Marine controllable source electromagnetic acquisition station position correction method based on near-field symmetry
By using a near-field symmetry-based method and employing nonlinear least squares and Levenberg-Marquardt algorithms to optimize the receiving station location, the problem of receiving station location deviation in ocean controlled-source electromagnetic detection was solved, achieving high-precision data correction and improved inversion accuracy.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-14
- Publication Date
- 2026-04-10
AI Technical Summary
In existing controlled-source electromagnetic detection in the ocean, the location of the receiving station is far from the deployment and recording point and the positioning accuracy is limited, which leads to serious inversion artifacts in data processing, especially in the interpretation of shallow targets.
By employing a near-field symmetry-based approach, the receiver location is optimized using a nonlinear least squares algorithm and the Levenberg-Marquardt algorithm. Correction is performed based on the data's own characteristics, and an optimization objective function is established. The symmetry of the near-field data pairs is then used for correction.
It improves the accuracy of receiving station position correction, reduces inversion artifacts, enhances the interpretation accuracy of shallow targets, and does not require additional hardware costs.
Smart Images
Figure CN121831931A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of marine geophysical exploration, and in particular to a marine controlled source electromagnetic acquisition station position correction method based on near-field symmetry. BACKGROUND
[0002] In marine controlled source electromagnetic detection, the actual position of the seabed electromagnetic acquisition station (hereinafter referred to as the receiving station) often deviates from the recorded point after being laid, and there is uncertainty of tens to hundreds of meters due to factors such as sea current. At the same time, the actual geometric shape of the towed transmitting antenna and the center position of the electric dipole also have uncertainty.
[0003] The prior art usually relies on underwater acoustic positioning or beacon positioning to obtain position information, and the accuracy is limited, and the above-mentioned system error cannot be effectively corrected. In data processing, especially for small source-receiver distance data of shallow targets (such as hydrate, submarine fresh water), this position uncertainty will cause the electromagnetic field "overflow point" to deviate, and then produce serious inversion artifacts (such as shallow false "bull's eye" anomaly), which seriously affects the reliability of geological interpretation. At present, in the prior art, the position information of the receiving station mainly depends on the GPS record during laying or the underwater acoustic positioning in the later operation. These methods are affected by factors such as sea current and sound velocity profile error, and the positioning accuracy is limited (usually in the order of tens to hundreds of meters), and the systematic deviation caused by positioning error cannot be further corrected and optimized in the data processing stage. Especially when processing near-field data which is extremely sensitive to position, the above-mentioned positioning error will directly lead to incorrect interpretation results.
[0004] Therefore, it is urgent to provide a method based on the characteristics of the data itself for fine correction in the data processing stage to make up for the shortcomings of the existing hardware positioning technology. SUMMARY
[0005] Therefore, the purpose of the present application is to overcome the defects in the prior art that rely on external positioning equipment with limited accuracy and cannot correct the actual position error of the acquisition station in the data processing link, and to provide a marine controlled source electromagnetic acquisition station position correction method based on the near-field characteristics of the data itself without increasing hardware costs.
[0006] The technical problem solved by the present application adopts the following technical scheme:
[0007] A marine controlled source electromagnetic acquisition station position correction method based on near-field symmetry, comprising the following steps:
[0008] Step S10, data preparation: obtaining the initial position coordinates of the target receiving station, marine controlled source electromagnetic measured time series data, and real-time spatial coordinates and azimuth angle data of the transmitting source;
[0009] Step S20, near-field Data extraction: The time series data is preprocessed to calculate the maximum amplitude along the principal axis of the elliptic polarization field, i.e. Near-field data is selected from all data where the transmitter-receiver distance is less than a set threshold.
[0010] Step S30, construct symmetrical data pairs and optimization model: In the near-field data, find data pairs that meet the following conditions: the transmitters pass through the receiving station from opposite directions on both sides and are approximately at the same distance from the receiving station, and the absolute value of the azimuth angle difference between the two transmitter positions is less than a set angle threshold; establish an optimization objective function based on the data pairs that meet the above conditions;
[0011] Step S40, iteratively solve for the optimal position: use a nonlinear least squares algorithm to minimize the objective function and obtain the optimal position.
[0012] Furthermore, in step S10, the initial position coordinates are derived from deployment records or underwater acoustic positioning data.
[0013] Furthermore, in step S20, the threshold is set to 1 to 2 times the seawater depth.
[0014] Furthermore, in step S20, each near-field data point records its... Amplitude, transmitter location, and calculated transmit / receive distance.
[0015] Furthermore, in step S30, the method for establishing the optimization objective function based on the data that meets the above conditions is as follows:
[0016] A record of a pair of data that satisfies the above conditions is ( , ), its corresponding The amplitudes are respectively and Establish the optimization objective function:
[0017]
[0018] in, Let be the horizontal offset of the receiving station position to be determined. and Based on the new position after offset Recalculated transmit / receive distance; This is the initial receiving station location;
[0019] Summation is performed on all selected valid symmetric data pairs.
[0020] Furthermore, in step S40, the method for obtaining the optimal position is as follows:
[0021] The Levenberg-Marquardt algorithm is used to evaluate the objective function. By minimizing the solution, we obtain the solution that makes both sides... The optimal offset with the smallest amplitude difference The final location of the corrected receiving station is: .
[0022] To prevent the solution from getting trapped in local minima or obtaining excessively large non-physical offsets, the optimization process can constrain the magnitude of the offset to be less than a certain proportion of the water depth (e.g., 10%).
[0023] Furthermore, step S50 is included: verification of the correction effect. Using the corrected position, the transmit and receive distances of all near-field data are recalculated and plotted. - Transmit / receive distance curve; if correctly calibrated, this curve exhibits a "bell-shaped" characteristic that is basically symmetrical about zero transmit / receive distance.
[0024] The present invention discloses a position correction method for a marine controllable source electromagnetic acquisition station based on near-field symmetry, which has the following beneficial effects:
[0025] (1) The principle is reliable: Based on the physical symmetry of the near-field primary field, the method has a solid theoretical foundation.
[0026] (2) Pure data processing: Only existing observation data is used, without adding any hardware costs or field operation procedures.
[0027] (3) Highly targeted: effectively solves the problem of data location sensitivity at small transmission and reception distances, and significantly improves the accuracy of shallow target inversion and interpretation. Attached Figure Description
[0028] Figure 1 This is a flowchart of the method of the present invention.
[0029] Figure 2 This is the curve of the preprocessing result before the location correction of the data acquisition station.
[0030] Figure 3 This is the curve of the result after the location of the data acquisition station is corrected. Detailed Implementation
[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0032] The purpose of this invention is to overcome the shortcomings of existing technologies that rely on external positioning equipment with limited accuracy and cannot correct the actual position error of the acquisition station in the data processing stage, and to provide a position correction method for a marine controllable source electromagnetic acquisition station based on the near-field characteristics of the data itself without increasing hardware costs.
[0033] refer to Figure 1 This invention provides a method for position correction of a marine controllable source electromagnetic acquisition station based on near-field symmetry, comprising the following steps:
[0034] Step S1, Data Preparation: Obtain the initial position coordinates of the target receiving station, the time series data of the electromagnetic field measurement of the marine controllable source, and the real-time spatial coordinates and azimuth data of the transmitting source; the initial position coordinates are obtained from the deployment record or underwater acoustic positioning data.
[0035] Step S2, near field Data extraction: The time series data is preprocessed to calculate the maximum amplitude along the principal axis of the elliptic polarization field, i.e. Near-field data is selected from all data points where the transmitter-receiver distance is less than a set threshold. This threshold is typically set to 1 to 2 times the seawater depth to ensure that the electromagnetic field signal within this distance range is dominated by the primary field directly from the transmitter. The data for each near-field data point is recorded. Amplitude, transmitter location, and calculated transmit / receive distance.
[0036] Step S3, construct symmetrical data pairs: In the near-field data, find data pairs that meet the following conditions: the transmitters pass through the receiving station from opposite directions on both sides and are approximately at the same distance from the receiving station, and the absolute value of the azimuth difference between the two transmitter positions is less than a set angle threshold.
[0037] Step S4, Establish the optimization model: Based on the data that meets the above conditions, establish the optimization objective function, using the following method:
[0038] A record of a pair of data that satisfies the above conditions is ( , ), its corresponding The amplitudes are respectively and Establish the optimization objective function:
[0039]
[0040] in, Let be the horizontal offset of the receiving station position to be determined. and Based on the new position after offset Recalculated transmit / receive distance; This is the initial receiving station location;
[0041] Summation is performed on all selected valid symmetric data pairs.
[0042] Step S5, iteratively solve for the optimal position: use a nonlinear least squares algorithm (such as the Levenberg-Marquardt algorithm) to solve the objective function. The optimal position is obtained by minimizing the solution.
[0043] The Levenberg-Marquardt algorithm is used to evaluate the objective function. By minimizing the solution, we obtain the solution that makes both sides... The optimal offset with the smallest amplitude difference The final location of the corrected receiving station is: .
[0044] To prevent the solution from getting trapped in local minima or obtaining excessively large non-physical offsets, the optimization process can constrain the magnitude of the offset to be less than a certain proportion of the water depth (e.g., 10%).
[0045] Step S6, Verification of Correction Effect: Using the corrected positions, recalculate the transmit / receive distance of all near-field data and plot the results. - Transmit / receive distance curve; if the correction is correct, this curve exhibits a "bell-shaped" characteristic that is basically symmetrical about zero transmit / receive distance (the corrected position). This can be used as an intuitive criterion for the reasonableness of the correction result.
[0046] Figure 2 The curves of magnetic field and electric field amplitude and transmit / receive distance obtained by electromagnetic processing of the actual marine controllable source were found to be significantly asymmetrical about point 0 (the location of the acquisition station) due to the inaccurate location of the receiving station. Figure 3 The processing result obtained by the optimization algorithm of this invention after the location of the acquisition station is corrected (ΔX=12m, ΔY=120m) should show a "bell-shaped" feature that is basically symmetrical about the zero transmit / receive distance (corrected location). The subsequent inversion interpretation also confirmed the effectiveness of the method.
[0047] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for position correction of a marine controllable source electromagnetic acquisition station based on the characteristics of measured data itself and without the need for additional hardware support. This method utilizes the physical principle that the near-field electromagnetic field (dominated by the primary field) should be strictly symmetrical with respect to the receiving station's position, and automatically optimizes the true horizontal position of the receiving station through an optimization algorithm.
[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for position correction of a marine controllable source electromagnetic acquisition station based on near-field symmetry, characterized in that, Includes the following steps: Step S10, Data Preparation: Obtain the initial position coordinates of the target receiving station, the time series data of electromagnetic measurements of the marine controllable source, and the real-time spatial coordinates and azimuth data of the transmitting source; Step S20, near field Data extraction: The time series data is preprocessed to calculate the maximum amplitude along the principal axis of the elliptic polarization field, i.e. Near-field data is selected from all data where the transmitter-receiver distance is less than a set threshold. Step S30, construct symmetrical data pairs and optimization model: In the near-field data, find data pairs that meet the following conditions: the transmitters pass through the receiving station from opposite directions on both sides and are approximately at the same distance from the receiving station, and the absolute value of the azimuth angle difference between the two transmitter positions is less than a set angle threshold; establish an optimization objective function based on the data pairs that meet the above conditions; Step S40, iteratively solve for the optimal position: use a nonlinear least squares algorithm to minimize the objective function and obtain the optimal position.
2. The method for position correction of a marine controllable source electromagnetic acquisition station based on near-field symmetry according to claim 1, characterized in that, In step S10, the initial position coordinates are derived from deployment records or underwater acoustic positioning data.
3. The method for position correction of a marine controllable source electromagnetic acquisition station based on near-field symmetry according to claim 2, characterized in that, In step S20, the threshold is set to 1 to 2 times the seawater depth.
4. The method for position correction of a marine controllable source electromagnetic acquisition station based on near-field symmetry according to claim 3, characterized in that, In step S20, each near-field data point records its... Amplitude, transmitter location, and calculated transmit / receive distance.
5. The method for position correction of a marine controllable source electromagnetic acquisition station based on near-field symmetry according to claim 4, characterized in that, In step S30, the method for establishing the optimization objective function based on the data that meets the above conditions is as follows: A record of a pair of data that satisfies the above conditions is ( , ), its corresponding The amplitudes are respectively and Establish the optimization objective function: in, Let be the horizontal offset of the receiving station position to be determined. and Based on the new position after offset Recalculated transmit / receive distance; This is the initial receiving station location; Summation is performed on all selected valid symmetric data pairs.
6. The method for position correction of a marine controllable source electromagnetic acquisition station based on near-field symmetry according to claim 5, characterized in that, In step S40, the method for obtaining the optimal position is as follows: The Levenberg-Marquardt algorithm is used to evaluate the objective function. By minimizing the solution, we obtain the solution that makes both sides... The optimal offset with the smallest amplitude difference The final location of the corrected receiving station is: .
7. The method for position correction of a marine controllable source electromagnetic acquisition station based on near-field symmetry according to claim 6, characterized in that, It also includes step S50, verification of the correction effect: using the corrected position, recalculate the transmit / receive distance of all near-field data, and plot the results. - Transmit / receive distance curve; if correctly calibrated, this curve exhibits a "bell-shaped" characteristic that is basically symmetrical about zero transmit / receive distance.