horizontal well.

According to the fractured horizontal well oil reservoir, fracture and shaft full-coupling simulation method, the three-dimensional two-phase oil reservoir model is established in advance in the following mode:

selecting a three-dimensional two-phase oil reservoir formed by stacking a plurality of three-dimensional grid unit bodies, wherein a one-dimensional shaft and a two-dimensional two-phase crack are arranged in the three-dimensional two-phase oil reservoir, and the two-dimensional two-phase crack is intersected with the one-dimensional shaft;

deducing a flow equation of two phases in the three-dimensional two-phase oil reservoir according to a mass conservation equation of the two phases;

acquiring a flow exchange term of the three-dimensional two-phase oil reservoir and the two-dimensional two-phase fracture;

substituting the flow exchange term into the flow equation to obtain a three-dimensional two-phase oil reservoir model:

water phase:

oil phase:

wherein phi is_rTo reservoir porosity, B_rw、B_roThe volume coefficients of a water phase and an oil phase in an oil reservoir are respectively; s_rw、S_roRespectively representing the water phase saturation and the oil phase saturation in the oil reservoir; q. q.s_rfw、q_rfoThe volume flow of water phase and oil phase flowing out of the oil reservoir to the fracture in unit time, T_rw、T_roVolume flow, p, of water and oil phases within the reservoir respectively, flowing from reservoir grid ri to adjacent reservoir grid rj at unit pressure difference_rw、p_roThe pressure of the water phase and the oil phase in the oil reservoir respectively.

Wherein A is_rIs the area of the interface between the reservoir grid ri and the adjacent grid rj, L_rIs the length, K, between the reservoir grid ri and the adjacent reservoir grid rj_riAs permeability of reservoir grid ri, K_rjPermeability of reservoir grid rj, k_rrwRelative permeability of the reservoir water phase, k_rroIs the relative permeability of oil phase of oil reservoir, mu_rwViscosity of the reservoir water phase, mu_roThe oil phase viscosity of the reservoir.

According to the fractured horizontal well oil reservoir, fracture and shaft full-coupling simulation method, a two-dimensional two-phase fracture model is established in advance in the following mode:

deducing a continuity equation of two phases in the two-dimensional two-phase fracture according to a mass conservation equation of the two phases;

respectively acquiring a first flow exchange term of the two-dimensional two-phase fracture and the three-dimensional two-phase oil deposit, a second flow exchange term of the two-dimensional two-phase fracture and the one-dimensional wellbore, and a motion equation expressed by Darcy formula in the two-dimensional two-phase fracture;

substituting the first flow exchange term, the second flow exchange term and the motion equation into the continuity equation to obtain a two-dimensional two-phase fracture model:

water phase:

oil phase:

wherein phi is_fIs the fracture porosity, S_fw、S_foRespectively the water phase saturation and the oil phase saturation in the fracture q_fww、q_fwoThe volume flow of water phase and oil phase flowing out of the fracture to the horizontal shaft in unit time, T_fw、T_foFlow from the fracture network fi to the oil phase within the fracture at unit pressure difference, respectivelyVolume flow, P, of adjacent fracture network fj_fw、p_foThe pressure of the aqueous phase and the oil phase in the fracture, respectively.

Wherein A is_fIs the area of the interface between the fracture grid fi and the adjacent grid fj, L_fIs the length, K, between the reservoir grid fi and the adjacent grid fj_fiIs the permeability of the crack grid fi, K_fjPermeability of the fracture grid fj, μ_fwIs the water phase viscosity in the fracture, mu_foViscosity of the oil phase in the fracture, B_fw、B_foThe volume coefficients of the water phase and the oil phase in the crack are respectively.

The invention relates to a full-coupling simulation method for oil reservoirs, fractures and mineshafts of fractured horizontal wells, wherein a one-dimensional mineshaft in a one-dimensional mineshaft variable mass flow model is divided into n +1 sections by n two-dimensional two-phase fractures, and the model is established in advance in the following mode:

respectively calculating the friction pressure drop and the accelerated pressure drop of each section of one-dimensional shaft, wherein the pressure drop generated by the second section wi and the second section wi-1 of the adjacent upstream well section is;

wherein p is_w，wiFor the second section wellbore pressure, p_w，wi-1Is the pressure of the w-1 section of the well bore, Δ p_w，wiIs the pressure drop between the wi th section and the wi-1 th section, f_wiCoefficient of friction, p, for the w-th section of the one-dimensional wellbore_wiThe mixing density of two-phase mixed fluid in the one-dimensional shaft of the second section, D is the shaft diameter of the one-dimensional shaft, Q_wiTwo phases in all well sections before the first section of the one-dimensional well shaftSum of flow rates of the mixed fluids, q_wiIs the flow rate L of two-phase mixed fluid in the one-dimensional shaft of the second section_wiThe length of the one-dimensional wellbore in the wi-th section.

According to the fractured horizontal well oil reservoir, fracture and shaft full-coupling simulation method, the first flow model is established in advance in the following mode:

assuming that the oil reservoir grid ri is adjacent to the fractured grid fi, respectively subtracting the water phase pressure and the oil phase pressure of the oil reservoir grid ri and the adjacent fractured grid fi to obtain a water phase pressure difference and an oil phase pressure difference;

and multiplying the volume flow of the oil reservoir grid ri and the adjacent fracture grid fi under the unit pressure difference by the pressure difference to obtain the first flow model:

water phase: q. q.s_rfw＝T_rfw[p_rw，ri-p_fw，fi]

Oil phase: q. q.s_rfo＝T_rfo[p_ro，ri-p_fo，fi]

Wherein, T_rfw、T_rfoWater phase volume flow and oil phase volume flow q under unit pressure difference of a three-dimensional two-phase oil reservoir grid ri and an adjacent two-dimensional two-phase fracture grid fi respectively_rfw、q_rfoVolume flow, p, of reservoir grid ri into adjacent fracture grid fj, respectively_rw，riAnd p_fw，fiWater phase pressure, p, of reservoir grid ri and adjacent fracture grid fj, respectively_ro，riAnd p_fo，fiThe oil phase pressures of the reservoir grid ri and the fracture grid fj, respectively.

Wherein A is_rfRespectively reservoir grid riArea of interface with adjacent fracture network fj, D_rDistance from center of reservoir grid to interface, D_fThe distance from the center of the fracture grid to the interface.

According to the fractured horizontal well oil reservoir, fracture and shaft full-coupling simulation method, the second flow model is established in advance in the following mode:

supposing that a well section wi with a one-dimensional shaft penetrates through a fracture grid fi, subtracting the water phase pressure and the oil phase pressure of the fracture grid fi and the well section wi respectively to obtain a water phase pressure difference and an oil phase pressure difference;

and multiplying the volume flow of the two-dimensional two-phase fracture grid and the one-dimensional two-phase well section passing through the grid under the unit pressure difference by the pressure difference to obtain the second flow model:

water phase: q. q.s_fww＝T_fww[p_fw，fi-p_w，wi]

Oil phase: q. q.s_fwo＝T_fwo[p_fo，fi-p_w，wi]

Wherein, T_fww、T_fwoWater phase volume flow and oil phase volume flow of a fracture grid fi and a one-dimensional two-phase well section wi penetrating through the grid under unit pressure difference respectively, q_fww，fi、q_fwo，fiThe water phase volume flow and the oil phase volume flow, p, respectively, flowing into the fracture grid fi through the grid well section wi_fw，fiAnd p_ww，wiThe pressure of the water phase, p, respectively, in the fracture grid fi and across the grid well section wi_fo，fiAnd p_wo，wiRespectively fracture grid fi and oil phase pressure across the grid well section wi.

Wherein r is_wIs the wellbore radius of a one-dimensional wellbore, omega is the fracture width, r_oIs the equivalent radius of the fracture mesh.

The invention discloses a fractured horizontal well oil reservoir, crack and shaft fully-coupled simulation method, wherein the fully-implicit differential solution is carried out on the coupled model, and the method specifically comprises the following steps:

carrying out full-implicit differential solution on the coupling model by utilizing a Newton-Lafferson N-R iterative method to obtain a coupling coefficient matrix for simultaneously solving parameters of a crack, an oil reservoir and a shaft; wherein,

the three-dimensional two-phase reservoir equation in the coupling coefficient matrix comprises:

water phase:

oil phase:

the two-dimensional two-phase fracture equation in the coupling coefficient matrix includes:

water phase:

oil phase:

the one-dimensional two-phase wellbore equation in the coupling coefficient matrix comprises:

wherein 1 is the 1 st iteration step number, n is the nth time step, Δ t is a time step, p_roFor the variation of reservoir grid pressure within each iteration step, S_rwFor the variation of the water saturation of the reservoir grid, p, in each iteration step_foFor the variation of the fracture grid pressure within each iteration step, S_fwFor the variation of the water saturation of the fracture network, p, within each iteration step_wThe variation of the interval pressure for each iteration step.

The invention discloses a fractured horizontal well oil reservoir, fracture and shaft full-coupling simulation method, wherein the input parameters comprise:

reservoir properties: reservoir porosity, reservoir permeability, reservoir size, reservoir depth, rock compressibility;

fracture properties: the crack porosity, the crack permeability, the crack size, the crack position, the crack number and the crack conductivity;

wellbore properties: well bore position, well bore radius, well bottom flowing pressure, well wall roughness;

the fluid properties: fluid density, fluid viscosity, fluid volume factor, capillary pressure, fluid relative permeability, fluid compressibility;

initial conditions: initial reservoir pressure, initial reservoir phase saturation, initial fracture pressure, initial fracture phase saturation.

According to the method, on the basis of a pre-established complete fracture-oil reservoir-shaft coupling model, the coupling model is subjected to full implicit difference on input parameters by using an N-R iteration method, so that the oil reservoir, fracture and shaft parameters are solved simultaneously. Therefore, the method considers the coupling relation among the oil deposit, the crack and the shaft, namely not only the oil deposit and the crack, but also the flow between the oil deposit and the crack and the flow between the crack and the shaft are considered, so that the obtained numerical model result of the well productivity prediction is more consistent with the actual condition of the fractured horizontal well.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:

FIG. 1 is a flow chart of a fractured horizontal well oil reservoir, fracture, and wellbore fully-coupled simulation method according to an embodiment of the invention;

FIG. 2 is a schematic view of a model for fracturing a single transverse fracture of a horizontal well according to an embodiment of the present invention;

FIG. 3 is a model schematic of a three-dimensional two-phase reservoir model with Cartesian coordinates according to an embodiment of the invention;

FIG. 4 is a schematic diagram of the two-dimensional two-phase fracture model in the three-dimensional two-phase reservoir model according to an embodiment of the present invention;

FIG. 5 is a schematic representation of a model of a one-dimensional wellbore traversing from a two-dimensional two-phase fracture in an embodiment of the present disclosure;

FIG. 6 is a schematic diagram of a model for fracturing a horizontal well to open a plurality of transverse fractures in an embodiment of the invention;

FIG. 7 is a schematic representation of a model of a one-dimensional wellbore sectioned through a plurality of transverse fractures in an embodiment of the present invention;

FIG. 8 is a schematic diagram of a model of flow between a reservoir and a fracture in an embodiment of the invention;

FIG. 9 is a schematic diagram of a coupling relationship of a coefficient matrix of a fully-implicit differential method for reservoir-fracture-wellbore coupling in an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the following embodiments and the accompanying drawings. The exemplary embodiments and descriptions of the present invention are provided to explain the present invention, but not to limit the present invention.

The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.

According to the fractured horizontal well oil deposit, fracture and shaft full-coupling simulation method, a coupling model for coupling among the fracture, the oil deposit and the shaft is pre-established, and the fractured horizontal well productivity prediction numerical simulation is performed according to the model after the coupling model is established. The coupling model comprises a three-dimensional two-phase oil reservoir model, a two-dimensional two-phase fracture model, a one-dimensional shaft variable mass flow model, a first flow model of flow between oil reservoirs and fractures and a second flow model of flow between fractures and shafts, wherein the two phases are oil and water. The following describes the construction processes of a three-dimensional two-phase oil reservoir model, a two-dimensional two-phase fracture model, a one-dimensional shaft variable mass flow model, a first flow model of flow between the oil reservoir and the fracture and a second flow model of flow between the fracture and the shaft one by one in the coupling model:

one-dimensional and three-dimensional two-phase oil reservoir model

As shown in fig. 2, the model is described by taking the example of horizontal well fracturing a single fracture, a whole oil reservoir is selected, a horizontal well is arranged in the center of the oil reservoir, and a rectangular transverse fracture symmetrical about a shaft is assumed to be arranged perpendicular to the horizontal shaft.

First, a three-dimensional reservoir volume is selected as shown in fig. 3, and the reservoir volume comprises 2 × 3 × 3 reservoir grids in a cartesian coordinate system as shown in fig. 3, wherein each grid represents a three-dimensional unit. In the numerical simulation model, the mathematical model of the reservoir describes a mathematical model of each three-dimensional unit body, i.e., each grid. In order to describe the basic characteristics of fluid flow in the oil reservoir, a three-dimensional two-phase mathematical model of the oil reservoir is established based on the three-dimensional oil reservoir grid, and a mass conservation equation, a motion equation, a state equation and a plurality of auxiliary equations are needed, wherein the state equation comprises a rock state equation and a fluid state equation.

(1) Assumption of conditions

Free gas does not exist in an oil reservoir, only two phases of oil and water exist, and fluid in the oil reservoir follows Darcy seepage and is isothermal seepage;

the oil reservoir is a rectangular oil reservoir, and the oil reservoir has heterogeneity and anisotropy;

thirdly, the stratum rock and the fluid are slightly compressible;

and fourthly, considering the influence of capillary pressure and gravity.

(2) Mathematical model

In an oil-water two-phase flow system, two fluid components are assumed, the oil and water components are immiscible, that is, there is no mass exchange between the oil and water phases. And because the flow is isothermal, the oil-water two-phase fluid is in thermodynamic equilibrium.

According to the mass conservation equation and the momentum equation of the oil phase and the water phase, the flow equations of the oil phase and the water phase in the oil reservoir can be deduced to be respectively:

water phase equation:

oil phase equation:

in the formula, phi_rTo reservoir porosity, B_rw、B_roThe volume coefficients of a water phase and an oil phase in an oil reservoir are respectively; s_rw、S_roRespectively representing the water phase saturation and the oil phase saturation in the oil reservoir; q. q.s_rfw、q_rfoThe volume flow of water phase and oil phase flowing out of the oil reservoir to the fracture in unit time, T_rw、T_roVolume flow, p, of water and oil phases within the reservoir respectively, flowing from reservoir grid ri to adjacent reservoir grid rj at unit pressure difference_rw、p_roThe pressure of the water phase and the oil phase in the oil reservoir respectively.

Wherein A is_rIs the area of the interface between the reservoir grid ri and the adjacent grid rj, L_rIs the length, K, between the reservoir grid ri and the adjacent reservoir grid rj_riAs permeability of reservoir grid ri, K_rjPermeability of reservoir grid rj, k_rrwRelative permeability of the reservoir water phase, k_rroIs the relative permeability of oil phase of oil reservoir, mu_rwViscosity of the reservoir water phase, mu_roThe oil phase viscosity of the reservoir.

Only the reservoir grids next to the fractured grids exist, and the reservoir-fractured flow exchange term q exists_rfwAnd q is_rfoWhile for other reservoir grids, the flow term does not exist.

Each reservoir grid satisfies the two equations, and the unknowns in the reservoir to be solved are fourThe method comprises the following steps: oil phase pressure p_roPressure of aqueous phase p_rwDegree of oil saturation S_roWater phase saturation degree S_rwThus, two additional equations are required.

Because only two phases of oil and water are considered, the oil saturation and the water saturation in the oil reservoir satisfy the following equations:

S_ro+S_rw＝1 (2.5)

the pressure equation of the oil-water two-phase capillary in the oil reservoir is as follows:

p_fcow＝p_ro-p_rw(2.6)

equations (2.1) - (2.4) form a two-phase flow model of oil and water in the reservoir, the four equations comprise four unknowns, equations (2.3) and (2.4) can be used to eliminate two of them, and the final equation can be simplified to two equations with two major unknowns_rwAnd p_ro。

(3) Boundary condition

Boundary conditions of numerical reservoir simulation are divided into outer boundary conditions and inner boundary conditions. The outer boundary condition refers to the state in which the outer boundary of the reservoir is located, and the inner boundary condition refers to the state in which a producing well or an injection well is located in the reservoir.

Assuming that the reservoir outer boundary is closed, the reservoir outer boundary conditions are as follows:

the oil-water two-phase fluid in the oil reservoir flows to the crack under the action of pressure difference, and the boundary conditions in the oil reservoir are as follows:

p_fw|_{crack grid}＝p_fw(fi，fj，t) (2.9)

p_fo|_{Crack grid}＝p_fo(fi，fj，t) (2.10)

Wherein fi, fj are the grid numbers of the cracks in fig. 5, and t is the production time.

(5) Initial conditions

The initial conditions refer to the pressure at each point of the reservoir and the saturation of each phase at the initial time or from a certain time when the reservoir is put into development.

p_ro(x，y，z，t)|_t＝0＝p_ro ⁰(2.11)

p_rw(x，y，z，t)|_t＝0＝p_rw ⁰(2.12)

S_ro(x，y，z，t)|_t＝0＝S_ro ⁰(2.13)

S_rw(x，y，z，t)|_t＝0＝S_rw ⁰(2.14)

In the formula, p_ro ⁰、p_rw ⁰Respectively the initial pressure of an oil phase and a water phase of an oil reservoir; s_ro ⁰、S_rw ⁰The initial saturation of the oil phase and the water phase of the oil reservoir respectively.

Two-dimensional and two-dimensional two-phase crack model

Because the width of the crack is only a few millimeters, when the seepage rule in the crack is researched, the flow in the width direction of the crack is not considered, and the flow in the plane of the crack is only considered, so that a two-dimensional two-phase crack mathematical model needs to be established. In the numerical simulation model, each fracture grid is placed between two adjacent reservoir grids, the grid division of the fracture plane is consistent with the grid division of the reservoir, and the thickness of the fracture grid is set to be the fracture thickness. Reservoir grid and fracture grid partitioning and matching as shown in fig. 4, the shaded portion represents the fracture grid, and the fracture volume contains 3 × 3 fracture grids.

The physical model, meshing and coordinate directions of the individual fractures are shown in fig. 5, and since the fractures are assumed to be symmetric about the wellbore, the horizontal wellbore passes through the center of the fracture volume center grid.

(1) Assumption of conditions

The cracks are equal-width vertical cracks which are symmetrical about a horizontal shaft, and a two-dimensional plane in the direction vertical to the shaft is rectangular;

considering the heterogeneity and anisotropy of the crack;

only oil and water seepage exists in the cracks, the oil and the water are not dissolved mutually, and the seepage conforms to Darcy's law;

considering the influence of capillary pressure and gravity;

rock and fluid are slightly compressible.

(2) Mathematical model

Similar to the three-dimensional model of the oil reservoir, according to the mass conservation equation, the continuity equations of the oil phase and the water phase in the fracture can be deduced as follows:

water phase equation:

oil phase equation:

in the formula, phi_fIs the fracture porosity, S_fw、S_foRespectively the water phase saturation and the oil phase saturation in the fracture q_fww、q_fwoThe volume flow of water phase and oil phase flowing out of the fracture to the horizontal shaft in unit time, T_fw、T_foFrom water phase and oil phase in the fracture respectively at unit pressure differenceVolume flow, p, of fracture grid fi to adjacent fracture grid fj_fw、p_foThe pressure of the aqueous phase and the oil phase in the fracture, respectively.

Wherein A is_fIs the area of the interface between the fracture grid fi and the adjacent grid fj, L_fIs the length, K, between the reservoir grid fi and the adjacent grid fj_fiIs the permeability of the crack grid fi, K_fjPermeability of the fracture grid fj, μ_fwIs the water phase viscosity in the fracture, mu_foViscosity of the oil phase in the fracture, B_fw、B_foThe volume coefficients of the water phase and the oil phase in the crack are respectively.

All the fracture grids have flow exchange with the adjacent reservoir grids on two sides, and only the fracture grid penetrated by the horizontal well cylinder has a flow term q_fwwAnd q is_fwoFor other fracture grids, q_fww＝0，q_fwo＝0。

Each fracture grid satisfies the two equations above, and the unknowns to be solved are four: oil phase pressure p_foPressure of aqueous phase p_fwDegree of oil saturation S_foWater phase saturation degree S_fwThus, two additional equations are required.

Because only two phases of oil and water are considered, the oil and water saturation in the fracture can satisfy the following equation:

S_fo+S_fw＝1 (2.19)

the pressure equation of the oil-water two-phase capillary in the crack is as follows:

p_fcow＝p_fo-p_fw(2.20)

(3) boundary condition

Assuming that the fracture outer boundary is closed, the fracture outer boundary conditions are:

the oil-water two-phase fluid in the crack flows to the horizontal shaft under the action of pressure difference, and the boundary conditions in the crack are as follows:

p_w|_{crack grid}＝p_w(wi，t) (2.23)

In the formula, wi is the well section number of the horizontal shaft, and t is the production time.

(5) Initial conditions

Similar to the initial conditions of the reservoir, the initial conditions of the pressure in the fracture and the oil and water phase saturation are as follows:

p_fo(y，z，t)|_t＝0＝p_fo ⁰(2.24)

p_fw(y，z，t)|_t＝0＝p_fw ⁰(2.25)

S_fo(y，z，t)|_t＝0＝S_fo ⁰(2.26)

S_fw(y，z，t)|_t＝0＝S_fw ⁰(2.27)

in the formula, p_fo ⁰、p_fw ⁰Respectively the initial pressure of the fracture oil phase and the initial pressure of the water phase; s_fo ⁰、S_fw ⁰The initial saturation of the fracture oil phase and the initial saturation of the water phase are respectively.

Three-dimensional and one-dimensional variable mass flow model of shaft

When the horizontal well section direction of the horizontal well coincides with the direction of the minimum principal stress, a lateral fracture perpendicular to the direction of the borehole is generated. To maximize the potential for breakthrough, multiple transverse fractures are typically forced open. We performed the analysis using three cracks as an example, as shown in fig. 6.

For the condition of a plurality of cracks, the oil reservoir model is the same as the oil reservoir model under the condition of a single crack, a three-dimensional two-phase model is established for the whole oil reservoir, the outer boundary of the oil reservoir is closed, and the oil reservoir grids adjacent to the crack grids have flow relations with the cracks; the mathematical model of the fracture model is the same as that of a single fracture, the outer boundary is still processed according to a closed condition, and only the bottom hole flowing pressure of the inner boundary needs to be calculated through the pressure drop of the shaft, so that the pressure drop model of the shaft needs to be established.

Selecting a horizontal well and pressing open three cracks, equally dividing the horizontal shaft into three sections by the three cracks, wherein each section takes the intersection of the crack and the shaft as the center, and the length of each section is assumed to be L, as shown in FIG. 7.

The numbers of the three fractures are shown in fig. 6, if the production is constant pressure production, and the bottom hole flowing pressure of the first fracture is assumed to be constant, then according to the pressure relationship between the two adjacent sections of the well, the bottom hole flowing pressures of the three fractures can be respectively shown as:

p_wf1＝C (2.28)

p_wf2＝p_wf1+0.5(Δp_wf1+Δp_wf2) (2.29)

p_wf3＝p_wf2+0.5(Δp_wf2+Δp_wf3) (2.30)

in the formula, p_wf1、p_wf2、p_wf3Respectively 1, 2 and 3 well section center pressures; Δ p_wf1、Δp_wf2、Δp_wf3Pressure drop across the 1 st, 2 nd, 3 rd well sections, respectively, with C being a constant.

Since the wellbore is horizontal, there is no loss of gravity, and the pressure drop in the wellbore can be expressed as the sum of the frictional pressure drop and the accelerated pressure drop:

Δp_wfi＝Δp_fi+Δp_ai(2.31)

in the formula,. DELTA.p_wfiIs the pressure drop across the ith interval; Δ p_fiA pressure drop due to friction loss across the i-th interval; Δ p_aiThe pressure drop caused by the acceleration loss through the i-th interval.

The frictional pressure drop is represented by the following formula:

the acceleration pressure drop is represented by the following equation:

Δp_ai＝ρ_i(v_i+v_i-1)(v_i-1-v_i) (2.34)

in the formula, ρ_iIs the fluid density in interval i; f. of_iThe coefficient of friction between the fluid in the well section i and the well bore is shown; d is the diameter of the shaft;is the average velocity of the well section fluid; v. of_i、v_i-1The rates of fluid flow into and out of the wellbore interval i, respectively.

As shown in fig. 7, we can obtain:

v₃＝0 (2.35)

v₂＝q₃/A (2.36)

v₁＝(q₂+q₃)/A (2.37)

v₀＝(q₁+q₂+q₃)/A (2.3)

wherein A is the cross-sectional area of the shaft.

The calculation formula of the friction coefficient is as follows:

laminar flow:

turbulent flow:

wherein,

in the formula, Re_iIs Reynolds number; e is the relative roughness of the well wall; mu.s_iIs the fluid viscosity in interval i.

In the case of mixed flow of oil and water phases, the mixing density of the two phases:

mixing viscosity of both phases:

in the formula, ρ_w、ρ_oThe densities of the water phase and the oil phase in the shaft are respectively; mu.s_w、μ_oRespectively the viscosity of the water phase and the oil phase in the shaft;respectively the average flow of the water phase and the average flow of the oil phase in the well section i;respectively, the average flow velocity in interval i.

Thus, the pressure drop over each interval can be expressed as:

fourth, the first flow model of the flow between the oil reservoir and the crack

In order to derive a flow calculation formula of flow between an oil reservoir and a crack, an oil reservoir grid ri and a crack grid fi adjacent to the oil reservoir grid ri are selected, as shown in fig. 8, the oil reservoir grid and the crack grid have the same size in the y direction and the z direction, and the dimension of the oil reservoir grid is D in the x direction_rThe thickness of the crack grid is the crack thickness D_f. The thickness of the crack is typically a few millimeters, and for ease of illustration, the crack thickness is shown as being larger.

Because the two-dimensional grid of the fracture model is assumed to be at the intersection of the three-dimensional grids of the reservoir model, the flow of the fracture is supplied to the reservoir grids from two adjacent sides. Assuming that the oil phase pressure of the interface of the crack and the oil reservoir is p, the oil phase pressure of the center of the oil reservoir unit block is p_ro(ri) oil phase pressure in the center of the fractured cell block of p_fo(fi) the flow between the two is realized through the interface, and the flow from the reservoir grid to the interface is equal to the flow from the interface to the fracture grid.

Oil phase flow from reservoir node ri to the interface:

q_ro(ri)＝j_ro(ri)[p_ro(ri)-p](2.50)

in the formula, q_ro(ri) is the oil or water phase flow rate of the reservoir grid blocks (ri) to the interface; p is a radical of_ro(ri) reservoir grid block ri oil phase pressure; p is the pressure at the interface of the oil reservoir grid and the fracture grid; k is a radical of_riPermeability of the reservoir grid ri; k is a radical of_rroRelative permeability of oil phase of oil reservoir; mu.s_roIs the oil phase viscosity of the oil reservoir; a. the_rfIs the area of the interface of the reservoir grid and the fracture grid, D_rThe distance from the center of the reservoir grid to the interface of the reservoir grid and the fracture grid.

Oil phase flow into fracture node (fi) from interface:

q_fo(fi)＝j_fo(fi)[p-p_fo(fi)](2.52)

in the formula, q_fo(fi) is the oil phase flow into the fracture network (fi) from the interface; p is a radical of_fo(ri) is the pressure of the oil or water phase of the fracture network (ri); k is a radical of_fiPermeability of the fracture mesh fi; k is a radical of_froRelative permeability of oil phase in the fracture; d_fThe distance from the center of the reservoir grid to the interface of the reservoir grid and the fracture grid.

Then there are:

p_ro(ri)-p＝q_ro(ri)/j_ro(ri) (2.54)

p-p_fo(fi)＝q_fo(fi)/j_fo(fi) (2.55)

the two formulas above are added to each other,

p_ro(ri)-p_fo(fi)＝q_ro(ri)/j_ro(ri)+q_fo(fi)/j_fo(fi) (2.56)

by the principle of flow continuity,

q_ro(ri)＝q_fo(fi)＝q_o(ri) (2.57)

p_ro(ri)-p_fo(fi)＝q_o(ri)(1/j_ro(ri)+1/j_fo(fi)) (2.58)

order:

q_o(ri)＝j_o(ri)[p_ro(ri)-p_fo(fi)](2.60)

the oil phase flow exchange coefficient at the interface is:

the water phase can be deduced according to the oil phase processing method, and the exchange coefficients of the water phase and the oil phase at the interface between the oil reservoir grid ri and the adjacent fracture grid fi are respectively obtained as follows:

the flow exchange coefficient is the average conductivity of the reservoir grid and the fracture grid, and the flow from the reservoir into the fractures can be obtained by multiplying the conductivity by the pressure difference between the two.

Fifth, a second flow model of the flow between the fracture and the wellbore

Supposing that a well section wi with a one-dimensional shaft penetrates through a fracture grid fi, subtracting the water phase pressure and the oil phase pressure of the fracture grid fi and the well section wi respectively to obtain a water phase pressure difference and an oil phase pressure difference;

and multiplying the volume flow of the two-dimensional two-phase fracture grid and the one-dimensional two-phase well section passing through the grid under the unit pressure difference by the pressure difference to obtain the second flow model:

water phase: q. q.s_fww＝T_fww[p_fw，fi-p_w，wi](2.64)

Oil phase: q. q.s_fwo＝T_fwo[p_fo，fi-p_w，wi](2.65)

Wherein, T_fww、T_fwoWater phase volume flow and oil phase volume flow of a fracture grid fi and a one-dimensional two-phase well section wi penetrating through the grid under unit pressure difference respectively, q_fww，fi、q_fwo，fiThe water phase volume flow and the oil phase volume flow, p, respectively, flowing into the fracture grid fi through the grid well section wi_fw，fiAnd p_ww，wiThe pressure of the water phase, p, respectively, in the fracture grid fi and across the grid well section wi_fo，fiAnd p_wo，wiRespectively fracture grid fi and oil phase pressure across the grid well section wi.

Wherein r is_wIs the wellbore radius of a one-dimensional wellbore, omega is the fracture width, r_oIs the equivalent radius of the fracture mesh.

Referring to fig. 1, after the model is established, the method for simulating the full coupling of the oil reservoir, the fracture and the shaft of the fractured horizontal well in the embodiment of the invention comprises the following steps:

step S101, obtaining input parameters of the capacity prediction numerical simulation. The input parameters include:

reservoir properties: reservoir porosity, reservoir permeability, reservoir size, reservoir depth, rock compressibility;

fracture properties: the crack porosity, the crack permeability, the crack size, the crack position, the crack number and the crack conductivity;

wellbore properties: well bore position, well bore radius, well bottom flowing pressure, well wall roughness;

the fluid properties: fluid density, fluid viscosity, fluid volume factor, capillary pressure, fluid relative permeability, fluid compressibility;

initial conditions: initial reservoir pressure, initial reservoir phase saturation, initial fracture pressure, initial fracture phase saturation.

And S102, inputting input parameters into a coupling model for coupling among the pre-established fracture, oil deposit and well bore.

And S103, carrying out fully-implicit differential solution on the coupling model to obtain a numerical simulation result of the fracturing horizontal well productivity prediction. Wherein the numerical simulation results may be dynamic data that changes over time, such as reservoir pressure distribution, fracture pressure distribution, fluid production, oil production, and water production of fractured horizontal wells. The following description of the solving process is provided:

in order to simultaneously solve a three-dimensional two-phase oil reservoir model, a two-dimensional two-phase fracture model and a one-dimensional variable mass flow model of a shaft, a fully-implicit solving method is adopted, and an N-R iteration method (namely a Newton-Lawson iteration method) is applied to carry out differential solving on a mathematical model to obtain a coupling matrix for simultaneously solving oil reservoir, fracture and shaft parameters. In order to realize the coupled solution, the fully-implicit differential processing needs to be performed on the flow between the oil reservoir and the fracture, the flow between the fracture and the shaft, the oil reservoir three-dimensional two-phase model and the fracture two-dimensional two-phase model.

Reservoir equations in the coupling matrix subjected to the fully implicit differential processing:

water phase:

oil phase:

the two-dimensional two-phase fracture equation in the coupling coefficient matrix includes:

water phase:

oil phase:

the one-dimensional two-phase wellbore equation in the coupling coefficient matrix comprises:

wherein 1 is the 1 st iteration step number, n is the nth time step, Δ t is a time step, p_roFor the variation of reservoir grid pressure within each iteration step, S_rwFor the variation of the water saturation of the reservoir grid, p, in each iteration step_foFor the variation of the fracture grid pressure within each iteration step, S_fwFor the variation of the water saturation of the fracture network, p, within each iteration step_wThe variation of the interval pressure for each iteration step.

In the embodiment of the invention, aiming at the numerical simulation model of the fracture-reservoir-wellbore coupling, the coupling of the reservoir model, the fracture model and the wellbore model is realized through flow exchange among the three. In the reservoir model, reservoir grids adjacent to the fracture grid have flow rates into the fracture, the flow rates being related to parameters of the adjacent fracture grids; meanwhile, when considering the fracture model, each two-dimensional fracture grid has inflow from two adjacent reservoir grids on two sides, and the inflow is related to the pressure of the reservoir grids on two adjacent sides.

Under the condition of a plurality of cracks, each crack can establish a two-dimensional model, the three-dimensional model of the oil reservoir is coupled with the two-dimensional model of each crack, and from the perspective of a model grid, a crack grid and oil reservoir grids at two adjacent sides have a coupling relation; meanwhile, the fracture model needs to be coupled with the wellbore pressure drop model, a sink exists in the central grid of each fracture model, namely the flow rate flowing from the fracture to the wellbore, and therefore the central grid of the fracture and well sections divided by the wellbore have a coupling relation.

In the embodiment of the invention, a coefficient matrix of a fully implicit difference method for coupling among an oil reservoir, a fracture and a shaft is shown in a figure 9, the matrix is a 'fringed' matrix based on a seven-diagonal coefficient matrix of a three-dimensional two-phase model oil reservoir, a black square part at the upper left corner is the seven-diagonal matrix of the three-dimensional two-phase model, a gray part at the lower right corner represents a five-diagonal matrix of the two-dimensional two-phase fracture model, white parts at the lower left corner and the upper right corner represent the coupling relation between the oil reservoir and the fracture, and five double-circle dot parts at the lower right corner represent the pressure relation of the. It can also be seen from the matrix that each fracture has a coupling relation with two adjacent rows of reservoir grids, and the wellbore pressure is related to the pressure of the grid in the center of the fracture.

Therefore, in order to realize the coupling among the oil reservoir, the crack and the shaft, the embodiment of the invention solves three main problems: firstly, flow flowing into an adjacent crack grid from an oil reservoir grid is deduced according to a flow continuity principle, the flow between an oil reservoir and a crack can be obtained by multiplying the average conductivity of the oil reservoir and the crack by the pressure difference between the oil reservoir grid and the crack grid, and for the oil reservoir grid close to the crack grid and the crack grid close to the oil reservoir grid, the flow term needs to be added into a mass conservation equation; secondly, the flow between the crack and the shaft is calculated, for the crack grid with the shaft passing through, the flow term needs to be added into a mass conservation equation, and the flow term also needs to be used in the pressure drop calculation of the horizontal shaft; and thirdly, coupling the constructed oil deposit mass conservation equation, the fracture mass conservation equation and the shaft momentum equation together to carry out full implicit solution, thereby realizing the full coupling simulation method of the oil deposit-fracture-shaft of the fractured horizontal well.

According to the embodiment of the invention, on the basis of a pre-established complete fracture-oil reservoir-shaft coupling model, the coupling model is subjected to full implicit difference on input parameters by using an N-R iteration method, so that a fringed matrix of the coupling of the fracture-oil reservoir-shaft is obtained, and the simultaneous solution of oil reservoir, fracture and shaft parameters is realized. Therefore, the method considers the coupling relation among the oil deposit, the crack and the shaft, namely not only the oil deposit and the crack, but also the flow between the oil deposit and the crack and the flow between the crack and the shaft are considered, so that the obtained numerical model result of the well productivity prediction is more consistent with the actual condition of the fractured horizontal well.

The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may be stored in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. For example, a storage medium may be coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC, which may be located in a user terminal. In the alternative, the processor and the storage medium may reside in different components in a user terminal.

In one or more exemplary designs, the functions described above in connection with the embodiments of the invention may be implemented in hardware, software, firmware, or any combination of the three. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media that facilitate transfer of a computer program from one place to another. Storage media may be any available media that can be accessed by a general purpose or special purpose computer. For example, such computer-readable media can include, but is not limited to, RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to carry or store program code in the form of instructions or data structures and which can be read by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Additionally, any connection is properly termed a computer-readable medium, and, thus, is included if the software is transmitted from a website, server, or other remote source via a coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL), or wirelessly, e.g., infrared, radio, and microwave. Such discs (disk) and disks (disc) include compact disks, laser disks, optical disks, DVDs, floppy disks and blu-ray disks where disks usually reproduce data magnetically, while disks usually reproduce data optically with lasers. Combinations of the above may also be included in the computer-readable medium.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (3)

1. A full-coupling simulation method for oil reservoirs, cracks and mineshafts of fractured horizontal wells is characterized by comprising the following steps:

acquiring input parameters of capacity prediction numerical simulation;

inputting the input parameters into a coupling model which is established in advance and is coupled among the crack, the oil reservoir and the shaft;

carrying out fully-implicit differential solution on the coupling model to obtain a numerical simulation result of the fracturing horizontal well productivity prediction;

the coupling model comprises a three-dimensional two-phase oil reservoir model, a two-dimensional two-phase fracture model, a one-dimensional shaft variable mass flow model, a first flow model of flow between an oil reservoir and a fracture and a second flow model of flow between the fracture and a shaft, wherein the two phases are oil and water; wherein:

the three-dimensional two-phase reservoir model is established in advance in the following mode:

selecting a three-dimensional two-phase oil reservoir formed by stacking a plurality of three-dimensional grid unit bodies, wherein a one-dimensional shaft and a two-dimensional two-phase crack are arranged in the three-dimensional two-phase oil reservoir, and the two-dimensional two-phase crack is intersected with the one-dimensional shaft;

deducing a flow equation of two phases in the three-dimensional two-phase oil reservoir according to a mass conservation equation of the two phases;

acquiring a flow exchange term of the three-dimensional two-phase oil reservoir and the two-dimensional two-phase fracture;

substituting the flow exchange term into the flow equation to obtain a three-dimensional two-phase oil reservoir model:

water phase:

oil phase:

wherein phi is_rTo reservoir porosity, B_rw、B_roThe volume coefficients of a water phase and an oil phase in an oil reservoir are respectively; s_rw、S_roRespectively representing the water phase saturation and the oil phase saturation in the oil reservoir; q. q.s_rfw、q_rfoThe volume flow of water phase and oil phase flowing out of the oil reservoir to the fracture in unit time, T_rw、T_roVolume flow, p, of water and oil phases within the reservoir respectively, flowing from reservoir grid ri to adjacent reservoir grid rj at unit pressure difference_rw、p_roThe pressure of the water phase and the oil phase in the oil reservoir respectively;

$T_{rw}=\frac{A_r}{L_r}\·\frac{2K_{ri}{K}_{rj}}{K_{ri}+K_{rj}}\·\frac{k_{rrw}}{{\mathrm{\μ}}_{rw}{B}_{rw}}$

$T_{ro}=\frac{A_r}{L_r}\·\frac{2K_{ri}{K}_{rj}}{K_{ri}+K_{rj}}\·\frac{k_{rro}}{{\mathrm{\μ}}_{ro}{B}_{ro}}$

wherein A is_rIs the area of the interface between the reservoir grid ri and the adjacent grid rj, L_rIs the length, K, between the reservoir grid ri and the adjacent reservoir grid rj_riAs permeability of reservoir grid ri, K_rjPermeability of reservoir grid rj, k_rrwRelative permeability of the reservoir water phase, k_rroIs the relative permeability of oil phase of oil reservoir, mu_rwViscosity of the reservoir water phase, mu_roIs the oil phase viscosity of the oil reservoir;

the two-dimensional two-phase fracture model is established in advance in the following mode:

deducing a continuity equation of two phases in the two-dimensional two-phase fracture according to a mass conservation equation of the two phases;

respectively acquiring a first flow exchange term of the two-dimensional two-phase fracture and the three-dimensional two-phase oil deposit, a second flow exchange term of the two-dimensional two-phase fracture and the one-dimensional wellbore, and a motion equation expressed by Darcy formula in the two-dimensional two-phase fracture;

substituting the first flow exchange term, the second flow exchange term and the motion equation into the continuity equation to obtain a two-dimensional two-phase fracture model:

water phase:

oil phase:

wherein phi is_fIs the fracture porosity, S_fw、S_foRespectively the water phase saturation and the oil phase saturation in the fracture q_fww、q_fwoThe volume flow of water phase and oil phase flowing out of the fracture to the horizontal shaft in unit time, T_fw、T_foVolume flow rates, p, of water and oil phases within the fracture, respectively, flowing from fracture mesh fi to adjacent fracture mesh fj at unit pressure difference_fw、p_foRespectively the pressure of the water phase and the oil phase in the crack;

$T_{fw}=\frac{A_f}{L_f}\·\frac{2K_{fi}{K}_{fj}}{K_{fi}+K_{fj}}\·\frac{k_{frw}}{{\mathrm{\μ}}_{fw}{B}_{fw}}$

$T_{fo}=\frac{A_f}{L_f}\·\frac{2K_{fi}{K}_{fj}}{K_{fi}+K_{fj}}\·\frac{k_{fro}}{{\mathrm{\μ}}_{fo}{B}_{fo}}$

wherein A is_fIs the area of the interface between the fracture grid fi and the adjacent grid fj, L_fIs the length, K, between the reservoir grid fi and the adjacent grid fj_fiAs the permeability of the fracture network fi,K_fjpermeability of the fracture grid fj, μ_fwIs the water phase viscosity in the fracture, mu_foViscosity of the oil phase in the fracture, B_fw、B_foThe volume coefficients of a water phase and an oil phase in the crack are respectively;

the one-dimensional shaft in the one-dimensional shaft variable mass flow model is divided into n +1 sections by n two-dimensional two-phase fractures, and the model is established in advance in the following mode:

respectively calculating the friction pressure drop and the accelerated pressure drop of each section of one-dimensional shaft, wherein the pressure drop generated by the second section wi and the second section wi-1 of the adjacent upstream well section is;

p_w,wi-p_w,wi-1＝Δp_w,wi

${\mathrm{\Δp}}_{w,wi}=\frac{2f_{wi}{\mathrm{\ρ}}_{wi}}{{\mathrm{\π}}^2{D}^5}{(2Q_{wi}+q_{wi})}^{2}L+\frac{16{\mathrm{\ρ}}_{wi}{q}_{wi}}{{\mathrm{\π}}^2{D}^4}(2Q_{wi}+q_{wi})$

wherein p is_w,wiFor the second section wellbore pressure, p_w,wi-1Is the pressure of the w-1 section of the well bore, Δ p_w,wiIs the pressure drop between the wi th section and the wi-1 th section, f_wiCoefficient of friction, p, for the w-th section of the one-dimensional wellbore_wiThe mixing density of two-phase mixed fluid in the one-dimensional shaft of the second section, D is the shaft diameter of the one-dimensional shaft, Q_wiIs the sum of the flow rates of two-phase mixed fluid in all well sections before the first section one-dimensional well bore, q_wiIs the flow rate L of two-phase mixed fluid in the one-dimensional shaft of the second section_wiThe length of the one-dimensional shaft of the first wi section;

the first flow model is established in advance by the following method:

assuming that the oil reservoir grid ri is adjacent to the fractured grid fi, respectively subtracting the water phase pressure and the oil phase pressure of the oil reservoir grid ri and the adjacent fractured grid fi to obtain a water phase pressure difference and an oil phase pressure difference;

and multiplying the volume flow of the oil reservoir grid ri and the adjacent fracture grid fi under the unit pressure difference by the pressure difference to obtain the first flow model:

water phase: q. q.s_rfw＝T_rfw[p_rw,ri-p_fw,fi]

Oil phase: q. q.s_rfo＝T_rfo[p_ro,ri-p_fo,fi]

Wherein, T_rfw、T_rfoRespectively three-dimensional two-phase reservoir grid ri and adjacent two-dimensional two-phase fracture grid fiWater phase volume flow and oil phase volume flow at unit pressure difference, q_rfw、q_rfoVolume flow, p, of reservoir grid ri into adjacent fracture grid fj, respectively_rw,riAnd p_fw,fiWater phase pressure, p, of reservoir grid ri and adjacent fracture grid fj, respectively_ro,riAnd p_fo,fiOil phase pressures of the oil reservoir grid ri and the fracture grid fj are respectively set;

$T_{rfw}=\frac{2K_{ri}{k}_{rrw}{K}_{fi}{k}_{frw}{A}_{rf}}{{\mathrm{\μ}}_{rw}{B}_{rw}{D}_r{K}_{fi}{k}_{frw}+{\mathrm{\μ}}_{fw}{B}_{fw}{D}_f{K}_{ri}{k}_{rrw}}$

$T_{rfo}=\frac{2K_{ri}{k}_{rro}{K}_{fi}{k}_{fro}{A}_{rf}}{{\mathrm{\μ}}_{ro}{B}_{ro}{D}_r{K}_{fi}{k}_{fro}+{\mathrm{\μ}}_{fo}{B}_{fo}{D}_f{K}_{ri}{k}_{rro}}$

wherein A is_rfAre the areas of the interfaces of the reservoir grid ri and the adjacent fracture grid fi, D_rDistance from center of reservoir grid to interface, D_fThe distance from the center of the fracture grid to the interface;

the second flow model is established in advance by the following method:

supposing that a well section wi with a one-dimensional shaft penetrates through a fracture grid fi, subtracting the water phase pressure and the oil phase pressure of the fracture grid fi and the well section wi respectively to obtain a water phase pressure difference and an oil phase pressure difference;

and multiplying the volume flow of the two-dimensional two-phase fracture grid and the one-dimensional two-phase well section passing through the grid under the unit pressure difference by the pressure difference to obtain the second flow model:

water phase: q. q.s_fww＝T_fww[p_fw,fi-p_w,wi]

Oil phase: q. q.s_fwo＝T_fwo[p_fo,fi-p_w,wi]

Wherein, T_fww、T_fwoIs a water phase body of a crack grid fi and a one-dimensional two-phase well section wi passing through the grid under unit pressure differenceVolume flow and oil phase volume flow, q_fww,fi、q_fwo,fiThe water phase volume flow and the oil phase volume flow, p, respectively, flowing into the fracture grid fi through the grid well section wi_fw,fiAnd p_ww,wiThe pressure of the water phase, p, respectively, in the fracture grid fi and across the grid well section wi_fo,fiAnd p_wo,wiThe pressure of the oil phase passing through the grid well section wi and the fracture grid fi respectively;

$T_{fww}=\frac{2{\mathrm{\π\ωK}}_{fi}{k}_{frw}}{{\mathrm{\μ}}_{fo}{B}_{fo}\ln \left(\frac{r_o}{r_w}\right)}$

$T_{fwo}=\frac{2{\mathrm{\π\ωK}}_{fi}{k}_{fro}}{{\mathrm{\μ}}_{fw}{B}_{fw}ln\left(\frac{r_o}{r_w}\right)}$

wherein r is_wIs the wellbore radius of a one-dimensional wellbore, omega is the fracture width, r_oIs the equivalent radius of the fracture mesh.

2. The fractured horizontal well oil reservoir, fracture and wellbore fully-coupled simulation method according to claim 1, wherein the fully-implicit differential solution is performed on the coupled model, and specifically comprises the following steps:

carrying out full-implicit differential solution on the coupling model by utilizing a Newton-Lafferson N-R iterative method to obtain a coupling coefficient matrix for simultaneously solving parameters of a crack, an oil reservoir and a shaft; wherein,

the three-dimensional two-phase reservoir equation in the coupling coefficient matrix comprises:

water phase:

oil phase:

the two-dimensional two-phase fracture equation in the coupling coefficient matrix includes:

water phase:

oil phase:

the one-dimensional two-phase wellbore equation in the coupling coefficient matrix comprises:

$\begin{array}{c}{\left(p_{w,wi}-p_{w,wi-1}\right)}^l+\[\∂\left(p_{w,wi}-p_{w,wi-1}\right)/\∂p_w\]{\mathrm{\δp}}_w\\ ={\[\frac{2f_{wi}{\mathrm{\ρ}}_{wi}}{{\mathrm{\π}}^2{D}^5}{\left(2Q_{wi}+q_{wi}\right)}^{2}L+\frac{16{\mathrm{\ρ}}_{wi}{q}_{wi}}{{\mathrm{\π}}^2{D}^4}\left(2Q_{wi}+q_{wi}\right)\]}^l\\ +\left\{\∂\[\frac{2f_{wi}{\mathrm{\ρ}}_{wi}}{{\mathrm{\π}}^2{D}^5}{\left(2Q_{wi}+q_{wi}\right)}^{2}L+\frac{16{\mathrm{\ρ}}_{wi}{q}_{wi}}{{\mathrm{\π}}^2{D}^4}\left(2Q_{wi}+q_{wi}\right)\]/\∂p_w\right\}{\mathrm{\δp}}_w\\ +\left\{\∂\[\frac{2f_{wi}{\mathrm{\ρ}}_{wi}}{{\mathrm{\π}}^2{D}^5}{\left(2Q_{wi}+q_{wi}\right)}^{2}L+\frac{16{\mathrm{\ρ}}_{wi}{q}_{wi}}{{\mathrm{\π}}^2{D}^4}\left(2Q_{wi}+q_{wi}\right)\]/\∂p_{fo}\right\}{\mathrm{\δp}}_{fo}\\ +\left\{\∂\[\frac{2f_{wi}{\mathrm{\ρ}}_{wi}}{{\mathrm{\π}}^2{D}^5}{\left(2Q_{wi}+q_{wi}\right)}^{2}L+\frac{16{\mathrm{\ρ}}_{wi}{q}_{wi}}{{\mathrm{\π}}^2{D}^4}\left(2Q_{wi}+q_{wi}\right)\]/\∂S_{fw}\right\}{\mathrm{\δS}}_{fw}\end{array}$

where l is the l iteration step number, n is the n time step, Δ t is a time step, p_roFor the variation of reservoir grid pressure within each iteration step, S_rwFor the variation of the water saturation of the reservoir grid, p, in each iteration step_foFor the variation of the fracture grid pressure within each iteration step, S_fwFor the variation of the water saturation of the fracture network, p, within each iteration step_wThe variation of the interval pressure for each iteration step.

3. The fractured horizontal well oil reservoir, fracture, and wellbore fully-coupled simulation method of claim 1, wherein the input parameters comprise:

reservoir properties: reservoir porosity, reservoir permeability, reservoir size, reservoir depth, rock compressibility;

fracture properties: the crack porosity, the crack permeability, the crack size, the crack position, the crack number and the crack conductivity;

wellbore properties: well bore position, well bore radius, well bottom flowing pressure, well wall roughness;

the fluid properties: fluid density, fluid viscosity, fluid volume factor, capillary pressure, fluid relative permeability, fluid compressibility;

initial conditions: initial reservoir pressure, initial reservoir phase saturation, initial fracture pressure, initial fracture phase saturation.