A geological structure framework based on adaptive deformable interface and its modeling method

Abstract

The present invention discloses a geological structure framework based on an adaptive deformable interface and a modeling method thereof. The modeling method comprises the following steps: S1: estimating the distribution range of underground velocities of a target stratum and constructing an initial model of the deformable geological structure framework based on this; S2: establishing a multi-scale, progressive deformation inversion mechanism for the geological structure framework; S3: picking first-arrival travel times based on the original seismic data of the target stratum and performing inversion in combination with the deformation inversion mechanism to obtain the geological structure framework of the target stratum. The present invention can achieve accurate and stable inversion of geological structure features at different scales underground, providing an accurate and reliable underground structure framework model without relying on seismic imaging results, and providing key geological structure regularization constraint information for technical links such as seismic tomography velocity modeling, full waveform inversion, and seismic attribute inversion.

Description

Technical Field

[0001] The present 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 tectonic framework contains key information such as the spatial position and dip of subsurface strata. Because the spatial distribution of the seismic velocity field aligns with the changing trends of tectonic structures, tectonic information provides important tectonic regularization constraints for seismic tomographic velocity modeling. This is a crucial approach to improving the accuracy of seismic velocity models and reducing the ambiguity of tomographic inversion solutions.

[0003] Currently, the geological structural information required for tomography is primarily extracted from seismic imaging results. Based on these results, various methods have been proposed to estimate the position and dip of seismic reflection interfaces, including the structural 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 treat seismic reflection interfaces as velocity-invariant interfaces and extract the position and dip of strata by determining the spatial continuity of the reflection interface's events.

[0004] However, structural information extraction methods based on seismic imaging have two major drawbacks. On the one hand, the accuracy of seismic imaging depends on the velocity model, which in turn requires regularization constraints based on the structural information extracted from seismic imaging. The strong coupling between the two requires multiple cycles of iterative optimization of the velocity model and seismic imaging. This problem is particularly evident when the initial velocity model is inaccurate 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 seismic reflection signals generated by strong wave impedance interfaces. When the velocity model changes gradually with depth rather than suddenly, the reflection signal may be missing, making seismic reflection wave imaging difficult. The method of extracting geological structures 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 solutions of the present invention are 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 velocities in the target formation and use this to construct an initial model of the deformable geological structure framework;

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

[0010] S3: Picking the first arrival travel time according to the original seismic data of the target stratum, performing inversion in combination with the deformation inversion mechanism, and obtaining the geological structural 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; and v is the reduced velocity.

[0014] Preferably, step S1 further 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 the underground velocity of the target formation.

[0015] Preferably, in step S2, the multi-scale, 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 travel time residual of seismic data 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 structural 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 dip angle of the formation 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 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; during 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 geological structural characteristics of different scales underground, and provide an accurate and reliable underground structural framework model without relying on seismic imaging results, providing key geological structural 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 following briefly introduces the drawings required for use in the embodiments or the description of the prior art. 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 any creative work.

[0029] Figure 1 Schematic diagram of the flow of the modeling method of the geological structure framework based on the adaptive deformable interface of the present invention;

[0030] Figure 2 1 is a diagram of earthquake first arrival travel time and offset in a specific embodiment;

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

[0032] Figure 4 Schematic diagram of the multi-scale, progressive deformation inversion mechanism of the geological structure framework of the present invention;

[0033] Figure 5 A schematic diagram of a test result 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 This is a superimposed image of the geological structure framework and seismic imaging results obtained by the present invention in a specific embodiment. DETAILED DESCRIPTION

[0036] The present invention is further described below with reference to the accompanying drawings and examples. 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 commonly understood by those of ordinary skill in the art to which this application belongs. The use of similar words such as "include" or "comprising" in the present invention means 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 this to construct an initial model of the deformable geological structure framework.

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

[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 in Figure 1, the slope of the first arrival traveltime-offset diagram can be obtained by using the reduced traveltime formula, that is, by scanning at different reduced speeds. The reduced traveltime formula is shown in Equation (1). By quickly scanning at different reduced speeds, the distribution range of underground seismic velocities can be quickly obtained using Equation (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; and 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 them to correct the distribution range of the underground velocity of the target formation.

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

[0045] In a specific embodiment, the multi-scale, progressive deformation inversion mechanism of the geological structure grid (i.e., the sensitive kernel of the multi-scale geological structure grid 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 travel time residuals of the seismic data 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 Figure 1, 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 cannon's first arrival travel time, and are obtained by comprehensively considering information such as vertical seismic profile velocity and micro-logging velocity, making the formation velocity range of the model more consistent with the actual underground situation.

[0049] After determining the layer velocity, the deformable interface of the geological structural framework is determined by the morphological control points distributed on the interface (red dots in the schematic diagram). 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 the deformation tomography inversion, the interface morphological control points can only move in the z direction (vertical) and cannot move in the x direction (lateral). The advantage of this method is that it can stably represent the fluctuation trend of the underground strata. However, since 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, 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, 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 coordinates (x, z), during the initial stage of deformable tomographic inversion, it first moves and deforms in the near-vertical direction, i.e., (R1, θ1) represents a large interface morphology deformation in the near-vertical direction. Because interface undulation deformations minimally alter ray paths, the grid interface morphology inversion can be approximated as a stable linear inversion problem, and the large deformation variable T1 allows the grid interface to converge rapidly with a small number of iterations. After obtaining the large-scale tectonic grid inversion results, the small-scale grid morphology inversion of complex structures is performed. In this step, the model interface morphology control point undergoes displacement deformation in the near-horizontal direction θ2.

[0052] S3: Picking the first arrival travel time according to the original seismic data of the target stratum, performing inversion in combination with the deformation inversion mechanism, and obtaining the geological structural 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 travel time residual of seismic data 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-mentioned embodiment, the complex deformation of thrust faults produces local velocity reversals, leading to significant variations in ray paths and exacerbating the nonlinearity of the inversion. The present invention, based on the inversion of the large-scale undulating morphology of the geological grid, introduces smaller deformation variables to achieve local, small-scale inversion of complex structures. This multi-scale, progressive inversion method prevents the grid inversion from falling into local minima and achieves an optimal inversion solution across the entire model space.

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

[0058]

[0059] Where: θ(x,z) is the dip angle of the formation 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 a geological structure framework based on an adaptive deformable interface.

[0061] In a specific embodiment, the modeling method of the geological structure grid 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 a horizontally distributed low-velocity near-surface weathering layer and a 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 grid 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 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 dip field accurately obtains the geological structural morphology of the horizontal weathering layer and the steep interface.

[0062] In another specific embodiment, taking the actual data of a certain piedmont region 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 geological structure change characteristics and trends that characterize the piedmont area.

[0063] In summary, the present invention can directly invert the tectonic grid structure based on seismic travel time data. This requires only the travel time of the first arrival of the earthquake, which can be obtained from the raw seismic data. This greatly reduces the difficulty of obtaining underground tectonic grid information and greatly improves the efficiency of obtaining tectonic grid information. This method can overcome the shortcomings of existing tectonic grid extraction methods, such as the need for an accurate seismic velocity model based on seismic reflection wave imaging and the cumbersome processing procedures required for reflected wave seismic data.

[0064] The present invention dynamically adjusts the deformation direction and magnitude of interface control points during the inversion process, enabling stable and accurate computation and characterization of complex geological structural frameworks. This addresses the shortcomings of existing deformable tomography techniques, which suffer from relatively simple deformation mechanisms, a single direction and scale of movement of interface control points, and an inability to characterize complex structural features such as thrust faults.

[0065] The above description is merely 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 this profession can make some changes or modifications to equivalent embodiments of the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications 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 are still 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 velocities in the target formation and use this to construct an initial model of the deformable geological structure framework; S2: Establish a multi-scale, progressive deformation inversion mechanism for the geological structural framework as shown below: Δt=K g Δr(θ) (2) Where: Δt is the travel time residual of seismic data; 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; S3: Picking the first arrival travel time according to the original seismic data of the target stratum, performing inversion in combination with the deformation inversion mechanism, and obtaining the geological structural 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; and 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 the 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: The Jacobian matrix is obtained by a small numerical perturbation method.

5. 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 using 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 travel time residual of seismic data 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.

6. The method for modeling a geological structure framework based on an adaptive deformable interface according to any one of claims 1 to 5, 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 using the following formula: Where: θ(x,z) is the dip angle of the formation at the coordinate (x,z); x is the horizontal coordinate; z is the vertical coordinate.

7. A geological structure 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 described in any one of claims 1-6.

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