CN112084718B - Shale gas reservoir single-phase gas three-hole three-permeation model construction method based on seepage difference - Google Patents

Shale gas reservoir single-phase gas three-hole three-permeation model construction method based on seepage difference Download PDF

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CN112084718B
CN112084718B CN202010973502.8A CN202010973502A CN112084718B CN 112084718 B CN112084718 B CN 112084718B CN 202010973502 A CN202010973502 A CN 202010973502A CN 112084718 B CN112084718 B CN 112084718B
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刘建仪
袁华
何汶亭
刘治彬
蒋橹
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Abstract

The invention discloses a shale gas reservoir single-phase gas three-hole three-permeation model construction method based on seepage difference, which comprises the following steps of: firstly, establishing a physical model of three-hole three-permeability pore characteristics, a shale gas reservoir single-phase gas flow three-hole three-permeability unstable model and a shale gas reservoir single-phase gas flow three-hole three-permeability quasi-stable model, wherein organic matters and inorganic matters are symbiotic in a spherical aggregate form and form a crack together; solving a shale gas reservoir three-hole three-permeability multi-stage fracturing horizontal well single-phase gas seepage model, and obtaining a bottom hole pressure expression by adopting a semi-analytical method to discretely solve hydraulic fractures by combining a source function method and a Laplace transformation mathematical method; drawing a pressure dynamic characteristic curve and a yield decreasing curve of the three-hole three-permeation model; a fitting method of actually measured well test data is adopted, and an interpretation program is compiled; and analyzing the influence of the adsorption constant of the organic matters and the clay minerals and analyzing the influence of the channeling mode and the channeling coefficient. The scheme can explain the field actual measurement well testing data based on the single-phase gas three-hole three-permeability model.

Description

Shale gas reservoir single-phase gas three-hole three-permeation model construction method based on seepage difference
Technical Field
The invention relates to the field of shale gas development, in particular to a shale gas reservoir single-phase gas three-hole three-permeation model construction method based on seepage difference.
Background
In recent years, scholars at home and abroad develop related theories of a multi-medium multiple migration mechanism seepage model on the basis of analysis of a shale gas reservoir traditional double-pore medium model, but differences of physical properties of organic matters and inorganic matters are not considered in the models, the organic matters are generally symbiotic with clay minerals in a shale reservoir in an aggregate form, a large number of nano-scale pores with adsorption characteristics are developed in the organic matters, the inorganic matters develop nano-micron-scale pores with water-wettability, and the clay minerals in the inorganic matters also have certain methane adsorption capacity due to special crystal structures.
At present, most models are mainly built on two systems of a matrix and a crack, and the method provides three systems for building the models by separating organic matters and inorganic matters in the matrix and forming the three systems together with the crack. Regarding the flow mechanism of gas in the matrix system, most scholars thought that the flow of gas in the matrix system is mainly subject to desorption and diffusion, and there is no gas seepage caused by pressure field, and more scholars such as Ozkan, guo crystal, nobilex and the like proposed in recent years that the flow of shale gas in the matrix is not only subject to desorption and diffusion, but also subject to gas seepage caused by pressure difference. A plurality of students analyze the shale gas reservoir single-phase gas seepage model, and the homogeneous shale gas reservoir seepage model is deduced by correcting the comprehensive compression coefficient through the Bumb and McKee (1896); kucuk and Sawyer (1980) establish a shale gas unsteady state analysis model without considering adsorption based on a Warren Root model; dehghanpour et al (2011) established a triple-medium seepage model based on a matrix, micro fractures and hydraulic fractures; huang et al (2015) considered kerogen alone as a pore medium created a new triple media percolation model, but only the solution gas diffusion effect in kerogen was considered in the model. The current shale gas reservoir single-phase gas seepage model has the following problems:
(1) organic matters and inorganic matters are not considered as two systems with independent physical properties in the seepage differential equation;
(2) the adsorption and desorption capacities of kerogen and clay minerals are not separated;
(3) the influence of the cross-flow phase between organic and inorganic matter on the production dynamics is not considered.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, and provides a shale gas reservoir single-phase gas flow well test interpretation model and a shale gas reservoir single-phase gas flow well test interpretation method based on organic matter-inorganic matter-crack three-hole three-permeability pore characteristics.
The purpose of the invention is realized by the following technical scheme:
the shale gas reservoir single-phase gas three-hole three-permeation model construction method based on the seepage difference comprises the following steps:
s1, obtaining basic assumed conditions of a shale gas reservoir single-phase gas flow three-hole three-permeation model, and constructing a physical model of three-hole three-permeation pore characteristics, wherein organic matters and inorganic matters coexist in a spherical aggregate form and form a three-hole three-permeation pore characteristic together with cracks on the basis of a De Swaan spherical model;
s2, constructing a shale gas reservoir single-phase gas flow three-hole three-permeation unsteady state model according to the physical model and the assumed conditions in the step S1, and solving the model to finally obtain a comprehensive differential equation of the shale gas reservoir three-hole three-permeation unsteady state model with organic matters and inorganic matters separated;
s3, constructing a shale gas reservoir single-phase gas flow three-hole three-penetration quasi-steady-state model according to the physical model and the assumed conditions in the step S1, solving the model, and finally obtaining a comprehensive seepage differential equation of the shale gas reservoir three-hole three-penetration quasi-steady-state model separating organic matters from inorganic matters;
s4, obtaining basic assumed conditions of shale gas reservoir multistage fracturing horizontal well seepage, solving a shale gas reservoir three-hole three-seepage multistage fracturing horizontal well single-phase gas seepage model, and obtaining a bottom hole pressure expression by discretely solving hydraulic fractures by combining a point source function method, a Laplace transformation method and a semi-analytical method;
s5, according to the bottom hole pressure expression, performing numerical inversion by Stehfest, calculating the value of dimensionless bottom hole flow pressure in a real space by utilizing Matlab programming, and drawing a three-hole three-permeability model pressure dynamic characteristic curve and a yield decreasing curve;
s6, fitting the on-site measured bottom hole pressure and pressure derivative curve by adopting an optimization algorithm, analyzing formation parameters, and compiling an interpretation program to interpret and analyze the on-site measured well test data;
s7, analyzing the influence of the organic matter and clay mineral adsorption constant on the dimensionless pressure and pressure derivative curve based on the three-hole three-penetration quasi-steady-state model, and simultaneously analyzing the influence of different channeling modes and channeling coefficients on the dimensionless pressure and pressure derivative curve.
Specifically, the comprehensive seepage differential equation of the shale gas reservoir three-hole three-permeability steady-state simulation model in step S2 is shown as follows:
Figure GDA0002735834640000021
in the formula: r isfDThe method is dimensionless radial distance of a crack system in a spherical coordinate system; s is a laplace variable; f(s) is a feature function;
Figure GDA0002735834640000022
is the dimensionless pseudo pressure of the fracture system in Laplace.
Specifically, the solving process of the shale gas reservoir single-phase gas flow three-hole three-permeability unsteady state model in the step S2 specifically includes:
s201, independently regarding the organic matter as a seepage medium, and respectively establishing seepage equations for an organic matter system, an inorganic matter system and a crack system;
and S202, introducing the dimensionless variables into the seepage equations of the organic matter system, the inorganic matter system and the crack system respectively, and performing dimensionless treatment to obtain the dimensionless seepage equation.
S203, solving a dimensionless seepage equation of the organic matter system, and after obtaining a dimensionless pressure expression of the organic matter system, carrying out derivation calculation on the dimensionless pressure expression;
s204, substituting the derived dimensionless pressure expression of the organic matter system into the dimensionless seepage equation of the inorganic matter system and solving the equation to obtain the dimensionless pressure expression of the inorganic matter system and then carrying out derivation;
and S205, substituting the derived dimensionless pressure expression of the inorganic matter system into the dimensionless seepage equation of the fracture system and solving the equation to finally obtain a comprehensive differential equation of the shale gas reservoir three-hole three-seepage unsteady state model separating organic matters from inorganic matters.
Specifically, the solving process of the shale gas reservoir single-phase gas flow three-hole three-permeability steady-state model in the step S3 includes:
s301, obtaining a three-hole three-permeation quasi-steady-state mathematical model based on a physical model and an assumed condition which are the same as those of the three-hole three-permeation non-steady-state model by a mass conservation law;
s302, inputting the dimensionless variable into the three-hole three-penetration quasi-steady-state mathematical model, and performing dimensionless processing to obtain the three-hole three-penetration quasi-steady-state dimensionless mathematical model;
s303, performing Laplace transformation and simplified arrangement on the three-hole three-penetration quasi-steady-state dimensionless mathematical model to finally obtain a comprehensive seepage differential equation of the shale gas reservoir three-hole three-penetration quasi-steady-state model for separating organic matters from inorganic matters.
Specifically, the expression of the bottom hole pressure in step S4 is shown as follows:
Figure GDA0002735834640000031
in the formula:
Figure GDA0002735834640000032
dimensionless bottom hole flow pressure in Laplace; s is the epidermis coefficient; cDDimensionless wellbore reservoir coefficients;
Figure GDA0002735834640000033
dimensionless bottom hole pseudo pressure in the Laplace.
Specifically, the solving process of the shale gas reservoir three-hole three-permeability multi-stage fracturing horizontal well single-phase gas seepage model in the step S4 includes:
s401, firstly, solving continuous point sources in the three-dimensional infinite shale gas reservoir by adopting a point source function method and Laplace transformation, and calculating a continuous point source solution of the infinite shale gas reservoir with the closed top and the closed bottom;
s402, dispersing hydraulic fractures by adopting a semi-analytical method to obtain pressure response of the shale gas reservoir multistage fracturing horizontal well, carrying out discretization treatment on each fracture to form 2n small units, dispersing the whole multistage fracturing horizontal well system into m multiplied by 2n units, and obtaining the pressure response of the horizontal well;
s403, determining production according to the model assumption conditions and the gas well, combining the pressure response of the horizontal well to form a matrix equation, and calculating the flow and the bottom hole pressure value of each discrete unit according to the matrix equation;
and S404, when the skin effect and the wellbore storage effect exist, correcting the bottom hole pressure expression by using the Duhamel principle.
Specifically, the step S6 further includes: obtaining an optimal solution meeting the requirement through a genetic algorithm, comparing a field measured bottom hole pressure and a derivative curve with a curve calculated by an established well testing interpretation model, taking the error of the curve as a target function, and expressing the target function as shown in the following formula:
Figure GDA0002735834640000041
in the formula: p is a radical ofcCalculating the obtained bottom hole pressure of the model in MPa; p is a radical ofiMeasured bottom hole pressure in situ, MPa; n is the number of experimental data.
The invention has the beneficial effects that:
(1) the method provides a physical model in which organic matters are symbiotic with inorganic matters in a spherical aggregate form according to the micro-pore structure characteristics of shale on the basis of a traditional model, and establishes a three-hole three-permeation model for single-phase gas flow of a shale gas reservoir on the basis of the physical model. The model separately extracts organic matters to be regarded as a seepage medium, considers that a shale gas reservoir consists of an organic matter system, an inorganic matter system and a crack system which have independent physical properties, establishes a seepage equation for the organic matters and the inorganic matters separately, supposes that gas flows from the organic matter system to the inorganic matter system firstly and then flows from the inorganic matter system to a natural crack, and comprehensively considers the actions of viscous flow of pressure difference, adsorption and desorption of organic matters and clay minerals and diffusion multiple mechanisms of concentration difference in shale gas flow, thereby establishing a three-hole three-seepage unsteady state model and a three-hole three-seepage quasi-steady state model of the shale gas reservoir.
(2) Based on a single-phase gas three-hole three-seepage basic model, a source function method, a Laplace transformation and other mathematical methods are combined, a semi-analytical method is adopted to solve hydraulic fractures discretely to obtain a solution of a single-phase gas seepage model of a shale gas reservoir multistage fracturing horizontal well, a dimensionless pressure double-logarithm curve and a dimensionless yield double-logarithm curve are programmed and drawn, a fitting method of actually measured well test data is provided, and the actually measured well test data on site can be explained.
Drawings
FIG. 1 is a flow chart of the method of the present invention.
FIG. 2 is a schematic diagram of a shale gas reservoir single-phase gas flow three-hole three-permeability physical model.
Fig. 3 is a schematic flow process diagram of the shale gas reservoir three-hole three-permeability model of the present invention.
Fig. 4 is a schematic diagram of a shale gas reservoir multi-stage fractured horizontal well physical model of the invention.
Fig. 5 is a schematic of a multi-stage fractured horizontal well of the present invention.
FIG. 6 is a schematic view of the fracture dispersion profile of the present invention.
FIG. 7 is a graph of dimensionless pressure versus pressure derivative for the shale gas reservoir three-hole triple-permeability model of the present invention.
Fig. 8 is a graph of log production for a three-hole, triple-permeability, multi-stage fractured horizontal well of a shale gas reservoir of the present invention.
FIG. 9 is the present inventionOrganic adsorption constant P of the inventionLoThe results are compared to the results for the dimensionless pseudo pressure derivative curve.
FIG. 10 shows the saturated adsorption quantity V of organic substances in accordance with the present inventionLoThe results are compared to the results for the dimensionless pseudo pressure derivative curve.
FIG. 11 shows the clay mineral adsorption constant P of the present inventionLcThe results are compared to the results for the dimensionless pseudo pressure derivative curve.
FIG. 12 shows the saturated adsorption capacity V of clay mineral according to the present inventionLcThe results are compared to the results for the dimensionless pseudo pressure derivative curve.
FIG. 13 is a graph comparing the effect of different modes of cross flow for a three-hole triple-permeability model of the present invention on a dimensionless pseudo-pressure derivative curve.
FIG. 14 is a cross-flow coefficient λ of the present inventioncfThe results are plotted against the effect of the dimensionless pressure vs. pressure derivative curve.
FIG. 15 is a cross-flow coefficient λ of the present inventionocThe results are plotted against the effect of the dimensionless pressure vs. pressure derivative curve.
Detailed Description
In order to more clearly understand the technical features, objects, and effects of the present invention, embodiments of the present invention will now be described with reference to the accompanying drawings.
In this embodiment, as shown in fig. 1, the method for constructing the shale gas reservoir single-phase gas three-hole three-permeability model based on the difference in permeability includes the following steps:
s1, obtaining basic assumed conditions of a shale gas reservoir single-phase gas flow three-hole three-permeation model, and constructing a physical model of three-hole three-permeation pore characteristics, wherein organic matters and inorganic matters coexist in a spherical aggregate form and form a three-hole three-permeation pore characteristic together with cracks on the basis of a DeSwaan spherical model;
s2, constructing a shale gas reservoir single-phase gas flow three-hole three-permeation unsteady state model according to the physical model and the assumed conditions in the step S1, and solving the model to finally obtain a comprehensive differential equation of the shale gas reservoir three-hole three-permeation unsteady state model with organic matters and inorganic matters separated;
s3, constructing a shale gas reservoir single-phase gas flow three-hole three-penetration quasi-steady-state model according to the physical model and the assumed conditions in the step S1, solving the model, and finally obtaining a comprehensive seepage differential equation of the shale gas reservoir three-hole three-penetration quasi-steady-state model separating organic matters from inorganic matters;
s4, obtaining basic assumed conditions of shale gas reservoir multistage fracturing horizontal well seepage, solving a shale gas reservoir three-hole three-seepage multistage fracturing horizontal well single-phase gas seepage model, and obtaining a bottom hole pressure expression by discretely solving hydraulic fractures by combining a point source function method, a Laplace transformation method and a semi-analytical method;
s5, according to the bottom hole pressure expression, performing numerical inversion by Stehfest, calculating the value of dimensionless bottom hole flow pressure in a real space by utilizing Matlab programming, and drawing a three-hole three-permeability model pressure dynamic characteristic curve and a yield decreasing curve;
s6, fitting the on-site measured bottom hole pressure and pressure derivative curve by adopting an optimization algorithm, analyzing formation parameters, and compiling an interpretation program to interpret and analyze the on-site measured well test data;
s7, analyzing the influence of the organic matter and clay mineral adsorption constant on the dimensionless pressure and pressure derivative curve based on the three-hole three-penetration quasi-steady-state model, and simultaneously analyzing the influence of different channeling modes and channeling coefficients on the dimensionless pressure and pressure derivative curve.
In step S1, a physical model and assumed conditions are mainly constructed. In the construction process of the physical model, the organic matter in the matrix is regarded as spherical, based on the concept of the De Swaan spherical model, the physical model in which the organic matter is symbiotic with the inorganic matter in the form of a spherical aggregate is provided, and the organic matter, the inorganic matter and the crack are regarded as triple media and considered separately, as shown in figure 2.
In the construction process of the assumed conditions, the gas flows from the organic matter system to the inorganic matter system, and then flows from the inorganic matter system to the crack system, and the flow process is shown in fig. 3:
the specific basic assumption conditions of the shale gas reservoir single-phase gas flow three-hole three-permeation model are as follows:
(1) the three mediums are respectively expressed as organic matter, subscript is o and inorganic matter, subscript is c and crack system, and subscript is f;
(2) the flow of free gas in a fracture system follows the classical darcy formula;
(3) the substrate consists of organic matters and inorganic matters, wherein the organic matters are symbiotic with the inorganic matters in a spherical aggregate form, and free gas and adsorbed gas exist in the organic matters and the inorganic matters;
(4) the flow of gas in organic matters and inorganic matters of the shale is subjected to the coupling action of a pressure field and a concentration field, the action of the pressure field follows Darcy's law, and the action of the concentration field follows Fick's diffusion law;
(5) interaction between an organic matter system and an inorganic matter system, and interaction between the inorganic matter system and a crack system follows an unsteady state law or a quasi-steady state law;
(6) describing desorption of adsorbed gas by adopting a Langmuir isothermal adsorption model;
(7) gas well fixed-volume production;
(8) the flowing process does not consider the change of temperature and the influence of gravity;
(9) neglecting the influence of the dissolved gas on the production thereof;
(10) shale gas reservoirs are in equilibrium prior to exploitation.
In step S2, the organic matter is regarded as a seepage medium, and seepage equations are respectively established for the organic matter system, the inorganic matter system, and the crack system, respectively, in consideration of the unsteady law that the gas interaction between the organic matter system and the inorganic matter system, and the gas interaction between the inorganic matter system and the crack system follows.
(1) Differential equation of organic matter system seepage
In order to better perform mathematical description on different adsorption, desorption and seepage rules of organic matters and inorganic matters, the method assumes that the shape of an organic matter aggregate is spherical, according to the assumed condition of a physical model, the flow of gas in the organic matters is under the coupling action of a pressure field and a concentration field, namely, seepage and diffusion exist in the organic matters at the same time, the seepage differential equation of a spherical organic matter system can be obtained according to the mass conservation law as follows, wherein the second term on the right of the equation is the desorption term considering the adsorbed gas of the organic matters:
Figure GDA0002735834640000061
in the formula, ρscIs the gas density under standard conditions, kg/m3；ρoIs the gas density of an organic matter system, kg/m3；ΦoThe porosity of an organic matter system is dimensionless; p is a radical ofoIs organic matter system pressure, Pa; vLoThe Langmuir volume of the organic matter represents the limit of gas that can be adsorbed by the organic matter per unit volume under standard conditions, sm3/m3；pLoThe Lane' S pressure of the organic matter represents the corresponding gas pressure when the adsorbed gas reaches 1/2 of a limit value, Pa and t are time and S; v. ofoThe total gas flow velocity in the organic matter system is m/s.
According to the analysis of Ertekin et al, the gas flow rates caused by the pressure field and concentration field can be coupled and superimposed, then voThe following can be written:
Figure GDA0002735834640000071
in the formula,
Figure GDA0002735834640000072
is the gas flow speed under the action of a pressure field, m/s;
Figure GDA0002735834640000073
is the gas flow velocity under the action of the concentration field, m/s.
The gas seepage due to the pressure field follows Darcy's law:
Figure GDA0002735834640000074
in the formula, koIs shale rock organic matter permeability m2(ii) a Mu is gas viscosity, Pa · s.
The diffusion of gases caused by concentration differences follows Fick's diffusion law:
Figure GDA0002735834640000075
in the formula, DoIs Fick diffusion coefficient, m2/s。
Substituting the formula (1-3) and the formula (1-4) into the seepage differential equation (1-1) of the organic matter system by combining the gas state equation to obtain:
Figure GDA0002735834640000076
wherein R is an ideal gas constant of 8.314pa · m3mol/K; t is temperature, K; z is an organic matter gas deviation coefficient and is dimensionless; m is the relative molecular mass of the gas, g/mol.
Isothermal compressibility definition:
Figure GDA0002735834640000077
in the formula, CgIs a compression factor, MPa-1And p is pressure, MPa.
Then:
Figure GDA0002735834640000078
substituting the formula (1-7) into the formula (1-5) can obtain:
Figure GDA0002735834640000079
in the formula, CgoIs the compression coefficient of organic gas, MPa-1。
Defining the reference gas slip factor according to the definition method:
Figure GDA00027358346400000710
in the formula, boIs a gas slip factor and has no dimension.
B is tooSubstituting the formula (1-8) can obtain:
Figure GDA0002735834640000081
in the processing of the equations (1-10), the first and second terms of the expressions in right-hand parentheses are the same, and an additional gas compressibility C can be defined according to the analysis of Bumb et aladsoComprises the following steps:
Figure GDA0002735834640000082
in the formula, CadsoFor adding a compression factor of gas, MPa-1。
Similar to the method of considering the slip effect, the apparent permeability of the organic matter system is defined as follows:
Figure GDA0002735834640000083
in the formula,
Figure GDA0002735834640000084
apparent permeability of the organic matter system, m2。
Dimensionless variables are defined:
Figure GDA0002735834640000085
the equations (1-12) can be expressed as:
Figure GDA0002735834640000086
the formula (1-10) can be further processed to obtain:
Figure GDA0002735834640000087
introducing pseudo pressure:
Figure GDA0002735834640000088
by definition of pseudo-pressure, substituting the formula (1-15) can result:
Figure GDA0002735834640000089
in the formula, #oIs the pseudo pressure of the organic matter system gas, pa2。
Taking mu and C by the above formula linearization treatmentgo、CadsoThe values at the initial pressure conditions are obtained:
Figure GDA00027358346400000810
in the formula, CgoiIs an initial compressibility of organic matter, Pa-1。CadsoiAdding a compression coefficient Pa to the organic matter-1
The total compression factor of the organic matter system is defined as follows:
Cto＝Cgo+Cadso (1-19)
in the formula, CtoIs the total compression coefficient, pa, of the organic matter system-1。
Substituting then yields:
Figure GDA0002735834640000091
in the formula, CtoiIs the initial total compression factor, pa, of the organic matter system-1。
The formula (1-20) is a spherical organic matter system differential equation comprehensively considering the coupling effect of the pressure field and the concentration field.
The initial conditions of the organic matter system are:
ψo(ro,0)＝ψi (1-21)
in the formula, #iIs the initial pseudo-pressure of the organic system, pa.
The inner boundary conditions at the center of the spherical organic matter are as follows:
Figure GDA0002735834640000092
the pressure of the spherical organic matter surface is equal to that of the inorganic matter system, so that the external boundary conditions of the organic matter system are as follows:
Figure GDA0002735834640000095
in the formula, #cThe organic system boundary pseudo-pressure, pa.
(2) Differential equation of inorganic system seepage
The seepage equation of an inorganic system is deduced, and according to the assumed conditions of the physical model of the method, the flow of gas in the inorganic system is under the coupling action of a pressure field and a concentration field, namely, seepage and diffusion exist in the inorganic system at the same time, and simultaneously, the organic system performs channeling to the inorganic system, and the seepage differential equation of the inorganic system under a spherical coordinate can be obtained according to the mass conservation law as follows, wherein the second term on the left side of the equation is a term of the channeling of organic matters to the inorganic system, and the second term on the right side of the equation is a term of desorption of clay mineral adsorbed gas:
Figure GDA0002735834640000093
in the formula, kcIs the inorganic permeability of shale rock, m2；ρscIs the gas density under standard conditions, kg/m3；ρcIs made withoutGas density of mechanical system, kg/m3(ii) a D is Fick diffusion coefficient, m2/s；
Figure GDA0002735834640000094
Porosity of inorganic system; p is a radical ofcInorganic system pressure, Pa; vLcIs the Langmuir volume of the clay mineral and represents the gas limit, sm, that the clay mineral can adsorb per unit volume under standard conditions3/m3；pLcThe Lane pressure of clay mineral represents the gas pressure, Pa, corresponding to the adsorbed gas reaching 1/2 of the limit value.
In conjunction with the gas equation of state, equations (1-24) can be transformed as:
Figure GDA0002735834640000101
the analog pressure is introduced to simplify the inorganic substance seepage equation, the simplification process is the same as that of an organic matter system, and is not repeated here, the subscript C in the formula represents inorganic substances, and the physical meanings and units of all parameters with the subscript C are the same as those of organic matters. A reduced form of the formula (1-25) is obtained:
Figure GDA0002735834640000102
wherein the parameters of the formulae (1-26) are defined as follows:
Figure GDA0002735834640000103
taking mu and Cgc、CadscThe values under the initial pressure condition are linearized to the equations (1-26) to obtain:
Figure GDA0002735834640000104
the formula (1-28) is the comprehensive seepage differential equation in the inorganic system.
The initial conditions for the inorganic system were:
ψc(rc,0)＝ψi (1-29)
the following internal boundary conditions are satisfied in the inorganic system:
Figure GDA0002735834640000105
at the interface of the inorganic system and the crack system, the pressure of the inorganic system should be equal to the pressure of the crack system, and the external boundary conditions can be obtained as follows:
Figure GDA0002735834640000106
in the formula, #fPseudo-pressure for the fracture system, pa.
(3) Differential equation of seepage of fracture system
Similarly, the seepage differential equation of the fracture system in the shale gas reservoir under the spherical coordinate can be obtained by the mass conservation law as follows, wherein the second term on the left side of the equation is a channeling term from an inorganic system to the fracture system:
Figure GDA0002735834640000111
in the formula, kfPermeability of shale rock fracture m2；ρfGas density of the fracture system, kg/m3；
Figure GDA0002735834640000112
Porosity for fracture systems; p is a radical offThe fracture system pressure, Pa.
The simulated pressure is introduced to simplify the seepage equation of the fracture system, the simplification process is the same as that of an organic matter system and an inorganic matter system, and is not repeated here, subscript f in the formula represents the fracture, the physical meaning and unit of all parameters with subscript f are the same as those of the organic matter, and the simplified form of the formula (1-32) is obtained:
Figure GDA0002735834640000113
taking mu and CfThe value under the initial pressure condition is linearized by the formula, and the following results are obtained:
Figure GDA0002735834640000114
the formula (1-34) is the comprehensive seepage equation of the fracture system.
(4) Three-hole three-permeation unsteady state model
In conclusion, the three-hole three-permeation unsteady mathematical model of the organic matter system, the inorganic matter system and the crack system provided by the method is the following formula, and the mathematical description can be better carried out on different adsorption, desorption and seepage laws of organic matters and inorganic matters.
Figure GDA0002735834640000115
The following dimensionless variables were introduced:
Figure GDA0002735834640000116
in the formula, roDIs an organic matter dimensionless radial distance; r iscDInorganic dimensionless radial distance; r isfDThere is no dimensional radial distance for the fracture. t is tDDimensionless time. PsioDThe pressure is an organic matter dimensionless pressure; psicDInorganic substance dimensionless pressure simulation is adopted; psifDNo dimensional pressure was simulated for the fracture.
Then the dimensionless form of the formula (1-35) is obtained:
Figure GDA0002735834640000121
wherein:
Figure GDA0002735834640000122
in the formula, λocThe non-dimensional cross flow coefficient of organic matters and inorganic matters is adopted; lambda [ alpha ]cfInorganic matter and crack non-dimensional channeling coefficient; omegaoThe storage volume ratio of organic matters is; omegacThe inorganic matter storage volume ratio; omegafThe fracture storage volume ratio.
Next, the seepage equation of the organic matter system is solved, and a consistent solution is adopted to make roDψoDSubstitution may give:
Figure GDA0002735834640000123
the Laplace of equation (1-39) is transformed:
Figure GDA0002735834640000124
the general solution of the above formula is:
Figure GDA0002735834640000125
from the inner boundary conditions:
Figure GDA0002735834640000126
then, a general solution can be obtained where B is 0, and the general solution is:
Figure GDA0002735834640000131
then, according to the expression of the outer boundary:
Figure GDA0002735834640000132
the coefficient A can be obtained simultaneously:
Figure GDA0002735834640000133
the dimensionless pressure in the organic matter system is obtained as follows:
Figure GDA0002735834640000134
definition etaoThe following were used:
Figure GDA0002735834640000135
then the formula (1-46) can be expressed as:
Figure GDA0002735834640000136
derivation is performed on equations (1-48):
Figure GDA0002735834640000137
then:
Figure GDA0002735834640000138
substituting the formula (1-50) into an inorganic system dimensionless seepage equation to simplify the method:
Figure GDA0002735834640000139
then let rcDψcDVariation on the above equation yields:
Figure GDA00027358346400001310
laplace transformation of equation (1-52) can be obtained:
Figure GDA0002735834640000141
the general solution of the above formula is:
Figure GDA0002735834640000142
order:
Figure GDA0002735834640000143
the dimensionless pressure in inorganic material can be calculated from the boundary conditions as follows:
Figure GDA0002735834640000144
the same derivation can be obtained:
Figure GDA0002735834640000145
substituting equations (1-57) into the dimensionless equation for the fracture system yields:
Figure GDA0002735834640000146
the Laplace transform can be obtained:
Figure GDA0002735834640000147
order:
Figure GDA0002735834640000148
then the formula can be written as follows:
Figure GDA0002735834640000149
the formulas (1-60) and (1-61) are the finally obtained comprehensive differential equations of the shale gas reservoir three-hole three-permeability unsteady state model separating organic matters from inorganic matters.
In step S3, the organic matter is also extracted separately and regarded as a percolation medium, the interaction between the organic matter system and the inorganic matter system is considered, the interaction between the inorganic matter system and the crack system follows a quasi-steady-state law, the adsorption and desorption capacities of the organic matter and the clay mineral are considered respectively, and the assumed conditions of the other physical models are the same as those of the three-hole three-permeation non-steady-state model.
From the mass conservation law, a three-hole three-permeation quasi-steady state mathematical model can be obtained as follows:
Figure GDA0002735834640000151
for the dimensionless treatment of equations (1-62), the following dimensionless variables were introduced:
Figure GDA0002735834640000152
the three-pore three-permeability quasi-steady state dimensionless mathematical model can be obtained as follows:
Figure GDA0002735834640000153
wherein:
Figure GDA0002735834640000154
the formula (1-65) relates to the parameters defined as follows:
Figure GDA0002735834640000161
the three-hole three-penetration quasi-steady state dimensionless mathematical model is subjected to Laplace transformation to obtain:
Figure GDA0002735834640000162
the formula (1-67) is simplified and can be obtained:
Figure GDA0002735834640000163
(s) the expression is:
Figure GDA0002735834640000164
the formulas (1-68) and (1-69) are the finally obtained comprehensive seepage differential equation of the shale gas reservoir three-hole three-seepage steady-state model separating organic matters from inorganic matters.
In step S4, first, basic assumed conditions of shale gas reservoir multistage fracturing horizontal well seepage are established, including:
(1) the shale gas reservoir multistage fracturing horizontal well seepage problem is analyzed based on the three-hole three-seepage model provided by the method, and the physical model is shown in figure 4;
(2) the schematic diagram of the multi-stage fracturing horizontal well is shown in fig. 5, the top and bottom of the gas reservoir are closed, the outer boundary is infinite, m cracks are pressed in the stratum, the height of the cracks is h, the interval between the cracks is delta L, the half length of the cracks is Lf, and the width of the cracks is ignored;
(3) considering that the flow in the hydraulic fracture and the horizontal shaft is infinite flow guide, neglecting the pressure drop consumed by gas flow;
(4) the shale gas reservoir is in a dynamic balance state before exploitation;
(5) gas well production at fixed production rates.
Solving by adopting a point source function method, comprising the following steps:
the point source exists at the origin of the three-dimensional infinite shale gas reservoir, the gas quantity of the instantaneous discharge volume dv of the point source is equal to the gas flow on a tiny sphere taking the point source as the center, and the following mathematical form can be written:
Figure GDA0002735834640000165
in the formula, TscIs the temperature under standard conditions, K; pscPressure under standard conditions, pa.
δ () is a dirac trigonometric function, satisfying the following condition:
Figure GDA0002735834640000171
Figure GDA0002735834640000172
further dimensionless to formulas (1-70) is:
Figure GDA0002735834640000173
in the formula, L is the length of a horizontal segment of the multi-stage fractured horizontal well, and m is the length of the horizontal segment; h is the formation thickness, m.
The lambda in the above formula has different definitions for different models, and the expression of the three-hole three-permeation model lambda is as follows:
Figure GDA0002735834640000174
laplace transformation is carried out on the formula (1-73) to obtain:
Figure GDA0002735834640000175
definition of
Figure GDA0002735834640000176
For single-site source intensity, the equations (1-75) can be expressed as:
Figure GDA0002735834640000177
the outer boundary conditions of the three-dimensional infinite space are as follows:
Figure GDA0002735834640000178
the comprehensive unified differential equation form of the shale gas reservoir single-phase seepage model deduced by the method is as follows:
Figure GDA0002735834640000179
the simultaneous equations (1-76), (1-77), and (1-78) can determine the pressure response caused by the unit intensity source as:
Figure GDA00027358346400001710
when the point source is not at the origin, the resulting pressure corresponds to:
Figure GDA00027358346400001711
wherein,
Figure GDA00027358346400001712
the pressure response when the point source intensity is not unity is:
Figure GDA00027358346400001713
order to
Figure GDA00027358346400001714
The instantaneous point source solution can be written as:
Figure GDA0002735834640000181
and performing Laplace inverse transformation on the expression (1-82), and converting the solution in Laplace space into the solution in real space:
Figure GDA0002735834640000182
assuming a continuous point source, the corresponding ground production is
Figure GDA0002735834640000183
By integrating the above equation over time, a continuous point source solution can be obtained:
Figure GDA0002735834640000184
laplace transform is performed on the equation (1-84):
Figure GDA0002735834640000185
the above formula is a continuous point source in a three-dimensional infinite shale gas reservoir
Figure GDA0002735834640000186
Solution in Laplace.
Figure GDA0002735834640000187
Is composed of
Figure GDA0002735834640000188
The result after the Laplace transform is obtained if
Figure GDA0002735834640000189
For a constant value, then the equation (1-85) can be simplified as:
Figure GDA00027358346400001810
by the mirror image reflection principle, a continuous point source solution of the infinite shale gas reservoir closed at the top and bottom can be obtained:
Figure GDA00027358346400001811
the formula adopts a Poisson summation formula, and a continuous point source solution of the shale gas reservoir with the top and the bottom closed infinite can be written as follows:
Figure GDA00027358346400001812
in the formula, K0() A modified bessel function of order 0.
The method adopts a semi-analytical method to obtain the pressure response of the shale gas reservoir multistage fractured horizontal well by dispersing hydraulic fractures, and comprises the following specific steps:
as shown in fig. 6, when each fracture is discretized into 2n small units, the whole multi-stage fractured horizontal well system is discretized into (m × 2n) units.
According to the fracture discrete distribution diagram, the coordinates of the middle points of the discrete sections (i, j) in the x direction are as follows:
Figure GDA00027358346400001813
the coordinates of the end points of the discrete segments (i, j) in the x direction are:
Figure GDA0002735834640000191
when the number n of discrete units is sufficiently large, the discrete unit flow can be approximately treated as being equal everywhere. Therefore, the continuous point source solution formula (1-88) of the shale gas reservoir with the infinite top and bottom closed is integrated in the z-axis direction (0, h) and then is aligned to the (x-axis direction)i,j，xi,j+1) Integration, the pressure response for discrete segment (i, j) can be found as:
Figure GDA0002735834640000192
because:
Figure GDA0002735834640000193
introducing dimensionless point source intensity, the formula (1-91) is dimensionless to obtain:
Figure GDA0002735834640000194
the pressure response of a discrete segment (i, j) is the sum of the pressures at which all (m × 2n) discrete units collectively produce, in mathematical form:
Figure GDA0002735834640000195
then the midpoint of the discrete segment
Figure GDA0002735834640000196
The pressure response at (a) is:
Figure GDA0002735834640000197
when the flow in both the hydraulic fracture and the horizontal wellbore is infinitely diverted, the pressures in the discrete units of the horizontal wellbore and the fracture are equal, and thus the pressure response of the horizontal wellbore can be expressed as:
Figure GDA0002735834640000198
from the above expressions, (m × 2n) equations can be written for discrete segments (K ═ 1,2, K, m; v ═ 1,2, K,2n), with the number of equations unknowns being (m × 2n +1), i.e. the number of equations is (m × 2n +1)
Figure GDA00027358346400001911
And
Figure GDA0002735834640000199
an equation is also needed to solve. According to the assumed conditions of the model, the gas well produces with fixed production quantity, and then the following results can be obtained:
Figure GDA00027358346400001910
equations (1-96) and (1-97) just form the (m × 2n +1) equation, which can be written as a matrix as follows:
Figure GDA0002735834640000201
therefore, the flow rate and the bottom hole pressure value of each discrete unit can be obtained according to the matrix equation.
When there is a skin effect and a wellbore reservoir effect, the downhole pressure expression can be modified by using the Duhamel principle to be:
Figure GDA0002735834640000202
in the formula, CDDimensionless well storage coefficients.
In step S5, the decreasing analysis of the dynamic characteristic curve of the three-hole triple-permeability pressure of the shale gas reservoir and the yield specifically includes:
(1) pressure dynamic characteristic curve
According to the deduced analytical expression of the dimensionless bottom flow pressure in the Laplace space, the method utilizes the Matlab programming to calculate the value of the dimensionless bottom flow pressure in the real space through Stehfest numerical inversion, and draws a dimensionless pressure double logarithmic curve.
The log-log typical well testing curve of the three-hole tri-permeability steady-state simulation model is shown in fig. 7, and according to the characteristics of the typical curve, the flow of the infinite shale gas reservoir multistage fracturing horizontal well can be divided into the following stages:
the first stage reflects the wellbore reservoir effect, the pressure and pressure derivative are coincident, and the slope value is a straight line of 1; the second stage is a well storage effect rear transition section; the third stage is a linear flowing section of the fracturing fracture, and in the stage, the shale gas reservoir fracturing fractures have no interference; the fourth stage is a channeling stage of inorganic substances to cracks, so that a pressure derivative curve is rapidly reduced to form an obvious 'concave seed', and the shape of the 'concave seed' is influenced by a Langmuir isothermal adsorption constant, a storage capacity ratio omega and a channeling coefficient lambda; the fifth stage is a radial flow stage, each single fracture forms pseudo-radial flow to cause a pressure derivative curve to be represented as a horizontal line, and whether the characteristics of the stage are influenced by the ratio of the interval of the fractures to the length of the fractures is judged; the sixth stage is a linear flowing section of the whole multi-stage fractured horizontal well, and the mutual interference of adjacent cracks is reflected; the seventh stage is a radial flow stage of the whole multi-stage fractured horizontal well, the interference phenomenon among cracks disappears, and a derivative curve is a horizontal line; the eighth stage is a channeling stage from organic matters to inorganic matters, and a pressure derivative curve is reduced along with the continuous reduction of pressure to form a second concave son; the ninth stage is the total system radial flow stage, and the pressure derivative curve is the "0.5" line.
(2) Yield decreasing curve
The bottom hole flow pressure expression when the production well is produced at the fixed production rate is obtained, and the dimensionless production can be expressed as:
Figure GDA0002735834640000203
in the formula,
Figure GDA0002735834640000211
the non-dimensional yield.
An analytical expression of the dimensionless yield in Laplace can be obtained according to the formula (1-100), and the value of the dimensionless yield in real space is calculated by using Matlab programming through a Stehfest numerical inversion method, so that a dimensionless yield log curve is drawn.
The dimensionless yield decreasing curve of the three-hole three-permeation quasi-steady-state model is shown in fig. 8, the dimensionless yield derivative curve of the conventional two-hole two-permeation model is only 'concave 2', the dimensionless yield derivative curve of the three-hole three-permeation model is one more 'concave 1', because the two-hole two-permeation model only considers the channeling effect between the matrix system and the crack system, and the three-hole three-permeation model not only considers the channeling between the inorganic matter system and the crack system, but also considers the interaction between organic matters and the inorganic matters, so that the derivative curve is represented as two channeling sections.
In step S6, the well testing curve in step S5 is fitted to the in-situ measured bottom hole pressure and derivative curve by an optimization algorithm to interpret formation parameters.
And fitting the in-situ measured bottom hole pressure and pressure derivative curve by adopting an optimization algorithm, and analyzing the formation parameters. Obtaining an optimal solution meeting requirements through a genetic algorithm, comparing a field actual measurement bottom hole pressure curve and a derivative curve with a curve calculated by an established well testing interpretation model, and taking the error of the curve as a target function:
Figure GDA0002735834640000212
in the formula: p is a radical ofcCalculating the obtained bottom hole pressure of the model in MPa; p is a radical ofi *The bottom hole pressure is measured in situ in MPa; n is the number of experimental data.
In step S7, the influence of the adsorption constants of the organic matter and clay minerals is mainly analyzed. Based on the triple-aperture tri-permeability quasi-steady-state model, the effects of different adsorption constants of organic matters and clay minerals on the dimensionless pressure and pressure derivative curve are shown in fig. 9, fig. 10, fig. 11 and fig. 12. The change of the adsorption constants of the organic matters and the clay minerals has certain influence on the yield of the shale gas well, when the adsorption and desorption constants of the clay minerals are increased, the deeper and wider the first concave shape on the dimensionless pseudo-pressure derivative curve is, the adsorption and desorption constants of the organic matters are increased, and the deeper and wider the second concave shape on the dimensionless pseudo-pressure derivative curve is, the larger the adsorption gas amount in the organic matters and the clay minerals is, the stronger the desorption and diffusion capacity is, and meanwhile, the adsorption and desorption effects of the organic matters and the clay minerals are further proved to be not negligible.
In addition, the invention also analyzes the influence of the channeling mode and the channeling coefficient. The effect of different modes of cross flow for the three-hole, three-permeability model on the dimensionless pressure vs. pressure derivative curve is shown in FIG. 13. It can be observed from the figure that different channeling modes mainly affect the shape of the 'pits', the 'pits' of the quasi-steady-state channeling pressure derivative curve are deeper and are in obvious wave valley shapes, while the 'pits' of the non-steady-state channeling are more gradual in shape and occur earlier in time.
Based on the three-hole triple-permeability pseudo-steady-state model, the effect of the cross-flow coefficient on the dimensionless pressure vs. pressure derivative curve is shown in fig. 14 and 15. It can be observed from the figure that the cross-flow coefficient λcfDetermining the time of occurrence of the first "dip" on the derivative curve, λcfThe smaller the value, the later the inorganic system has drifted into the natural fracture system, lambdaocDetermining the time of occurrence of the second "dip" on the derivative curve, λocThe smaller the value, the later the organic system will cross-flow to the inorganic system.
The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims (7)

1. The shale gas reservoir single-phase gas three-hole three-permeation model construction method based on the seepage difference is characterized by comprising the following steps of:
s1, obtaining basic assumed conditions of a shale gas reservoir single-phase gas flow three-hole three-permeation model, and constructing a physical model of three-hole three-permeation pore characteristics, wherein organic matters and inorganic matters coexist in a spherical aggregate form and form a three-hole three-permeation pore characteristic together with cracks on the basis of a De Swaan spherical model;
s2, constructing a shale gas reservoir single-phase gas flow three-hole three-permeation unsteady state model according to the physical model and the assumed conditions in the step S1, and solving the model to finally obtain a comprehensive seepage differential equation of the shale gas reservoir three-hole three-permeation unsteady state model with organic matters and inorganic matters separated;
s3, constructing a shale gas reservoir single-phase gas flow three-hole three-penetration steady-state simulation model according to the physical model and the assumed conditions in the step S1, solving the model, and finally obtaining a comprehensive seepage differential equation of the shale gas reservoir three-hole three-penetration steady-state simulation model with separated organic matters and inorganic matters;
s4, obtaining basic assumed conditions of shale gas reservoir multistage fracturing horizontal well seepage, solving a shale gas reservoir three-hole three-seepage multistage fracturing horizontal well single-phase gas seepage model, and obtaining a bottom hole pressure expression by discretely solving hydraulic fractures by combining a point source function method, a Laplace transformation method and a semi-analytical method;
s5, according to the bottom hole pressure expression, performing numerical inversion by Stehfest, calculating the value of dimensionless bottom hole flow pressure in a real space by utilizing Matlab programming, and drawing a three-hole three-permeability model pressure dynamic characteristic curve and a yield decreasing curve;
s6, fitting the on-site measured bottom hole pressure and pressure derivative curve by adopting an optimization algorithm, analyzing formation parameters, and compiling an interpretation program to interpret and analyze the on-site measured well test data;
s7, analyzing the influence of the organic matter and clay mineral adsorption constant on the dimensionless pressure and pressure derivative curve based on the three-hole three-penetration quasi-steady-state model, and simultaneously analyzing the influence of different channeling modes and channeling coefficients on the dimensionless pressure and pressure derivative curve.
2. The method for constructing the shale gas reservoir single-phase gas three-hole three-permeability model based on the seepage difference as claimed in claim 1, wherein the comprehensive seepage differential equation of the shale gas reservoir three-hole three-permeability unsteady state model with the separation of organic matters and inorganic matters in the step S2 is shown as follows:
Figure FDA0002977258410000011
in the formula: r isfDThe method is dimensionless radial distance of a crack system in a spherical coordinate system; f(s) is a feature function;
Figure FDA0002977258410000012
is the dimensionless pressure of the fracture system in Laplace.
3. The shale gas reservoir single-phase gas three-hole three-permeability model construction method based on seepage difference as claimed in claim 1, wherein the solving process of the shale gas reservoir single-phase gas flow three-hole three-permeability unsteady state model in the step S2 specifically comprises:
s201, independently regarding the organic matter as a seepage medium, and respectively establishing seepage equations for an organic matter system, an inorganic matter system and a crack system;
s202, introducing the dimensionless variables into the seepage equations of an organic matter system, an inorganic matter system and a crack system respectively, and performing dimensionless treatment to obtain a dimensionless seepage equation;
s203, solving a dimensionless seepage equation of the organic matter system, and after obtaining a dimensionless pressure expression of the organic matter system, carrying out derivation calculation on the dimensionless pressure expression;
s204, substituting the derived dimensionless pressure expression of the organic matter system into the dimensionless seepage equation of the inorganic matter system and solving the equation to obtain the dimensionless pressure expression of the inorganic matter system and then carrying out derivation;
and S205, substituting the derived dimensionless pressure expression of the inorganic matter system into the dimensionless seepage equation of the crack system and solving the equation to finally obtain a comprehensive seepage differential equation of the three-hole three-seepage unsteady state model of the shale gas reservoir with the separation of the organic matters and the inorganic matters.
4. The shale gas reservoir single-phase gas three-hole three-permeability model construction method based on seepage difference as claimed in claim 1, wherein the solving process of the shale gas reservoir single-phase gas flow three-hole three-permeability steady-state simulation model in the step S3 comprises:
s301, obtaining a three-hole three-permeation quasi-steady-state mathematical model based on a physical model and an assumed condition which are the same as those of the three-hole three-permeation non-steady-state model by a mass conservation law;
s302, inputting the dimensionless variable into the three-hole three-penetration quasi-steady-state mathematical model, and performing dimensionless processing to obtain the three-hole three-penetration quasi-steady-state dimensionless mathematical model;
s303, performing Laplace transformation and simplified arrangement on the three-hole three-penetration quasi-steady-state dimensionless mathematical model to finally obtain a comprehensive seepage differential equation of the shale gas reservoir three-hole three-penetration quasi-steady-state model for separating organic matters from inorganic matters.
5. The shale gas reservoir single-phase gas three-hole three-permeability model construction method based on seepage difference as claimed in claim 1, wherein the bottom hole pressure expression in the step S4 is as follows:
Figure FDA0002977258410000021
in the formula:
Figure FDA0002977258410000022
dimensionless bottom hole flow pressure in Laplace; s is a laplace variable; s is the epidermis coefficient; cDDimensionless wellbore reservoir coefficients;
Figure FDA0002977258410000023
dimensionless bottom hole pseudo pressure in the Laplace.
6. The shale gas reservoir single-hole three-permeability model construction method based on the seepage difference as claimed in claim 1, wherein the solving process of the shale gas reservoir three-hole three-permeability multi-stage fracturing horizontal well single-phase gas seepage model in the step S4 comprises:
s401, firstly, solving continuous point sources in the three-dimensional infinite shale gas reservoir by adopting a point source function method and Laplace transformation, and calculating a continuous point source solution of the infinite shale gas reservoir with the closed top and the closed bottom;
s402, dispersing hydraulic fractures by adopting a semi-analytical method to obtain pressure response of the shale gas reservoir multistage fracturing horizontal well, carrying out discretization treatment on each fracture to form 2n small units, dispersing the whole multistage fracturing horizontal well system into m multiplied by 2n units, and obtaining the pressure response of the horizontal well;
s403, determining production according to the model assumption conditions and the gas well, combining the pressure response of the horizontal well to form a matrix equation, and calculating the flow and the bottom hole pressure value of each discrete unit according to the matrix equation;
s404, correcting the bottom hole pressure expression by utilizing the Duhamel principle when the skin effect and the wellbore reservoir effect exist.
7. The shale gas reservoir single-phase gas three-hole three-permeability model construction method based on seepage difference as claimed in claim 1, wherein the step S6 further comprises: obtaining an optimal solution meeting the requirement through a genetic algorithm, comparing a field measured bottom hole pressure and a derivative curve with a curve calculated by an established well testing interpretation model, taking the error of the curve as a target function, and expressing the target function as shown in the following formula:
Figure FDA0002977258410000031
in the formula: p is a radical ofcCalculating the obtained bottom hole pressure of the model in MPa; p is a radical ofiMeasured bottom hole pressure in situ, MPa; n is the number of experimental data.
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