Method and system for determining stress sensitive permeability of oil reservoir fracture system

Abstract

The invention provides a method and a system for determining stress sensitive permeability of an oil reservoir fracture system. The determination method comprises the following steps: converting crustal stress change into shear stress and normal stress change of a fracture surface; simulating and solving crack opening change based on a crack deformation mechanism; solving a permeability tensor of a single fracture based on a coordinate transformation principle; and solving the total permeability tensor of the multiple groups of fractures based on parallel connection and superposition principles. The directionality of fractures is considered, the fractures with different azimuth angles, dip angles and opening degrees are comprehensively considered, full-tensor permeability superposition representation is adopted, the permeability tensor changes along with stress changes, and actual formation flow is met.

Description

Technical Field

[0001] The invention relates to the field of fractured oil reservoirs, and in particular to a method and system for determining stress-sensitive permeability of an oil reservoir fracture system. Background Art

[0002] As the internal fluid of the reservoir continues to decrease due to factors such as oil and gas migration or production, the effective stress on the rock skeleton gradually increases, which in turn causes the internal pores and microcracks to compress. This ultimately leads to permeability loss and reduced production capacity. The development of fractures in fractured reservoirs will increase the stress sensitivity of the reservoir, seriously restricting the seepage and effective development of the reservoir. Therefore, it is of great significance to study the stress-sensitive seepage model of fractured reservoirs [1,2].

[0003] Since the 1950s and 1960s, when Fatt, Davis and other scholars[3] discovered that the pressure changes in overburden strata of different rocks have different effects on permeability, research on stress sensitivity has continued to this day. The stress sensitivity of fractures is more complex. Its own complexity is one of the reasons, and another important reason is that the fracture strain characteristics simulated in indoor tests are difficult to accurately reflect the characteristics of fractures in actual reservoirs.

[0004] Indoor experiments mainly use the method of variable confining pressure and constant pore pressure to simulate the change of overlying stratum pressure. Jiang Haijun [4] conducted an experimental study on the stress sensitivity of fractured reservoirs and found that the permeability of fractured cores changes exponentially with the increase of effective stress. According to a large number of experimental fittings, the relationship between rock permeability and effective stress mainly has three forms: power relationship, exponential relationship and quadratic polynomial relationship.

[0005] The stress-sensitive permeability model can be divided into two categories: empirical model and theoretical model. The empirical model is mainly obtained through core experiments, changing the internal pressure or external pressure for testing and summarizing, but the core experiment cannot simulate the anisotropy of reservoir stress and does not consider the directionality of fractures. For the theoretical model, the characteristics of the fracture are analyzed and derived, but the anisotropy of stress is not considered. It cannot reflect the phenomenon that the stress sensitivity of fractures in different directions is different in the actual production process. Summary of the invention

[0006] In view of the above problems, the present invention is proposed to provide a method and system for determining stress-sensitive permeability of a reservoir fracture system that overcomes the above problems or at least partially solves the above problems.

[0007] According to one aspect of the present invention, a method for determining stress-sensitive permeability of a reservoir fracture system is provided, the method comprising:

[0008] Convert the ground stress changes into shear stress and normal stress changes on the fracture surface;

[0009] The crack opening change is solved based on the crack deformation mechanism simulation;

[0010] Solve the permeability tensor of a single fracture based on the principle of coordinate transformation;

[0011] The overall permeability tensor of multiple groups of fractures is solved based on the parallel and superposition principles.

[0012] Optionally, the converting of the ground stress change into the shear stress and normal stress change of the fracture surface specifically includes: converting the ground stress change into the shear stress and normal stress change of the fracture surface by using a coordinate transformation method.

[0013] Optionally, the method of using coordinate transformation to convert the ground stress change into the shear stress and normal stress change of the fracture surface specifically includes:

[0014] Convert the effective stress change into the shear stress and normal stress change on the fracture surface;

[0015] Take a unit cell containing a fracture in the reservoir, assume that the coordinate system is consistent with the direction of the stress principal axis, and the effective stress tensor is a diagonal tensor, expressed as:

[0016]

[0017] Among them, σ eff represents effective stress, Pa;

[0018] Taking the example of a triangular cross section formed by the intersection of the crack surface and the unit body, the normal stress and shear stress on the crack surface are solved;

[0019] Assume that for any fracture surface in the reservoir, the intersection line of the fracture surface and the XY plane forms an angle β with the positive direction of the Y axis, and the fracture surface forms an angle α with the XY plane. If the positive direction of the Y axis is consistent with the due north direction and the positive direction of the X axis is consistent with the due east direction, β is also called the azimuth, and α is also called the inclination;

[0020] The normal stress on the crack surface is expressed as follows:

[0021] Δσ n =Δσ eff-x sin 2 αcos 2 β+Δσ eff-y sin 2 αsin 2 β+Δσ eff-z cos 2 α (14)

[0022] Among them, Δσ n is the change in normal stress on the crack surface, Pa, Δσ eff-x is the increment of effective stress in the x direction;

[0023] The crack surface shear stress is expressed as follows:

[0024]

[0025] Among them, Δσ s is the change in shear stress on the crack surface, Pa.

[0026] Optionally, the simulation based on the crack deformation mechanism to solve the crack opening change specifically includes:

[0027] There are two mechanisms in the crack deformation process: normal tension and compression and shear expansion. The critical point of shear expansion of the crack is: The crack deformation is divided into two stages. The first stage does not produce shear expansion, and the second stage has shear expansion. The crack opening change models are established for the two different stages.

[0028] Optionally, the fracture aperture variation models established in the two different stages specifically include:

[0029] First stage:

[0030]

[0031] Second stage:

[0032]

[0033] Among them, d f is the crack opening, m; d f0 is the crack opening at the initial moment, m; c f is the crack compression coefficient, Pa-1; R s is the crack shear stiffness, Pa / m; ζ represents the anti-expansion coefficient, m / Pa; σ s is the fracture surface shear stress, Pa; σ n is the normal stress on the crack surface, Pa; ψ represents the shear expansion angle, usually expressed as to calculate the shear dilation angle, JRC represents the roughness coefficient, and JCS represents the compressive strength.

[0034] Optionally, solving the permeability tensor of a single fracture based on the coordinate transformation principle specifically includes:

[0035] In the actual simulation calculation, what is needed is the seepage capacity in all directions along the grid coordinate system. The seepage capacity of the crack in all directions along the grid coordinate system is calculated according to the crack opening, and the permeability tensor of a single crack in the grid coordinate system;

[0036] The relationship between the aperture of a single fracture and the intrinsic permeability of the fracture is:

[0037]

[0038] Among them, k f represents the intrinsic permeability of the fracture, d f Indicates the crack opening;

[0039] Calculate the intrinsic permeability of a single fracture in two stages.

[0040] Optionally, the calculation of the intrinsic permeability of a single fracture in two stages specifically includes:

[0041] First stage:

[0042]

[0043] Second stage:

[0044]

[0045] The intrinsic permeability of a fracture is the permeability along the fracture direction. The actual reservoir simulation calculation is based on the grid direction. The permeability of a single fracture in the grid coordinate is solved by the coordinate transformation principle:

[0046]

[0047] Optionally, solving the overall permeability tensors of multiple groups of fractures based on the parallel connection and superposition principle specifically includes:

[0048] In actual oil reservoirs, there are multiple groups of parallel fractures distributed in certain directions. The overall permeability tensor of multiple groups of fractures is solved through the parallel and superposition principles for use in reservoir simulation calculations.

[0049] Optionally, multiple groups of parallel fractures may be distributed in certain directions in the actual reservoir, and solving the overall permeability tensor of multiple groups of fractures by parallel connection and superposition principle specifically includes:

[0050] Assume that there are N groups of fractures in a unit in the reservoir, and the azimuth angle of the i-th group of fractures is β i , whose inclination angle is α i , l i is the linear density of the i-th group of cracks, lines / m; the total length of the study area is b, m; then the number of cracks is bl i , strip; crack opening is d fi , m; permeability k i , m 2 ; The same group of cracks are equivalent to a parallel relationship;

[0051] Based on the parallel principle, the equivalent permeability of a single group of parallel fractures is:

[0052]

[0053] is the equivalent permeability of the jth fracture in the i-th group, m 2 , expressed as:

[0054]

[0055] The permeability tensor of the i-th group of fractures in the grid coordinate system is:

[0056]

[0057] For N groups of fractures, the permeability tensor of multiple groups of fractures can be obtained by superposition principle:

[0058]

[0059] The present invention also provides a system for determining stress-sensitive permeability of a reservoir fracture system, which uses the above-mentioned method for determining stress-sensitive permeability of a reservoir fracture system. The system comprises:

[0060] Convert the ground stress changes into shear stress and normal stress changes on the fracture surface;

[0061] The crack opening change is solved based on the crack deformation mechanism simulation;

[0062] Solve the permeability tensor of a single fracture based on the principle of coordinate transformation;

[0063] The overall permeability tensor of multiple groups of fractures is solved based on the parallel and superposition principles.

[0064] The present invention provides a method and system for determining the stress-sensitive permeability of a reservoir fracture system, the determination method comprising: converting the ground stress change into the shear stress and normal stress change of the fracture surface; solving the fracture opening change based on the fracture deformation mechanism simulation; solving the permeability tensor of a single fracture based on the coordinate transformation principle; solving the overall permeability tensor of multiple groups of fractures based on the parallel and superposition principle. Considering the directionality of the fracture, the fractures of different azimuths, inclinations, and openings are comprehensively considered, and the full tensor permeability superposition is used to represent it, and the permeability tensor changes with the stress change, which is consistent with the actual formation flow.

[0065] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0067] Figure 1 A flow chart of a method for determining stress-sensitive permeability of a reservoir fracture system provided by an embodiment of the present invention;

[0068] Figure 2 A schematic diagram of a crack-containing unit provided in an embodiment of the present invention;

[0069] Figure 3 A schematic diagram of parallel calculation provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0070] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0071] The terms "comprises" and "having" and any variations thereof in the description embodiments, claims and drawings of the present invention are intended to cover non-exclusive inclusions, for example, including a series of steps or units.

[0072] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0073] This method takes into account the directionality of stress changes and fracture distribution during reservoir development, aiming to more accurately reflect the dynamic deformation process of fractures and their dynamic impact on the seepage field. Figure 1 shown.

[0074] (1) The effective stress change is converted into the shear stress and normal stress change of the fracture surface through coordinate transformation

[0075] Reservoir development will cause mechanical changes in the formation and changes in the effective stress of the formation. The calculation of this change usually relies on geomechanical simulation. The calculated effective stress tensor is based on the grid direction of the simulation calculation, while the fracture deformation is directly controlled by the shear stress and normal stress of the fracture, and cannot be directly solved by the stress based on the grid direction. Therefore, it is necessary to first convert the effective stress change into the shear stress and normal stress change of the fracture surface.

[0076] Take a unit cell containing a fracture in the reservoir and assume that the coordinate system is consistent with the direction of the stress principal axis. At this time, the effective stress tensor is a diagonal tensor, expressed as:

[0077]

[0078] Among them, σ eff represents effective stress, Pa

[0079] Consider the example of a triangular cross section formed by the intersection of the crack surface and the unit body. Figure 2 As shown, the normal stress and shear stress on the crack surface are solved.

[0080] Assume that for any fracture surface in the reservoir, the intersection line of the fracture surface and the XY plane makes an angle β with the positive direction of the Y axis, and the fracture surface makes an angle α with the XY plane (if the positive direction of the Y axis is consistent with the due north direction, and the positive direction of the X axis is consistent with the due east direction, β is also called the azimuth, and α is also called the inclination).

[0081] Then the normal stress on the crack surface can be expressed as follows:

[0082] Δσ n =Δσ eff-x sin 2 αcos 2 β+Δσ eff-y sin 2 αsin 2 β+Δσ eff-z cos 2 α (14)

[0083] Among them, Δσ n is the change in normal stress on the crack surface, Pa, Δσ eff-x is the increment of effective stress in the x direction.

[0084] The crack surface shear stress can be expressed as follows:

[0085]

[0086] Among them, Δσ s is the change in shear stress on the crack surface, Pa.

[0087] (2) Solving the change of single crack opening based on the crack deformation mechanism model

[0088] There are two mechanisms in the crack deformation process: normal tension and compression and shear expansion. The critical point of shear expansion of the crack is: Therefore, the crack deformation is divided into two stages. The first stage does not produce shear expansion, and the second stage has shear expansion. The crack opening change model is established for these two different stages.

[0089] First stage:

[0090]

[0091] Second stage:

[0092]

[0093] Among them, d f is the crack opening, m; d f0 is the crack opening at the initial moment, m; c f is the crack compression coefficient, Pa-1; R s is the crack shear stiffness, Pa / m; ζ represents the anti-expansion coefficient, m / Pa; σ s is the fracture surface shear stress, Pa; σ n is the normal stress on the crack surface, Pa; ψ represents the shear expansion angle, usually expressed as to calculate the shear dilation angle, JRC represents the roughness coefficient, and JCS represents the compressive strength.

[0094] (3) Solving the permeability tensor of a single fracture based on the principle of coordinate transformation

[0095] The fracture aperture determines the seepage capacity of a single fracture, but the fracture aperture reflects the seepage capacity of the fracture itself along the fracture direction. In actual simulation calculations, the seepage capacity along all directions of the grid coordinate system is needed. Therefore, it is necessary to calculate the seepage capacity of the fracture along all directions of the grid coordinate system based on the fracture aperture, that is, the permeability tensor of a single fracture in the grid coordinate system.

[0096] The relationship between the aperture of a single fracture and the intrinsic permeability of the fracture is:

[0097]

[0098] Among them, k f represents the intrinsic permeability of the fracture, d f Indicates the crack opening.

[0099] Calculate the intrinsic permeability of a single fracture in two stages:

[0100] First stage:

[0101]

[0102] Second stage:

[0103]

[0104] The intrinsic permeability of a fracture is the permeability along the fracture direction, but the actual reservoir simulation calculation is based on the grid direction. Therefore, the permeability of a single fracture in the grid coordinates needs to be solved by the coordinate transformation principle:

[0105]

[0106] (4) Solve the overall permeability tensor of multiple groups of fractures based on the parallel and superposition principles

[0107] The above method only obtains the permeability tensor of a single fracture. In actual reservoirs, there are often multiple sets of parallel fractures distributed in certain directions. Therefore, it is necessary to solve the overall permeability tensor of multiple sets of fractures through the parallel and superposition principles for use in reservoir simulation calculations.

[0108] Assume that there are N groups of fractures in a unit in the reservoir, and the azimuth angle of the i-th group of fractures is β i , whose inclination angle is α i , l i is the linear density of the i-th group of cracks, lines / m; the total length of the study area is b, m; then the number of cracks is bl i , strip; crack opening is d fi , m; permeability k i , m 2 ; The same group of cracks are equivalent to a parallel relationship. Figure 3 shown.

[0109] Based on the parallel principle, the equivalent permeability of a single group of parallel fractures can be obtained as:

[0110]

[0111] is the equivalent permeability of the jth fracture in the i-th group, m 2 , expressed as:

[0112]

[0113] The permeability tensor of the i-th group of fractures in the grid coordinate system is:

[0114]

[0115] For N groups of fractures, the permeability tensor of multiple groups of fractures can be obtained by superposition principle:

[0116]

[0117] Example 2

[0118] Assume that a unit has two groups of cracks, one of which has β1 of 45°, α of 160°, and an opening d f1 =0.1mm. The second group of cracks has β2 of 30°, α2 of 45°, and opening d f2 =0.2mm (one crack in each group). Initial stress tensor Mpa, the fluid flows out, the pore pressure decreases by 10MPa, and the effective stress changes MPa. The density of crack lines in both groups is 0.001 / mm, the anti-expansion coefficient ζ is 0.06mm / MPa, and the shear stiffness R s 4MPa / mm, expansion angle 1°, compression coefficient 0.06MPa -1 .

[0119] (1) Calculate the normal stress and shear stress of each crack surface

[0120] σ 1n =σ eff-x sin 2 α1cos 2 β1+σ eff-y sin 2 α1sin 2 β1+σ eff-z cos 2 α1=24.125(MPa) (48)

[0121]

[0122]

[0123] The first set of cracks does not expand

[0124] σ 2n =σ eff-x sin 2 α2cos 2 β2+σ eff-y sin 2 α2sin 2 β2+σ eff-z cos 2 α2=25.875(MPa) (51)

[0125]

[0126]

[0127] The second set of cracks expands.

[0128] Calculate the changes in normal stress of the two groups of cracks respectively:

[0129] Δσ 1n =Δσ eff-x sin 2 α1cos 2 β1+Δσ eff-y sin 2 α1sin 2 β1+Δσ eff-zcos 2 α1=4.625(MPa) (54)

[0130] Δσ 2n =Δσ eff-x sin 2 α2cos 2 β2+Δσ eff-y sin 2 α2sin 2 β2+Δσ eff-z cos 2 α2=5.375(MPa) (55)

[0131] 2. Calculate the crack opening

[0132]

[0133]

[0134] 3. Calculate the permeability of the crack

[0135]

[0136]

[0137] 4. Superimposed fracture permeability

[0138] Convert the two sets of cracks to the same coordinate system and superimpose them.

[0139]

[0140]

[0141]

[0142] Beneficial effects: The present invention takes into account the directionality of stress and cracks. The model can reflect the phenomenon that the degree of deformation of cracks in different directions is different during the development process, and realizes the accurate characterization of the dynamic permeability of complex fracture networks.

[0143] The present invention first converts the anisotropic stress tensor change into the shear stress and shear stress change of a specific crack. On this basis, the deformation state of a single crack is solved through the crack deformation mechanism model. Finally, the permeability of multiple groups of cracks is obtained by tensor superposition.

[0144] The above specific implementation methods further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific implementation methods of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for determining stress-sensitive permeability of a reservoir fracture system, characterized in that: The determination method comprises: Convert the ground stress changes into shear stress and normal stress changes on the fracture surface; The crack opening change is solved based on the crack deformation mechanism simulation; Solve the permeability tensor of a single fracture based on the principle of coordinate transformation; The overall permeability tensor of multiple groups of fractures is solved based on the parallel and superposition principles.

2. A method for determining stress-sensitive permeability of a reservoir fracture system according to claim 1, characterized in that: The converting of the ground stress change into the shear stress and normal stress change of the fracture surface specifically includes: converting the ground stress change into the shear stress and normal stress change of the fracture surface by using a coordinate transformation method.

3. A method for determining stress-sensitive permeability of a reservoir fracture system according to claim 2, characterized in that: The method of using coordinate transformation to convert the ground stress change into the shear stress and normal stress change of the fracture surface specifically includes: Convert the effective stress change into the shear stress and normal stress change on the fracture surface; Take a unit cell containing a fracture in the reservoir, assume that the coordinate system is consistent with the direction of the stress principal axis, and the effective stress tensor is a diagonal tensor, expressed as: Among them, σ eff represents effective stress, Pa; Taking the example of a triangular cross section formed by the intersection of the crack surface and the unit body, the normal stress and shear stress on the crack surface are solved; Assume that for any fracture surface in the reservoir, the intersection line of the fracture surface and the XY plane forms an angle β with the positive direction of the Y axis, and the fracture surface forms an angle α with the XY plane. If the positive direction of the Y axis is consistent with the due north direction and the positive direction of the X axis is consistent with the due east direction, β is also called the azimuth, and α is also called the inclination; The normal stress on the crack surface is expressed as follows: Board n =Ds eff-x sin 2 acos 2 b+Ds eff-y sin 2 asin 2 b+Ds eff-z cos 2 a (14) Among them, Δσ n is the change in normal stress on the crack surface, Pa, Δσ eff-x is the increment of effective stress in the x direction; The crack surface shear stress is expressed as follows: Among them, Δσ s is the change in shear stress on the crack surface, Pa.

4. A method for determining stress-sensitive permeability of a reservoir fracture system according to claim 1, characterized in that: The simulation and solution of the crack opening change based on the crack deformation mechanism specifically includes: There are two mechanisms in the crack deformation process: normal tension and compression and shear expansion. The critical point of shear expansion of the crack is: The crack deformation is divided into two stages. The first stage does not produce shear expansion, and the second stage has shear expansion. The crack opening change models are established for the two different stages.

5. A method for determining stress-sensitive permeability of a reservoir fracture system according to claim 4, characterized in that: The crack opening variation models established in the two different stages specifically include: First stage: Second stage: Among them, d f is the crack opening, m; d f0 is the crack opening at the initial moment, m; c f is the crack compression coefficient, Pa-1; R s is the crack shear stiffness, Pa / m; ζ represents the anti-expansion coefficient, m / Pa; σ s is the fracture surface shear stress, Pa; σ n is the normal stress on the crack surface, Pa; ψ represents the shear expansion angle, usually expressed as to calculate the shear dilation angle, JRC represents the roughness coefficient, and JCS represents the compressive strength.

6. A method for determining stress-sensitive permeability of a reservoir fracture system according to claim 1, characterized in that: The method of solving the permeability tensor of a single fracture based on the coordinate transformation principle specifically includes: In the actual simulation calculation, what is needed is the seepage capacity in all directions along the grid coordinate system. The seepage capacity of the crack in all directions along the grid coordinate system is calculated according to the crack opening, and the permeability tensor of a single crack in the grid coordinate system; The relationship between the aperture of a single fracture and the intrinsic permeability of the fracture is: Among them, k f represents the intrinsic permeability of the fracture, d f Indicates the crack opening; Calculate the intrinsic permeability of a single fracture in two stages.

7. A method for determining stress-sensitive permeability of a reservoir fracture system according to claim 6, characterized in that: The calculation of the intrinsic permeability of a single fracture in two stages specifically includes: First stage: Second stage: The intrinsic permeability of a fracture is the permeability along the fracture direction. The actual reservoir simulation calculation is based on the grid direction. The permeability of a single fracture in the grid coordinate is solved by the coordinate transformation principle:

8. A method for determining stress-sensitive permeability of a reservoir fracture system according to claim 1, characterized in that: The method of solving the overall permeability tensor of multiple groups of fractures based on the parallel connection and superposition principle specifically includes: In actual oil reservoirs, there are multiple groups of parallel fractures distributed in certain directions. The overall permeability tensor of multiple groups of fractures is solved through the parallel and superposition principles for use in reservoir simulation calculations.

9. A method for determining stress-sensitive permeability of a reservoir fracture system according to claim 8, characterized in that: In the actual reservoir, multiple sets of parallel fractures are distributed in certain directions. Solving the overall permeability tensor of multiple sets of fractures by parallel connection and superposition principle specifically includes: Assume that there are N groups of fractures in a unit in the reservoir, and the azimuth angle of the i-th group of fractures is β i , whose inclination angle is α i , l i is the linear density of the i-th group of cracks, lines / m; the total length of the study area is b, m; then the number of cracks is bl i , strip; crack opening is d fi , m; permeability k i , m 2 ; The same group of cracks are equivalent to a parallel relationship; Based on the parallel principle, the equivalent permeability of a single group of parallel fractures is: is the equivalent permeability of the jth fracture in the i-th group, m 2 , expressed as: The permeability tensor of the i-th group of fractures in the grid coordinate system is: For N groups of fractures, the permeability tensor of multiple groups of fractures can be obtained by superposition principle:

10. A system for determining stress-sensitive permeability of a reservoir fracture system, using a method for determining stress-sensitive permeability of a reservoir fracture system as described in any one of claims 1 to 9, characterized in that: The determination system comprises: Convert the ground stress changes into shear stress and normal stress changes on the fracture surface; The crack opening change is solved based on the crack deformation mechanism simulation; Solve the permeability tensor of a single fracture based on the principle of coordinate transformation; The overall permeability tensor of multiple groups of fractures is solved based on the parallel and superposition principles.

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