A method for modeling orthogonal anisotropy parameters of a fractured shale

Abstract

This invention discloses a method for modeling orthogonal anisotropic parameters of fractured shale. The method includes: Step S1: collecting well logging datasets; Step S2: calculating the equivalent VTI background stiffness coefficient matrix for fracture-free shale; Step S3: calculating the fracture density based on fast and slow shear wave logging velocities; Step S4: calculating the equivalent orthogonal anisotropic elastic stiffness matrix for fractured shale; Step S5: calculating the anisotropic parameters of the fractured shale to be inverted based on the equivalent orthogonal anisotropic elastic stiffness matrix. This method can conveniently and accurately calculate the elastic stiffness coefficients of the VTI medium, reducing dependence on core measurement data. It has excellent applicability in situations where core analysis data is lacking and the mineral composition and elastic properties of the rock cannot be clearly defined, while also reducing the number of variables in traditional methods.

Description

Technical Field

[0001] This invention relates to the field of anisotropic parameter estimation, and more particularly to a method for modeling orthotropic parameters of fractured shale. Background Technology

[0002] Shale-type oil and gas reservoirs, a crucial area for oil and gas exploration and development in China, differ from conventional sandstone or carbonate reservoirs in that they generally exhibit strong anisotropic characteristics, primarily characterized by lateral isotropic properties (VTI). The development of vertical structural fractures, leading to high-intensity isotropic properties (HTI), further contributes to the complex orthotropic properties of shale formations. The development of vertical structural fractures plays a significant role in oil and gas storage and migration. To better utilize seismic waves for inversion prediction of fractured reservoirs, establishing a more practical, convenient, and orthotropic shale petrophysical model is of great importance for estimating fracture density and orthotropic parameters of fractured shale reservoirs.

[0003] Current rock physical modeling of fracture-free shale largely relies on inclusion theory, which involves combining components one by one. This process is complex, involves numerous assumptions and variables, is prone to errors, and is highly dependent on core measurement data, making it unsuitable for situations where such data is unavailable. Rock physical simulations of vertical fractures in shale primarily utilize Hudson theory, Schoenberg linear slip theory, the Eshelby-Cheng model, the Aniso-DEM (Aniso-Differential Equivalent Model), and the Aniso-SCA (Aniso-Compatible Model). Hudson theory, the most commonly used model, considers both the interaction between fractures and the rock background, as well as the interaction between fractures themselves. It can simulate the anisotropy caused by a single set of thin penny-shaped fractures arranged along a specific direction, and allows for the simultaneous introduction of fluids within the fractures. It requires isolated and sparsely distributed fractures and has some applicability to shale reservoirs. Besides the choice of modeling theory, the initial fracture parameters given in the simulation also affect the model's accuracy. In existing rock physics modeling processes for fractured shale, most do not have a clear initial fracture parameter model. A few determine the porosity of horizontal and vertical fractures based on resistivity logging, or determine the initial input fracture density based on the shear wave splitting phenomenon caused by vertical structural fractures and the empirical relationship between shear wave anisotropy and vertical fracture density.

[0004] Chinese patent application CN202011106301.4, concerning a method and system for characterizing fracture parameters, mentions a similar method for estimating anisotropic parameters based on a rock physics model. This method first introduces fractures and fluid substitution into an isotropic background matrix using the Hudson model to obtain an anisotropic medium. Finally, it estimates the anisotropy of the medium based on the characterization formulas for fracture and anisotropic parameters established by Schoenberg theory. However, the construction of the isotropic background requires mineral composition data from core measurements, making it difficult to apply when core measurements are unavailable. Furthermore, the addition of fluids requires fluid substitution theory that emphasizes interconnected pores and fractures, which increases the complexity of the model and computational errors for shale with isolated pores and fractures.

[0005] Chinese patent application CN202311338257.3, concerning a method and apparatus for forward modeling anisotropic seismic gathers in buried hill fractured reservoirs, also constructs a petrophysical model of the fractures. The rock background matrix is ​​obtained by equivalent mixing of various minerals. Then, Hudson theory, Schoenberg theory, and fluid substitution theory are used to add fluid-containing fractures to the matrix to complete the modeling. However, the modeling does not provide explicit initial fracture parameters, requires core measurement data for rock background matrix modeling, and the use of fluid substitution theory increases model error.

[0006] The Chinese patent application CN201910423956.5, concerning the analysis method and computer system for the distribution law of rock physical characteristics, establishes an orthogonal rock physical model containing both horizontal bedding fractures and vertical fractures under a laterally isotropic background. However, this model incorporates fracture fluids using fluid substitution theory, which may introduce certain errors when applied to shale with poor pore-fracture connectivity.

[0007] Chinese patent application CN201811480140.8 proposes a rock physics model for fractured reservoirs based on the spatial distribution of fractures. The model can describe different spatial distributions of fractures. However, the parameters used to characterize the spatial distribution of fractures in the model need to be obtained from geological outcrops and core data of the fractured reservoir. In practice, it is difficult to apply the model when such data is lacking.

[0008] Current methods for rock physics modeling of fractured reservoirs are often designed for a specific lithology when constructing VTI media, making them difficult to apply to different lithological formations. The model inputs require numerous data points, including mineral composition and varying porosity, and contain multiple uncertain parameters such as pore aspect ratio and clay orientation. The resulting predictions are highly ambiguous and lack practical applicability. Summary of the Invention

[0009] In view of the above problems, the present invention is proposed to provide a method for modeling orthotropic parameters of fractured shale that overcomes or at least partially solves the above problems.

[0010] According to one aspect of the present invention, a method for modeling orthotropic parameters of fractured shale is provided, the parameter modeling method comprising:

[0011] Step S1: Collect well logging data;

[0012] Step S2: Calculate the equivalent VTI background stiffness coefficient matrix for fracture-free shale;

[0013] Step S3: Calculate fracture density based on fast and slow shear wave logging velocities;

[0014] Step S4: Calculate the equivalent orthogonal anisotropic elastic stiffness matrix of fractured shale;

[0015] Step S5: Calculate the anisotropic parameters of the fractured shale to be inverted based on the equivalent orthogonal anisotropic elastic stiffness matrix.

[0016] Optionally, step S1: collecting well logging dataset specifically includes: obtaining well logging data, pore composition and fluid elastic parameters through well logging in the work area.

[0017] Optionally, the well logging data specifically includes:

[0018] Vertical P-wave velocity V at various depth points p0 Vertical transverse wave velocity V s0 Fast transverse wave velocity V sf Slow transverse wave velocity V ss Stoneley wave velocity V st Rock density v, water saturation S w Fluid density ρ f Bulk modulus K f and shear modulus μ f .

[0019] Optionally, step S2: calculating the equivalent VTI background stiffness coefficient matrix for fracture-free shale specifically includes:

[0020] The equivalent VTI background stiffness coefficient matrix C of the fracture-free shale VTI This includes 6 quantities to be calculated;

[0021] Among them, C 33 and C 44 The values ​​were calculated from the vertical P-wave velocity, the vertical S-wave velocity, and the formation density logging curves, respectively.

[0022] C in the well 66It is calculated by combining the Stoneley wave velocity with the estimated horizontal shear wave velocity;

[0023] C was calculated based on the empirical relationship between the anisotropy parameter δ and the P-wave / S-wave velocity ratio in rock physics. 13 ;

[0024] According to the ANNIE model, by C 12 and C 66 Calculate C 11 Calculate 5 independent stiffness coefficients in VTI medium with C 13 =C 12 .

[0025] Optionally, step S2: the formula for calculating the equivalent VTI background stiffness coefficient matrix of fracture-free shale is as follows:

[0026]

[0027] C 13 =C 12 =(2C 33 δ(C 33 -C 44 )+(C 33 -C 44 ) 2 ) 0.5 -C 44 ,

[0028]

[0029] C 11 =2C 66 +C 12 ,

[0030]

[0031] Among them, V p0 V s0 ρ and V represent the logging P-wave velocity, S-wave velocity, and rock density at each depth point, respectively; mud ρ mud These represent the velocity and density of the drilling mud, respectively. The reference value for the drilling mud velocity is 1500 m / s, and the reference value for the drilling mud density is 1.2 g / cm³. 3 .

[0032] Optionally, step S3: calculating the fracture density based on fast and slow shear wave logging velocities specifically includes:

[0033] Logging speeds and shear wave velocities can determine the shear wave anisotropy parameter γ. s The following formula is used for calculation:

[0034]

[0035] Among them, V ss V sf These represent the slow shear wave velocity and fast shear wave velocity at each depth point.

[0036] Optionally, the crack density e and the shear wave anisotropy parameter γ s There is a close empirical relationship in rock physics, and the calculation formula is as follows:

[0037]

[0038] Optionally, step S4: calculating the equivalent orthogonal anisotropic elastic stiffness matrix of fractured shale specifically includes: using the Hudson model to calculate the stiffness coefficient matrix of fractured rock, and obtaining the equivalent orthogonal anisotropic elastic stiffness matrix of fractured shale.

[0039] Optionally, the formula for calculating the stiffness coefficient matrix of fractured rock using the Hudson model is as follows:

[0040] Calculate using the following formula:

[0041] C ORT =C VTI +C 1 +C 2 ,

[0042] Among them, C VTI For the stiffness coefficient matrix of the background VTI medium, C 1 C 2 These are first-order and second-order corrections, respectively. When a single set of fractures with perpendicular fracture surfaces exists in the rock, the rock as a whole exhibits HTI properties, and its first-order correction is:

[0043]

[0044] The second-order correction is:

[0045]

[0046] Where e is the crack density, and λ and μ are the Lamé constants of the background medium, respectively. For fluid-containing cracks, terms U1 and U3 are calculated using the following formulas:

[0047]

[0048] in, α is the aspect ratio of the crack, given as 0.01. K' and μ' are the bulk modulus and shear modulus of the medium filling the crack, respectively, calculated using the following formula:

[0049]

[0050] Among them, S w K represents the water saturation level. w μ w These are the bulk modulus and shear modulus of water, K. f μ f These are the bulk modulus and shear modulus of another fluid, respectively.

[0051] Optionally, step S5: calculating the anisotropic parameters of the fractured shale to be inverted based on the equivalent orthogonal anisotropic elastic stiffness matrix specifically includes:

[0052] The anisotropy parameters of the fractured rock to be inverted are calculated using the following formula:

[0053]

[0054] in, The elastic stiffness coefficient of the fractured rock is calculated using the orthotropic formula used by Tsvankin.

[0055] This invention provides a method for modeling orthogonal anisotropic parameters of fractured shale. The method includes: Step S1: collecting well logging datasets; Step S2: calculating the equivalent VTI background stiffness coefficient matrix for fracture-free shale; Step S3: calculating the fracture density based on fast and slow shear wave logging velocities; Step S4: calculating the equivalent orthogonal anisotropic elastic stiffness matrix for fractured shale; Step S5: calculating the anisotropic parameters of the fractured shale to be inverted based on the equivalent orthogonal anisotropic elastic stiffness matrix. This method can conveniently and accurately calculate the elastic stiffness coefficients of the VTI medium, reducing dependence on core measurement data. It has excellent applicability in situations where core analysis data is lacking and the mineral composition and elastic properties of the rock cannot be clearly defined, while also reducing the number of variables in traditional methods.

[0056] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0057] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0058] Figure 1This is a flowchart of a method for modeling orthogonal anisotropy parameters of fractured shale provided in Embodiment 1 of the present invention;

[0059] Figure 2 The measured P-wave velocity V in a shale oilfield provided in Embodiment 1 of the present invention is shown in the well logging data. p0 Shear wave velocity V s0 Stoneley wave velocity V st Density (Den), slow transverse wave velocity (V) ss Fast transverse wave velocity V sf Water saturation S w ;

[0060] Figure 3 The elastic stiffness coefficients of the equivalent VTI background (without fractures) of shale oilfield, constructed using actual well logging data from a shale oilfield, are provided in Embodiment 1 of this invention.

[0061] Figure 4 The shear wave anisotropy γ calculated using actual logging data from a shale oilfield, as provided in Embodiment 1 of this invention. s and crack density e;

[0062] Figure 5 The equivalent orthogonal anisotropic elastic stiffness coefficient obtained from the rock physics model of fractured shale provided in Embodiment 1 of the present invention

[0063] Figure 6 The orthogonal anisotropy parameters and P-wave and S-wave velocities V obtained from the rock physics model of fractured shale provided in Embodiment 1 of the present invention are... pORT V sORT Compared with the original logging P-wave and S-wave velocities V p0 V s0 The contrast;

[0064] Figure 7 The measured P-wave velocity V in a shale oilfield provided in Embodiment 2 of the present invention is shown in the well logging data. p0 Shear wave velocity V s0 Stoneley wave velocity V st Density (Den), slow transverse wave velocity (V) ss Fast transverse wave velocity V sf Water saturation S w ;

[0065] Figure 8 The elastic stiffness coefficients of the equivalent VTI background (without fractures) of shale oilfield, constructed using actual well logging data from a shale oilfield, are provided in Embodiment 2 of the present invention.

[0066] Figure 9The shear wave anisotropy γ calculated using actual logging data from a shale oilfield, as provided in Embodiment 2 of the present invention. s and crack density e;

[0067] Figure 10 The equivalent orthogonal anisotropic elastic stiffness coefficient obtained from the rock physics model of fractured shale provided in Embodiment 2 of the present invention

[0068] Figure 11 The orthogonal anisotropy parameters and P-wave and S-wave velocities V obtained from the rock physics model of fractured shale provided in Embodiment 2 of the present invention are... pORT V sORT Compared with the original logging P-wave and S-wave velocities V p0 V s0 The contrast;

[0069] Figure 12 The measured P-wave velocity V in a shale oilfield provided in Embodiment 3 of the present invention is shown in the well logging data. p0 Shear wave velocity V s0 Stoneley wave velocity V st Density (Den), slow transverse wave velocity (V) ss Fast transverse wave velocity V sf Water saturation S w .

[0070] Figure 13 The elastic stiffness coefficients of the equivalent VTI background (without fractures) of shale oilfield, constructed using actual well logging data from a shale oilfield, are provided in Embodiment 3 of this invention.

[0071] Figure 14 The shear wave anisotropy γ calculated using actual logging data from a shale oilfield, as provided in Embodiment 3 of this invention. s and crack density e.

[0072] Figure 15 The equivalent orthogonal anisotropic elastic stiffness coefficient obtained from the rock physics model of fractured shale provided in Embodiment 3 of the present invention

[0073] Figure 16 The orthogonal anisotropy parameters and P-wave and S-wave velocities V obtained from the rock physics model of fractured shale provided in Embodiment 3 of the present invention are... pORT V sORT Compared with the original logging P-wave and S-wave velocities V p0 V s0 The comparison. Detailed Implementation

[0074] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0075] The terms "comprising" and "having," and any variations thereof, in the specification, embodiments, claims, and drawings of this invention are intended to cover non-exclusive inclusion, such as including a series of steps or units.

[0076] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0077] like Figure 1 As shown, this invention provides a method for modeling orthogonal anisotropy parameters of fractured shale for seismic inversion, comprising:

[0078] Basic data preparation involves obtaining the required logging data, pore composition, and fluid elastic parameters through well logging in the work area.

[0079] The stiffness coefficient matrix of the equivalent VTI background without fractured shale was calculated based on actual well logging data.

[0080] The crack density of the model input is determined by using the empirical relationship between fast and slow shear wave velocities, shear wave anisotropy, and crack density.

[0081] A rock physics model of shale with vertical fractures was established based on the Hudson model. The equivalent orthogonal anisotropic elastic stiffness matrix of the fractured shale and the orthogonal anisotropic parameters to be inverted were calculated.

[0082] Example 1, as Figure 2-6 As shown:

[0083] A method for modeling orthogonal anisotropic parameters of fractured shale for seismic inversion includes:

[0084] Step S1: Data collection: The work area is a shale oil work area. Collect its logging data and determine the fluid type and its density, bulk modulus and shear modulus as given in Table 1.

[0085] Table 1

[0086] Components <![CDATA[Density (Kg / m 3 )]]> Bulk modulus (Pa) Shear modulus (Pa) water 1000 <![CDATA[2.2×10 9 ]]> <![CDATA[0.1×10 9 ]]> Oil 795 <![CDATA[1.2×10 9 ]]> <![CDATA[0.1×10 9 ]]>

[0087] Step S2: Construct the equivalent VTI background stiffness coefficient matrix C based on well logging data for fracture-free shale. VTI ;

[0088] C 33and C 44 The C1 of the formation was calculated from the vertical P-wave, vertical S-wave velocity, and formation density logging curves collected in step S1, respectively. 66 C is calculated by combining the Stoneley wave velocity with an estimated horizontal shear wave velocity. 13 The anisotropy parameter δ is calculated based on the empirical relationship between rock physics and the P-wave / S-wave velocity ratio. Furthermore, according to the ANNIE model, C... 12 (VTI media and C) 13 (equal) and C 66 Calculate C 11 This allows for the calculation of five independent stiffness coefficients. The specific formula used is as follows:

[0089]

[0090] C 13 =C 12 =(2C 33 δ(C 33 -C 44 )+(C 33 -C 44 ) 2 ) 0.5 -C 44 ,

[0091]

[0092] C 11 =2C 66 +C 12 ,

[0093]

[0094] Among them, V p0 V s0 ρ and V represent the logging P-wave velocity, S-wave velocity, and rock density at each depth point, respectively; mud ρ mud These represent the velocity and density of the drilling mud, with reference values ​​of 1500 m / s and 1.2 g / cm³, respectively. 3 .

[0095] Step S3: Calculate fracture density based on fast and slow shear wave logging velocities;

[0096] Well speed determines the shear wave anisotropy parameter γ s The following formula is used for calculation:

[0097]

[0098] Among them, V ss V sfThese represent the slow shear wave velocity and fast shear wave velocity at each depth point.

[0099] Crack density e and transverse wave anisotropy parameter γ s There exists a close empirical relationship in rock physics, which can be calculated using the following formula:

[0100]

[0101] Step S4: Calculate the equivalent orthogonal anisotropic elastic stiffness coefficient matrix C of the fractured shale. ORT :

[0102] C ORT =C VTI +C 1 +C 2 ,

[0103] Among them, the first-order correction C 1 :

[0104]

[0105] Second-order correction C 2 :

[0106]

[0107] in,

[0108]

[0109] Where e is the crack density, λ and μ are the Lamé constants of the background medium, α is the crack aspect ratio, given as 0.01, and K w μ w These are the bulk modulus and shear modulus of water, K. f μ f These are the bulk modulus and shear modulus of oil, respectively.

[0110] Step S5: Calculate the anisotropy parameters of the fractured shale to be inverted using the stiffness coefficients obtained in Step S4.

[0111]

[0112] The orthogonal anisotropy parameters of each depth point are obtained.

[0113] Example 2

[0114] For the second well logging operation, the fluid parameter settings and implementation process were the same as in Example 1. Since there was no water saturation data, the water saturation was fixed at 75%. Figure 7-11 As shown.

[0115] Example 3

[0116] For the third work area logging, the fluid parameter settings and implementation process were the same as in Example 1. Since there was no water saturation data, the water saturation was fixed at 75%. Figures 12-15 As shown.

[0117] Beneficial Effects: This paper proposes a more practical and convenient method for modeling orthotropic parameters of fractured shale for inversion. Utilizing conventional logging data such as vertical P-wave, S-wave, and Stoneley wave velocities, combined with empirical formulas, the elastic stiffness coefficient of VTI media can be calculated conveniently and accurately, reducing reliance on core measurement data. This method is highly applicable in situations where core analysis data is unavailable or the mineral composition and elastic properties of the rock cannot be clearly defined. It also reduces errors caused by multiple variables and theoretical assumptions in traditional methods, making it suitable for various lithological formations. Considering the sensitivity of S-waves to fractures and the fact that their relationship is largely unaffected by fluid changes, high-resolution fracture density varying with depth is obtained relatively accurately using fast and slow S-wave velocity logging data combined with empirical formulas. This provides an important basis for subsequent modeling of the elastic stiffness coefficient of orthotropic media. Furthermore, the Tsvankin orthotropic formula is used to calculate anisotropic parameters, quantifying the degree of orthotropic anisotropy and further simplifying the traditional reflectivity equation characterized by nine independent elastic stiffness coefficients, which is more conducive to subsequent inversion work.

[0118] The above specific embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are merely specific embodiments 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 within the scope of protection of the present invention.

Claims

1. A method for modeling orthogonal anisotropy parameters of fractured shale, characterized in that, The parameter modeling method includes: Step S1: Collect well logging data; Step S2: Calculate the equivalent VTI background stiffness coefficient matrix for fracture-free shale; Step S3: Calculate fracture density based on fast and slow shear wave logging velocities; Step S4: Calculate the equivalent orthogonal anisotropic elastic stiffness matrix of fractured shale; Step S5: Calculate the anisotropic parameters of the fractured shale to be inverted based on the equivalent orthogonal anisotropic elastic stiffness matrix.

2. The method for modeling orthogonal anisotropic parameters of fractured shale according to claim 1, characterized in that, Step S1: Collecting well logging datasets specifically includes: obtaining well logging data, pore composition, and fluid elastic parameters through well logging in the work area.

3. The method for modeling orthogonal anisotropy parameters of fractured shale according to claim 1, characterized in that, The well logging data specifically includes: Vertical P-wave velocity V at various depth points p0 Vertical transverse wave velocity V s0 Fast transverse wave velocity V sf Slow transverse wave velocity V ss Stoneley wave velocity V st Rock density ρ, water saturation S w Fluid density ρ f Bulk modulus K f and shear modulus μ f .

4. The method for modeling orthogonal anisotropy parameters of fractured shale according to claim 3, characterized in that, Step S2: Calculating the equivalent VTI background stiffness coefficient matrix of fracture-free shale specifically includes: The equivalent VTI background stiffness coefficient matrix C of the fracture-free shale VTI This includes 6 quantities to be calculated; Among them, C 33 and C 44 The values ​​were calculated from the vertical P-wave velocity, the vertical S-wave velocity, and the formation density logging curves, respectively. C in the well 66 It is calculated by combining the Stoneley wave velocity with the estimated horizontal shear wave velocity; C was calculated based on the empirical relationship between the anisotropy parameter δ and the P-wave / S-wave velocity ratio in rock physics. 13 ; According to the ANNIE model, by C 12 and C 66 Calculate C 11 Calculate 5 independent stiffness coefficients in VTI medium with C 13 =C 12 .

5. The method for modeling orthogonal anisotropy parameters of fractured shale according to claim 1, characterized in that, Step S2: The formula for calculating the equivalent VTI background stiffness coefficient matrix of fracture-free shale is as follows: C 13 *C 12 =(2C 33 δ(C 33 -C 44 )+(C 33 -C 44 ) 2 ) 0.5 -C 44 , C 11 <2C 66 +C 12 , Among them, V p0 V s0 ρ and V represent the logging P-wave velocity, S-wave velocity, and rock density at each depth point, respectively; mud ρ mud These represent the velocity and density of the drilling mud, respectively. The reference value for the drilling mud velocity is 1500 m / s, and the reference value for the drilling mud density is 1.2 g / cm³. 3 .

6. The method for modeling orthogonal anisotropic parameters of fractured shale according to claim 1, characterized in that, Step S3, calculating fracture density based on fast and slow shear wave logging velocities, specifically includes: Logging speeds and shear wave velocities can determine the shear wave anisotropy parameter γ. s The following formula is used for calculation: Among them, V ss V sf These represent the slow shear wave velocity and fast shear wave velocity at each depth point.

7. The method for modeling orthogonal anisotropic parameters of fractured shale according to claim 6, characterized in that, The crack density e and the shear wave anisotropy parameter γ s There is a close empirical relationship in rock physics, and the calculation formula is as follows:

8. The method for modeling orthogonal anisotropy parameters of fractured shale according to claim 1, characterized in that, Step S4: Calculating the equivalent orthogonal anisotropic elastic stiffness matrix of fractured shale specifically includes: using the Hudson model to calculate the stiffness coefficient matrix of fractured rock, and obtaining the equivalent orthogonal anisotropic elastic stiffness matrix of fractured shale.

9. A method for modeling orthogonal anisotropic parameters of fractured shale according to claim 1, characterized in that, The formula for calculating the stiffness coefficient matrix of fractured rock using the Hudson model is as follows: Calculate using the following formula: C ORT =C VTI +C 1 +C 2 , Among them, C VTI For the stiffness coefficient matrix of the background VTI medium, C 1 C 2 These are first-order and second-order corrections, respectively. When a single set of fractures with perpendicular fracture surfaces exists in the rock, the rock as a whole exhibits HTI properties, and its first-order correction is: The second-order correction is: Where e is the crack density, and λ and μ are the Lamé constants of the background medium, respectively. For fluid-containing cracks, terms U1 and U3 are calculated using the following formulas: in, α is the aspect ratio of the crack, given as 0.

01. K' and μ' are the bulk modulus and shear modulus of the medium filling the crack, respectively, calculated using the following formula: Among them, S w K represents the water saturation level. w μ w These are the bulk modulus and shear modulus of water, K. f μ f These are the bulk modulus and shear modulus of another fluid, respectively.

10. A method for modeling orthogonal anisotropic parameters of fractured shale according to claim 1, characterized in that, Step S5: Calculating the anisotropic parameters of the fractured shale to be inverted based on the equivalent orthogonal anisotropic elastic stiffness matrix specifically includes: The anisotropy parameters of the fractured rock to be inverted are calculated using the following formula: in, The elastic stiffness coefficient of the fractured rock is calculated using the orthotropic formula used by Tsvankin.

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