Tight reservoir fracturing index prediction method based on tectonic crustal stress field

Abstract

The invention provides a tight reservoir fracturing index prediction method based on a tectonic crustal stress field. The prediction method comprises the steps that 101, a three-dimensional data body of elastic parameters is obtained; step 102, establishing a relationship between a strain component and a displacement component of any point in the elastomer based on an elastic thin plate bending theory; step 103, realizing three-dimensional space distribution prediction of the principal stress and the principal stress direction based on the analysis of the tectonic crustal stress field; and step 104, establishing a fracturing index prediction model according to the three-dimensional space distribution prediction, forming quantitative evaluation parameters for deep tight reservoir sweet spot prediction, and establishing a clear tight reservoir fracturing adaptive area evaluation standard. According to the method, the fracturing property of the tight reservoir is effectively evaluated, the evaluation standard of the fracturing adaptive area of the tight reservoir is established, a sweet spot prediction technology suitable for exploration and development of the deep tight reservoir is formed, a basis is provided for development of the tight reservoir, and the method has a good application effect and a good popularization prospect.

Description

Technical Field

[0001] The invention relates to the technical field of petroleum geophysical exploration, and in particular to a method for predicting a tight reservoir fracturing index based on a tectonic geostress field. Background Art

[0002] In recent years, the exploration and development of unconventional oil and gas resources has attracted much attention from experts at home and abroad. As an important component of it, tight oil and gas reservoirs have become a hot spot and difficulty in oil and gas exploration. Tight oil and gas refers to oil and gas that exists in tight sandstone, tight carbonate rock and other reservoirs with extremely low permeability. The single well production fails to form industrial oil and gas flow, but can form industrial oil flow under certain mining measures. This type of reservoir has the characteristics of low permeability, complex pore structure, complex mineral composition, and obvious brittle characteristics. Compared with shallow layers, the development of oil and gas in deep tight reservoirs faces many difficulties, such as: more complex geological conditions, unclear resource occurrence forms and production dynamics, long drilling cycles, and difficulty in forming fracture networks by fracturing. Effective compressibility evaluation is needed to accurately understand the reservoir and achieve better fracturing effects.

[0003] The compressibility of reservoirs only reflects the physical and geomechanical characteristics of the formation reservoir, as well as the comprehensive influence of the mechanical behaviors such as the initiation and expansion of rock fractures by pumping high-pressure fracturing fluid during volume fracturing, and has nothing to do with volume fracturing construction. The current compressibility evaluation methods mainly include qualitative and quantitative evaluation methods. The qualitative method mainly uses the method of directly comparing the research block data with the shale gas high-yield advantageous strata, well locations, and block data, and selects the well locations and strata for shale gas fracturing through geological, rock mechanics, logging, geophysics, and test production data. However, this method requires a large amount of previous historical data and is suitable for mature shale gas development blocks, and the error is sometimes large. The quantitative method is mainly based on the brittleness index or compressibility index. The brittleness index is the core indicator for selecting favorable strata for reservoir fracturing and is the most widely used reservoir compressibility evaluation method. However, the existing brittleness index evaluation method can only reflect the permanent destruction capacity of rocks after inelastic strain under simple mechanical environment, and cannot consider the influence of external environment (such as ground stress) on rock destruction. At the same time, the brittleness index needs to be indirectly obtained from other parameters and cannot be directly tested. In addition to the brittleness index factor, the compressibility evaluation method can also consider other factors, such as ground stress differences, the degree of natural fracture development, etc. However, the brittleness index and compressibility index methods generally require sufficient indoor experimental data, so they have defects such as high testing costs and long testing cycles. At the same time, sometimes there are not enough cores on site, so only discrete compressibility evaluation data of different layers can be obtained, which is difficult to support the fracturing design work of the entire well section.

[0004] In summary, the existing technology has obvious deficiencies in the prediction of the fine fracturing properties of tight reservoirs. The development effect of tight oil reservoirs is affected by the reservoir properties and the compressibility properties. Therefore, the evaluation of the compressibility properties has an important impact on the development effect of tight oil reservoirs. However, there is no effective method for evaluating the fracturing adaptation zone of tight reservoirs in the existing technology, and no clear process and standards have been established. Summary of the invention

[0005] In view of the above problems, the present invention is proposed to provide a method for predicting the fracturing index of a tight reservoir based on a tectonic stress field, which overcomes the above problems or at least partially solves the above problems.

[0006] According to one aspect of the present invention, a method for predicting a tight reservoir fracturing index based on a tectonic geostress field is provided, the prediction method comprising:

[0007] Step 101: Obtain a three-dimensional data volume of elastic parameters;

[0008] Step 102: Establish the relationship between the strain component and the displacement component at any point in the elastic body based on the elastic thin plate bending theory;

[0009] Step 103: Based on the analysis of the tectonic geostress field, the three-dimensional spatial distribution prediction of the principal stress and the principal stress direction is realized;

[0010] Step 104: A fracturing index prediction model is established based on the three-dimensional spatial distribution prediction, a quantitative evaluation parameter is formed for predicting sweet spots in deep tight reservoirs, and a clear evaluation standard for tight reservoir fracturing adaptability zones is established.

[0011] Optionally, the elastic parameters specifically include: longitudinal and transverse wave velocities, and density.

[0012] Optionally, the step 101: obtaining a three-dimensional data volume of elastic parameters specifically includes: performing pre-stack seismic elastic parameter inversion to obtain a three-dimensional data volume of elastic parameters.

[0013] Optionally, in step 102: establishing the relationship between the strain component and the displacement component at any point in the elastic body based on the elastic thin plate bending theory, the elastic thin plate is a plate-like component surrounded by two parallel planes whose thickness is much smaller than the dimensions in other directions.

[0014] Optionally, the step 102: establishing the relationship between the strain component and the displacement component at any point in the elastic body based on the elastic thin plate bending theory specifically includes:

[0015] Assume the midplane of the thin plate as the coordinate plane, z = 0;

[0016] The coordinate origin O is a point in the midplane, and the x and y axes are in the midplane;

[0017] The displacement generated in the positive direction of the x-axis is u, the displacement generated in the positive direction of the y-axis is v, the displacement generated in the positive direction of the z-axis is the disturbance w(x,y), and in the z-axis direction, the time thickness of the thin plate is z (in seconds);

[0018] The elastic properties of thin plate media are expressed by the following elastic mechanics equations;

[0019] Geometric equation: It describes the relationship between the strain component and the displacement component at any point in the elastic body. Its expression is:

[0020]

[0021]

[0022] u z =w (3)

[0023] Where: x , ε y , ε z are the normal strain components of the x, y, and z sections, respectively, xy is the shear strain component of the xy section;

[0024] From the thin plate theory, we know that:

[0025]

[0026] And there are:

[0027]

[0028] Define the curvature deformation components:

[0029]

[0030] Where: K x , K y are the curvature deformation components in the x and y directions, K xy is the curvature deformation component in the xy direction;

[0031] For a thin plate with thickness z, the strain components are written as:

[0032] ε x =-zK x , ε y =-zK y , γ xy =-2zK xy (7).

[0033] Optionally, the step 103: realizing the three-dimensional spatial distribution prediction of the principal stress and the principal stress direction based on the tectonic geostress field analysis specifically includes:

[0034] The physical constitutive relationship equation describes the relationship between the stress component and the strain component of the elastic body, and its expression is as follows:

[0035]

[0036]

[0037]

[0038] Its inverse relationship is:

[0039] σ x =2με x +λθ,τ xy =μγ xy (11)

[0040] σ y =2με y +λθ,τ yz =μγ yz (12)

[0041] σ z =2με z +λθ,τ xz =μγ xz (13)

[0042] θ=ε x +ε y +ε z (14)

[0043] Where: λ is the Lame constant, μ is the shear modulus, ν is the Poisson's ratio, θ is the volume strain, E is the Young's modulus, σ is the normal stress component, and τ is the shear stress component;

[0044] Substituting equations (8, 9, 10) into the equations, we obtain:

[0045]

[0046] So we have:

[0047]

[0048]

[0049]

[0050] From equations (16, 17, and 18), we can see that when the ground surface is convex upward, the curvature is greater than zero, corresponding to the convex ground surface being subjected to tensile stress, and the tensile stress is positive;

[0051] The tensile stress is uniformly negative and the compressive stress is uniformly positive, so if the curvature is less than zero, it means that the formation is convex;

[0052] After calculating the stress along the coordinates of the point, the maximum horizontal principal stress σmax, the minimum horizontal principal stress σmin and their corresponding main directions can be obtained:

[0053]

[0054]

[0055] If the angle between σmax and the x-axis is α, and the angle between σmin and the x-axis is β, then

[0056]

[0057] Optionally, the step 104: establishing a fracturing index prediction model according to the three-dimensional spatial distribution prediction specifically includes:

[0058] Obtain the disturbance equation of the ground plane or the curvature of the ground at a point on the surface and estimate the corresponding stress field;

[0059] Calculate the fracturing index that characterizes the fracturing properties of tight reservoirs, effectively evaluate the fracturing properties of tight reservoirs, and establish evaluation standards for the fracturing adaptation zone of tight reservoirs.

[0060] Optionally, the calculation method of the formation curvature includes:

[0061] Fitting of formation trend surface: find out the stress field on the formation surface and calculate the curvature component of the formation surface;

[0062] The calculation method adopts the trend surface fitting method to fit the trend function of the ground surface to obtain the result;

[0063] Assume that the undetermined coefficient function of the trend surface is:

[0064] w(x,y)=a0+a1x+a2y+a3x 2 +a4xy+a5y 2 (twenty two)

[0065] The least squares equation is established based on the coordinate values ​​(x, y, z) of the scattered points on the plane. For a scattered point:

[0066] ε i =z i -w i (x i ,y i ) (twenty three)

[0067]

[0068] When a trend surface is fitted by n scattered points, a fitting equation system is obtained, where the summation sign represents the summation of points 1, 2, ..., n; solving this linear equation system, the trend surface function is obtained;

[0069] The curvature calculation formula of the trend surface;

[0070]

[0071] Optionally, the calculation method for constructing the stress field includes:

[0072] Curvature parameters: Solve the equations to obtain the fitting surface coefficients a3, a4, a5, and use equation (25) to obtain the curvature at the corresponding point;

[0073] Strain parameter: The strain value is obtained by formula (7);

[0074] Stress parameters: The corresponding stresses, principal stresses and principal stress directions are calculated by equations (16), (17), (18), (19), (20) and (21).

[0075] Optionally, the method for calculating the fracturing index characterizing the fracturing properties of a tight reservoir specifically includes:

[0076] The difference between the maximum horizontal principal stress and the minimum horizontal principal stress is used as a fracturing index FI:

[0077] FI=(σ max -σ min ) / max|σ max -σ min |

[0078] Among them, FI is the fracturing index, σmax is the maximum horizontal principal stress, and σmin is the minimum horizontal principal stress.

[0079] The present invention provides a method for predicting the fracturing index of a tight reservoir based on a tectonic geostress field, the method comprising: step 101: obtaining a three-dimensional data body of elastic parameters; step 102: establishing the relationship between the strain component and the displacement component at any point in the elastic body based on the elastic thin plate bending theory; step 103: realizing the three-dimensional spatial distribution prediction of the principal stress and the principal stress direction based on the tectonic geostress field analysis; step 104: establishing a fracturing index prediction model based on the three-dimensional spatial distribution prediction, forming quantitative evaluation parameters for predicting sweet spots in deep tight reservoirs, and establishing clear evaluation standards for the fracturable adaptation zone of tight reservoirs. Effectively evaluating the fracturable properties of tight reservoirs, establishing evaluation standards for the fracturable adaptation zone of tight reservoirs, forming a "sweet spot" prediction technology suitable for the exploration and development of deep tight reservoirs, providing a basis for the development of tight reservoirs, and having good application effects and promotion prospects.

[0080] 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

[0081] 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.

[0082] Figure 1 A flowchart of a method for predicting a tight reservoir fracturing index based on a tectonic geostress field provided in an embodiment of the present invention;

[0083] Figure 2 The longitudinal wave velocity well section in a specific embodiment 1 of the present invention;

[0084] Figure 3 The shear wave velocity well section in a specific embodiment 1 of the present invention;

[0085] Figure 4 The density well-connected profile in a specific embodiment 1 of the present invention;

[0086] Figure 5 The maximum horizontal principal stress well-connected section in a specific embodiment 1 of the present invention;

[0087] Figure 6 is the plane distribution of the maximum horizontal principal stress in a specific embodiment 1 of the present invention;

[0088] Figure 7 The minimum horizontal principal stress well-connecting section in a specific embodiment 1 of the present invention;

[0089] Figure 8 This is the plane distribution of the minimum horizontal principal stress in a specific embodiment 1 of the present invention.

[0090] Fig. 9 A fracture index well section in a specific embodiment 1 of the present invention;

[0091] Fig.10 The plane distribution of the fracturing index in a specific embodiment 1 of the present invention;

[0092] Fig.11 A histogram of reservoir identification by fracturing index in a specific embodiment 1 of the present invention;

[0093] Fig.12The longitudinal wave velocity well section in a specific embodiment 2 of the present invention;

[0094] Fig.13 The shear wave velocity well-connected profile in a specific embodiment 2 of the present invention;

[0095] Fig.14 It is a density well-connected profile in a specific embodiment 2 of the present invention;

[0096] Fig.15 The maximum horizontal principal stress well section in a specific embodiment 2 of the present invention;

[0097] Fig.16 2 is the plane distribution of the maximum horizontal principal stress in a specific embodiment of the present invention;

[0098] Fig.17 The minimum horizontal principal stress well-connecting section in a specific embodiment 2 of the present invention;

[0099] Fig.18 This is the plane distribution of the minimum horizontal principal stress in a specific embodiment 2 of the present invention.

[0100] Fig.19 A fracture index well section in a specific embodiment 2 of the present invention;

[0101] Fig. 20 The plane distribution of the fracturing index in a specific embodiment 2 of the present invention;

[0102] Fig.21 A schematic diagram of an elastic thin plate model provided for a specific embodiment of the present invention. DETAILED DESCRIPTION

[0103] 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.

[0104] 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.

[0105] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0106] The method for predicting the tight reservoir fracturing index based on tectonic geostress field analysis of the present invention utilizes the tight reservoir fracturing index based on tectonic geostress field analysis to effectively evaluate the fracturing properties of the tight reservoir, thereby providing a basis for the development of the tight reservoir. The method has good application effects and promotion prospects.

[0107] like Figure 1 As shown, the present invention provides a method for predicting the fracturing index of a tight reservoir based on a tectonic geostress field, the prediction method comprising: step 101: obtaining a three-dimensional data body of elastic parameters; step 102: establishing the relationship between the strain component and the displacement component at any point in the elastic body based on the elastic thin plate bending theory; step 103: realizing the three-dimensional spatial distribution prediction of the principal stress and the principal stress direction based on the tectonic geostress field analysis; step 104: establishing a fracturing index prediction model based on the three-dimensional spatial distribution prediction, forming quantitative evaluation parameters for predicting the sweet spot of a deep tight reservoir, and establishing a clear evaluation standard for the fracturable adaptation zone of a tight reservoir. Effectively evaluate the fracturable properties of a tight reservoir, establish an evaluation standard for the fracturable adaptation zone of a tight reservoir, form a "sweet spot" prediction technology suitable for the exploration and development of a deep tight reservoir, provide a basis for the development of a tight reservoir, and have good application effects and promotion prospects.

[0108] Step 102: Establishing the relationship between the strain component and the displacement component at any point in the elastic body based on the elastic thin plate bending theory specifically includes:

[0109] Assume the midplane of the thin plate as the coordinate plane, z = 0;

[0110] The coordinate origin O is a point in the midplane, and the x and y axes are in the midplane;

[0111] The displacement generated in the positive direction of the x-axis is u, the displacement generated in the positive direction of the y-axis is v, the displacement generated in the positive direction of the z-axis is the disturbance w(x,y), and the time thickness of the thin plate in the z-axis direction is z (in seconds); the thin plate model is as follows Fig.21 shown.

[0112] The elastic properties of thin plate media are expressed by the following elastic mechanics equations;

[0113] Geometric equation: It describes the relationship between the strain component and the displacement component at any point in the elastic body. Its expression is:

[0114]

[0115]

[0116] u z =w (3)

[0117] Where: x , εy , ε z are the normal strain components of the x, y, and z sections, respectively, xy is the shear strain component of the xy section;

[0118] From the thin plate theory, we know that:

[0119]

[0120] And there are:

[0121]

[0122] Define the curvature deformation components:

[0123]

[0124] Where: K x , K y are the curvature deformation components in the x and y directions, K xy is the curvature deformation component in the xy direction;

[0125] For a thin plate with thickness z, the strain components are written as:

[0126] ε x =-zK x , ε y =-zK y , γ xy =-2zK xy (7).

[0127] Embodiment 1:

[0128] In a specific embodiment 1 of the present invention, the method for predicting the tight reservoir fracturing index based on tectonic geostress field analysis of the present invention includes the following steps:

[0129] Step 1: For the target layer of Qigu Formation in Yong1-3 well area, based on prestack seismic elastic inversion, obtain the three-dimensional spatial distribution of elastic parameters such as P-wave velocity and S-wave velocity and density, among which: Figure 2 This is the well-to-well section of the Qigu Formation P-wave velocity in the Yong1-3 well area. Figure 3 This is the shear wave velocity well-to-well section of the Qigu Formation in the Yong1-3 well area; Figure 4 This is the density well connection profile of the Qigu Formation in the Yong1-3 well area.

[0130] Step 2: Establish a geological model based on the elastic thin plate bending theory and establish the relationship between the strain component and the displacement component at any point in the elastic body.

[0131] Step 3: Based on the analysis of the tectonic stress field, the three-dimensional spatial distribution prediction of the principal stress and the principal stress direction is realized, where: Figure 5This is the well-connected section of the maximum horizontal principal stress of the Qigu Formation in the Yong1-3 well area. Figure 6 This is the plane distribution diagram of the maximum horizontal principal stress of the main sand body of the Qigu Formation in the Yong1-3 well area; Figure 7 This is the well-connected section of the minimum horizontal principal stress of the Qigu Formation in the Yong1-3 well area. Figure 8 This is the plane distribution diagram of the minimum horizontal principal stress of the main sand body of the Qigu Formation in the Yong1-3 well area.

[0132] Step 4: Based on the analysis of the tectonic stress field, calculate the fracturing index that characterizes the fracturing properties of the tight reservoir, and establish the evaluation criteria for the fracturing adaptation zone of the tight reservoir according to the well point rock physics analysis. Fig. 9 This is the well-connected section of the Qigu Formation fracturing index in the Yong1-3 well area; Fig.10 This is the plane distribution map of the fracturing index of the main sand body of the Qigu Formation in the Yong1-3 well area. Fig.11 The fracturing index histogram of different lithologies of the Qigu Formation in the Yong1-3 well area is shown in Figure 2. Fig.11 It can be seen that the fracturing index value of most sandstones is low (FI<0.165), and the corresponding difference between the maximum horizontal principal stress and the minimum horizontal principal stress is small. The fracturing fluid can easily enter the microcracks from multiple directions and can produce numerous shear cracks and tensile cracks, forming a relatively developed seepage network, so the corresponding fracturing effect is better; the fracturing index value of mudstone is high (FI>0.165), and the corresponding difference between the maximum horizontal principal stress and the minimum horizontal principal stress is large, so the corresponding fracturing effect is poor.

[0133] Embodiment 2:

[0134] In a specific embodiment 2 of the present invention, the method for predicting the tight reservoir fracturing index based on tectonic geostress field analysis of the present invention includes the following steps:

[0135] Step 1: For the target layer of Qigu Formation in Yong3 well area, based on prestack seismic elastic inversion, obtain the three-dimensional spatial distribution of elastic parameters such as P-wave velocity and S-wave velocity and density, among which: Fig.12 This is the well-to-well section of the Qigu Formation P-wave velocity in the Yong3 well area. Fig.13 This is the shear wave velocity well section of Qigu Formation in Yong3 well area; Fig.14 This is the density well-connected profile of the Qigu Formation in the Yong3 well area.

[0136] Step 2: Establish a geological model based on the elastic thin plate bending theory and establish the relationship between the strain component and the displacement component at any point in the elastic body.

[0137] Step 3: Based on the analysis of the tectonic stress field, the three-dimensional spatial distribution prediction of the principal stress and the principal stress direction is realized, where: Fig.15 This is the well section with the maximum horizontal principal stress of the Qigu Formation in the Yong3 well area. Fig.16 This is the plane distribution diagram of the maximum horizontal principal stress of the main sand body of the Qigu Formation in the Yong3 well area; Fig.17 This is the well-connected section of the minimum horizontal principal stress of the Qigu Formation in the Yong3 well area. Fig.18 This is the plane distribution diagram of the minimum horizontal principal stress of the main sand body of the Qigu Formation in the Yong3 well area.

[0138] Step 4: Based on the analysis of the tectonic stress field, calculate the fracturing index that characterizes the fracturing properties of the tight reservoir, and establish the evaluation criteria for the fracturing adaptation zone of the tight reservoir according to the well point rock physics analysis. Fig.19 This is the well section of the Qigu Formation fracturing index in the Yong3 well area; Fig. 20 This is the plane distribution diagram of the fracturing index of the main sand body of Qigu Formation in Yong3 well area. Fig.11 The fracturing index histogram of different lithologies of the Qigu Formation in the Yong1-3 well area is shown in Figure 2. Fig.11 It can be seen that the fracturing index value of most sandstones is low (FI<0.165), and the corresponding difference between the maximum horizontal principal stress and the minimum horizontal principal stress is small. The fracturing fluid can easily enter the microcracks from multiple directions and can produce numerous shear cracks and tensile cracks, forming a relatively developed seepage network, so the corresponding fracturing effect is better; the fracturing index value of mudstone is high (FI>0.165), and the corresponding difference between the maximum horizontal principal stress and the minimum horizontal principal stress is large, and the corresponding fracturing effect is poor.

[0139] Beneficial effect: The present invention provides a method for predicting the fracturing index of tight reservoirs based on tectonic geostress field analysis. The fracturing index of tight reservoirs based on tectonic geostress field analysis is used to effectively evaluate the fracturing properties of tight reservoirs, thereby improving the reliability of prediction of crack development in tight reservoirs and providing a basis for the development of tight reservoirs.

[0140] 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 predicting the fracturing index of a tight reservoir based on tectonic geostress field, characterized in that: The prediction method comprises: Step 101: Obtain a three-dimensional data volume of elastic parameters; Step 102: Establish the relationship between the strain component and the displacement component at any point in the elastic body based on the elastic thin plate bending theory; Step 103: Based on the analysis of the tectonic geostress field, the three-dimensional spatial distribution prediction of the principal stress and the principal stress direction is realized; Step 104: A fracturing index prediction model is established based on the three-dimensional spatial distribution prediction, a quantitative evaluation parameter is formed for predicting sweet spots in deep tight reservoirs, and a clear evaluation standard for tight reservoir fracturing adaptability zones is established.

2. The method for predicting the fracturing index of a tight reservoir based on tectonic stress field according to claim 1, characterized in that: The elastic parameters specifically include: longitudinal and transverse wave velocity, and density.

3. The method for predicting the fracturing index of a tight reservoir based on tectonic stress field according to claim 1, characterized in that: The step 101: obtaining a three-dimensional data volume of elastic parameters specifically includes: performing pre-stack seismic elastic parameter inversion to obtain a three-dimensional data volume of elastic parameters.

4. The method for predicting the fracturing index of a tight reservoir based on tectonic stress field according to claim 1, characterized in that: The step 102: establishing the relationship between the strain component and the displacement component at any point in the elastic body based on the elastic thin plate bending theory, wherein the elastic thin plate is a plate-like component surrounded by two parallel planes whose thickness is much smaller than the dimensions in other directions.

5. The method for predicting the fracturing index of a tight reservoir based on tectonic geostress field according to claim 1, characterized in that: The step 102 of establishing the relationship between the strain component and the displacement component at any point in the elastic body based on the elastic thin plate bending theory specifically includes: Assume the midplane of the thin plate as the coordinate plane, z = 0; The coordinate origin O is a point in the midplane, and the x and y axes are in the midplane; The displacement generated in the positive direction of the x-axis is u, the displacement generated in the positive direction of the y-axis is v, the displacement generated in the positive direction of the z-axis is the disturbance w(x,y), and the time thickness of the thin plate in the z-axis direction is z (in seconds); The elastic properties of thin plate media are expressed by the following elastic mechanics equations; Geometric equation: It describes the relationship between the strain component and the displacement component at any point in the elastic body. Its expression is: u z =w(3) Where: x , ε y , ε z are the normal strain components of the x, y, and z sections, respectively, xy is the shear strain component of the xy section; From the thin plate theory, we know that: And there are: Define the curvature deformation components: Where: K x , K y are the curvature deformation components in the x and y directions, K xy is the curvature deformation component in the xy direction; For a thin plate with thickness z, the strain components are written as: e x =-zK x ,he y =-zK y ,c xy =-2zK xy (7)。 6. The method for predicting the fracturing index of a tight reservoir based on tectonic stress field according to claim 1, characterized in that: The step 103: realizing the three-dimensional spatial distribution prediction of the principal stress and the principal stress direction based on the tectonic geostress field analysis specifically includes: The physical constitutive relationship equation describes the relationship between the stress component and the strain component of the elastic body, and its expression is as follows: Its inverse relationship is: s x =2with x +λθ,τ xy =μγ xy (11) s y =2with y +λθ,τ yz =μγ yz (12) s z =2with z +λθ,τ xz =μγ xz (13) θ=e x +e y +e z (14) Where: λ is the Lame constant, μ is the shear modulus, ν is the Poisson's ratio, θ is the volume strain, E is the Young's modulus, σ is the normal stress component, and τ is the shear stress component; Substituting equations (8, 9, 10) into the equations, we obtain: So we have: From equations (16, 17, and 18), we can see that when the ground surface is convex upward, the curvature is greater than zero, corresponding to the convex ground surface being subjected to tensile stress, and the tensile stress is positive; The tensile stress is uniformly negative and the compressive stress is uniformly positive, so if the curvature is less than zero, it means that the formation is convex; After calculating the stress along the coordinates of the point, the maximum horizontal principal stress σmax, the minimum horizontal principal stress σmin and their corresponding main directions can be obtained: If the angle between σmax and the x-axis is α, and the angle between σmin and the x-axis is β, then 7. The method for predicting the fracturing index of a tight reservoir based on tectonic stress field according to claim 1, characterized in that: The step 104: establishing a fracturing index prediction model according to the three-dimensional spatial distribution prediction specifically includes: Obtain the disturbance equation of the ground plane or the curvature of the ground at a point on the surface and estimate the corresponding stress field; Calculate the fracturing index that characterizes the fracturing properties of tight reservoirs, effectively evaluate the fracturing properties of tight reservoirs, and establish evaluation standards for the fracturing adaptation zone of tight reservoirs.

8. The method for predicting the fracturing index of a tight reservoir based on tectonic geostress field according to claim 7, characterized in that: The calculation method of the formation curvature includes: Fitting of formation trend surface: find out the stress field on the formation surface and calculate the curvature component of the formation surface; The calculation method adopts the trend surface fitting method to fit the trend function of the ground surface to obtain the result; Assume that the undetermined coefficient function of the trend surface is: w(x,y)=a0+a1x+a2y+a3x 2 +a4xy+a5y 2 (22) The least squares equation is established based on the coordinate values ​​(x, y, z) of the scattered points on the plane. For a scattered point: ε i =z i -w i (x i ,y i )(23) When a trend surface is fitted by n scattered points, a fitting equation system is obtained, where the summation sign represents the summation of points 1, 2, ..., n; solving this linear equation system, the trend surface function is obtained; The curvature calculation formula of the trend surface; 9. The method for predicting the fracturing index of a tight reservoir based on tectonic stress field according to claim 7, characterized in that: The calculation method for constructing the stress field includes: Curvature parameters: Solve the equations to obtain the fitting surface coefficients a3, a4, a5, and use equation (25) to obtain the curvature at the corresponding point; Strain parameter: The strain value is obtained by formula (7); Stress parameters: The corresponding stresses, principal stresses and principal stress directions are calculated by equations (16), (17), (18), (19), (20) and (21).

10. The method for predicting the tight reservoir fracturing index based on tectonic geostress field according to claim 7, characterized in that: The method for calculating the fracturing index characterizing the fracturing properties of a tight reservoir specifically includes: The difference between the maximum horizontal principal stress and the minimum horizontal principal stress is used as a fracturing index FI: FI=(σ max -s min ) / max|σ max -s min | Among them, FI is the fracturing index, σmax is the maximum horizontal principal stress, and σmin is the minimum horizontal principal stress.

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