A method and apparatus for obtaining full-depth VTI anisotropy.

Abstract

This invention discloses a method and apparatus for obtaining full-depth VTI anisotropic bodies, specifically including: acquiring the first arrival data recorded by the bottom-hole geophones of two microlobe logging systems in the local area, establishing a single-well microlobe logging isotropic velocity model, and obtaining near-surface anisotropic δ and ε values ​​through ray tracing, travel-time forward modeling, and inversion iterations; based on the surface seismic first arrival data and the single-well microlobe logging isotropic velocity model, tomographically retrieving the surface seismic tomographic velocity field before and after microlobe logging constraints and calculating the surface velocity difference, thereby obtaining the near-surface VTI anisotropic medium δ field; based on the correspondence between the near-surface anisotropic δ values ​​and the near-surface anisotropic ε values, using the near-surface VTI anisotropic medium δ field to obtain the near-surface VTI anisotropic medium ε field; finally obtaining the near-surface VTI anisotropic body. The velocity field, combined with the anisotropic field, improves the accuracy of velocity modeling, which is beneficial for improving imaging accuracy and imaging effects.

Description

Technical Field

[0001] This invention relates to the velocity modeling, velocity field correction, and migration imaging processing components of seismic data processing methods, and particularly to a method and apparatus for obtaining full-depth VTI anisotropic bodies. Background Technology

[0002] Vertical-to-lateral isotropy (VTI) is prevalent in most sedimentary rocks; therefore, accurate estimation of VTI anisotropy parameters (ε and δ) is a key factor in the anisotropic migration process of seismic data. The Walkaway VSP observation system provides a uniquely valuable method for estimating formation anisotropy parameters. Accurate vertical formation velocities can be obtained from the first arrival of direct waves recorded by zero-source-distance VSP records, while the first arrival of VSP records with varying offset distances reflects the influence of medium anisotropy on incident waves at different angles. Horne and Leaney proposed in 2000 to invert anisotropy parameters in laterally isotropic media using polarization and slowness components. Bakulin and Grechka proposed in 2001 to estimate lateral anisotropy using multi-directional Walkaway VSP data. Blias proposed in 2010 to estimate anisotropy parameters above the geophone using Walkaway and 3D VSP data. In 2015, M. Lou used the process function equation to forward model the first arrival travel time of direct waves and estimated the anisotropic parameters in the lateral non-uniform velocity model using the first arrival times recorded by Walkaway VSP. However, this method lacks integration with well-ground combined acquisition data and is hampered by a lack of realistic near-surface anisotropic velocity modeling methods. This results in limited accuracy in anisotropic parameter calculation and fails to reflect the true propagation patterns of shallow seismic waves. Furthermore, because it only focuses on local anisotropic parameters at the target layer depth, limitations in the observation system and assumptions during anisotropic parameter calculation lead to poor matching between the velocity model and anisotropic parameters. This results in limited coverage of the entire well section in the mid-to-deep layers, making it impossible to complete the full-depth VTI anisotropic volume calculation, thus reducing the accuracy of subsequent imaging. Summary of the Invention

[0003] The purpose of this invention is to provide a method and apparatus for obtaining full-depth VTI anisotropic bodies. By utilizing dual-well micrologging records, the near-surface anisotropic δ and ε values ​​are obtained through forward and inverse iterative methods. Combined with the near-surface tomographic velocity field of ground seismic data before and after micrologging constraints, a near-surface anisotropic field is generated, reflecting the true propagation law of shallow seismic waves and improving the accuracy of velocity modeling. This makes the near-surface velocity and anisotropy more well matched, which is beneficial to improving imaging accuracy and imaging effect.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] On the one hand, this application provides a method for obtaining full-depth VTI anisotropy, including the process of obtaining near-surface VTI anisotropy, the specific steps of which include:

[0006] S1. Obtain the initial arrival of several excitation points at different depths recorded by the bottom hole geophones of the dual-well micrologging in this area, and establish an isotropic velocity model of single-well micrologging. Then, obtain the near-surface anisotropic δ and ε values ​​through ray tracing, travel-time forward modeling, and inversion iterations.

[0007] S2. Obtain first arrival data of surface earthquakes in this area. Perform tomographic inversion based on the first arrival data to obtain a near-surface VTI anisotropic medium velocity model. Use the single-well micrologging isotropic velocity model to perform constrained tomographic inversion on the first arrival data of surface earthquakes to obtain a near-surface VTI isotropic medium micrologging constrained velocity model. Calculate the surface velocity difference based on the near-surface VTI anisotropic medium velocity model and the near-surface VTI isotropic medium micrologging constrained velocity model. Calculate the near-surface VTI anisotropic medium δ field based on the surface velocity difference.

[0008] S3. Based on the correspondence between the near-surface anisotropy δ value and the near-surface anisotropy ε value, the near-surface VTI anisotropy medium ε field is obtained using the near-surface VTI anisotropy medium δ field;

[0009] S4. Obtain a near-surface VTI anisotropic body from the near-surface VTI anisotropic medium δ field and the near-surface VTI anisotropic medium ε field.

[0010] In existing technologies, the determination of near-surface anisotropy parameters does not incorporate combined well-to-surface data, lacking a realistic near-surface anisotropic velocity modeling method. This results in limited accuracy in anisotropic parameter determination, failing to reflect the true propagation patterns of shallow seismic waves and thus affecting imaging accuracy and quality. In this application, the combined well-to-surface data includes bottom-hole data from dual-well micrologging and first-arrival data from surface seismic data. Therefore, this application utilizes dual-well micrologging records and employs forward and inverse iterative methods to determine near-surface anisotropy values ​​δ and ε. Combined with near-surface tomographic velocity fields from surface seismic data before and after micrologging constraints, a near-surface anisotropic field is generated. This ensures the velocity field aligns with the anisotropic field; velocity and anisotropy are distinct yet mutually compatible. This near-surface anisotropic velocity modeling method better reflects the true propagation patterns of shallow seismic waves, thereby improving imaging accuracy and quality.

[0011] Furthermore, the specific process of S1 is as follows:

[0012] A fast ray tracing method for horizontal layered media between two points was used to calculate the direct arrival travel time of the first wave from the excitation point at different depths to the detector point at the bottom of the adjacent well.

[0013] Based on the epicentral distance equation and the isotropic velocity model of single-well micrologging, the isotropic initial ray parameters are calculated, and the initial ray angle is determined based on the isotropic initial ray parameters.

[0014] Based on the initial ray angle, the anisotropic velocity of each layer is updated using the weak anisotropic approximation formula;

[0015] The ray path is calculated iteratively based on the epicentral distance equation, and the initial anisotropic parameters δ and ε are obtained based on the relationship between the first arrival travel time of the direct wave and the incident angle and anisotropic velocity of each layer.

[0016] Based on the first arrival travel time of the direct wave, a forward modeling of the travel time is performed, and the actual first arrival curve is fitted. The initial anisotropy parameters δ and ε are then corrected using the actual first arrival curve. The corrected anisotropy parameters δ and ε are then obtained.

[0017] Based on the corrected anisotropic δ and ε parameters, the anisotropic velocities of each layer are updated, and then the inversion iteration is performed until the first arrival travel time error of the direct wave is minimized, thus obtaining the near-surface anisotropic δ and ε values.

[0018] Furthermore, the steps between steps S2 and S3 include:

[0019] Determine whether the coverage rate of dual-well micro-logging in this area meets the preset standard;

[0020] If the preset standard is met, proceed to step S3;

[0021] If the preset standard is not met, the near-surface anisotropic δ value obtained by the micro-logging of the two wells in this area is used to perform quality control and smoothing correction on the near-surface VTI anisotropic medium δ field obtained in step S2, so as to obtain the corrected near-surface VTI anisotropic medium δ field.

[0022] Based on the correspondence between the near-surface anisotropy δ value and the near-surface anisotropy ε value, the near-surface VTI anisotropy medium ε field is obtained using the corrected near-surface VTI anisotropy medium δ field.

[0023] Furthermore, it also includes the process of obtaining the anisotropic body of the mid-to-deep VTI, the specific steps of which include:

[0024] Obtain information on the well-to-surface combined mining scheme in this area; based on the information on the well-to-surface combined mining scheme in this area, determine the δ and ε values ​​of the anisotropic medium in the mid-deep VTI layer;

[0025] By interpolating and smoothing the δ and ε values ​​of the mid-deep VTI anisotropic medium along the geological strata, the δ field and ε field of the mid-deep VTI anisotropic medium are obtained.

[0026] The anisotropic medium of medium-deep VTI is obtained by using the δ field and ε field of the medium-deep VTI.

[0027] Furthermore, it also includes the process of obtaining the full-depth VTI anisotropic volume:

[0028] Based on the near-surface VTI anisotropy and the mid-deep VTI anisotropy, the full-depth VTI anisotropy is obtained.

[0029] Furthermore, obtaining data on the well-to-ground combined mining scheme in this area includes obtaining Walkaway VSP data, which includes zero-well-source-distance VSP and variable-offset VSP data;

[0030] An isotropic velocity model was established based on the vertical velocity of the zero-well source distance VSP data.

[0031] Based on variable offset VSP data and isotropic velocity model, forward modeling calculations of travel time of anisotropic direct waves in VTI media with different offsets are performed to obtain forward modeling travel times.

[0032] The error between the forward travel time and the actual observed travel time is optimized using the boundary constraint optimization method to obtain the forward travel time with the smallest error.

[0033] Inverting the forward travel time with the smallest error yields the anisotropy parameter δ and ε values ​​layer by layer from shallow to deep.

[0034] By combining velocity modeling layer information, the anisotropic parameters δ and ε values ​​of each layer are interpolated and smoothed along the layer to form the δ field and ε field of the mid-deep VTI anisotropic medium.

[0035] Furthermore, obtaining data on the well-to-ground combined mining plan for this area includes obtaining 3D-VSP data.

[0036] Based on 3D-VSP data, the anisotropic slowness intersection curve was fitted using the method of horizontal and vertical visual slowness intersection to obtain the anisotropic parameter δ and ε values ​​layer by layer from shallow to deep.

[0037] By combining geological stratification information from joint mining data, the anisotropic parameters δ and ε values ​​of each layer are interpolated and smoothed along the layer to form the δ field and ε field of the mid-deep VTI anisotropic medium.

[0038] In addition, this application provides an apparatus for determining a full-depth VTI anisotropic body, comprising:

[0039] One or more processors;

[0040] A storage unit is used to store one or more programs that, when executed by one or more processors, enable the one or more processors to implement the above-described method for obtaining a full-depth VTI anisotropic body.

[0041] The beneficial effects of this invention are as follows:

[0042] 1. This invention utilizes dual-well micrologging records and employs forward and inverse iterative methods to obtain near-surface anisotropy values ​​δ and ε. Combined with near-surface tomographic velocity fields of ground seismic events before and after micrologging constraints, a near-surface anisotropic field is generated. The near-surface anisotropic velocity modeling method better conforms to the actual propagation law of shallow seismic waves, improves the accuracy of velocity modeling, and is beneficial for improving imaging accuracy and imaging effect.

[0043] 2. This invention also fully leverages the advantages of wide lateral coverage and high vertical accuracy of VSP in well-ground combined acquisition schemes. In the mid-to-deep layers, it eliminates multiple solutions and uncertainties by using a layer-by-layer inversion method from shallow to deep or by using apparent slowness intersection fitting. It organically combines surface seismic and VSP in obtaining anisotropy of VTI media at all depths, achieving complementary advantages. It can fully utilize the advantages of VSP velocity bridge and high-precision travel time of single-path waves, and can also reasonably and objectively drive surface seismic to improve imaging accuracy and imaging effect. Attached Figure Description

[0044] Figure 1 This is a flowchart of the method for obtaining full-depth VTI anisotropy of the present invention;

[0045] Figure 2 This is a flowchart of the method for obtaining near-surface VTI anisotropy in an embodiment of the present invention;

[0046] Figure 3 This is a schematic diagram of isotropic and anisotropic ray paths for dual-well micro-logging in an embodiment of the present invention;

[0047] Figure 4 This is an anisotropic forward travel-time diagram from the embodiment;

[0048] Figure 5 This example illustrates the iterative convergence process of the forward walk-time and the observed walk-time.

[0049] Figure 6 This is a system principle block diagram of the present invention. Detailed Implementation

[0050] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention.

[0052] At the same time, it should be understood that, for ease of description, the dimensions of the various parts shown in the accompanying drawings are not drawn according to actual scale.

[0053] Furthermore, for clarity and brevity, descriptions of well-known structures, functions, and configurations may have been omitted. Those skilled in the art will recognize that various changes and modifications can be made to the examples described herein without departing from the spirit and scope of this disclosure.

[0054] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0055] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0056] Example 1

[0057] The overall concept of this application is as follows:

[0058] To address the issue that the near-surface anisotropy parameter calculation process fails to reflect the true propagation patterns of shallow seismic waves, this embodiment utilizes the initial arrival records from the bottom-hole geophones of the dual-well micrologging system in this area. Near-surface anisotropy δ and ε values ​​are then obtained using ray tracing, travel-time forward modeling, and inversion iterative methods. Based on the progress of the dual-well micrologging in this area, the generated near-surface anisotropy δ and ε values ​​are used along the layer difference to calculate the near-surface VTI anisotropic medium δ and ε fields. By combining the near-surface tomographic velocity fields from surface seismic logging before and after micrologging constraints, a near-surface anisotropic delta field is generated. The near-surface anisotropic delta values ​​obtained from dual-well micrologging in this area are used to perform quality control and smoothing correction on the anisotropic medium delta field, resulting in a corrected near-surface VTI anisotropic medium delta field. Based on the correspondence between near-surface anisotropic delta values ​​and anisotropic ε values, the near-surface VTI anisotropic medium ε field is obtained using the near-surface VTI anisotropic medium delta field, making the shallow anisotropic velocity modeling more realistic. On the other hand, to address the problems in existing technologies where well-ground combined logging data is not integrated, the velocity model and anisotropic parameters do not match well, the coverage of the entire well section in the middle and deep layers is limited, and the full-depth VTI anisotropic body cannot be obtained, further research is needed. Therefore, in this application, the combined well-to-surface acquisition data includes bottom-hole data from dual-well micrologging, first arrival data from surface seismic data, and Walkaway VSP or 3D-VSP data from the combined well-to-surface acquisition scheme in this area. Based on the combined well-to-surface acquisition scheme in this area, the δ and ε fields of the anisotropic medium in the mid-deep VTI layer are obtained. Combined with the geological stratification or velocity modeling stratification information from the combined acquisition data, the δ and ε fields of the mid-deep VTI anisotropic medium are smoothly formed by interpolation along the layers. This is used for subsequent pre-stack depth migration, which improves the velocity accuracy. Furthermore, when obtaining the δ and ε fields of the mid-deep VTI anisotropic medium, the method of layer-by-layer inversion from shallow to deep and the fitting method that removes uncertainties improves the resolution of lateral and longitudinal velocity parameters, which is beneficial for detail characterization, improves the deep imaging effect, and meets the actual processing requirements.

[0059] This embodiment 1 provides a method for obtaining a full-depth VTI anisotropic body, such as Figure 1 As shown, including

[0060] Process 1: Determining the near-surface VTI anisotropy, such as Figure 2 As shown, the specific process includes:

[0061] S1. Obtain the initial arrival data of several excitation points at different depths recorded by the bottom-hole geophones of the dual-well micrologging system in this area. Establish a single-well isotropic velocity model using the surface velocity data from the single-well micrologging system within the same well. Calculate the near-surface anisotropic δ and ε values ​​using ray tracing, travel-time forward modeling, and inversion iterations. Figure 3As shown, the dual-well micrologging system consists of an excitation well and a receiving well. The excitation well is used to generate excitation at different depths to obtain several excitation points. The receiving well is equipped with a bottom-hole geophone. The isotropic velocity model of the single-well micrologging system is an isotropic velocity model established based on the surface velocity results of the excitation well in the near-surface formation.

[0062] Specifically, the process of S1 is as follows:

[0063] S11. Using the fast ray tracing method for horizontal layered media between two points, the travel time t of the direct arrival wave from the excitation point at different depths to the detector point at the bottom of the adjacent well is calculated.

[0064] S12. Based on the epicentral distance equation and the isotropic velocity model of single-well micrologging, calculate the isotropic initial ray parameter p, and determine the initial ray angle based on the isotropic initial ray parameter.

[0065] The given equation for epicentral distance is:

[0066]

[0067] Where p is the ray parameter, v k The isotropic velocity of wave propagation at layer k is obtained from the isotropic velocity model of single-well micrologging, h. k Let the thickness be the k-th layer. l Δ represents the total number of media layers; △ represents the epicentral distance, which is the distance from the earthquake epicenter to the ground observation point. The earthquake epicenter is the projection of the hypocenter onto the ground. In the embodiments of this application, the isotropic and anisotropic ray paths of the dual-well micrologging are as follows: Figure 3 As shown.

[0068] S13. Update the anisotropic velocity V of each layer based on the initial ray angle using the weak anisotropic approximation formula. k ;

[0069]

[0070] V k Let θ be the anisotropic velocity of the wave at the k-th layer. k Let be the incident angle of the k-th layer;

[0071] S14. Calculate the ray path iteratively based on the epicentral distance equation, and calculate the path based on the first arrival travel time t of the direct wave and the incident angle θ of each layer. k and the anisotropic velocity V of each layer k The relationship is used to obtain the initial anisotropy parameters δ and ε;

[0072]

[0073] S15. Perform forward modeling of the travel time t based on the first arrival time of the direct wave, fit the actual first arrival curve, and use the actual first arrival curve to correct the initial anisotropy parameters δ and ε; obtain the corrected anisotropy parameters δ and ε.

[0074] S16. Based on the corrected anisotropic δ and ε parameters, update the anisotropic velocities of each layer, and then iterate until the first arrival travel time error of the direct wave is minimized, to obtain the near-surface anisotropic δ and ε values.

[0075] S2. Obtain first arrival data of surface earthquakes in this area. Perform tomographic inversion based on the first arrival data to obtain a near-surface VTI anisotropic medium velocity model. Use the single-well microlog isotropic velocity model to perform constrained tomographic inversion on the first arrival data of surface earthquakes to obtain a near-surface VTI isotropic medium microlog constrained velocity model. Calculate the surface velocity difference based on the near-surface VTI anisotropic medium velocity model and the near-surface VTI isotropic medium microlog constrained velocity model. Calculate the near-surface VTI anisotropic medium δ field based on the surface velocity difference. The tomographic inversion based on the first arrival data of surface earthquakes yields the surface seismic surface tomographic velocity field before microlog constraint, while the constrained tomographic inversion based on the single-well microlog isotropic velocity model of surface earthquakes yields the surface seismic surface tomographic velocity field after microlog constraint.

[0076] Specifically,

[0077] in, v iso The isotropic velocity in the micro-logging constrained velocity model of near-surface VTI isotropic medium isotropic medium isotropic. v ani For anisotropic velocities in the near-surface VTI anisotropic medium velocity model, The δ field value represents the near-surface VTI anisotropic medium.

[0078] S3. Determine whether the coverage rate of dual-well micro-logging in this area meets the preset standard;

[0079] S31. If the preset standard is met, it indicates that a large number of dual-well micrologging operations have been carried out in this area, uniformly covering the area. In this case, the following two methods can be used to determine the ε field of the near-surface VTI anisotropic medium:

[0080] Method 1: Based on the correspondence between the near-surface anisotropy δ value and the near-surface anisotropy ε value, the near-surface VTI anisotropy medium ε field is obtained using the near-surface VTI anisotropy medium δ field in step S2;

[0081] Method 2: Utilize the near-surface anisotropic ε value from step S1 to directly interpolate along the layer anisotropically to obtain the ε field of the near-surface VTI anisotropic medium;

[0082] S32. If the preset standards are not met, fewer micro-logging operations will be conducted in this area, serving only as control points.

[0083] S321. Using the near-surface anisotropic δ value obtained from the micro-logging of the two wells in this area, the near-surface VTI anisotropic medium δ field obtained in step S2 is subjected to quality control and smoothing correction to obtain the corrected near-surface VTI anisotropic medium δ field.

[0084] S322. Based on the correspondence between the near-surface anisotropy δ value and the near-surface anisotropy ε value obtained in step S1, the near-surface VTI anisotropy medium ε field is obtained using the corrected near-surface VTI anisotropy medium δ field. Specifically, there is a correlation coefficient between the δ value and the ε value, and the ε field can be obtained using the δ field based on the correlation coefficient.

[0085] S4. Obtain a near-surface VTI anisotropic body from the near-surface VTI anisotropic medium δ field and the near-surface VTI anisotropic medium ε field.

[0086] Process 2: Determining the anisotropic volume of the mid-to-deep VTI, specifically including:

[0087] S100. Obtain data on the well-to-surface mining scheme for this area; determine the δ and ε values ​​of the medium-deep VTI anisotropic medium based on the data on the well-to-surface mining scheme for this area.

[0088] Information obtained regarding the well-to-ground combined mining plan for this area includes:

[0089] Method 1:

[0090] S110. Obtaining data on the well-to-ground joint mining scheme in this area includes obtaining Walkaway VSP data, which includes zero-well-source-distance VSP and variable-offset-distance VSP data.

[0091] S111. Establish an isotropic velocity model based on the vertical velocity of the zero-well-spacing VSP data;

[0092] S112. Based on the variable offset VSP data and the isotropic velocity model, perform forward modeling calculations of the travel time of anisotropic direct waves in VTI media with different offsets to obtain the forward modeling travel time; in this embodiment, the anisotropic forward modeling travel time is as follows: Figure 4 As shown, the state diagrams of the direct wave during its forward travel to each medium layer are presented.

[0093] S113. Optimize the error between the forward travel time and the actual observed travel time using the boundary constraint optimization method to obtain the forward travel time with the smallest error.

[0094] S114. Invert the forward travel time with the minimum error to obtain the anisotropic parameters δ and ε values ​​layer by layer from shallow to deep. Using a boundary constraint optimization method, the error between the forward travel time and the observed travel time is minimized, thereby obtaining the anisotropic parameters ε and δ values ​​layer by layer from shallow to deep. In the embodiments of this application, the iterative convergence process of the forward travel time and the observed travel time is as follows: Figure 5 As shown.

[0095] Method 2:

[0096] S120. Obtain information on the well-to-ground combined mining plan for this area, including obtaining 3D-VSP data;

[0097] S121. Based on 3D-VSP data, the anisotropic slowness intersection curve is fitted using the method of horizontal and vertical visual slowness intersection to obtain the anisotropic parameter δ and ε values ​​layer by layer from shallow to deep.

[0098] S200. Combining velocity modeling layer information or geological layer information from joint mining data, the δ and ε values ​​of the mid-deep VTI anisotropic medium are interpolated and smoothed along the geological strata to obtain the δ field and ε field of the mid-deep VTI anisotropic medium.

[0099] S300. The medium-deep VTI anisotropic medium is obtained from the δ field and ε field of the medium-deep VTI anisotropic medium.

[0100] Process 3: Based on the near-surface VTI anisotropy and the mid-deep VTI anisotropy, the full-depth VTI anisotropy is obtained.

[0101] In the embodiments of this application, during the anisotropic forward walk, as follows: Figure 3 As shown. Finally, the boundary constraint optimization method is used to minimize the error between the forward travel time and the observed travel time, thereby obtaining the anisotropic parameters ε and δ values ​​layer by layer from shallow to deep. In the embodiments of this application, the iterative convergence process of the forward travel time and the observed travel time is as follows: Figure 4 As shown.

[0102] Example 2

[0103] This embodiment provides an apparatus for determining full-depth VTI anisotropy, including:

[0104] One or more processors;

[0105] A storage unit is used to store one or more programs that, when executed by one or more processors, enable the one or more processors to implement the method for obtaining the full-depth VTI anisotropic body of Embodiment 1.

[0106] Specifically, such as Figure 6 As shown, it includes:

[0107] The ray tracing travel-time forward modeling and anisotropic parameter inversion module is used to acquire the first arrival of several excitation points at different depths recorded by the bottom-hole geophones of each of the two-well microlobe in this area, and to establish an isotropic velocity model of a single-well microlobe. The near-surface anisotropic δ and ε values ​​are obtained by iteratively using ray tracing, travel-time forward modeling and inversion.

[0108] The near-surface VTI anisotropic parameter acquisition module is used to obtain the first arrival data of surface earthquakes in this area. Based on the first arrival data of surface earthquakes, a near-surface VTI anisotropic medium velocity model is obtained through tomographic inversion. The single-well micrologging isotropic velocity model is used to perform constrained tomographic inversion on the first arrival data of surface earthquakes to obtain a near-surface VTI isotropic medium micrologging constrained velocity model. The surface velocity difference is obtained based on the near-surface VTI anisotropic medium velocity model and the near-surface VTI isotropic medium micrologging constrained velocity model. The near-surface VTI anisotropic medium δ field is obtained based on the surface velocity difference.

[0109] The dual-well micrologging coverage rate judgment module is used to determine whether the coverage rate of dual-well micrologging in this area meets the preset standard; if the standard is met, the near-surface VTI medium anisotropic field construction module is executed; if the standard is not met, the smoothing correction module is executed.

[0110] The smoothing correction module is used to perform quality control and smoothing correction on the near-surface VTI anisotropic medium δ field by using the near-surface anisotropic δ value obtained by the micro logging of the two wells in this area, so as to obtain the corrected near-surface VTI anisotropic medium δ field; and to execute the near-surface VTI medium anisotropic field construction module.

[0111] The near-surface VTI medium anisotropic field construction module calculates the near-surface VTI anisotropic medium ε field based on the correspondence between the near-surface anisotropic δ value and the near-surface anisotropic ε value.

[0112] The module for obtaining anisotropic parameters of medium-deep VTI media is used to obtain anisotropic parameters of medium-deep VTI media from Walkaway VSP or 3D-VSP data in the well-to-situ mining scheme in this area.

[0113] The full-depth VTI anisotropic body acquisition module is used to obtain the full-depth VTI anisotropic body based on the δ field and ε field of the near-surface VTI anisotropic medium and the anisotropic parameters of the mid-deep VTI medium.

[0114] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Based on the technical essence of the present invention, any simple modifications, equivalent substitutions, and improvements made to the above embodiments within the spirit and principles of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for determining a full-depth VTI anisotropic body, characterized in that, This includes the process of determining the near-surface VTI anisotropy, with specific steps including: S1. Obtain the initial arrival of several excitation points at different depths recorded by the bottom hole geophones of the dual-well micrologging in this area, and establish an isotropic velocity model of single-well micrologging. Then, obtain the near-surface anisotropic δ and ε values ​​through ray tracing, travel-time forward modeling, and inversion iterations. S2. Obtain first arrival data of surface earthquakes in this area. Perform tomographic inversion based on the first arrival data to obtain a near-surface VTI anisotropic medium velocity model. Use the single-well micrologging isotropic velocity model to perform constrained tomographic inversion on the first arrival data of surface earthquakes to obtain a near-surface VTI isotropic medium micrologging constrained velocity model. Calculate the surface velocity difference based on the near-surface VTI anisotropic medium velocity model and the near-surface VTI isotropic medium micrologging constrained velocity model. Calculate the near-surface VTI anisotropic medium δ field based on the surface velocity difference. S3. Based on the correspondence between the near-surface anisotropy δ value and the near-surface anisotropy ε value, the near-surface VTI anisotropy medium ε field is obtained using the near-surface VTI anisotropy medium δ field; S4. Obtain a near-surface VTI anisotropic body from the near-surface VTI anisotropic medium δ field and the near-surface VTI anisotropic medium ε field; It also includes the process of obtaining the anisotropic volume of the mid-to-deep VTI, and the specific steps include: Obtain information on the well-to-surface combined mining scheme in this area; based on the information on the well-to-surface combined mining scheme in this area, determine the δ and ε values ​​of the anisotropic medium in the mid-deep VTI layer; By interpolating and smoothing the δ and ε values ​​of the mid-deep VTI anisotropic medium along the geological strata, the δ field and ε field of the mid-deep VTI anisotropic medium are obtained. The anisotropic medium of medium-deep VTI is obtained from the δ field and ε field of the medium-deep VTI. Obtaining data on the well-to-ground combined mining scheme in this area includes obtaining Walkaway VSP data, which includes zero-well-source-distance VSP and variable-offset VSP data; An isotropic velocity model was established based on the vertical velocity of the zero-well source distance VSP data. Based on variable offset VSP data and isotropic velocity model, forward modeling calculations of travel time of anisotropic direct waves in VTI media with different offsets are performed to obtain forward modeling travel times. The error between the forward travel time and the actual observed travel time is optimized using the boundary constraint optimization method to obtain the forward travel time with the smallest error; Inverting the forward travel time with the smallest error yields the anisotropy parameter δ and ε values ​​layer by layer from shallow to deep. By combining velocity modeling layer information, the anisotropic parameters δ and ε values ​​of each layer are interpolated and smoothed along the layer to form the δ field and ε field of the mid-deep VTI anisotropic medium.

2. The method for obtaining a full-depth VTI anisotropic body according to claim 1, characterized in that, The specific process of S1 is as follows: A fast ray tracing method for horizontal layered media between two points was used to calculate the direct arrival travel time of the first wave from the excitation point at different depths to the detector point at the bottom of the adjacent well. Based on the epicentral distance equation and the isotropic velocity model of single-well micrologging, the isotropic initial ray parameters are calculated, and the initial ray angle is determined based on the isotropic initial ray parameters. Based on the initial ray angle, the anisotropic velocity of each layer is updated using the weak anisotropic approximation formula; The ray path is calculated iteratively based on the epicentral distance equation, and the initial anisotropic parameters δ and ε are obtained based on the relationship between the first arrival travel time of the direct wave and the incident angle and anisotropic velocity of each layer. Based on the first arrival travel time of the direct wave, a forward modeling of the travel time is performed, and the actual first arrival curve is fitted. The initial anisotropy parameters δ and ε are then corrected using the actual first arrival curve. The corrected anisotropy parameters δ and ε are then obtained. Based on the corrected anisotropic δ and ε parameters, the anisotropic velocities of each layer are updated, and then the inversion iteration is performed until the first arrival travel time error of the direct wave is minimized, thus obtaining the near-surface anisotropic δ and ε values.

3. The method for obtaining a full-depth VTI anisotropic body according to claim 1, characterized in that, The steps between step S2 and step S3 include: Determine whether the coverage rate of dual-well micro-logging in this area meets the preset standard; If the preset standard is met, proceed to step S3; If the preset standard is not met, the near-surface anisotropic δ value obtained by the micro-logging of the two wells in this area is used to perform quality control and smoothing correction on the near-surface VTI anisotropic medium δ field obtained in step S2, so as to obtain the corrected near-surface VTI anisotropic medium δ field. Based on the correspondence between the near-surface anisotropy δ value and the near-surface anisotropy ε value, the near-surface VTI anisotropy medium ε field is obtained using the corrected near-surface VTI anisotropy medium δ field.

4. The method for obtaining a full-depth VTI anisotropic body according to claim 1, characterized in that, It also includes the process of obtaining the full-depth VTI anisotropic body: Based on the near-surface VTI anisotropy and the mid-deep VTI anisotropy, the full-depth VTI anisotropy is obtained.

5. The method for obtaining a full-depth VTI anisotropic body according to claim 1, characterized in that, Obtaining information on the well-to-ground combined mining plan for this area includes obtaining 3D-VSP data; Based on 3D-VSP data, the anisotropic slowness intersection curve was fitted using the method of horizontal and vertical visual slowness intersection to obtain the anisotropic parameter δ and ε values ​​layer by layer from shallow to deep. By combining geological stratification information from joint mining data, the anisotropic parameters δ and ε values ​​of each layer are interpolated and smoothed along the layer to form the δ field and ε field of the mid-deep VTI anisotropic medium.

6. An apparatus for determining full-depth VTI anisotropy, characterized in that, include: One or more processors; A storage unit for storing one or more programs that, when executed by one or more processors, enable the one or more processors to implement a method for obtaining a full-depth VTI anisotropic body as described in any one of claims 1-5.

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