Seismic data combined slope tomography method

Abstract

The invention provides a seismic data combined slope tomography method. The imaging method comprises the following steps: preprocessing seismic data of submarine cables and submarine nodes; picking reflected wave travel time, a reflected wave travel time slope and first-motion wave travel time from the preprocessed seismic data; constructing an objective function of submarine cable and submarine node seismic data combined slope tomography; calculating the gradient of the target function to the speed and the gradient of the space coordinates of the reflection points; calculating updating parameters of the speed and the space coordinates of the reflection points; and judging whether the updated speed meets the requirement or not, if so, outputting the speed and the space coordinates of the reflection points, otherwise, continuing iterative inversion. The ray coverage frequency of the middle-deep stratum is increased, and the defect that the speed of the middle-deep stratum is difficult to accurately invert due to the fact that only reflected wave data in submarine cable seismic data are used in an existing slope tomography method is overcome; the method is simple in calculation and easy to implement, has high adaptability and is high in inversion result reliability.

Description

Technical Field

[0001] This invention relates to the field of inversion of subsurface medium velocity models, and in particular to a method for combined slope tomography of seismic data. Background Technology

[0002] In marine oil and gas exploration, tomographic imaging using the travel time and travel slope of reflected waves picked from submarine cable seismic data is one of the current methods for establishing macroscopic velocity models of subsurface media. This method only needs to pick the travel time and travel slope of locally coherent phase axes in the submarine cable seismic data, without needing to pick the travel time and travel slope of reflected waves from the same impedance interface. Moreover, during velocity inversion, it is not necessary to correspond the picked reflected wave data one-to-one with the impedance interface. Therefore, this method is suitable for geologically complex areas.

[0003] However, submarine cables are typically short, resulting in a lack of reflected wave data from mid-to-deep strata in observed submarine cable seismic data. Due to the lack of reflected wave coverage in these mid-to-deep strata, slope tomography cannot accurately invert their velocities, especially in geologically complex areas.

[0004] After reviewing a large amount of literature, scholars both domestically and internationally have proposed several slope tomography methods. Currently, the main identification methods include:

[0005] Patent CN202110655576.1 proposes a depth-weighted seismic slope tomography method. The method involves preprocessing seismic data; extracting the travel time and slope of reflected waves to form observation data; establishing an initial velocity model and initial ray segment parameters to form a model space; jointly inverting the ray segment parameters and velocity model; and performing quality control on the inversion results. If the inversion results do not converge, the inversion iteration continues; if the inversion results converge, the velocity model and ray segment parameters are output.

[0006] Patent CN201910020541.3 proposes a three-dimensional undulating observation surface seismic slope tomography method. The method involves acquiring raw three-dimensional seismic data and preprocessing it; extracting seismic slope and travel time data to form an observation data space; establishing an initial velocity model and initial ray parameters to form a model space; performing forward modeling based on the initial model to obtain the computational data space; jointly inverting the ray parameters and velocity model; quality control of the inversion results and updating the model; determining whether the inversion results meet the requirements; if they do, outputting the velocity model; otherwise, continuing iterations until the inversion results meet the requirements.

[0007] A slope tomography method for qP-waves in two-dimensional VTI media. Slope tomography is a special case of stereo tomography. During the reconstruction of stereo tomographic data space via kinematic inverse migration, situations arise where the shot-receiver locations and travel time information are matched, but the horizontal components of the surface ray parameters (hereinafter referred to as surface px parameters) cannot be matched. In such cases, the px residuals can be used to update the velocity model and reflection point coordinates. This paper extends the slope tomography method in isotropic media to the qP-wave case in two-dimensional VTI media. A linear equation set for qP-wave slope tomography in two-dimensional VTI media is established using the partial derivatives of the surface px parameters with respect to the three anisotropic parameters. Based on this linear equation set and typical theoretical data, qP-wave slope tomography inversion in two-dimensional VTI media is performed. The results show that combining kinematic migration / inverse migration in VTI media with the linear equation set for qP-wave slope tomography in two-dimensional VTI media can achieve anisotropic parameter reconstruction in two-dimensional VTI media, providing a new approach for parameter modeling of VTI media.

[0008] Two-dimensional stereo tomographic inversion under stratigraphic framework regularization constraints. By applying stratigraphic framework information to the stereo tomographic Fréchet derivative matrix, the updated velocity model exhibits blocky characteristics consistent with geological patterns. The stratigraphic framework information is obtained by irregular B-spline interpolation fitting based on the reflection point positions obtained in the stereo tomographic inversion; therefore, it will naturally update as the reflection point positions are updated during the inversion. Compared with the edge-preserving tomography algorithm or multi-layer stereo tomography algorithm proposed in the previous paper, the stratigraphic framework regularization proposed in this paper does not require the introduction of a mixed regularization term or the definition of a complex mixed velocity scheme, making it more direct and easier to implement. Theoretical and practical data examples verify the robustness and reliability of this regularization technique, and can obtain geologically consistent inversion results that are more consistent with the actual geological structural characteristics.

[0009] In marine oil and gas exploration, tomographic imaging using the travel time and travel slope of reflected waves picked from submarine cable seismic data is one of the current methods for establishing macroscopic velocity models of subsurface media. This method only needs to pick the travel time and travel slope of locally coherent phase axes in the submarine cable seismic data, without needing to pick the travel time and travel slope of reflected waves from the same impedance interface. Moreover, during velocity inversion, it is not necessary to correspond the picked reflected wave data one-to-one with the impedance interface. Therefore, this method is suitable for geologically complex areas.

[0010] However, submarine cables are typically short, resulting in a lack of reflected wave data from mid-to-deep strata in observed submarine cable seismic data. Due to the lack of reflected wave coverage in these mid-to-deep strata, slope tomography cannot accurately invert their velocities, especially in geologically complex areas. Summary of the Invention

[0011] In view of the above problems, the present invention is proposed to provide a seismic data combined slope tomography method to overcome or at least partially solve the above problems.

[0012] According to one aspect of the present invention, a method for combined slope tomography of seismic data is provided, the imaging method comprising:

[0013] Preprocessing of seismic data for submarine cables and submarine nodes;

[0014] Extract the travel time of reflected waves, the travel slope of reflected waves, and the travel time of first arrival waves from the preprocessed seismic data;

[0015] Construct an objective function for combined slope tomography imaging of submarine cable and submarine node seismic data;

[0016] Calculate the gradient of the objective function with respect to velocity and the gradient of the spatial coordinates of the reflection point;

[0017] Calculate the update parameters for velocity and spatial coordinates of the reflection point;

[0018] Determine if the updated velocity meets the requirements. If it does, output the velocity and the spatial coordinates of the reflection point; otherwise, continue the iterative inversion.

[0019] Optionally, the update parameters specifically include: update step size, update speed, and update spatial coordinates of the reflection point.

[0020] Optionally, the step of extracting the travel time of reflected waves, the travel slope of reflected waves, and the travel time of first arrival waves from the preprocessed seismic data specifically includes:

[0021] Locally coherent reflected wave travel times and travel slopes are extracted from preprocessed seismic data of submarine cables and submarine nodes.

[0022] First arrival travel times are extracted from preprocessed seismic data of submarine cables and submarine nodes.

[0023] Optionally, the objective function for constructing joint slope tomography of submarine cable and submarine node seismic data specifically includes:

[0024] The formula for calculating the objective function is as follows:

[0025]

[0026] Where E represents the objective function, σ1 represents the standard deviation of the first arrival travel time in the seismic data of the submarine cable and the submarine node, σ2 represents the standard deviation of the reflected wave travel time in the seismic data of the submarine cable and the submarine node, σ3 represents the standard deviation of the reflected wave travel time slope in the seismic data of the submarine cable and the submarine node, and T fb_obc T represents the first arrival wave travel time in submarine cable seismic data. fb_obnT represents the first arrival travel time in the seismic data of the seafloor node. re_obc T represents the travel time of reflected waves in seismic data of submarine cables. re_obn P represents the travel time of reflected waves in seismic data from seafloor nodes. s re_obc P represents the travel time slope at the shot point of the reflected wave in submarine cable seismic data. r re_obc P represents the travel time slope at the receiver end of the reflected wave in seismic data of submarine cables. s re _obn P represents the travel time slope of the reflected wave at the shot point in the seismic data of the seafloor node. r re_obn N represents the travel time slope at the receiver end of the reflected wave in the seismic data of the seafloor node. fb_obc N represents the total number of first-arrival travel times retrieved from submarine cable seismic data. fb_obn N represents the total number of first arrival travel times retrieved from the seismic data of the seafloor nodes. re_obc N represents the total number of reflected wave travel time data picked up from submarine cable seismic data. re_obn This represents the total number of reflected wave travel time data picked up from seafloor node seismic data. The superscript * indicates data picked up from actual observed seismic data.

[0027] Optionally, calculating the gradient of the objective function with respect to velocity specifically includes:

[0028] The gradient of the objective function with respect to velocity is calculated using the following formula:

[0029]

[0030] Where E represents the objective function, v represents the velocity, and N... s_obc N represents the total number of shot points in submarine cable seismic data. r_obc N represents the total number of receivers in the submarine cable seismic data. s_obn N represents the total number of shot points in the seabed nodal seismic data. r_obn This represents the total number of receivers in the seabed nodal seismic data, is represents the shot point number, ir represents the receiver number, and λ represents the receiver number. obc λ represents the associated state variable corresponding to submarine cable seismic data. obn This represents the associated state variables corresponding to the submarine node seismic data; the associated state variables corresponding to the submarine cable seismic data are calculated jointly from the first arrival wave travel time fitting error, reflected wave travel time fitting error, reflected wave shot point end travel time slope fitting error, and reflected wave receiver end travel time slope fitting error in the submarine cable seismic data; the first arrival wave travel time fitting error in the submarine cable seismic data is calculated using the following formula:

[0031] ΔT fb_obc =T fb_obc -T *,fb_obc (3)

[0032] Where, ΔT fb_obc T represents the fitting error of the first arrival wave travel time in submarine cable seismic data. fb_obc The first arrival travel time in submarine cable seismic data is represented by the superscript *, indicating data picked up from actual observed seismic data. The fitting error of the reflected wave travel time in submarine cable seismic data is calculated using the following formula:

[0033] ΔT re_obc =T re_obc -T *,re_obc (4)

[0034] Where, ΔT re_obc T represents the travel time fitting error of reflected waves in seismic data of submarine cables. re_obc The travel time of reflected waves in submarine cable seismic data is represented by the superscript *, indicating data picked up from actual observational seismic data. The fitting error of the travel time slope at the shot point of reflected waves in submarine cable seismic data is calculated using the following formula:

[0035]

[0036] in, This indicates the fitting error of the travel-time slope at the shot point of the reflected wave in the seismic data of submarine cables. This represents the travel time slope at the shot point of the reflected wave in submarine cable seismic data. The superscript * indicates data picked up from actual observed seismic data. The fitting error of the travel time slope at the receiver point of the reflected wave in submarine cable seismic data is calculated using the following formula:

[0037]

[0038] in, This indicates the fitting error of the travel time slope at the receiver end of the reflected wave in seismic data of submarine cables. This represents the travel time slope at the receiver end of the reflected wave in the submarine cable seismic data. The superscript * indicates data picked up from actual observed seismic data. The associated state variables corresponding to the submarine node seismic data are calculated jointly from the first arrival wave travel time fitting error, the reflected wave travel time fitting error, the shot point end travel time slope fitting error, and the receiver end travel time slope fitting error in the submarine node seismic data. The first arrival wave travel time fitting error in the submarine node seismic data is calculated using the following formula:

[0039] ΔT fb_obn =T fb_obn -T *,fb_obn (7)

[0040] Where, ΔT fb_obn T represents the fitting error of the first arrival wave travel time in the seismic data of the seafloor node. fb_obn The first arrival travel time in the seismic data of the seafloor node is represented by the superscript *, indicating data picked from actual observed seismic data. The fitting error of the reflected wave travel time in the seismic data of the seafloor node is calculated using the following formula:

[0041] ΔT re_obn =T re_obn -T *,re_obn (8)

[0042] Where, ΔT re_obn T represents the travel time fitting error of reflected waves in seismic data from seafloor nodes. re_obn The value represents the travel time of reflected waves in the seismic data of the seafloor node. The superscript * indicates that the data was picked up from the actual observed seismic data. The fitting error of the travel time slope of reflected waves at the shot point in the seismic data of the seafloor node is calculated using the following formula:

[0043]

[0044] in, This represents the fitting error of the travel-time slope at the shot point of the reflected wave in the seismic data of the seafloor node. This represents the travel time slope at the shot point of the reflected wave in the seismic data of the seafloor node. The superscript * indicates that the data was picked up from the actual observed seismic data. The fitting error of the travel time slope at the receiver point of the reflected wave in the seismic data of the seafloor node is calculated using the following formula:

[0045]

[0046] in, This represents the fitting error of the travel time slope at the receiver end of the reflected wave in the seismic data of the seabed node. This represents the travel time slope at the receiver end of the reflected wave in the seismic data of the seafloor node. The superscript * indicates that the data was picked up from the actual observed seismic data.

[0047] Optionally, calculating the gradient of the objective function with respect to the spatial coordinates of the reflection point specifically includes:

[0048] The gradient of the objective function with respect to the spatial coordinates of the reflection point corresponding to the reflected wave in the seismic data of submarine cables is calculated using the following formula:

[0049]

[0050] Where E represents the objective function, σ1 represents the spatial coordinates of the reflection point corresponding to the reflected wave in the seismic data of the submarine cable, σ2 represents the standard deviation of the travel time of the reflected wave in the seismic data of the submarine cable and the submarine node, σ3 represents the standard deviation of the travel time slope of the reflected wave in the seismic data of the submarine cable and the submarine node, and T represents the standard deviation of the travel time slope of the reflected wave in the seismic data of the submarine cable and the submarine node. re_obc This indicates the travel time of reflected waves in seismic data of submarine cables. This represents the travel-time slope at the shot point of the reflected wave in seismic data of submarine cables. This represents the travel time slope at the receiver end of the reflected wave in the seismic data of submarine cables. The superscript * indicates that the data was picked up from the actual observed seismic data.

[0051] Optionally, the update step size for calculating the velocity of the current iteration is defined using the following formula:

[0052]

[0053] Where, η v The update step size, μ, represents the velocity. v E1 represents the trial step size for velocity updates, where E1 represents a step size of 0 times μ. v The updated objective function value, E2, represents the value updated by 1 μ. v The updated objective function value, E3, represents the value at twice the μ value. v The objective function value after updating the speed.

[0054] Optionally, the update step size for calculating the spatial coordinates of the reflection points corresponding to the reflected waves in the seismic data of the submarine cable and submarine nodes in the current iteration is as follows:

[0055]

[0056] Where, η c μ represents the update step size of the spatial coordinates of the reflection point. c E4 represents the trial step size for updating the spatial coordinates of the reflection point, where E4 indicates a step size of 0 times μ. c The objective function value after updating the spatial coordinates of the reflection point, E5 represents the value after multiplying by 1 μ. c The objective function value after updating the spatial coordinates of the reflection point, E6 represents a value increased by 2 times μ. c The objective function value after updating the spatial coordinates of the reflection point.

[0057] Optionally, the update speed; the speed update representation:

[0058]

[0059] Where k represents the current iteration number, v represents the speed, and η v The update step size represents the velocity. This represents the gradient of the objective function with respect to velocity.

[0060] Optionally, after calculating the speed and updating the spatial coordinates of the reflection point, the method may further include updating the spatial coordinates of the reflection point corresponding to the reflected wave in the seismic data of the submarine cable and submarine node.

[0061] Optionally, the method for preprocessing seismic data of submarine cables and submarine nodes specifically includes: random noise suppression, multiple wave suppression, and reflected wave amplitude equalization.

[0062] This invention provides a combined slope tomography method for seismic data. The method includes: preprocessing seismic data from submarine cables and submarine nodes; extracting reflected wave travel time, reflected wave travel time slope, and first arrival wave travel time from the preprocessed seismic data; constructing an objective function for combined slope tomography of submarine cable and submarine node seismic data; calculating the gradient of the objective function with respect to velocity and the gradient of the spatial coordinates of the reflection point; calculating update parameters for velocity and spatial coordinates of the reflection point; determining whether the updated velocity meets the requirements; if so, outputting the velocity and spatial coordinates of the reflection point; otherwise, continuing iterative inversion. This method increases the number of ray coverage times for mid-deep strata and overcomes the shortcomings of existing slope tomography methods that rely solely on reflected wave data from submarine cable seismic data, making accurate inversion of mid-deep strata velocities difficult. This invention is computationally simple, easy to implement, highly adaptable, and provides highly reliable inversion results.

[0063] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0064] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0065] Figure 1 A flowchart of a seismic data combined slope tomography method provided in an embodiment of the present invention;

[0066] Figure 2 This is a diagram of the actual speed model of the present invention;

[0067] Figure 3 This is a diagram of the initial velocity model of the present invention;

[0068] Figure 4This is a diagram of the inversion velocity model of the present invention;

[0069] Figure 5 This is a diagram showing the velocity model retrieved using a conventional slope tomography method. Detailed Implementation

[0070] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0071] The terms "comprising" and "having," and any variations thereof, in the specification, embodiments, claims, and drawings of this invention are intended to cover non-exclusive inclusion, such as including a series of steps or units.

[0072] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0073] like Figure 1 As shown, this invention is a method for combined slope tomography imaging using seismic data from submarine cables and submarine nodes. The processing flow includes the following steps:

[0074] Step 1: Preprocess the seismic data of submarine cables and submarine nodes;

[0075] Step 2: Extract the travel time and travel slope of locally coherent reflected waves from the preprocessed seismic data of submarine cables and submarine nodes;

[0076] Step 3: Extract the first arrival travel time from the preprocessed seismic data of submarine cables and submarine nodes;

[0077] Step 4: Construct the objective function for combined slope tomography of submarine cable and submarine node seismic data; the formula for calculating the objective function is as follows:

[0078]

[0079] Where E represents the objective function, σ1 represents the standard deviation of the first arrival travel time in the seismic data of the submarine cable and submarine node, σ2 represents the standard deviation of the reflected wave travel time in the seismic data of the submarine cable and submarine node, σ3 represents the standard deviation of the reflected wave travel time slope in the seismic data of the submarine cable and submarine node, and T fb_obc T represents the first arrival wave travel time in submarine cable seismic data. fb_obn T represents the first arrival travel time in the seismic data of the seafloor node. re_obc T represents the travel time of reflected waves in seismic data of submarine cables. re_obnThis indicates the travel time of reflected waves in seismic data from seabed nodes. This represents the travel-time slope at the shot point of the reflected wave in seismic data of submarine cables. This represents the travel time slope at the receiver end of the reflected wave in seismic data of submarine cables. This represents the travel-time slope at the shot point of the reflected wave in the seismic data of the seafloor node. N represents the travel time slope at the receiver end of the reflected wave in the seismic data of the seafloor node. fb_obc N represents the total number of first-arrival travel times retrieved from submarine cable seismic data. fb_obn N represents the total number of first arrival travel times retrieved from the seismic data of the seafloor nodes. re_obc N represents the total number of reflected wave travel time data picked up from submarine cable seismic data. re_obn This indicates the total number of reflected wave travel time data picked up from the seismic data of the seabed node. The superscript * indicates data picked up from the actual observed seismic data.

[0080] Step 5: Calculate the gradient of the objective function with respect to velocity; the gradient of the objective function with respect to velocity is calculated using the following formula:

[0081]

[0082] Where E represents the objective function, v represents the velocity, and N represents the velocity. s_obc N represents the total number of shot points in submarine cable seismic data. r _obc N represents the total number of receivers in the submarine cable seismic data. s_obn N represents the total number of shot points in the seabed nodal seismic data. r _obn This represents the total number of receivers in the seabed nodal seismic data, is represents the shot point number, ir represents the receiver number, and λ represents the receiver number. obc λ represents the associated state variable corresponding to submarine cable seismic data. obn This represents the associated state variables corresponding to the submarine node seismic data; the associated state variables corresponding to the submarine cable seismic data are calculated jointly from the first arrival wave travel time fitting error, reflected wave travel time fitting error, reflected wave shot point end travel time slope fitting error, and reflected wave receiver end travel time slope fitting error in the submarine cable seismic data; the first arrival wave travel time fitting error in the submarine cable seismic data is calculated using the following formula:

[0083] ΔT fb_obc =T fb_obc -T *,fb _ obc (3)

[0084] Where, ΔT fb_obcT represents the fitting error of the first arrival wave travel time in submarine cable seismic data. fb_obc The first arrival travel time in submarine cable seismic data is represented by the superscript *, indicating data picked up from actual observed seismic data. The fitting error of the reflected wave travel time in submarine cable seismic data is calculated using the following formula:

[0085] ΔT re_obc =T re_obc -T *,re_obc (4)

[0086] Where, ΔT re_obc T represents the travel time fitting error of reflected waves in seismic data of submarine cables. re_obc The travel time of reflected waves in submarine cable seismic data is represented by the superscript *, indicating data picked up from actual observational seismic data. The fitting error of the travel time slope at the shot point of reflected waves in submarine cable seismic data is calculated using the following formula:

[0087]

[0088] in, This indicates the fitting error of the travel-time slope at the shot point of the reflected wave in the seismic data of submarine cables. This represents the travel time slope at the shot point of the reflected wave in submarine cable seismic data. The superscript * indicates data picked up from actual observed seismic data. The fitting error of the travel time slope at the receiver point of the reflected wave in submarine cable seismic data is calculated using the following formula:

[0089]

[0090] in, This indicates the fitting error of the travel time slope at the receiver end of the reflected wave in seismic data of submarine cables. This represents the travel time slope at the receiver end of the reflected wave in the submarine cable seismic data. The superscript * indicates data picked up from actual observed seismic data. The associated state variables corresponding to the submarine node seismic data are calculated jointly from the first arrival wave travel time fitting error, the reflected wave travel time fitting error, the shot point end travel time slope fitting error, and the receiver end travel time slope fitting error in the submarine node seismic data. The first arrival wave travel time fitting error in the submarine node seismic data is calculated using the following formula:

[0091] ΔT fb_obn =T fb_obn -T *,fb_obn (7)

[0092] Where, ΔT fb_obn T represents the fitting error of the first arrival wave travel time in the seismic data of the seafloor node. fb_obnThe first arrival travel time in the seismic data of the seafloor node is represented by the superscript *, indicating data picked from actual observed seismic data. The fitting error of the reflected wave travel time in the seismic data of the seafloor node is calculated using the following formula:

[0093] ΔT re_obn =T re_obn -T *,re_obn (8)

[0094] Where, ΔT re_obn T represents the travel time fitting error of reflected waves in seismic data from seafloor nodes. re_obn The value represents the travel time of reflected waves in the seismic data of the seafloor node. The superscript * indicates that the data was picked up from the actual observed seismic data. The fitting error of the travel time slope of reflected waves at the shot point in the seismic data of the seafloor node is calculated using the following formula:

[0095]

[0096] in, This represents the fitting error of the travel-time slope at the shot point of the reflected wave in the seismic data of the seafloor node. This represents the travel time slope at the shot point of the reflected wave in the seismic data of the seafloor node. The superscript * indicates that the data was picked up from the actual observed seismic data. The fitting error of the travel time slope at the receiver point of the reflected wave in the seismic data of the seafloor node is calculated using the following formula:

[0097]

[0098] in, This represents the fitting error of the travel time slope at the receiver end of the reflected wave in the seismic data of the seabed node. This represents the travel time slope at the receiver end of the reflected wave in the seismic data of the seafloor node. The superscript * indicates that the data was picked up from the actual observed seismic data.

[0099] Step Six: Calculate the gradient of the objective function with respect to the spatial coordinates of the reflection point corresponding to the reflected wave in the submarine cable seismic data; the gradient of the objective function with respect to the spatial coordinates of the reflection point corresponding to the reflected wave in the submarine cable seismic data is calculated using the following formula:

[0100]

[0101] Where E represents the objective function, σ1 represents the spatial coordinates of the reflection point corresponding to the reflected wave in the seismic data of the submarine cable, σ2 represents the standard deviation of the travel time of the reflected wave in the seismic data of the submarine cable and the submarine node, σ3 represents the standard deviation of the travel time slope of the reflected wave in the seismic data of the submarine cable and the submarine node, and T represents the standard deviation of the travel time slope of the reflected wave in the seismic data of the submarine cable and the submarine node. re _ obc This indicates the travel time of reflected waves in seismic data of submarine cables. This represents the travel-time slope at the shot point of the reflected wave in seismic data of submarine cables. This represents the travel time slope at the receiver end of the reflected wave in the seismic data of submarine cables. The superscript * indicates that the data was picked up from the actual observed seismic data.

[0102] Step 7: Calculate the gradient of the objective function with respect to the spatial coordinates of the reflection points corresponding to the reflected waves in the seafloor node seismic data; the gradient of the objective function with respect to the spatial coordinates of the reflection points corresponding to the reflected waves in the seafloor node seismic data is calculated using the following formula:

[0103]

[0104] Where E represents the objective function, σ1 represents the spatial coordinates of the reflection point corresponding to the reflected wave in the seismic data of the submarine cable and the submarine node, σ2 represents the standard deviation of the travel time of the reflected wave in the seismic data of the submarine cable and the submarine node, σ3 represents the standard deviation of the travel time slope of the reflected wave in the seismic data of the submarine cable and the submarine node, and T represents the standard deviation of the travel time slope of the reflected wave in the seismic data of the submarine cable and the submarine node. re_obn This indicates the travel time of reflected waves in seismic data from seabed nodes. This represents the travel-time slope at the shot point of the reflected wave in the seismic data of the seafloor node. This represents the travel time slope at the receiver end of the reflected wave in the seismic data of the seafloor node. The superscript * indicates that the data was picked up from the actual observed seismic data.

[0105] Step 8: Calculate the update step size for the current iteration's velocity; the formula for calculating the velocity update step size is as follows:

[0106]

[0107] Where, η v The update step size, μ, represents the velocity. v E1 represents the trial step size for velocity updates, where E1 represents a step size of 0 times μ. v The updated objective function value, E2, represents the value updated by 1 μ. v The updated objective function value, E3, represents the value at twice the μ value. v The objective function value after updating the velocity;

[0108] Step 9: Calculate the update step size of the spatial coordinates of the reflection points corresponding to the reflected waves in the seismic data of the submarine cables and submarine nodes in the current iteration; the formula for calculating the update step size of the spatial coordinates of the reflection points is as follows:

[0109]

[0110] Where, η c μ represents the update step size of the spatial coordinates of the reflection point. c E4 represents the trial step size for updating the spatial coordinates of the reflection point, where E4 indicates a step size of 0 times μ.c The objective function value after updating the spatial coordinates of the reflection point, E5 represents the value after multiplying by 1 μ. c The objective function value after updating the spatial coordinates of the reflection point, E6 represents a value increased by 2 times μ. c The objective function value after updating the spatial coordinates of the reflection point;

[0111] Step 10: Update the speed; the speed update can be represented as follows:

[0112]

[0113] Where k represents the current iteration number, v represents the speed, and η v The update step size represents the velocity. This represents the gradient of the objective function with respect to velocity;

[0114] Step 11: Update the spatial coordinates of the reflection points corresponding to the reflected waves in the seismic data of submarine cables and submarine nodes;

[0115] Step 12: Determine if the updated velocity meets the requirements: If it does, output the velocity and spatial coordinates of the reflection point; if it does not, return to Step 4, and use the updated velocity as the new velocity and the updated spatial coordinates of the reflection point as the new spatial coordinates of the reflection point.

[0116] In step one, the seismic data of submarine cables and submarine nodes are preprocessed, including random noise suppression, multiple wave suppression, and reflected wave amplitude equalization.

[0117] Step S1: Use the model containing the high-speed buried hill as the true velocity model (e.g., Figure 2 (As shown). The actual velocity model is 50km long, 5km wide, and 5km deep. It is discretized using a square mesh with a mesh size of 10m.

[0118] Step S2: Observation System: Shot lines and receiver points are laid out along the X-direction. The spacing between shot lines and receiver points is 100m. The spacing between shot points is 200m, and the spacing between receiver points is 100m. The seismic record sampling time is 5s, and the sampling interval is 1ms.

[0119] Step S3: From the real velocity model (e.g.) Figure 2 (As shown) and a Ricker wavelet with a source function of 15Hz, seismic records were obtained through forward modeling using a regular grid acoustic equation with second-order time and 12th-order spatial accuracy, and with perfectly matched layer boundary conditions. These records were then used as the observed seismic records. Seismic records with offsets less than 5km were selected from the observed seismic records as the submarine cable seismic records. Seismic records with offsets less than 40km were selected from the observed seismic records as the submarine node seismic records.

[0120] Step S4: Preprocess the observed seismic records of submarine cables and submarine nodes, and then extract the travel time and travel slope of reflected waves from the preprocessed seismic records, obtaining a total of 131,816 sets of data.

[0121] Step S5: Extract the first arrival wave travel time data from the preprocessed seismic records, obtaining a total of 4,762,119 sets of data.

[0122] Step S6: Establish a model where velocity increases linearly with depth as the initial velocity model (e.g., ...). Figure 3 (As shown); the initial velocity model has the same dimensions as the actual model. It is discretized using a square mesh with a mesh size of 200m.

[0123] Step S7: Construct the objective function for joint slope tomography of submarine cable and submarine node seismic data using formula (1), and set the maximum number of inversion iterations to 30.

[0124] Step S8: Calculate the gradient of the objective function with respect to velocity using formula (2).

[0125] Step S9: Calculate the gradient of the objective function with respect to the spatial coordinates of the reflection points corresponding to the reflected waves in the seismic data of submarine cables and submarine nodes using formulas (11) and (12), respectively.

[0126] Step S10: Update the speed with trial step sizes of 0, 1 and 2 times respectively, calculate the corresponding objective function value, and then use formula (13) to calculate the speed update step size of the current iteration.

[0127] Step S11: Update the spatial coordinates of the reflection point with trial step sizes of 0, 1 and 2 times the spatial coordinates of the reflection point respectively, calculate the corresponding objective function value, and then use formula (14) to calculate the update step size of the spatial coordinates of the reflection point in the current iteration.

[0128] Step S12: Update the speed using formula (15).

[0129] Step S13: Update the spatial coordinates of the reflection points corresponding to the reflected waves in the seismic data of submarine cables and submarine nodes.

[0130] Step S14: Determine whether the updated speed meets the requirements, whether the objective function value of the current iteration no longer decreases, or whether the current iteration number has reached the maximum iteration number; if yes, output the speed and spatial coordinates of the reflection point; if not, return to step S7.

[0131] Figure 4 This is a diagram of the inversion velocity model of the present invention. From Figure 4 It can be clearly seen that the inversion velocity model of this invention has high-speed buried hills in the middle and deep parts. Figure 5This is a velocity model inverted using a conventional slope tomography method. Comparing the velocity models inverted by this invention and those of the conventional slope tomography method with the actual velocity models, it is clear that the velocity model inverted by this invention is closer to the actual velocity model, and high-speed buried hills in the middle and deep parts are accurately inverted.

[0132] Beneficial effects: This invention proposes a combined slope tomography method using seismic data from submarine cables and submarine nodes. It combines the first arrival travel time, reflected wave travel time, and reflected wave travel time slope data from both submarine cable and submarine node seismic data, thus solving the problem that existing slope tomography methods in marine oil and gas seismic exploration cannot accurately invert macroscopic velocities in the middle and deep strata by only using the reflected wave travel time and travel time slope picked up from submarine cable seismic data.

[0133] The above specific embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for combined slope tomography of seismic data, characterized in that, The imaging method includes: Preprocessing of seismic data for submarine cables and submarine nodes; Extract the travel time of reflected waves, the travel slope of reflected waves, and the travel time of first arrival waves from the preprocessed seismic data; Construct an objective function for combined slope tomography imaging of submarine cable and submarine node seismic data; Calculate the gradient of the objective function with respect to velocity and the gradient of the spatial coordinates of the reflection point; Calculate the update parameters for velocity and spatial coordinates of the reflection point; Determine if the updated velocity meets the requirements. If it does, output the velocity and the spatial coordinates of the reflection point; otherwise, continue the iterative inversion.

2. The method for combined slope tomography of seismic data according to claim 1, characterized in that, The update parameters specifically include: update step size, update speed, and update spatial coordinates of the reflection point.

3. The method for combined slope tomography of seismic data according to claim 1, characterized in that, The specific steps of extracting reflected wave travel time, reflected wave travel time slope, and first arrival wave travel time from preprocessed seismic data include: Locally coherent reflected wave travel times and travel slopes are extracted from preprocessed seismic data of submarine cables and submarine nodes. First arrival travel times are extracted from preprocessed seismic data of submarine cables and submarine nodes.

4. The method for combined slope tomography of seismic data according to claim 1, characterized in that, The objective function for constructing joint slope tomography of submarine cable and submarine node seismic data specifically includes: The formula for calculating the objective function is as follows: Where E represents the objective function, |σ1| represents the standard deviation of the first arrival travel time in the seismic data of the submarine cable and submarine node, σ2 represents the standard deviation of the reflected wave travel time in the seismic data of the submarine cable and submarine node, σ3 represents the standard deviation of the reflected wave travel time slope in the seismic data of the submarine cable and submarine node, and T fb_obc T represents the first arrival wave travel time in submarine cable seismic data. fb_obn T represents the first arrival travel time in the seismic data of the seafloor node. re_obc T represents the travel time of reflected waves in seismic data of submarine cables. re_obn This indicates the travel time of reflected waves in seismic data from seabed nodes. This represents the travel-time slope at the shot point of the reflected wave in seismic data of submarine cables. This represents the travel time slope at the receiver end of the reflected wave in seismic data of submarine cables. This represents the travel-time slope at the shot point of the reflected wave in the seismic data of the seafloor node. N represents the travel time slope at the receiver end of the reflected wave in the seismic data of the seafloor node. fb_obc N represents the total number of first-arrival travel times retrieved from submarine cable seismic data. fb_obn N represents the total number of first arrival travel times retrieved from the seismic data of the seafloor nodes. re_obc N represents the total number of reflected wave travel time data picked up from submarine cable seismic data. re_obn This represents the total number of reflected wave travel time data picked up from seafloor node seismic data. The superscript * indicates data picked up from actual observed seismic data.

5. The method for combined slope tomography of seismic data according to claim 1, characterized in that, The calculation of the gradient of the objective function with respect to velocity specifically includes: The gradient of the objective function with respect to velocity is calculated using the following formula: Where E represents the objective function, v represents the velocity, and N represents the velocity. s_obn N represents the total number of shot points in submarine cable seismic data. r_obc N represents the total number of receivers in the submarine cable seismic data. s_obn N represents the total number of shot points in the seabed nodal seismic data. r_obn This represents the total number of receivers in the seabed nodal seismic data, is represents the shot point number, ir represents the receiver number, and λ represents the receiver number. obc λ represents the associated state variable corresponding to submarine cable seismic data. obn This represents the associated state variables corresponding to the submarine node seismic data; the associated state variables corresponding to the submarine cable seismic data are calculated jointly from the first arrival wave travel time fitting error, reflected wave travel time fitting error, reflected wave shot point end travel time slope fitting error, and reflected wave receiver end travel time slope fitting error in the submarine cable seismic data; the first arrival wave travel time fitting error in the submarine cable seismic data is calculated using the following formula: ΔT fb_obc =T fb_obc -T *,fb_obc (3) Where, ΔT fb_obc T represents the fitting error of the first arrival wave travel time in submarine cable seismic data. fb_obc The first arrival travel time in submarine cable seismic data is represented by the superscript *, indicating data picked up from actual observed seismic data. The fitting error of the reflected wave travel time in submarine cable seismic data is calculated using the following formula: ΔT re_obc =T re_obc -T *,re_obc , (4) Where, ΔT re_obc T represents the travel time fitting error of reflected waves in seismic data of submarine cables. re_obc The travel time of reflected waves in submarine cable seismic data is represented by the superscript *, indicating data picked up from actual observational seismic data. The fitting error of the travel time slope at the shot point of reflected waves in submarine cable seismic data is calculated using the following formula: in, This indicates the fitting error of the travel-time slope at the shot point of the reflected wave in the seismic data of submarine cables. This represents the travel time slope at the shot point of the reflected wave in submarine cable seismic data. The superscript * indicates data picked up from actual observed seismic data. The fitting error of the travel time slope at the receiver point of the reflected wave in submarine cable seismic data is calculated using the following formula: in, This indicates the fitting error of the travel time slope at the receiver end of the reflected wave in seismic data of submarine cables. This represents the travel time slope at the receiver end of the reflected wave in the submarine cable seismic data. The superscript * indicates data picked up from actual observed seismic data. The associated state variables corresponding to the submarine node seismic data are calculated jointly from the first arrival wave travel time fitting error, the reflected wave travel time fitting error, the shot point end travel time slope fitting error, and the receiver end travel time slope fitting error in the submarine node seismic data. The first arrival wave travel time fitting error in the submarine node seismic data is calculated using the following formula: ΔT fb_obn =T fb_obn -T *,fb_obn , (7) Where, ΔT fb_obn T represents the fitting error of the first arrival wave travel time in the seismic data of the seafloor node. fb_obn The first arrival travel time in the seismic data of the seafloor node is represented by the superscript *, indicating data picked from actual observed seismic data. The fitting error of the reflected wave travel time in the seismic data of the seafloor node is calculated using the following formula: ΔT re_obn =T re_obn -T *,re_obn , (8) Where, ΔT re_obn T represents the travel time fitting error of reflected waves in seismic data from seafloor nodes. re_obn The value represents the travel time of reflected waves in the seismic data of the seafloor node. The superscript * indicates that the data was picked up from the actual observed seismic data. The fitting error of the travel time slope of reflected waves at the shot point in the seismic data of the seafloor node is calculated using the following formula: in, This illustrates the fitting error of the travel-time slope at the shot point of reflected waves in seismic data from seafloor nodes. The travel time slope at the shot point of the reflected wave in the seismic data of the seafloor node is shown. The superscript * indicates data picked from actual observed seismic data. The fitting error of the travel time slope at the receiver point of the reflected wave in the seismic data of the seafloor node is calculated using the following formula: in, This represents the fitting error of the travel time slope at the receiver end of the reflected wave in the seismic data of the seabed node. This represents the travel time slope at the receiver end of the reflected wave in the seismic data of the seafloor node. The superscript * indicates that the data was picked up from the actual observed seismic data.

6. The method for combined slope tomography of seismic data according to claim 1, characterized in that, The calculation of the gradient of the objective function with respect to the spatial coordinates of the reflection point specifically includes: The gradient of the objective function with respect to the spatial coordinates of the reflection point corresponding to the reflected wave in the seismic data of submarine cables is calculated using the following formula: Where E represents the objective function, σ1 represents the spatial coordinates of the reflection point corresponding to the reflected wave in the seismic data of the submarine cable, σ2 represents the standard deviation of the travel time of the reflected wave in the seismic data of the submarine cable and the submarine node, σ3 represents the standard deviation of the travel time slope of the reflected wave in the seismic data of the submarine cable and the submarine node, and T represents the standard deviation of the travel time slope of the reflected wave in the seismic data of the submarine cable and the submarine node. re_obc This indicates the travel time of reflected waves in seismic data of submarine cables. This represents the travel-time slope at the shot point of the reflected wave in seismic data of submarine cables. This represents the travel time slope at the receiver end of the reflected wave in the seismic data of submarine cables. The superscript * indicates that the data was picked up from the actual observed seismic data.

7. The method for combined slope tomography of seismic data according to claim 2, characterized in that, The update step size for calculating the velocity of the current iteration is as follows: Where, η v The update step size, μ, represents the velocity. v E1 represents the trial step size for velocity updates, where E1 represents a step size of 0 times μ. v The updated objective function value, E2, represents the value updated by 1 μ. v The updated objective function value, E3, represents the value at twice the μ value. v The objective function value after updating the speed.

8. The method for combined slope tomography of seismic data according to claim 2, characterized in that, The update step size for the spatial coordinates of the reflection points corresponding to the reflected waves in the seismic data of the submarine cables and submarine nodes in the current iteration is calculated; the formula for calculating the update step size of the spatial coordinates of the reflection points is as follows: Where, η c μ represents the update step size of the spatial coordinates of the reflection point. c E4 represents the trial step size for updating the spatial coordinates of the reflection point, where E4 indicates a step size of 0 times μ. c The objective function value after updating the spatial coordinates of the reflection point, E5 represents the value after multiplying by 1 μ. c The objective function value after updating the spatial coordinates of the reflection point, E6 represents a value increased by 2 times μ. c The objective function value after updating the spatial coordinates of the reflection point.

9. The method for combined slope tomography of seismic data according to claim 2, characterized in that, The update speed; the speed update is represented as: Where k represents the current iteration number, v represents the speed, and η v The update step size represents the velocity. This represents the gradient of the objective function with respect to velocity.

10. A method for combined slope tomography of seismic data according to claim 2, characterized in that, The update parameters for calculating velocity and spatial coordinates of reflection points also include updating the spatial coordinates of reflection points corresponding to reflected waves in the seismic data of submarine cables and submarine nodes.

11. The method for combined slope tomography of seismic data according to claim 1, characterized in that, The method for preprocessing seismic data of submarine cables and submarine nodes specifically includes: random noise suppression, multiple wave suppression, and reflected wave amplitude equalization.

Images