Geological structure framework based on self-adaptive deformable interface and modeling method thereof

Abstract

The invention discloses a geologic structure framework based on a self-adaptive deformable interface and a modeling method thereof, and the modeling method comprises the following steps: S1, estimating the distribution range of the underground speed of a target stratum, and constructing an initial model of the deformable geologic structure framework; s2, establishing a multi-scale and progressive deformation inversion mechanism of the geologic structure framework; and S3, picking up first arrival wave travel time according to the original seismic data of the target stratum, performing inversion in combination with the deformation inversion mechanism, and obtaining the geologic structure framework of the target stratum. According to the method, accurate and stable inversion of underground geological structure characteristics of different scales can be realized, an accurate and reliable underground structure framework model is provided without depending on an earthquake imaging result, and key geological structure regularization constraint information is provided for technical links such as earthquake chromatography velocity modeling, full-waveform inversion and earthquake attribute inversion.

Description

Technical Field

[0001] The invention relates to the technical field of geological structure grids, and in particular to a geological structure grid based on an adaptive deformable interface and a modeling method thereof. Background Art

[0002] The geological structure framework contains key information such as the spatial position and dip of underground strata. Since the spatial distribution of the seismic velocity field is consistent with the changing trend of the geological structure, the geological structure information provides important geological structure regularization constraints for seismic tomography velocity modeling. This is an important way to improve the accuracy of the seismic velocity model and reduce the multi-solution of tomography inversion.

[0003] At present, the geological structure information required for tomography is mainly extracted through seismic imaging results. Based on the seismic imaging results, a variety of methods have been proposed to estimate the position and dip information of the seismic reflection interface, including the structure tensor method (Van Vliet & Verbeek 1995; Weickert 1997; Fehmers & Hocker 2003), the plane wave decomposition method (Fomel 2002) and the dynamic image regularization method (Arias 2016). These methods regard the seismic reflection interface as a velocity-invariant interface and extract the position and dip information of the stratum by determining the spatial continuity of the event axis of the reflection interface.

[0004] However, there are two major defects in the structural information extraction method based on seismic imaging. On the one hand, the accuracy of seismic imaging depends on the velocity model, and the velocity model needs to be regularized and constrained by the structural information extracted from seismic imaging. The strong coupling relationship between the two requires multiple cycles of velocity model-seismic imaging iterative optimization. This problem is particularly obvious when the initial velocity model is not accurate enough or the signal-to-noise ratio of the seismic data is low, resulting in low iterative optimization efficiency. On the other hand, the structural information extracted by seismic imaging is mainly based on the seismic reflection signal generated by the strong wave impedance interface. When the velocity model changes gradually with depth rather than suddenly, the reflection signal may be missing, and seismic reflection wave imaging is difficult. The method of extracting geological structure based on seismic reflection imaging is difficult to apply in this case. Summary of the invention

[0005] In view of the above problems, the present invention aims to provide a geological structure framework based on an adaptive deformable interface and a modeling method thereof.

[0006] The technical solution of the present invention is as follows:

[0007] In one aspect, a method for modeling a geological structure framework based on an adaptive deformable interface is provided, comprising the following steps:

[0008] S1: Estimate the distribution range of underground velocity in the target formation and use it to construct an initial model of the deformable geological structure framework;

[0009] S2: Establish a multi-scale and progressive deformation inversion mechanism for the geological structural framework;

[0010] S3: Pick up the first arrival wave travel time according to the original seismic data of the target stratum, and perform inversion in combination with the deformation inversion mechanism to obtain the geological structure framework of the target stratum.

[0011] Preferably, in step S1, the distribution range of the underground velocity of the target formation is estimated by the following formula:

[0012] τ=tX / v (1)

[0013] Where: τ is the reduced travel time; t is the first arrival travel time of the seismic wave; X is the offset; v is the reduced velocity.

[0014] Preferably, step S1 further includes the step of obtaining micro-logging velocity profile and / or near-surface geological survey information, and using the information to correct the distribution range of underground velocity of the target formation.

[0015] Preferably, in step S2, the multi-scale and progressive deformation inversion mechanism of the geological structure framework is:

[0016] Δt=K g Δr(θ) (2)

[0017] Where: Δt is the residual error of seismic data travel time; K g is the Jacobian matrix that quantifies the relationship between the travel time residual of seismic data and the model interface deformation; Δr(θ) is the model interface deformation.

[0018] Preferably, the Jacobian matrix is ​​obtained by a small numerical perturbation method.

[0019] Preferably, in step S3, the inversion is performed by the following formula:

[0020]

[0021] Where: Δt is the residual error of seismic data travel time; K g The Jacobian matrix that quantifies the relationship between the residual error of seismic data travel time and the model interface deformation; R itr is the regularization constraint weight related to the number of tomography cycles; Δr(θ) is the model interface deformation.

[0022] Preferably, in step S3, when obtaining the geological structure framework of the target stratum, the stratum dip angle at each spatial position is calculated by the following formula:

[0023]

[0024] Where: θ(x,z) is the formation dip angle at the coordinate (x,z); x is the horizontal coordinate; z is the vertical coordinate.

[0025] On the other hand, a geological structure framework based on an adaptive deformable interface is also provided, which is established by using any of the above-mentioned modeling methods for the geological structure framework based on an adaptive deformable interface.

[0026] The beneficial effects of the present invention are:

[0027] The present invention updates the interface morphology of deformable model parameters through tomographic inversion, so that the model interface morphology can adaptively fit the undulation trend of the actual underground structure; in the inversion process, by introducing a multi-scale model parameter characterization method, that is, through multi-scale model parameter decomposition and synthesis, under the strict condition that the total number of model parameters is controllable, the large-scale characteristics such as stratum undulation and dip angle change and the small-scale characteristics such as local normal faults and thrust faults are accurately characterized; in summary, the present invention can realize the accurate and stable inversion of underground geological structure characteristics of different scales, and provide an accurate and reliable underground structure framework model without relying on seismic imaging results, providing key geological structure regularization constraint information for technical links such as seismic tomography velocity modeling, full waveform inversion, and seismic attribute inversion. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0029] Figure 1 It is a schematic flow chart of a modeling method of a geological structure framework based on an adaptive deformable interface according to the present invention;

[0030] Figure 2 It is a diagram of earthquake first arrival travel time-offset in a specific embodiment;

[0031] Figure 3 A schematic diagram of an initial model of a deformable geological structure framework in a specific embodiment;

[0032] Figure 4 It is a schematic diagram of the multi-scale and progressive deformation inversion mechanism of the geological structure framework of the present invention;

[0033] Figure 5 It is a schematic diagram of the test results of an example of the present invention on a synthetic model in a specific embodiment;

[0034] Figure 6 A schematic diagram of a geological structure framework obtained by the present invention in a specific embodiment;

[0035] Figure 7 It is a superimposed image of the geological structure framework and the seismic imaging result obtained by the present invention in a specific embodiment. DETAILED DESCRIPTION

[0036] The present invention is further described below in conjunction with the accompanying drawings and embodiments. It should be noted that, in the absence of conflict, the embodiments in this application and the technical features in the embodiments can be combined with each other. It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meanings as those generally understood by those of ordinary skill in the art to which this application belongs. The words "including" or "comprising" and the like used in the disclosure of the present invention mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0037] On the one hand, if Figure 1 As shown, the present invention provides a modeling method of a geological structure framework based on an adaptive deformable interface, comprising the following steps:

[0038] S1: Estimate the distribution range of underground velocities in the target formation and use it to construct an initial model of the deformable geological structural framework.

[0039] In order to determine the consistency between the deformable geological structure framework model and the actual underground geological structure, it is necessary to determine the distribution range of the formation velocity in the framework model, so as to more accurately invert the underground geological structure framework.

[0040] In a specific embodiment, based on the slope analysis of the first arrival travel time data, the maximum and minimum values ​​of the near-surface velocity are estimated from the first arrival travel time-offset diagram of the single shot seismic, thereby obtaining the distribution range of the underground velocity of the target formation. Figure 2 As shown, the slope of the first arrival travel time-offset diagram can be obtained by the reduced travel time formula, that is, by scanning at different reduced speeds. The reduced travel time formula is shown in formula (1), that is, by quickly scanning different reduced speeds, the distribution range of underground seismic velocity can be quickly obtained using formula (1), providing key velocity information for the establishment of a multi-scale deformable geological structure framework model.

[0041] τ=tX / v (1)

[0042] Where: τ is the reduced travel time; t is the first arrival travel time of the seismic wave; X is the offset; v is the reduced velocity.

[0043] In a specific embodiment, the method further includes obtaining micro-logging velocity profiles and / or near-surface geological survey information, and using these to correct the distribution range of underground velocity of the target formation.

[0044] S2: Establish a multi-scale and progressive deformation inversion mechanism for the geological structural framework.

[0045] In a specific embodiment, the multi-scale, progressive deformation inversion mechanism of the geological structure framework (i.e., the sensitive kernel of the multi-scale geological structure framework deformation and the seismic data residual) is:

[0046] Δt=K g Δr(θ) (2)

[0047] Where: Δt is the residual error of seismic data travel time; K g is the Jacobian matrix that quantifies the relationship between the residual error of seismic data travel time and the model interface deformation; Δr(θ) is the model interface deformation. Optionally, the Jacobian matrix is ​​obtained by a small numerical perturbation method.

[0048] In a specific embodiment, taking a three-layer two-dimensional model as an example, the initial model of the deformable geological structure framework established in step S1 is as follows: Figure 3 As shown in the figure, the formation velocities from shallow to deep are v1, v2, and v3, respectively. The formation velocities are calculated and analyzed by step S1 based on the first arrival time of the cannon, and are obtained by comprehensively considering the vertical seismic profile velocity, micro-logging velocity and other information, so that the formation velocity range of the model is more consistent with the actual underground situation.

[0049] After the layer velocity is determined, the deformable interface of the geological structure framework is determined by the morphological control points (red dots in the schematic diagram) distributed on the interface. The coordinate position of the morphological control points in the two-dimensional model is (x, z). In the existing deformable tomography method, in order to ensure the stability of deformation tomography inversion, the interface morphological control points can only move in the z direction (vertical) and cannot move in the x direction (laterally). The advantage of this method is that it can stably characterize the fluctuation trend of underground strata, but because the morphological control points cannot move laterally, the tomography model cannot deform to fit complex geological features such as steep interfaces and thrust faults.

[0050] The multi-scale and progressive deformation inversion mechanism of the geological structure framework shown in formula (2) established by the present invention can give the interface morphology control points a large deformation freedom in the z direction in the early stage of the geological structure framework inversion, so that the interface morphology can stably and reliably fit large-scale geological structure characteristics such as stratum fluctuation changes through deformation; as the inversion optimization progresses, the freedom of the interface morphology control points is adjusted, and the deformation freedom in the x direction is given, so that the interface morphology can further accurately invert small-scale geological structure characteristics such as local thrust faults on the basis of characterizing large-scale structural fluctuation characteristics.

[0051] like Figure 4 As shown in the figure, the deformation direction of the interface morphology control point is controlled by (r,θ), where θ controls the deformation direction and r controls the deformation distance. For the model interface morphology control point located at the coordinate (x,z), in the early stage of deformable tomography inversion, it first moves and deforms in the vertical direction, that is, (R1,θ1) represents a larger interface morphology deformation variable in the vertical direction. Thanks to the small change of the interface undulation deformation on the ray path, the grid interface morphology inversion can be approximated as a stable linear inversion problem, and the larger deformation variable T1 can make the grid interface converge quickly with fewer cyclic iterations. After obtaining the large-scale geological structure grid inversion results, the small-scale complex structure grid morphology inversion is performed. In this step, the model interface morphology control point is displaced and deformed in the horizontal direction θ2.

[0052] S3: Pick up the first arrival wave travel time according to the original seismic data of the target stratum, and perform inversion in combination with the deformation inversion mechanism to obtain the geological structure framework of the target stratum.

[0053] In a specific embodiment, the inversion is performed by the following formula:

[0054]

[0055] Where: Δt is the residual error of seismic data travel time; K g The Jacobian matrix that quantifies the relationship between the residual error of seismic data travel time and the model interface deformation; R itr is the regularization constraint weight related to the number of tomography cycles; Δr(θ) is the model interface deformation.

[0056] In the above embodiment, the complex deformation of the thrust fault will produce local velocity reversal, resulting in large changes in the ray path, which aggravates the nonlinear problem of inversion. The present invention achieves local small-scale complex structural inversion by introducing smaller deformation variables based on the large-scale undulating morphology of the geological grid obtained by inversion. This multi-scale, progressive inversion method can avoid the grid inversion from falling into the local minimum and achieve the optimal inversion solution of the entire model space.

[0057] In a specific embodiment, when obtaining the geological structure framework of the target stratum, the stratum dip angle at each spatial position is calculated by the following formula:

[0058]

[0059] Where: θ(x,z) is the formation dip angle at the coordinate (x,z); x is the horizontal coordinate; z is the vertical coordinate.

[0060] On the other hand, the present invention also provides a geological structure framework based on an adaptive deformable interface, which is established using any of the above-mentioned modeling methods for the geological structure framework based on an adaptive deformable interface.

[0061] In a specific embodiment, the modeling method of the geological structure framework based on the adaptive deformable interface of the present invention is used to perform a case test on a synthetic model, and the results are as follows: Figure 5 As shown. Among them, Figure 5 (a) is the true velocity model, which includes the horizontally distributed low-velocity near-surface weathering layer and the high-velocity bedrock with a stepped structure. Figure 5 (b) is the result of the multi-scale deformable structural grid inversion of the present invention, Figure 5 (c) is the ray coverage of the first arrival travel time under this result. Figure 5 (d) is the geological structure inclination field extracted based on the geological structure framework inversion results. Figure 5 (a)- Figure 5 (c) It can be seen that through the multi-scale, progressive inversion method of the present invention, the deformable geological structure framework adaptively fits the real model through deformation inversion, and more accurately fits the large-scale structural dip distribution changes and the local small-scale stepped high-steep structures. Figure 5 (d) It can be seen that by superimposing and comparing with the high-speed bedrock interface (white dotted line) in the figure, the inclination field accurately obtains the geological structural morphology of the horizontal weathering layer and the high-steep interface.

[0062] In another specific embodiment, taking the actual data of a certain piedmont area in my country as an example, the modeling method of the geological structure framework based on the adaptive deformable interface of the present invention is used to determine its geological structure framework, and the geological structure framework is obtained based on seismic imaging. The geological structure framework result obtained by the present invention is as follows: Figure 6 As shown, the superimposed image of the seismic imaging result and the result of the present invention is as follows Figure 7 As shown. Figure 6 and Figure 7 It can be seen that the results of the present invention show a high degree of consistency with the superimposed images of seismic imaging, which verifies the effectiveness and practicality of the method of the present invention. The present invention can accurately obtain the characteristics and trends of the geological structure changes that characterize the piedmont area.

[0063] In summary, the present invention can directly invert and obtain the geological structure grid form based on the seismic travel time data, and only requires the travel time of the first arrival wave of the earthquake, which can be obtained on the original seismic data, greatly reducing the difficulty of obtaining the underground geological structure grid information and greatly improving the efficiency of obtaining the geological structure grid information. It can solve the shortcomings of the existing geological structure grid obtaining method based on seismic reflection wave imaging, which requires an accurate seismic velocity model and the reflection wave seismic data requires a cumbersome processing process.

[0064] The present invention can dynamically adjust the deformation direction and deformation amount of the interface control point during the inversion process, and can stably and accurately obtain and characterize the complex geological structure framework. It can solve the shortcomings of the existing deformable tomography technology, such as the relatively simple deformation mechanism, the single movement direction of the interface control point, the single scale of the movement amount, and the inability to characterize complex structural features such as thrust faults.

[0065] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A modeling method for a geological structure framework based on an adaptive deformable interface, characterized in that: The following steps are involved: S1: Estimate the distribution range of underground velocity in the target formation and use it to construct an initial model of the deformable geological structure framework; S2: Establish a multi-scale and progressive deformation inversion mechanism for the geological structural framework; S3: Pick up the first arrival wave travel time according to the original seismic data of the target stratum, and perform inversion in combination with the deformation inversion mechanism to obtain the geological structure framework of the target stratum.

2. The method for modeling a geological structure framework based on an adaptive deformable interface according to claim 1, characterized in that: In step S1, the distribution range of the underground velocity of the target formation is estimated by the following formula: τ=tX / v (1) Where: τ is the reduced travel time; t is the first arrival travel time of the seismic wave; X is the offset; v is the reduced velocity.

3. The method for modeling a geological structure framework based on an adaptive deformable interface according to claim 1, characterized in that: Step S1 also includes the step of obtaining micro-logging velocity profiles and / or near-surface geological survey information, and using them to correct the distribution range of underground velocity of the target formation.

4. The method for modeling a geological structure framework based on an adaptive deformable interface according to claim 1, characterized in that: In step S2, the multi-scale and progressive deformation inversion mechanism of the geological structure framework is: Δt=K g Δr(θ) (2) Where: Δt is the residual error of seismic data travel time; K g is the Jacobian matrix that quantifies the relationship between the travel time residual of seismic data and the model interface deformation; Δr(θ) is the model interface deformation.

5. The method for modeling a geological structure framework based on an adaptive deformable interface according to claim 4, characterized in that: The Jacobian matrix is ​​obtained by a small numerical perturbation method.

6. The method for modeling a geological structure framework based on an adaptive deformable interface according to claim 1, characterized in that: In step S3, the inversion is performed by the following formula: Where: Δt is the residual error of seismic data travel time; K g The Jacobian matrix that quantifies the relationship between the residual error of seismic data travel time and the model interface deformation; R itr is the regularization constraint weight related to the number of tomography cycles; Δr(θ) is the model interface deformation.

7. The method for modeling a geological structure framework based on an adaptive deformable interface according to any one of claims 1 to 6, characterized in that: In step S3, when obtaining the geological structure framework of the target stratum, the stratum dip angle at each spatial position is calculated by the following formula: Where: θ(x,z) is the formation dip angle at the coordinate (x,z); x is the horizontal coordinate; z is the vertical coordinate.

8. A geological structural framework based on an adaptive deformable interface, characterized in that: It is established by adopting the modeling method of the geological structure framework based on the adaptive deformable interface as described in any one of claims 1-7.

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