Shallow sea seabed node redirection method based on first arrival polarization characteristic constraint, medium and equipment

Abstract

The invention relates to a shallow sea seabed node redirection method based on first arrival polarization characteristic constraint, a medium and equipment, and belongs to the technical field of geophysical exploration data processing. The method comprises the following steps that a common detection point gather is extracted from four-component seismic data collected in a simulated or field mode, first arrival time and a propagation azimuth angle are obtained, and a target function is constructed according to seismic record energy distribution, polarization characteristics and P and Z component correlation common constraint in a first arrival time window; solving orientation parameters; and performing orientation correction on seismic data acquired by the seabed nodes. Besides, the detector is redirected by comprehensively utilizing the energy, the polarization characteristic and the P and Z component correlation of the first-motion wave, so that the problems of application condition limitation and insufficient precision existing in a conventional method for redirecting by only utilizing the direct wave and multiplicity of solutions existing in a reflected wave energy method can be solved.

Description

Technical Field

[0001] The present invention belongs to the field of exploration geophysics, and particularly relates to a method, medium and device for redirecting shallow sea bottom nodes based on the constraint of first arrival polarization characteristics. Background Art

[0002] At present, multi-component seismic observation on the seabed has become an important technical means for oil and gas resource exploration and geological structure research. With the continuous development of the Ocean Bottom Node (OBN) technology, by deploying hydrophones and three-component geophones on the seabed, the omnidirectional recording of seismic wave fields can be realized, providing a solid data foundation for the fine imaging of formation structures and the joint interpretation of multi-physical fields. However, affected by various factors such as the complex seabed topography and ocean current disturbances, the actual deployed node attitudes often deviate from the preset coordinate system, resulting in energy aliasing between component signals. If the node attitudes are not corrected and subsequent data processing is directly carried out, serious interference artifacts will be introduced, affecting the accuracy of seismic data interpretation.

[0003] At present, common node orientation methods mostly rely on direct wave signals, and calculate node orientation parameters by analyzing the polarization characteristics of direct waves to achieve accurate energy repositioning between components. However, affected by various factors such as seabed topography shielding, source interference, and shallow sea sedimentary environment, direct waves in shallow sea OBN data often interfere with multiple arrivals, making it difficult to accurately pick up the first arrival of direct waves; in addition, there is a certain difference between the polarization direction of direct waves and the actual propagation direction, and this difference gradually increases with the increase of the offset. The above factors all have an adverse impact on the node orientation results. In recent years, relevant scholars have proposed methods for constructing objective functions based on the characteristics of reflected waves or refracted waves and then solving orientation parameters. However, the existing methods are generally relatively single in constructing objective functions, failing to fully integrate the physical constraints of multi-component wave fields and the correlation between data. At the same time, traditional angle scanning means are mostly used in the process of solving objective functions, with low calculation efficiency and difficult to meet the requirements of high-efficiency and high-precision processing. In view of the above problems, there is an urgent need to develop a node attitude redirection method that can comprehensively utilize multi-component wave field information, has global optimization capabilities, and adapts to the extremely shallow sea operation environment to further improve the data processing accuracy and imaging quality of multi-component seismic exploration. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the present invention provides a shallow sea bottom node redirection method based on the constraint of first arrival polarization characteristics. This method has simple steps and reasonable design, and can make full use of the energy, polarization characteristics of the first arrival wave, and the correlation between P and Z components to achieve high-precision node orientation correction. Compared with the problems of insufficient accuracy and limited applicable environment existing in redirection relying only on direct waves, and the multi-solution problem prone to occur when only using the first arrival energy method for constraint, the method of the present invention has higher practicability and reliability.

[0005] To solve the above technical problems, the present invention adopts the following technical solutions: A shallow sea bottom node redirection method based on the constraint of first arrival polarization characteristics, the method comprising the following steps: Step S10: Extract the common geophone gather from the simulated or field-collected four-component seismic data; Step S20: Obtain the first arrival time and propagation azimuth angle; Step S30: Jointly construct an objective function suitable for bottom node redirection based on the energy distribution within the first arrival time window, the polarization characteristics of direct waves and refracted waves, and the correlation between P and Z components; specifically including: First, according to the calculated azimuth angle parameters, rotate the horizontal components X and Y of the seismic record to obtain the radial component and the tangential component respectively, and by adjusting the node attitude parameters, minimize the energy of the tangential component within the first arrival time window, so as to optimize the node orientation parameters; at the same time, combining the polarization characteristics of the first arrival wave and the correlation between P and Z components, add multiple constraints; The objective function is as follows: ; In the formula, is the sampling time of the seismic data; are the radial, tangential and vertical components after rotation of the horizontal components respectively, where is the shot number in the common geophone gather, is the total number of channels participating in the calculation in the common geophone gather; and are the start and end times of the time window; respectively represent the constraint logic values of direct wave, refracted wave, P and Z component correlations, is the penalty coefficient of the corresponding item. If the corrected X, Y, Z components are in the correct coordinate system, then are all 1, and the first three terms of the function do not play a constraint role at this time; if the X and Y axes are reversed after correction, then ; if the Y and Z axes are reversed after correction: ; if the X and Z axes are reversed after correction: ; when in formula (1) The corresponding value at the minimum is the optimal orientation angle; Step S40: By obtaining the minimum value of the objective function, the optimal orientation parameters are obtained: By optimizing the objective function constructed in step S30, the optimal orientation parameters are obtained; Step S50: Orientation correction of the seismic data of the subsea nodes.

[0006] Furthermore, in the above step S10: According to a preset velocity model, through elastic wave forward modeling or field acquisition of an actual observation system, four-component seismic data including hydrophones and three-component geophones are obtained, and the collected data is converted into a common receiver gather; Furthermore, in the above step S20: During the process that the seismic waves are excited by the source ship at N shot points and propagate to the seabed, the first arrival time of the seismic records received by the geophone points is picked up. By means including the secondary positioning technology, the accurate spatial position coordinates of the geophone points are obtained. Combining the spatial position coordinates of the shot points and the geophone points, and according to the formula the propagation azimuth angle of the seismic wave is calculated, where and respectively represent the position coordinates of the geophone point and the shot point. From the calculated azimuth angle, according to formula (2), the horizontal coordinate system X-Y is rotated to the radial-tangential R-T coordinate system.

[0007] ; Furthermore, the multiple constraint conditions in step S30: ① For the direct wave, using its polarization characteristics, the constraint condition is added, where , respectively represent the projections of the direct wave polarization vector on the XOZ plane; ② For the refracted wave, using its polarization characteristics, the constraint condition is added, where , respectively represent the projections of the refracted wave polarization vector on the XOZ plane; ③ Even when the X and Z axes are reversed, the above constraint conditions are still valid. By calculating the correlation coefficient between the corrected Z component and the P component, and selecting the combination with a positive correlation coefficient, further ambiguity is excluded to ensure the uniqueness and accuracy of the orientation result.

[0008] Furthermore, the optimization in the above step S40: The whale optimization algorithm (Whale Optimization Algorithm, BWO) is used to globally optimize the objective function. This algorithm experiences three stages of exploration, exploitation, and whale fall in sequence during the optimization process, corresponding to global exploration, local fine-tuning, and random perturbation respectively.

[0009] Further, in step S50: obtain the optimal orientation parameters according to step S40 , and perform orientation correction processing on the three-component seismic records in the subsea nodes according to formula (3) to obtain the seismic records collected and received in the preset coordinate system; (3); In the formula respectively represent the Euler matrices rotating around the X, Y, and Z axes, is the angle of rotation around the corresponding rotation axis, is the unrotated data, is the data after rotation, where can be expressed as: (4); The present invention also provides a computer-readable storage medium, on which a computer program is stored. The computer program can be loaded and executed by a processor to implement the method for redirecting subsea nodes based on the constraint of first-arrival polarization characteristics.

[0010] The present invention also provides a computer device, which includes a memory and a processor. A computer program is stored in the memory. When the processor executes the computer program, it can implement the method for redirecting subsea nodes based on the constraint of first-arrival polarization characteristics.

[0011] The beneficial effects of the present invention compared with the prior art are as follows: 1. The method steps of the present invention are concise and reasonably designed, significantly improving the accuracy and efficiency of redirecting the geophones of subsea nodes.

[0012] 2. The operation process of the present invention is simple and has excellent application effects, specifically including: obtaining four-component seismic data including hydrophones and three-component geophones; picking up the first-arrival time in the common receiver gather, selecting an appropriate time window length, and calculating the propagation azimuth angle according to the source-receiver coordinates; then, using the beluga optimization algorithm to solve the minimum value of the objective function to obtain the optimal orientation parameters; finally, performing orientation correction on the X, Y, and Z three-component seismic records based on the obtained orientation parameters.

[0013] 3. When constructing the objective function of the present invention, the energy distribution, polarization characteristics of the first-arrival wave, and the correlation between the P and Z components are comprehensively utilized. Through multiple physical constraints, the robustness and reliability of the node attitude inversion results are effectively improved.

[0014] In summary, the method steps of the present invention are simple and reasonable in design. Based on the initial arrival wave energy, polarization characteristics, and the correlation between P and Z components, the efficient redirection of three-component geophones is realized, overcoming the deficiencies of the existing methods that only rely on the polarization characteristics of direct waves or the initial arrival energy method, and having strong practicality and popularization value. Description of the Drawings

[0015] Figure 1 It is a flowchart of the working process of the four-component seafloor node redirection method; Figure 2 It is a schematic diagram of the polarization characteristics of the initial arrival waves (direct waves and refracted waves); (a), (c), (e), (g) represent the incidence of direct waves, and the projection of the polarization vector on the XOZ plane; (b), (d), (f), (h) represent the incidence of refracted waves, and the projection of the polarization vector on the XOZ plane; Figure 3 It is the X, Y, Z three-component seismic records collected by simulating the unoriented seafloor nodes Figure 4 It is the projection of the unoriented polarization vector on the XOZ and XOY planes. a is the projection of the initial arrival wave polarization vector on the XOZ plane, and b is the projection of the initial arrival wave polarization vector on the XOY plane; Figure 5 It is the X, Y, Z three-component seismic records after redirection and correction using the present invention; Figure 6 It is the projection of the polarization vector on the XOZ and XOY planes after orientation using the present invention. a is the symmetric distribution of the oriented polarization vector on both sides of the geophone point along the XOZ plane, and b is the projection of the oriented polarization vector on the XOY plane. Detailed Embodiment

[0016] Next, the technical solution of the present invention will be further explained through embodiments, but the protection scope of the present invention is not limited in any form by the embodiments.

[0017] Embodiment 1 As Figure 1 A new shallow-sea seafloor node redirection technology based on the constraint of initial arrival polarization characteristics shown, includes the following steps: Step S10: Acquisition of four-component seismic data: According to the established velocity model, through elastic wave forward modeling, or designing a corresponding observation system for actual field acquisition, four-component seismic data including hydrophones and three-component geophones are obtained, and the obtained data is converted into a common geophone gather.

[0018] Step S20: Acquisition of the initial arrival time and propagation azimuth angle: During the process that the seismic source ship generates seismic waves at N shot points and the waves propagate to the seabed, pick up the first arrival time of the seismic records at the geophone points. Through means such as the secondary positioning technology, obtain the accurate spatial position coordinates of the geophone points, utilize the spatial position coordinates of the shot points and the geophone points, and based on the formula Calculate the propagation azimuth angle of the seismic wave, where and respectively represent the position coordinates of the geophone point and the shot point.

[0019] 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, jointly construct an objective function applicable to the redirection of the subsea nodes, providing a basis for the subsequent inversion and optimization of the node attitude parameters.

[0020] The objective of step S30 is to obtain the optimal geophone orientation angle . In order to overcome the problem of multi-solution that is prone to occur in the method of geophone orientation using only the first arrival energy method, the present invention jointly utilizes 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 to construct an objective function applicable to the redirection of the subsea nodes. Specifically, first, according to the calculated azimuth angle parameter, rotate the horizontal components X and Y of the seismic record to obtain the radial component (R) and the tangential component (T) respectively. Theoretically, the vibration directions of the P wave and the P-SV converted wave are 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, minimize the energy of the tangential component within the first arrival time window, thereby realizing the optimization of 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, add multiple constraints to further improve the accuracy and stability of the inversion of the actual node attitude parameters.

[0021] The objective function is as follows: (1); In the formula, is the sampling time of the seismic data; are respectively the radial, tangential and vertical components after the rotation of the horizontal components, where is the shot number in the common geophone gather, is the total number of channels participating in the calculation in the common geophone gather; and are the start and end times of the time window; respectively represent the constraint logic values of the direct wave, the refracted wave, and the correlation between the P and Z components, 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, and the first three terms of the function do not play a constraint role at this time; 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) is the smallest, the corresponding is the optimal orientation angle.

[0022] Figure 2 shows the projection of the polarization vectors of the first-arrival waves (including direct waves and refracted waves) on the XOZ plane in different calibration coordinate systems. In the figure, and are the shot points symmetrically distributed on both sides of the geophone point ( ). The dashed line represents the propagation direction of the seismic wave, and the solid line represents the polarization direction. Figure 2 In (a) and (b) of , the projections of the polarization vectors of the direct wave and the refracted wave on the XOZ plane in the correct coordinate system are shown respectively. When the X and Y axes are reversed ( Figure 2 in (c) and (d) of ) and the Y and Z axes are reversed ( Figure 2 in (e) and (f) of ), horizontal component rotation of the three-component seismic data may still make the latter part of formula (1) reach a minimum value, resulting in multiple solutions for the orientation result.

[0023] To avoid the above-mentioned multiple solutions, the following constraint conditions are proposed: ① For the direct wave, using its polarization characteristics, add the constraint condition , where , respectively represent the projections of the direct wave polarization vector on the XOZ plane; ② For the refracted wave, using its polarization characteristics, add the constraint condition , where , respectively represent the projections of the refracted wave polarization vector on the XOZ plane; ③ Even in the case where the X and Z axes are reversed ( Figure 2 in (g) and (h) of ), the above constraint conditions are still valid. In addition, since the P component is a pressure-type sensor and is not affected by the geophone attitude, and the waveforms of the P component and the Z component are highly similar, the correlation coefficient between the calibrated Z component and the P component is calculated, and the combination with a positive correlation coefficient is selected to further exclude multiple solutions and ensure the uniqueness and accuracy of the orientation result.

[0024] Step S40: Obtain the optimal orientation parameters by finding the minimum value of the objective function: To balance computational accuracy and efficiency, the present invention uses the Whale Optimization Algorithm (WOA) to globally optimize the objective function and obtain the optimal orientation parameters. This algorithm effectively improves the convergence speed and result stability through staged global search, local fine-tuning, and combined with random perturbation, achieving efficient and accurate inversion of the node spatial attitude.

[0025] In the exploration stage, the algorithm enhances the global optimization ability through large-range jumping search to prevent falling into local extrema; in the exploitation stage, it focuses on fine-tuning near the current excellent solutions to improve the solution accuracy and achieve local optimization; in the whale fall stage, random perturbation is introduced to enhance population diversity and the ability to jump out of local optima and prevent premature convergence.

[0026] 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 actual spatial attitude of the nodes.

[0027] Step S50: Seismic data orientation correction for subsea nodes: Obtain the orientation parameters according to step S40 Calculate the three-component seismic records after orientation according to formula (3), (3); In the formula respectively represent the Euler matrices rotating around the X, Y, and Z axes, is the angle of rotation around the corresponding rotation axis, is the unrotated data, is the data after rotation, where can be expressed as: (4); In this example, the time window length selected in step S30 is = 40 sampling points. The selection of the time window has an important impact on the polarization analysis result. An overly long window will introduce clutter and obscure the true polarization state of local signals; an overly short window will have insufficient statistical samples and make it difficult to accurately identify the polarization direction. Therefore, the time window length needs to be reasonably set to balance signal purity and statistical stability.

[0028] In this example, the Whale Optimization Algorithm is used to solve the objective function in step S40. The initial parameters of the algorithm are set as: parameter lower limit , upper limit , population size is 50, and the maximum number of iterations is 300. Combined with the objective function proposed in this embodiment, the inversion calculation of the node attitude parameters is carried out.

[0029] Figure 3As shown, in the X, Y, and Z three-component seismic records simulating the acquisition of seafloor nodes before orientation, the Z component not only contains P-wave signals but also is mixed with a large amount of S-wave energy. At the same time, there is a polarity reversal phenomenon in some of the in-phase axes on both sides of the geophone points in the Y component, indicating that the attitude of the geophones has changed. To qualitatively evaluate the rationality of the orientation result, Figure 4 The first-arrival wave polarization vectors are respectively projected onto the XOZ plane (a) and the XOY plane (b). It is observed that the projections of the unoriented vectors in the XOZ and XOY planes are relatively disordered.

[0030] Calculate the propagation azimuth angle according to the source-receiver coordinates, and rotate the horizontal components to the radial and tangential directions (i.e., the source-receiver connection direction and the direction perpendicular to the source-receiver connection). Figure 5 As shown, after applying the method of the present invention for redirection correction, the X, Y, and Z three-component seismic records are significantly improved, the wavefield information of each component is effectively relocated, the S-waves in the Z component are significantly attenuated, the polarities on both sides of the in-phase axis in the Y component are basically symmetric, and a polarity reversal reappears on the X component. Figure 6 It shows that the polarized vectors after orientation are symmetrically distributed along both sides of the geophone points in the XOZ plane (a), and in the XOY plane (b), the projections at large offset positions are more convergent. As the offset increases, the angle between the vector and the X-axis gradually decreases, indicating that it is more consistent with the observation system in terms of polarization characteristics.

[0031] The method of the present invention effectively solves the problems of wavefield leakage and energy coupling caused by the attitude deflection of the geophones, verifies the accuracy and practicability of the method in this paper, and has important guiding significance for the actual seafloor node orientation work.

[0032] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A shallow sea bottom node redirection method based on the constraint of first arrival polarization characteristics, characterized in that The method includes the following steps: S10: Extract a common geophone gather from the simulated or field-collected four-component seismic data; Step S20: Obtain the first arrival time and propagation azimuth angle; Step S30: Jointly construct an objective function applicable to seafloor node redirection based on the energy distribution within the first arrival time window, the polarization characteristics of direct waves and refracted waves, and the correlation between P and Z components; specifically including: First, according to the calculated azimuth angle parameters, rotate the horizontal components X and Y of the seismic record to obtain the radial component R and the tangential component T respectively. By adjusting the node attitude parameters, minimize the energy of the tangential component within the first arrival time window, thereby optimizing the node orientation parameters; at the same time, combine the polarization characteristics of the first arrival wave and the correlation between P and Z components to add multiple constraints; 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 horizontal component rotation, where is the shot number in the common receiver gather, is the total number of traces participating in the calculation in the common receiver gather; and are the start and end times of the time window; respectively represent the constraint logic values of the direct wave, refracted wave, P, and Z component correlations, is the penalty coefficient for the corresponding term, is the angle of rotation about the corresponding rotation axis; Step S40: Obtain the optimal orientation parameters by finding the minimum value of the objective function: Optimize the objective function constructed in step S30 to obtain the optimal orientation parameters; Step S50: Directional correction of seafloor node seismic data.

2. The method according to claim 1, wherein In the said step S10: According to a pre-set velocity model, obtain four-component seismic data including hydrophones and three-component geophones through elastic wave forward simulation or field collection of the actual observation system, and convert the collected data into a common geophone gather.

3. The method according to claim 1, wherein Step S20: During the process that seismic waves are excited by the seismic source ship at N shot points and propagate to the seabed, pick up the first arrival time of the seismic records received by the geophone points. By means including the secondary positioning technology, obtain the accurate spatial position coordinates of the geophone points. Combine the spatial position coordinates of the shot points and the geophone points, and based on the formula calculate the propagation azimuth angle of the seismic wave, where and respectively represent the position coordinates of the geophone point and the shot point. The azimuth angle is obtained by calculation. According to formula (2), rotate the horizontal coordinate system X-Y to the radial-tangential R-T coordinate system (2)。 4. The method according to claim 1, wherein The multiple constraints described in step S30: ① For the direct wave, by using its polarization characteristics, constraint conditions are added , where and respectively represent the projections of the direct wave polarization vector on the XOZ plane; ② For the refracted wave, using its polarization characteristics, add constraint conditions , where 、 respectively represent the projections of the polarization vectors of the refracted wave on the XOZ plane; ③ Even when the X and Z axes are reversed, the above constraints are still valid. By calculating the correlation coefficient between the corrected Z component and the P component and selecting the combination with a positive correlation coefficient, further eliminate multiple solutions to ensure the uniqueness and accuracy of the orientation result.

5. The method according to claim 1, characterized in that, The optimization described in the said step S40: Use the beluga optimization algorithm to globally optimize the objective function.

6. The method according to claim 1, characterized in that, Step S50 described above: Obtain the optimal orientation parameters according to Step S40 , perform orientation correction processing on the three-component seismic records in the subsea nodes according to Formula (3) to obtain the seismic records acquired and received in the preset coordinate system; (3) where represent the Euler matrices for rotation about the X, Y, and Z axes respectively, is the angle of rotation about the corresponding rotation axis, is the unrotated data, is the data after rotation, where 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 sea seafloor node redirection method based on first arrival polarization characteristic constraints described in any one of claims 1-6.

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

Images