A method for crack detection by elliptic fitting of azimuth amplitude in directional calculation

Abstract

This invention discloses a trace-based azimuth amplitude ellipse fitting method for fracture detection, belonging to the field of oil and gas exploration technology. It solves the technical problems of high computational load and low computational efficiency in existing pre-stack seismic fracture prediction methods. Based on HTI medium theory, this invention re-derives the ellipse formula and establishes an equation for ellipse fitting per trace. The singular value decomposition (SVD) algorithm is used for rapid solution, efficiently obtaining high-precision fracture development intensity and azimuth data, thus solving the problems of high computational load and low computational efficiency in conventional pre-stack seismic fracture prediction methods. The computational speed of this invention is 60 times that of existing pre-stack seismic azimuth amplitude ellipse fitting methods, significantly reducing computation time and saving computational costs.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas exploration technology, specifically relating to a method for crack detection by elliptical fitting of azimuth amplitude in trace calculation. Background Technology

[0002] Currently, oil and gas exploration and development in major oilfields both domestically and internationally has gradually shifted towards the vast potential of deep unconventional oil and gas reservoirs. However, deep reservoirs are mostly low-porosity, low-permeability tight and shale oil reservoirs with poor matrix conditions. Natural fractures can provide storage and permeability space for tight oil and shale oil enrichment, making them a crucial factor affecting the productivity of low-porosity, low-permeability reservoirs. However, fracture orientation is closely related to fracture effectiveness. Different angles between the fracture orientation and the direction of the maximum horizontal principal stress in the region result in significant differences in fracture effectiveness and conductivity. In other words, only when the fracture orientation and the direction of the maximum horizontal principal stress in the region are at a specific angle can they become advantageous storage and permeability spaces for oil and gas. Therefore, the identification and evaluation of fractures in deep unconventional oil and gas reservoirs must consider both the degree of fracture development and the fracture orientation.

[0003] Seismic fracture prediction is one of the important geophysical technologies in oil exploration and development. It is a key means of fracture identification and evaluation. The prediction scale can range from regional large faults to micro fractures. Based on the data used, prediction methods can be divided into post-stack seismic fracture prediction methods and pre-stack seismic fracture prediction methods.

[0004] Conventional post-stack seismic fracture prediction methods primarily rely on fracture geometry for detection, only able to identify large-scale fractures with significant displacement, but not small-scale fractures without displacement. However, because small-scale fractures tend to cluster, they cause stratigraphic anisotropy (HTI), which results in different response characteristics across different azimuths in wide-azimuth seismic data. Therefore, the anisotropy characteristics of pre-stack seismic data at different azimuths can be used to identify small-scale fractures, simultaneously providing important information such as fracture direction and intensity. However, the complex data processing steps and massive computational load limit the application efficiency and development of pre-stack fracture prediction methods, necessitating a greater need for faster and more efficient fracture prediction methods and technologies. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a crack detection method by elliptic fitting of azimuth amplitude in trace operation, which solves the technical problems of large computational load and low computational efficiency of existing front-stack seismic crack prediction methods.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention discloses a method for crack detection using elliptic fitting of azimuth amplitude in trace operation, comprising the following steps:

[0008] S1: After processing the wide azimuth seismic data collected in the target work area, the root mean square velocity is extracted for pre-stack migration imaging. Then, the wide azimuth vector offset range gather data is extracted and stacked by azimuth to obtain several partially stacked seismic data volumes by azimuth.

[0009] S2: Derive the azimuth amplitude ellipse fitting equation based on the reflection coefficient relationship equation of HTI medium;

[0010] S3: Based on the azimuth amplitude ellipse fitting equation and based on several azimuth partial superimposed seismic data volumes, the ellipse fitting equation is established according to the trace, and the singular value decomposition is used on the ellipse fitting equation to obtain the crack azimuth and crack intensity data volumes.

[0011] S4: Use the logging interpretation results of the target work area to verify the correctness of the obtained fracture orientation and fracture intensity data, calibrate and correct the fracture orientation, and use the obtained fracture orientation and fracture intensity data to provide a basis for well location deployment and optimization.

[0012] Furthermore, the processing of the acquired wide-azimuth seismic data includes static correction, noise suppression, energy compensation, and deconvolution processing.

[0013] Furthermore, the number of azimuth-divided superimposed seismic data volumes is six; the starting trace positions of the six azimuth-divided superimposed seismic data volumes are the same.

[0014] Furthermore, the equation relating the reflection coefficient of the HTI medium is: HTI medium seismic P-wave reflection coefficient amplitude R p The expression for the amplitude R of the seismic P-wave reflection coefficient in the HTI medium. p The expression is as follows:

[0015]

[0016] Where i is the incident angle of the incident wave, φ is the angle between the survey line direction and the axis of symmetry of the HTI medium, and I p V is the longitudinal wave impedance, μ is the shear modulus, and V is the longitudinal wave impedance. p V is the longitudinal wave velocity. s Let ΔI be the transverse wave velocity. p Δμ is the difference in longitudinal wave impedance between the upper and lower interfaces, ΔV is the difference in shear modulus between the upper and lower interfaces, and ΔV is the difference in longitudinal wave impedance between the upper and lower interfaces. p Let Δγ and Δε be the longitudinal wave velocity differences between the upper and lower interfaces. (v) , Δδ (v) This represents the difference in the anisotropy description parameters of the upper and lower interfaces by Thomsen.

[0017] Furthermore, in seismic exploration, when the incident wave angle is less than 30°, the amplitude R of the seismic P-wave reflection coefficient in the HTI medium is... p sin in the expression 2 itan 2 When i equals 0, the amplitude R of the seismic P-wave reflection coefficient in the HTI medium is... p The expression is adjusted to obtain the amplitude R of the seismic P-wave reflection coefficient in the HTI medium. p The expression is as follows:

[0018]

[0019] Furthermore, in S2, the steps for deriving the azimuth amplitude ellipse fitting equation based on the reflection coefficient relationship equation of the HTI medium are as follows:

[0020] Step 1: Set Let θ be the azimuth angle of the crack development, and φ be the azimuth angle of the survey line. Then, the angle φ between the survey line and the axis of symmetry of the HTI medium, and the azimuth angle of the crack development... The relationship between the survey line azimuth angle θ and the survey line azimuth angle θ is shown in the following formula:

[0021]

[0022] Step 2: Perform cosine on the relation obtained in Step 1. 2 After reducing the order of φ, we obtain the equation expressing the angle φ between the symmetry axes of the HTI medium, as shown below:

[0023]

[0024] Step 3: Substitute the equations obtained in Step 1 and Step 2 into the adjusted amplitude R of the seismic P-wave reflection coefficient in the HTI medium. p After simplification, the intermediate equation is obtained from the expression, as shown below:

[0025]

[0026] Subsequently,

[0027] The intermediate equation is then adjusted to obtain the equation of the ellipse, which is expressed as follows:

[0028]

[0029] Furthermore, the major axis of the ellipse in the ellipse equation is A0+a, and the minor axis of the ellipse equation is A0-a.

[0030] Furthermore, the ratio of the major axis to the minor axis of the ellipse is the crack development intensity F.

[0031] Furthermore, in S3, the step of establishing the ellipse fitting equation based on the azimuth amplitude ellipse fitting equation and based on several azimuth-part superimposed seismic data volumes by trace is as follows:

[0032] Step 1: After expanding the expression for the ellipse equation, the expanded expression for the ellipse equation is shown below:

[0033]

[0034] Step 2: Solve the equation of the expanded ellipse for the entire seismic trace. The expression for the solution is shown below:

[0035]

[0036] The parameters in the expression for solving the equation are set with two levels of subscripts. The first level of subscripts is a numeric subscript, representing the number of the input azimuth-based superimposed seismic data volume. The second level of subscripts is a numeric subscript with parentheses, representing the sampling point number of the seismic trace corresponding to the azimuth-based superimposed seismic data. The numeric range of the first level of subscripts is 1 to 6. The numeric range of the second level of subscripts is 1 to n, where n represents the number of sampling points of the seismic trace of the azimuth-based superimposed seismic data.

[0037] Furthermore, in S3, the step of obtaining crack parameter data by using singular value decomposition to fit the ellipse equation is as follows:

[0038] Step 1: Express the solution equation using an overdetermined system of equations. The expression for the overdetermined system of equations is as follows:

[0039] Gm = d

[0040] Where G is a 6×3 matrix, m is the crack parameter matrix to be obtained, and d is the spatial matrix of azimuth seismic data.

[0041] Step 2: By decomposing matrix G using SVD, matrix G can be represented as the product of three matrices:

[0042] G = UΛV T

[0043] Where U is the extended space of GG T The eigenvalue matrix, V, is the GG of the extended model parameter space. T Eigenvalue matrix, Λ is GG T Singular value matrix;

[0044] At the same time, the generalized inverse matrix of matrix G The expression is as follows:

[0045]

[0046] Where σ is the singular value of the matrix;

[0047] Step 3: Based on the generalized inverse matrix The formula for calculating the crack parameter matrix m is as follows:

[0048]

[0049] A0 is obtained from the formula for calculating the crack parameter matrix m. and The value;

[0050] Step 4: Based on the obtained A0, and The values ​​are used to calculate the major axis l and minor axis s of the ellipse; the formula for calculating the major axis l is shown below:

[0051]

[0052] The formula for calculating the minor axis s of the ellipse is as follows:

[0053]

[0054] Step 5: The formula for calculating the crack development strength F is as follows:

[0055]

[0056] Azimuth of crack development The calculation formula is shown below:

[0057]

[0058] Based on the formula for calculating crack development intensity F and crack development azimuth angle The calculation formula yields the crack strength and crack orientation data.

[0059] Compared with the prior art, the present invention has the following beneficial effects:

[0060] This invention discloses a trace-based azimuth amplitude ellipse fitting crack detection method. Based on HTI medium theory, and using azimuth amplitude ellipse fitting crack detection as the principle, the ellipse formula is re-derived, and an equation for ellipse fitting by trace is established. The singular value decomposition (SVD) algorithm is used for rapid solution, efficiently obtaining high-precision crack development intensity and azimuth data. This solves the problems of high computational load and low computational efficiency in conventional pre-stack seismic crack prediction methods, providing important crack parameters such as crack direction and crack intensity for fine crack identification. Model testing and actual field application results show that this invention can accurately predict small-scale cracks, with a computation speed 60 times faster than existing pre-stack seismic azimuth amplitude ellipse fitting crack prediction methods, significantly reducing computation time and saving computational costs. Attached Figure Description

[0061] Figure 1 This is a schematic diagram showing the relationship between the amplitude of a seismic P-wave and the observed azimuth angle after propagation through a medium containing high-angle natural fractures (HTI).

[0062] Figure 2 An HTI medium model containing high-angle cracks was established to verify the accuracy of the elliptical fitting crack detection method disclosed in this invention.

[0063] Where: a - P-wave velocity model; b - S-wave velocity model; c - density model; d - Thomsen parameter γ model; e - Thomsen parameter ε model; f - Thomsen parameter δ model;

[0064] Figure 3 This is a schematic diagram comparing the elliptical fitting of crack density using the method disclosed in this invention and existing methods, as well as the elliptical fitting of crack density to noisy seismic data.

[0065] Wherein: a-existing method for elliptical fitting of crack density; b-existing method for elliptical fitting of crack density of noisy seismic data; c-the method disclosed in this invention for elliptical fitting of crack density; d-the method disclosed in this invention for elliptical fitting of crack density of noisy seismic data.

[0066] Figure 4 A schematic diagram comparing the crack prediction results of existing methods and the method disclosed in this invention in the target layer of the study area;

[0067] Wherein: a- fracture interpretation results from well logging of wells 1 and 3; b- fracture prediction plan view using existing methods; c- fracture prediction plan view using the method disclosed in this invention;

[0068] Figure 5 This is a schematic diagram illustrating the crack prediction result detection of the method disclosed in this invention;

[0069] Wherein: a- Local plan view of fracture prediction in the target layer of the study area; b- Fracture FMI interpretation results in the horizontal section of Well 2. Detailed Implementation

[0070] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0071] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0072] The present invention will now be described in further detail with reference to the accompanying drawings:

[0073] The embodiments will demonstrate the implementation effect of the crack prediction method of the present invention in the model and in the actual seismic field. The specific steps are as follows:

[0074] Step 1: Obtain 6 high-quality azimuth-based partial stacked seismic data volumes. The specific method is as follows:

[0075] Based on wide-azimuth seismic data acquired in the field, after processing such as static correction, noise suppression, energy compensation, and deconvolution, the root mean square velocity is extracted for pre-stack migration imaging. OVT domain gather data is extracted, and after residual time difference correction, azimuth-based stacking is performed to obtain six high-quality azimuth-based partially stacked seismic data volumes. The above processing procedure is complex and is generally operated by seismic professionals. Seismic interpreters and other non-processing professionals can request the six high-quality azimuth-based partially stacked seismic data volumes from the processing personnel when implementing this invention.

[0076] Step 2: Derive the fitting equation for the azimuth amplitude ellipse, the specific method is as follows:

[0077] Rüger, combining Thomsen's anisotropic descriptive parameters γ, ε, and δ, proposed an equation relating the reflection coefficient of (anisotropic) HTI media, laying the theoretical foundation for detecting cracks based on the relationship between P-wave amplitude and azimuth. Rüger's proposed equation for the reflection coefficient amplitude R of seismic P-waves in HTI media... p The expression is:

[0078]

[0079] Where i is the incident angle of the incident wave, φ is the angle between the survey line direction and the axis of symmetry of the HTI medium, and I p V is the longitudinal wave impedance, μ is the shear modulus, and V is the longitudinal wave impedance. p V is the longitudinal wave velocity. s Let ΔI be the transverse wave velocity. p Δμ is the difference in longitudinal wave impedance between the upper and lower interfaces, ΔV is the difference in shear modulus between the upper and lower interfaces, and ΔV is the difference in longitudinal wave impedance between the upper and lower interfaces. p The difference in longitudinal wave velocity between the upper and lower interfaces, ΔV s Δγ, Δε(V), and Δδ(V) represent the difference in transverse wave velocity between the upper and lower interfaces, while Δγ, Δε(V), and Δδ(V) represent the difference in Thomsen anisotropy description parameters between the upper and lower interfaces.

[0080] In seismic exploration, the incident angle i of the incident wave is generally less than 30°, and the sin in the third term of equation (1-1) 2 itan 2 i is approximately equal to 0. In this case, the third term in equation (1-1) can be ignored, and the following approximate relationship can be obtained:

[0081]

[0082] set up Let θ be the azimuth angle of the crack development, and φ be the azimuth angle of the survey line. Then, the angle φ between the survey line and the axis of symmetry of the HTI medium, and the azimuth angle of the crack development... The relationship between the survey line azimuth angle θ and the survey line azimuth angle θ is shown in the following formula:

[0083]

[0084] cos 2 φ is obtained by reducing the order:

[0085]

[0086] Substituting equations (1-3) and (1-4) into equation (1-2) and rearranging, we get:

[0087]

[0088] make

[0089]

[0090] Where i and θ are known quantities, equation (1-5) can be rewritten as:

[0091]

[0092] Equation (1-8) is the equation of an ellipse, with the major axis being A0+a and the minor axis being A0-a. The ratio of the major to the minor axis represents the crack strength, such as... Figure 1 As shown, the seismic reflected wave travels along the crack direction. During propagation, the amplitude is at its maximum, A0+a; while the seismic reflected wave is perpendicular to the crack direction. During propagation, the amplitude reaches its minimum value, which is A0-a.

[0093] like Figure 1 As shown, the seismic reflected wave travels along the crack direction. During propagation, the amplitude is at its maximum, A0+a; while the seismic reflected wave is perpendicular to the crack direction. During propagation, the amplitude reaches its minimum value, which is A0-a.

[0094] Step 3: Establish ellipse fitting equations for each crack and use singular value decomposition (SVD) to obtain crack orientation and crack strength data volumes. The specific method is as follows:

[0095] Expanding equation (1-8):

[0096]

[0097] In equation (1-9), the known quantity is θ, and the unknown quantity is A0. and Based on equation (1-9), a solution can be established for the entire seismic trace in one step, and the solution equation is as follows:

[0098]

[0099] Equation (1-10) involves multiple variables. To effectively distinguish them, a two-level subscript representation is set. The first subscript is a normal numeric subscript, representing the number of the input azimuth-based superimposed seismic data volume. The second subscript is a numeric subscript with parentheses, representing the sampling point number of the seismic trace corresponding to the azimuth-based superimposed seismic data. The input of this invention consists of 6 azimuth-based superimposed seismic data volumes. Therefore, the value range of the first subscript is 1 to 6, and the value range of the second subscript is 1 to n, where n represents the number of sampling points of the seismic trace of the azimuth-based superimposed seismic data. This invention requires that the starting trace positions of the 6 input azimuth-based superimposed seismic data volumes be the same; otherwise, the calculation results will have a large error.

[0100] In theory, by observing seismic data from only three different directions, the three parameters (A0, a, and ...) of the elliptical model can be determined. However, since actual observation data is always affected by various interferences, using only the amplitudes of the superimposed seismic data volumes from three azimuths for elliptic fitting will inevitably result in significant errors. Therefore, seismic data from six azimuths are used for amplitude elliptic fitting. In this case, equation (1-10) is an overdetermined system of equations, which can be expressed as:

[0101] Gm=d (1-11)

[0102] Where G is a 6×3 matrix; m is the fracture parameter matrix to be obtained, which is a 3×n matrix; d is the azimuth seismic data spatial matrix, which is a 6×n matrix; G can be expressed as the product of three matrices through SVD decomposition:

[0103] G = UΛV T (1.12)

[0104] Where U is the extended space of GG T The eigenvalue matrix, V, is the GG of the extended model parameter space. T Eigenvalue matrix, Λ is GG T The singular value matrix Λ is such that only its diagonal elements are non-zero and arranged in descending diagonal order. Therefore, the generalized inverse matrix G can be defined as:

[0105]

[0106] Where σ is the singular value of the matrix. This yields the generalized inverse matrix. Then, the formula for calculating m can be obtained as follows:

[0107]

[0108] Based on the obtained m, i.e. A0, and Then the crack strength and crack orientation can be calculated. The formula for calculating the major axis l of the ellipse is:

[0109]

[0110] The formula for calculating the minor axis s of an ellipse is:

[0111]

[0112] The crack development intensity F can be expressed as:

[0113]

[0114] The corresponding crack azimuth is:

[0115]

[0116] Based on equations (1-17) and (1-18), the crack strength and crack orientation data can be calculated.

[0117] Step 4: Use well logging results from the target work area to interpret fractures and verify the accuracy of the seismic prediction of fracture intensity. Mark and correct fracture orientation, and use the prediction results to provide a basis for well location deployment and optimization.

[0118] Figure 2 To verify the accuracy of crack detection using elliptical fitting, an HTI medium model containing high-angle cracks was established. Below the longitudinal axis of the original horizontal layered model, an anisotropic layer containing a large number of high-angle cracks was set. From the calculated model, it can be found that isotropic elastic parameters cannot effectively reflect anisotropy, while Thomsen's anisotropic parameters are more sensitive to formation anisotropy and can accurately reflect the anisotropic characteristics of formation.

[0119] To verify the accuracy and efficiency of the method disclosed in this invention, the existing pre-stack seismic ellipse fitting method was used to predict cracks in the model. Figure 3 A comparison of the crack detection performance of existing methods and the method disclosed in this invention reveals that existing methods have some predictive ability for cracks, but the prediction error is relatively large, and the error increases further after adding noise, indicating that the calculation method is unstable. This method can accurately detect crack development segments, has high crack prediction accuracy, and the prediction result has no significant error after adding noise, indicating that the algorithm of this method is stable and accurate. At the same time, this method only takes 2 hours to calculate 2Gb of data, while the existing method takes 7 days, indicating that the calculation efficiency of this method is significantly improved compared with the existing method.

[0120] This invention uses seismic data superimposed from six azimuth sections, eliminating complex data processing and making it applicable to a wider range of targets. Figure 4 (a) is a diagram showing the integrated interpretation results of well logging of well 1 and well 3 in the study area. Comparison of the same target layer reveals that the fractures in well 1 are more developed than those in well 3. Figure 4 (b) and (c) show the results of predicting fractures in the target layer of the study area using existing pre-stack fracture prediction technology and the present invention, respectively. It is not difficult to find that the existing pre-stack fracture prediction technology predicts that the fracture intensity of well 3 is similar to that of well 1, which is inconsistent with the actual situation; while the prediction results of the present invention show that the fracture intensity of well 1 is significantly greater than that of well 3, which is consistent with the well logging interpretation results.

[0121] Figure 5 This is a schematic diagram illustrating the crack prediction result detection of the method disclosed in this invention, wherein... Figure 5 (a) is a local plan view of fracture prediction in the study area using the method disclosed in this invention. Well 2 is a horizontal well in the study area. Figure 5 (b) shows the comprehensive interpretation results of the horizontal section logging of the well. The logging interpretation shows that the fractures in the horizontal section are concentrated in three areas. The development of the fractures is compared with the fracture prediction results of the present invention. The two fracture development intensity are in good agreement and the fracture azimuth is consistent, which confirms the accuracy of the method disclosed in the present invention in predicting fracture intensity and azimuth.

[0122] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for crack detection using elliptic fitting of azimuth amplitude in linear computation, characterized in that, Includes the following steps: S1: After processing the wide azimuth seismic data collected in the target work area, the root mean square velocity is extracted for pre-stack migration imaging. Then, the wide azimuth vector offset range gather data is extracted and stacked by azimuth to obtain several partially stacked seismic data volumes by azimuth. S2: Derive the azimuth amplitude ellipse fitting equation based on the reflection coefficient relationship equation of HTI medium; S3: Based on the azimuth amplitude ellipse fitting equation and based on several azimuth partial superimposed seismic data volumes, the ellipse fitting equation is established by trace, and the singular value decomposition is used on the ellipse fitting equation to obtain the crack azimuth and crack intensity data volumes. S4: Use the well logging interpretation results of the target work area to verify the correctness of the obtained fracture orientation and fracture intensity data, calibrate and correct the fracture orientation, and use the obtained fracture orientation and fracture intensity data to provide a basis for well location deployment and optimization. In S2, the equation relating the reflection coefficients of the HTI medium is: [Equation for the amplitude of the seismic P-wave reflection coefficient in the HTI medium]. The expression for the amplitude of the seismic P-wave reflection coefficient in the HTI medium. The expression is as follows: ； in, Let be the angle of incidence of the incident wave. The angle between the survey line direction and the axis of symmetry of the HTI medium. For longitudinal wave impedance, Shear modulus For the longitudinal wave velocity, For transverse wave velocity, This represents the difference in longitudinal wave impedance between the upper and lower interfaces. This represents the difference in shear modulus between the upper and lower interfaces. This represents the difference in longitudinal wave velocity between the upper and lower interfaces. , , The difference between the Thomsen anisotropy description parameters of the upper and lower interfaces; In seismic exploration, when the incident wave angle is less than 30°, the amplitude of the P-wave reflection coefficient in the HTI medium is... In the expression The amplitude of the P-wave reflection coefficient for seismic events in the HTI medium is equal to 0. The expression is adjusted to obtain the amplitude of the seismic P-wave reflection coefficient in the HTI medium. The expression is as follows: 。 2. The method for crack detection by elliptic fitting of azimuth amplitude according to claim 1, characterized in that, In S1, the processing of the acquired wide-azimuth seismic data includes static correction, noise suppression, energy compensation, and deconvolution processing.

3. The method for crack detection by elliptic fitting of azimuth amplitude according to claim 1, characterized in that, In S1, the number of azimuth-divided superimposed seismic data volumes is six; the starting trace positions of the six azimuth-divided superimposed seismic data volumes are the same.

4. The method for crack detection by elliptic fitting of azimuth amplitude according to claim 1, characterized in that, In S2, the steps to derive the azimuth amplitude ellipse fitting equation based on the reflection coefficient relationship equation of the HTI medium are as follows: Step 1: Set The azimuth angle for crack development. Let be the azimuth angle of the survey line, then the angle between the survey line and the axis of symmetry of the HTI medium. azimuth of crack development and survey line azimuth The relationship between the three is shown in the following formula: ； Step 2: Perform the following steps on the relational expression obtained in Step 1: After reducing the number of operations, the included angle about the axis of symmetry of the HTI medium is obtained. The equation is as follows: ； Step 3: Substitute the equations obtained in Step 1 and Step 2 into the adjusted amplitude of the seismic P-wave reflection coefficient in the HTI medium. After simplification, the intermediate equation is obtained from the expression, as shown below: ； Subsequently, ; ; The intermediate equation is then adjusted to obtain the equation of the ellipse, which is expressed as follows: 。 5. The method for crack detection by elliptic fitting of azimuth amplitude according to claim 4, characterized in that, The major axis of the ellipse in the equation of the ellipse is... The minor axis of the ellipse is given by the equation of the ellipse. .

6. The method for crack detection by elliptic fitting of azimuth amplitude according to claim 5, characterized in that, The ratio of the major axis to the minor axis of the ellipse is the crack development intensity. .

7. The method for crack detection by elliptic fitting of azimuth amplitude according to claim 4, characterized in that, In S3, the step of establishing the ellipse fitting equation based on the azimuth amplitude ellipse fitting equation and based on several azimuth-part superimposed seismic data volumes by trace is as follows: Step 1: After expanding the expression for the ellipse equation, the expanded expression for the ellipse equation is shown below: ； Step 2: Solve the equation of the expanded ellipse for the entire seismic trace. The expression for the solution is shown below: ； The parameters in the expression for solving the equation are set with two levels of subscripts. The first level of subscripts is a numeric subscript, representing the number of the input azimuth-divided superimposed seismic data volume. The second level of subscripts is a numeric subscript with parentheses, representing the sampling point number of the seismic trace corresponding to the azimuth-divided superimposed seismic data. The numeric range of the first level of subscripts is 1~6; the numeric range of the second level of subscripts is 1~ ,in This indicates the number of sampling points in the seismic traces of the azimuth-based superimposed seismic data.

8. The method for detecting cracks by elliptic fitting of azimuth amplitude according to claim 7, characterized in that, In S3, the step of obtaining crack parameter data by using singular value decomposition to fit the equation of the ellipse is as follows: Step 1: Express the solution equation using an overdetermined system of equations. The expression for the overdetermined system of equations is as follows: in, It is a 6×3 matrix. The required crack parameter matrix is... This is the spatial matrix of azimuth seismic data; Step 2: Decompose the matrix using SVD The matrix can be Represented as the product of three matrices: in, It expands the space. eigenvalue matrix, It is an extension of the model parameter space. eigenvalue matrix, yes Singular value matrix; at the same time, matrix generalized inverse matrix The expression is as follows: in, These are the singular values ​​of the matrix; Step 3: Based on the generalized inverse matrix Obtain the crack parameter matrix The calculation formula for the crack parameter matrix The calculation formula is shown below: From the crack parameter matrix The calculation formula is obtained , and The value; Step 4: Based on the obtained , and Calculate the value of the major axis of the ellipse and the minor axis of the ellipse The major axis of the ellipse The calculation formula is shown below: ； The minor axis of the ellipse The calculation formula is shown below: ； Step 5: Crack Development Strength The calculation formula is shown below: ； Azimuth of crack development The calculation formula is shown below: ； Based on crack development intensity Calculation formula and crack development azimuth The calculation formula yields the crack strength and crack orientation data.

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