Shallow water node relocation method, medium and device based on first arrival polarization characteristic constraint

Abstract

The present application relates to a kind of shallow sea seabed node redirection method based on first arrival polarization characteristic constraint, medium and equipment, belong to geophysical exploration data processing technical field.The method includes the following steps: extracting common receiver gather from analog or field collected four-component seismic data, obtaining first arrival time and propagation azimuth, according to the energy distribution of first arrival time window, polarization characteristic and P, Z component correlation jointly constrained construction target function;Directional parameter solution and seabed node acquisition seismic data directional correction.In addition, the present application comprehensively utilizes the energy of first arrival wave, polarization characteristic and P, Z component correlation to carry out geophone redirection, can solve the application condition restriction, insufficient precision in the method of conventional only using direct wave to carry out redirection and the multi-solution problem existing in reflection wave energy method itself.

Description

Technical Field

[0001] The present invention belongs to the field of exploration geophysics, and in particular relates to a shallow seabed node redirection method, medium and equipment based on first-arrival polarization characteristic constraints. Background Art

[0002] Currently, multi-component seafloor seismic observations have become an important technical tool for oil and gas resource exploration and geological structure research. With the continuous development of Ocean Bottom Node (OBN) technology, the deployment of hydrophones and three-component geophones on the seafloor enables comprehensive recording of seismic wavefields, providing a solid data foundation for detailed imaging of stratigraphic structures and multi-physics interpretation. However, due to factors such as complex seafloor topography and ocean current disturbances, the actual node posture often deviates from the preset coordinate system, resulting in energy aliasing between component signals. If subsequent data processing is performed directly without correcting the node posture, severe interference artifacts will be introduced, affecting the accuracy of seismic data interpretation.

[0003] Currently, commonly used node orientation methods rely on direct wave signals. By analyzing the polarization characteristics of direct waves, node orientation parameters are inferred to accurately locate the energy between components. However, due to factors such as seafloor topography shielding, source interference, and shallow-water sedimentary environments, direct waves in shallow-water OBN data often interfere with subsequent arrivals, making it difficult to accurately pick up the first arrival of the direct wave. Furthermore, there is a certain discrepancy between the polarization direction of the direct wave and the actual propagation direction, and this discrepancy gradually increases with increasing offset. These factors all have a negative impact on node orientation results. In recent years, relevant scholars have proposed methods that construct objective functions based on the characteristics of reflected or refracted waves to solve for orientation parameters. However, existing methods are generally relatively simple in constructing objective functions and fail to fully integrate the physical constraints of multi-component wavefields and the correlation between data. Furthermore, traditional angle scanning methods are often used in the objective function solution process, resulting in low computational efficiency and difficulty in meeting the requirements of efficient and high-precision processing. In view of the above problems, there is an urgent need to develop a node attitude redirection method that can integrate multi-component wave field information, has global optimization capabilities, and is adaptable to extremely shallow sea operating environments, so as to further improve the data processing accuracy and imaging quality of multi-component seismic exploration. Summary of the Invention

[0004] The present invention addresses the shortcomings of existing technologies and provides a method for redirecting shallow-water seabed nodes based on first-arrival polarization characteristic constraints. This method is simple in steps and rationally designed, fully utilizing the energy, polarization characteristics, and correlation between the P and Z components of the first-arrival wave to achieve high-precision node orientation correction. Compared to the problems of insufficient accuracy and limited applicable environments associated with redirection relying solely on direct waves, as well as the multiple solutions that can arise when using only the first-arrival energy constraint, the method of the present invention offers greater practicality and reliability.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A shallow seabed node redirection method based on first-arrival polarization characteristic constraints, the method comprising the following steps:

[0007] Step S10: extracting common detection point gathers from the four-component seismic data collected in simulation or in the field;

[0008] Step S20: Acquire the first arrival time and propagation azimuth;

[0009] Step S30: Based on the energy distribution within the first arrival time window, the polarization characteristics of the direct wave and the refracted wave, and the correlation between the P and Z components, a target function suitable for seafloor node redirection is jointly constructed. Specifically, the target function includes: first, rotating the horizontal components X and Y of the seismic record according to the calculated azimuth parameters to obtain radial and tangential components, respectively. By adjusting the node attitude parameters, the energy of the tangential component within the first arrival time window is minimized, thereby optimizing the node orientation parameters; at the same time, combining the polarization characteristics of the first arrival wave and the correlation between the P and Z components, multiple constraints are added;

[0010] The objective function is as follows:

[0011] ;

[0012] Where, is the sampling time of seismic data; are the radial, tangential and vertical components after the horizontal component is rotated, respectively, where is the shot number in the common detection point gather, is the total number of channels involved in the calculation in the common detection point gather; and The start and end time of the time window; Represent the constraint logic values ​​of the direct wave, refracted wave, P, and Z component correlation respectively, is the penalty coefficient of the corresponding item. If the corrected X, Y, and Z components are in the correct coordinate system, then are all 1, then the first three terms of the function have no constraint effect; if the X and Y axes are reversed after correction, then ; If the Y and Z axes are reversed after calibration: ; If the X and Z axes are reversed after calibration: ; When in formula (1) The minimum corresponding That is the optimal orientation angle;

[0013] Step S40: Obtaining the optimal orientation parameter by finding the minimum value of the objective function: Obtaining the optimal orientation parameter by optimizing the objective function constructed in step S30;

[0014] Step S50: Directional correction of the seafloor node seismic data.

[0015] Furthermore, in step S10: according to a preset velocity model, four-component seismic data including hydrophones and three-component geophones are obtained through elastic wave forward modeling or field acquisition using an actual observation system, and the acquired data are converted into common detection point gathers;

[0016] Furthermore, in step S20, when the source ship excites seismic waves at N shot points and propagates to the seabed, the first arrival time of the seismic record received by the geophone point is picked up, and the accurate spatial coordinates of the geophone point are obtained by means of secondary positioning technology, and the spatial coordinates of the shot point and the geophone point are combined, and the coordinates are calculated according to the formula Calculate the propagation azimuth of the seismic wave, where and Denote the position coordinates of the receiver point and the shot point respectively. The azimuth is obtained by calculation, and according to formula (2), the horizontal coordinate system XY is rotated to the radial tangential RT coordinate system.

[0017] ;

[0018] Furthermore, the multiple constraints described in step S30: ① For the direct wave, using its polarization characteristics, add the constraint ,in 、 They represent the projection of the direct wave polarization vector on the XOZ plane;

[0019] ② For the refracted wave, use its polarization characteristics and add constraints ,in 、 They represent the projection of the refracted wave polarization vector on the XOZ plane;

[0020] ③ Even when the X and Z axes are in reverse, the above constraints are still valid. By calculating the correlation coefficient between the corrected Z component and the P component and selecting combinations with positive correlation coefficients, multiple solutions can be further eliminated to ensure the uniqueness and accuracy of the orientation results.

[0021] Furthermore, the optimization described in step S40 employs the Whale Optimization Algorithm (BWO) to globally optimize the objective function. During the optimization process, the algorithm sequentially undergoes three phases: exploration, development, and whale fall, which respectively implement global exploration, local fine-tuning, and random perturbation.

[0022] Further, the step S50: according to step S40, the optimal orientation parameters are obtained. , perform directional correction processing on the three-component seismic records in the seabed node according to formula (3) to obtain the seismic records collected and received in the preset coordinate system;

[0023] (3);

[0024] In the formula Represents the Euler matrix of rotation around the X, Y and Z axes respectively, is the angle of rotation around the corresponding axis of rotation, is the unrotated data, is the data after rotation, where It can be expressed as:

[0025] (4);

[0026] The present invention also provides a computer-readable storage medium having a computer program stored thereon. The computer program can be loaded and executed by a processor to implement a shallow seabed node redirection method based on first-arrival polarization characteristic constraints.

[0027] The present invention also provides a computer device, which includes a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, it can implement a shallow seabed node redirection method based on first-arrival polarization characteristic constraints.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The method of the present invention has simple steps and reasonable design, which significantly improves the accuracy and efficiency of seabed node detector redirection.

[0030] 2. The present invention has a simple operational process and excellent application effects. Specifically, it includes: obtaining four-component seismic data including a hydrophone and a three-component geophone; picking the first arrival time within the common detection gather, selecting an appropriate time window length, and calculating the propagation azimuth based on the shot detection point coordinates; then, using the Beluga optimization algorithm to solve the minimum value of the objective function and obtain the optimal directional parameters; finally, performing directional correction on the X, Y, and Z three-component seismic records based on the obtained directional parameters.

[0031] 3. When constructing the objective function, the present invention comprehensively utilizes the energy distribution, polarization characteristics and correlation between the P and Z components of the first arrival wave, and effectively improves the robustness and reliability of the node attitude inversion results through multiple physical constraints.

[0032] In summary, the method of the present invention has simple steps and reasonable design. It realizes efficient redirection of the three-component detector based on the first-arrival wave energy, polarization characteristics and the correlation between P and Z components, overcomes the shortcomings of the existing method that only relies on the direct wave polarization characteristics or the first-arrival energy, and has strong practicality and promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is the workflow diagram of the four-component seafloor node redirection method;

[0034] Figure 2 Schematic diagram of the polarization characteristics of the first arrival waves (direct wave and refracted wave); (a), (c), (e), and (g) represent the projection of the polarization vector on the XOZ plane for the direct wave incident; (b), (d), (f), and (h) represent the projection of the polarization vector on the XOZ plane for the refracted wave incident;

[0035] Figure 3 To simulate the X, Y, and Z three-component seismic records collected by unoriented seabed nodes

[0036] Figure 4 is the projection of the unoriented polarization vector in the XOZ and XOY planes, a is the projection of the first-arrival polarization vector in the XOZ plane, and b is the projection of the first-arrival polarization vector in the XOY plane;

[0037] Figure 5 The X, Y, and Z three-component seismic records after the redirection correction using the present invention are as follows;

[0038] Figure 6 The polarization vector after orientation in the present invention is projected on the XOZ and XOY planes. a is the symmetrical distribution of the polarization vector on both sides of the detection point in the XOZ plane, and b is the projection of the polarization vector in the XOY plane. DETAILED DESCRIPTION

[0039] The technical solution of the present invention is further explained below through examples, but the protection scope of the present invention is not limited in any form by the examples.

[0040] Example 1

[0041] like Figure 1 A new shallow seabed node redirection technology based on first-arrival polarization characteristic constraint is shown, which includes the following steps:

[0042] Step S10: Acquisition of four-component seismic data:

[0043] Based on the established velocity model, elastic wave forward simulation is performed, or a corresponding observation system is designed for actual field acquisition to obtain seismic data of four components including hydrophones and three-component geophones, and the obtained data are converted into common detection point gathers.

[0044] Step S20: Acquisition of first arrival time and propagation azimuth:

[0045] When the source ship excites seismic waves at N shot points and propagates to the seabed, the first arrival time of the seismic record received by the geophone point is picked up. The accurate spatial coordinates of the geophone point are obtained by means of secondary positioning technology, and the spatial coordinates of the shot point and the geophone point are used, and according to the formula Calculate the propagation azimuth of the seismic wave, where and Represent the position coordinates of the detection point and the shot point respectively.

[0046] Step S30: Based on the energy distribution in the first arrival time window, the polarization characteristics of the direct wave and the refracted wave, and the correlation between the P and Z components, a target function suitable for seabed node redirection is jointly constructed to provide a basis for the inversion and optimization of the subsequent node attitude parameters.

[0047] The goal of step S30 is to find the optimal detector orientation angle . In order to overcome the multi-solution problem that is prone to occur when using only the first-arrival energy method for detector orientation, the present invention jointly utilizes the energy distribution in the first-arrival time window, the polarization characteristics of the direct wave and the refracted wave, and the correlation between the P and Z components to construct an objective function suitable for seabed node redirection. Specifically, it includes: first, according to the calculated azimuth parameters, the horizontal components X and Y of the seismic record are rotated to obtain the radial component (R) and the tangential component (T), respectively. In theory, the vibration direction of the P wave and the P-SV conversion wave is mainly concentrated in the radial component and the vertical component, and the energy of the tangential component should be close to the minimum. Therefore, by adjusting the node attitude parameters, the energy of the tangential component in the first-arrival time window is minimized, thereby realizing the optimization of the node orientation parameters. At the same time, combined with the polarization characteristics of the first-arrival wave and the correlation between the P and Z components, multiple constraints are added to further improve the accuracy and stability of the inversion of the actual attitude parameters of the node.

[0048] The objective function is as follows:

[0049] (1);

[0050] Where, is the sampling time of seismic data; are the radial, tangential and vertical components after the horizontal component is rotated, respectively, where is the shot number in the common detection point gather, is the total number of channels involved in the calculation in the common detection point gather; and The start and end time of the time window; Represents the constraint logic value of direct wave, refracted wave, P and Z component correlation respectively, is the penalty coefficient of the corresponding item, which is set to 100 in this embodiment. If the corrected X, Y, and Z components are in the correct coordinate system, then are all 1, then the first three terms of the function have no constraint effect; if the X and Y axes are reversed after correction, then ; If the Y and Z axes are reversed after calibration: ; If the X and Z axes are reversed after calibration: ; When in formula (1) The minimum corresponding This is the optimal orientation angle.

[0051] Figure 2 The projection of the polarization vector of the first arrival wave (including direct wave and refracted wave) on the XOZ plane in different correction coordinate systems is shown in the figure. and is the detection point ( ) The shot points are symmetrically distributed on both sides of the earthquake. The dotted line represents the propagation direction of the seismic wave, and the solid line represents the polarization direction. Figure 2 (a) and (b) in the figure are the projections of the polarization vectors of the direct wave and the refracted wave on the XOZ plane in the correct coordinate system. Figure 2 (c) and (d)) and Y and Z axis reverse direction ( Figure 2 When the horizontal component of the three-component seismic data is rotated, it is still possible to make the second half of formula (1) reach a minimum value, resulting in multiple solutions for the orientation results.

[0052] In order to avoid the above multiple solutions, the following constraints are proposed:

[0053] ① For direct waves, use their polarization characteristics and add constraints ,in 、 They represent the projection of the direct wave polarization vector on the XOZ plane;

[0054] ② For the refracted wave, use its polarization characteristics and add constraints ,in 、 They represent the projection of the refracted wave polarization vector on the XOZ plane;

[0055] ③ Even if the X and Z axes are reversed ( Figure 2 In the cases (g) and (h) above, the above constraints are still valid. In addition, since the P component is a pressure-type sensor and is not affected by the detector attitude, and the P component and Z component waveforms are highly similar, the correlation coefficient between the corrected Z component and the P component is calculated, and combinations with positive correlation coefficients are selected to further eliminate multiple solutions and ensure the uniqueness and accuracy of the orientation results.

[0056] Step S40: Obtain the optimal orientation parameters by finding the minimum value of the objective function:

[0057] To balance computational accuracy and efficiency, this paper uses the White Whale Optimization Algorithm (WOA) to globally optimize the objective function and determine the optimal orientation parameters. This algorithm uses a phased global search and local fine-tuning, combined with random perturbations, to effectively improve convergence speed and result stability, achieving efficient and accurate inversion of the node's spatial pose.

[0058] During the exploration phase, the algorithm enhances global optimization capabilities through large-scale jump searches to prevent falling into local extremes; during the development phase, it focuses on fine-tuning near the current excellent solution to improve the accuracy of the solution and achieve local optimization; during the whale fall phase, random perturbations are introduced to improve population diversity and enhance the ability to escape local optimality and prevent premature convergence.

[0059] After each iteration, the current Euler angle solution is evaluated according to the objective function defined in S30, and the population position is updated accordingly. This optimization process significantly improves the global convergence speed and robustness of the node attitude parameter inversion, achieving efficient and accurate orientation of the node's actual spatial attitude.

[0060] Step S50: Directional correction of seismic data collected by seabed nodes:

[0061] Obtain the orientation parameters according to step S40 According to formula (3), the three-component seismic record after orientation is calculated:

[0062] (3);

[0063] In the formula Represents the Euler matrix of rotation around the X, Y and Z axes respectively, is the angle of rotation around the corresponding axis of rotation, is the unrotated data, is the data after rotation, where It can be expressed as:

[0064] (4);

[0065] In this example, the time window length selected in step S30 is = 40 sampling points. The choice of time window has a significant impact on polarization analysis results. A window that is too long introduces clutter, obscuring the true polarization state of the local signal. A window that is too short results in insufficient statistical samples, making it difficult to accurately identify the polarization direction. Therefore, the time window length must be appropriately set to balance signal purity and statistical stability.

[0066] In this example, the White Whale optimization algorithm is used to solve the objective function in step S40. The initial parameters of the algorithm are set as follows: , upper limit , the population size is 50, and the maximum number of iterations is 300. The inverse calculation of the node attitude parameters is performed in combination with the objective function proposed in this embodiment.

[0067] Figure 3 As shown in the figure, in the X, Y, and Z component seismic records collected by the seabed node before orientation, the Z component contains not only the P-wave signal, but also a large amount of S-wave energy. At the same time, the polarity of some of the phase axes on both sides of the Y component detection point is reversed, indicating that the attitude of the detector has changed. In order to qualitatively evaluate the rationality of the orientation result, Figure 4 The polarization vector of the first-arrival wave is projected into the XOZ plane (a) and the XOY plane (b) respectively. It is observed that the projection distribution of the undirected vector in the XOZ and XOY planes is relatively messy.

[0068] The propagation azimuth is calculated based on the shot detection coordinates, and the horizontal component is rotated to the radial and tangential directions (i.e., the direction of the shot detection line and the direction perpendicular to the shot detection line). Figure 5 As shown in the figure, after the redirection correction is performed using the method of the present invention, the X, Y, and Z component seismic records are significantly improved, the wave field information of each component is effectively restored, the shear wave in the Z component is significantly attenuated, the polarity on both sides of the Y component phase axis is basically symmetrical, and polarity reversal reappears on the X component. Figure 6 It shows that the oriented polarization vector is symmetrically distributed along both sides of the detection point in the XOZ plane (a), and in the XOY plane (b), the projection at the far offset position is more convergent. As the offset increases, the angle between the vector and the X-axis gradually decreases, indicating that the polarization characteristics are more consistent with the observation system.

[0069] The method of the present invention effectively solves the problems of wave field leakage and energy coupling caused by the deflection of the detector attitude, verifies the accuracy and practicality of the method in this paper, and has important guiding significance for the actual seabed node orientation work.

[0070] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with this technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered by the scope of protection of the present invention.

Claims

1. A shallow seabed node redirection method based on first arrival polarization characteristic constraint, characterized in that: The method includes the following Step: S10: extracting common detection point gathers from the four-component seismic data collected in simulation or in the field; Step S20: Acquire the first arrival time and propagation azimuth; Step S30: Based on the energy distribution within the first arrival time window, the polarization characteristics of the direct wave and the refracted wave, and the correlation between the P and Z components, a target function suitable for seabed node redirection is jointly constructed. Specifically, the target function includes: first, rotating the horizontal components X and Y of the seismic record according to the calculated azimuth parameters to obtain the radial component R and the tangential component T, respectively. By adjusting the node attitude parameters, the energy of the tangential component within the first arrival time window is minimized, thereby optimizing the node orientation parameters; at the same time, combining the polarization characteristics of the first arrival wave and the correlation between the P and Z components, multiple constraints are added; The objective function is as follows: (1) Where, F new represents the objective function with multiple constraints, is the sampling time of seismic data; are the radial, tangential and vertical components after the horizontal component is rotated, respectively, where is the shot number in the common detection point gather, is the total number of channels involved in the calculation in the common detection point gather; and The start and end time of the time window; Represent the constraint logic values ​​of the direct wave, refracted wave, P, and Z component correlation respectively, is the penalty coefficient of the corresponding item, is the angle of rotation around the corresponding axis of rotation; Step S40: Obtaining the optimal orientation parameter by finding the minimum value of the objective function: Obtaining the optimal orientation parameter by optimizing the objective function constructed in step S30; Step S50: Directional correction of the seafloor node seismic data.

2. The method according to claim 1, characterized in that In step S10, four-component seismic data including hydrophones and three-component geophones are obtained according to a preset velocity model through elastic wave forward modeling or field acquisition using an actual observation system, and the acquired data are converted into a common detection point gather.

3. The method according to claim 1, characterized in that Step S20: When the source ship excites seismic waves at N shot points and propagates to the seabed, the first arrival time of the seismic record received by the geophone point is picked up, and the accurate spatial coordinates of the geophone point are obtained by means of secondary positioning technology, and the spatial coordinates of the shot point and the geophone point are combined, and the coordinates are calculated according to the formula Calculate the propagation azimuth of the seismic wave, where and Represent the position coordinates of the detection point and the shot point respectively. The azimuth is obtained by calculation. According to formula (2), the horizontal coordinate system XY is rotated to the radial tangential RT coordinate system (2)。 4. The method according to claim 1, wherein The multiple constraints described in step S30: ① For direct waves, use their polarization characteristics and add constraints ,in 、 They represent the projection of the direct wave polarization vector on the XOZ plane; ② For the refracted wave, use its polarization characteristics and add constraints ,in 、 They represent the projection of the refracted wave polarization vector on the XOZ plane; ③ Even when the X and Z axes are in reverse, the above constraints are still valid. By calculating the correlation coefficient between the corrected Z component and the P component and selecting combinations with positive correlation coefficients, multiple solutions can be further eliminated to ensure the uniqueness and accuracy of the orientation results.

5. The method according to claim 1, wherein The optimization described in step S40: using the White Whale optimization algorithm to perform global optimization on the objective function.

6. The method according to claim 1, characterized in that Step S50: Obtaining the optimal orientation parameters according to step S40 , perform directional correction processing on the three-component seismic records in the seabed node according to formula (3) to obtain the seismic records collected and received in the preset coordinate system; (3) In the formula Represents the Euler matrix of rotation around the X, Y and Z axes respectively, is the angle of rotation around the corresponding axis of rotation, is the unrotated data, is the data after rotation, where It can be expressed as: (4)。 7. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, which can be loaded and executed by a processor to implement the shallow seabed node redirection method based on the first-arrival polarization characteristic constraint as described in any one of claims 1-6.

8. A computer device, characterized in that: The computer device includes a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, it can implement the shallow seabed node redirection method based on the first-arrival polarization characteristic constraint as described in any one of claims 1-6.

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