Bottom-supported ocean controllable source electromagnetic data batch processing method

Abstract

The invention discloses a bottom-supported ocean controllable source electromagnetic data batch processing method, which comprises the following steps: carrying out integrity check and time / frequency sequence preview on recorder data, emission source data and navigation data to obtain key data information; converting the time domain observation data into a frequency domain; performing normalization and correction on the observation data; rotating the electromagnetic field vector to the main axis direction of the elliptical polarization field; performing time window superposition processing on the corrected and rotated data, and synchronously estimating a data error; filtering the navigation data; projecting the filtered navigation data to a preset 2D profile orientation through coordinate rotation; time sequences of the navigation data and the electromagnetic acquisition data are aligned through interpolation, the transceiving distance of each time point is calculated, and an amplitude-transceiving distance curve and a phase-transceiving distance curve for inversion are generated. According to the method, the normalized electromagnetic field spectrum response which can be used for underground resistivity inversion can be efficiently and accurately extracted from the original time sequence data.

Description

Technical Field

[0001] This invention relates to the field of marine electromagnetic exploration data processing technology, and in particular to a bottom-mounted method for batch processing of marine controllable source electromagnetic data. Background Technology

[0002] In controlled-source electromagnetic detection (CEP) of the ocean, time-series observation data needs to be processed to extract information reflecting the subsurface resistivity structure. The influence of the data acquisition system itself (such as transmitter intensity, receiving antenna length, circuit gain, and clock drift) directly affects the shape and amplitude of the data. Furthermore, bottom-mounted electromagnetic acquisition stations are deployed on the seabed in a free-fall manner, resulting in uncertainty in their orientation. Simultaneously, the transmitter towed by the exploration vessel is affected by ocean currents and waves, and its orientation and trajectory may deviate from the designed route. These factors lead to random directions of the observed electromagnetic field components, posing difficulties for subsequent inversion interpretation. Existing data processing methods often fall short in eliminating these systematic influences, correcting orientation uncertainties, and achieving efficient batch processing, resulting in cumbersome inversion data preparation processes and susceptibility to human error.

[0003] Therefore, how to provide a method for batch processing of ocean-based controllable source electromagnetic data has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a batch processing method for bottom-mounted marine controllable source electromagnetic data, which aims to effectively eliminate the systematic errors introduced by the data acquisition system, correct clock drift, and overcome the influence of transmit-receive azimuth uncertainty through elliptic polarization analysis, and finally efficiently and accurately extract the normalized electromagnetic field spectrum response that can be used for subsurface resistivity inversion from the original time series data.

[0005] The present invention solves the technical problem by adopting the following technical solution:

[0006] A method for batch processing of electromagnetic data from a bottom-mounted, controllable marine source includes the following steps:

[0007] Step S10, Preliminary Data Analysis: Perform integrity checks and time / frequency sequence previews on the recorder data, transmitter data, and navigation data collected in the field, assess the acquisition quality, and obtain key data information;

[0008] Step S20, Fourier transform: Convert the time-domain observation data to the frequency domain;

[0009] Step S30, Normalization and System Correction: Normalize and correct the observed data;

[0010] Step S40, Rotation of Elliptical Polarization and Electric Principal Axis: Rotate the electromagnetic field vector to the direction of the principal axis of the elliptical polarization field;

[0011] Step S50, Data overlay: Perform time window overlay processing on the corrected and rotated data to suppress random noise, reduce data redundancy, and simultaneously estimate data error;

[0012] Step S60, Navigation data merging and positioning: Filter the navigation data from the transmitter and acquisition station to remove abnormal "flying points"; project the filtered navigation data onto a preset 2D profile orientation by coordinate rotation; align the navigation data with the time series of electromagnetic acquisition data through interpolation, calculate the transmit / receive distance at each time point, and finally generate amplitude-transmit / receive distance and phase-transmit / receive distance curves for inversion.

[0013] Furthermore, in step S10, the key data information includes: signal acquisition time, duration, excitation frequency, and signal-to-noise ratio distribution.

[0014] Furthermore, in step S20, the method for converting the time-domain observation data to the frequency domain is as follows: for discrete signals, a Fourier transform with the period of the transmitted waveform as the window length is adopted, and the least squares method is used to solve for the real part A and the imaginary part B of the frequency domain amplitude, thereby obtaining the initial spectrum data.

[0015] Further, step S30, normalization and system correction includes:

[0016] Step S31, Source normalization: Normalize the observed electromagnetic signal to the source dipole moment;

[0017] Step S32, receiver station calibration: For the electric field channel, normalize the potential difference to the electric field strength using the length of the receiving antenna; for all channels, eliminate the influence of circuit gain; for the magnetic field channel, perform sensor sensitivity conversion.

[0018] Step S33, Clock Drift Correction: Based on the synchronization information of the recorder's built-in clock and GPS before deployment and after retrieval, assuming that the clock drift is a linear change, the drift amount at each acquisition moment is calculated, and the phase of the electromagnetic field signal is accurately corrected to restore the true phase.

[0019] Furthermore, in step S40, the method for rotating the electromagnetic field vector to the principal axis direction of the elliptical polarization field is as follows:

[0020] Based on the two orthogonal electric field components E x With E y Based on the waveform data and the phase difference between them, the elliptic polarization equation is constructed, and the major axis a, minor axis b, and polarization angle θ of the ellipse are calculated; the electromagnetic field energy is projected onto the direction of the major axis of the ellipse.

[0021] The present invention discloses a method for batch processing of ocean-based controllable source electromagnetic data on a bottom-mounted platform, which has the following beneficial effects:

[0022] (1) Systematic: It provides a complete and coherent data processing flow, covering all key links from raw data to inversion preparation data.

[0023] (2) Strong robustness: The introduction of elliptic polarization analysis effectively overcomes the difficulties in data interpretation caused by the uncertainty of the orientation of the emission source and the acquisition station, and improves the reliability of the inversion data.

[0024] (3) Efficient batch processing: The method has a clear process and is easy to program. It can automatically process large amounts of marine CSEM data from multiple stations, which significantly improves work efficiency and reduces errors caused by human intervention. Attached Figure Description

[0025] Figure 1 This is a flowchart of the method of the present invention.

[0026] Figure 2 For receiving time series.

[0027] Figure 3 These are the transmit and receive data curves after normalization and system correction.

[0028] Figure 4 The MVO and PVO curves after merging navigation data. Detailed Implementation

[0029] 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.

[0030] refer to Figure 1 A method for batch processing of ocean-based controllable source electromagnetic data on a bottom-mounted platform includes the following steps:

[0031] Step S10, Preliminary Data Analysis: Perform integrity checks and time / frequency sequence previews on the recorder data, transmitter data, and navigation data collected in the field, assess the acquisition quality, and obtain key data information; key data information includes: signal acquisition time, duration, excitation frequency, and signal-to-noise ratio distribution, etc.

[0032] Step S20, Fourier Transform: Convert the time-domain observation data to the frequency domain. For discrete signals, a Fourier transform with the period of the transmitted waveform as the window length is used, and the least squares method is used to solve for the real part A and imaginary part B of the frequency domain amplitude, thus obtaining the initial spectrum data.

[0033] Step S30, Normalization and System Correction: Normalize and correct the observed data;

[0034] Normalization and system correction include:

[0035] Step S31, Source Normalization: Normalize the observed electromagnetic signal with respect to the source dipole distance (transmitting current intensity × transmitting antenna length);

[0036] Step S32, receiver station calibration: For the electric field channel, normalize the potential difference to the electric field strength using the length of the receiving antenna; for all channels, eliminate the influence of circuit gain; for the magnetic field channel, perform sensor sensitivity conversion.

[0037] Step S33, Clock Drift Correction: This invention implements clock correction using both time and frequency domain methods. Based on the synchronization information between the recorder's built-in clock and GPS before deployment and after retrieval, assuming the clock drift is linear, the drift amount at each acquisition moment is calculated, and the phase of the electromagnetic field signal is precisely corrected to restore the true phase.

[0038] Step S40, Elliptical Polarization and Principal Axis Rotation: To overcome the influence of the uncertainty of the azimuth of the transmitter and acquisition station on the orthogonal electromagnetic field components, the electromagnetic field vector is rotated to the principal axis direction of the elliptical polarization field. Based on the waveform data of the two orthogonal electric field components Ex and Ey and the phase difference between them, the elliptical polarization equation is constructed, and the major axis a, minor axis b, and polarization angle θ of the ellipse are calculated. The electromagnetic field energy is projected onto the major axis direction of the ellipse, where the signal energy is concentrated, the signal-to-noise ratio is high, and it is insensitive to changes in the system's azimuth.

[0039] Step S50, Data overlay: Time window overlay processing is performed on the corrected and rotated data to suppress random noise, reduce data redundancy, and simultaneously estimate data errors; This invention uses a specific length time window and weighted overlay method to design an overlay method for the characteristics of marine CSEM signals.

[0040] Step S60, Navigation data merging and positioning: Filter the navigation data from the transmitter and acquisition station to remove abnormal "flying points"; project the filtered navigation data onto a preset 2D profile orientation by coordinate rotation; align the navigation data with the time series of electromagnetic acquisition data through interpolation, calculate the transmit / receive distance at each time point, and finally generate amplitude-transmit / receive distance (MVO) and phase-transmit / receive distance (PVO) curves for inversion.

[0041] To achieve true batch processing and automation, this invention employs a configuration file-based automatic parameter loading technology in the normalization and system calibration steps. This technology can read and process parameters such as antenna length and gain from multiple acquisition stations simultaneously. These specific technical implementations collectively constitute a solution oriented towards industrial applications.

[0042] The present invention discloses a method for batch processing of ocean-based controllable source electromagnetic data on a bottom-mounted platform, which has the following beneficial effects:

[0043] (1) Systematic: It provides a complete and coherent data processing flow, covering all key links from raw data to inversion preparation data.

[0044] (2) Strong robustness: The introduction of elliptic polarization analysis effectively overcomes the difficulties in data interpretation caused by the uncertainty of the orientation of the emission source and the acquisition station, and improves the reliability of the inversion data.

[0045] (3) Efficient batch processing: The method has a clear process and is easy to program. It can automatically process large amounts of marine CSEM data from multiple stations, which significantly improves work efficiency and reduces errors caused by human intervention.

[0046] Example

[0047] Combination Figure 1 The flowchart shown illustrates a method for batch processing of electromagnetic data from a bottom-mounted, controllable marine source, comprising the following steps:

[0048] First, the raw time-series data (including electromagnetic field signals, navigation data, and system parameters) stored on the server is used for preliminary analysis to confirm the data's validity. Figure 2 As shown.

[0049] Subsequently, the program automatically performs a Fourier transform on the valid electromagnetic field time series, converting it to the frequency domain.

[0050] Next, parameters such as the transmitter dipole moment, receiver antenna length, system gain, and magnetic field sensitivity are used to normalize and correct the frequency domain data. Simultaneously, based on the first and last GPS time synchronization records, the clock drift of each data point is calculated and corrected. Figure 3 As shown.

[0051] Then, the program reads the orthogonal electric field components E. x and E y The elliptic polarization parameters are calculated, and the electric and magnetic field data are rotated to the direction of the major axis (electric principal axis) of the ellipse. Then, the data along the principal axis are superimposed to suppress noise and estimate errors.

[0052] Finally, the program reads in, filters, and interpolates the navigation data, aligns it in time with the processed electromagnetic data, calculates the transmit / receive distance, and automatically outputs the final amplitude-transmit / receive distance (MVO) and phase-transmit / receive distance (PVO) data files for use by the inversion software, such as... Figure 4 As shown. The entire process is program-controlled, enabling unattended batch operations.

[0053] 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 batch processing of bottom-mounted ocean-controlled source electromagnetic data, characterized in that, Includes the following steps: Step S10, Preliminary Data Analysis: Perform integrity checks and time / frequency sequence previews on the recorder data, transmitter data, and navigation data collected in the field, assess the acquisition quality, and obtain key data information; Step S20, Fourier transform: Convert the time-domain observation data to the frequency domain; Step S30, Normalization and System Correction: Normalize and correct the observed data; Step S40, Rotation of Elliptical Polarization and Electric Principal Axis: Rotate the electromagnetic field vector to the direction of the principal axis of the elliptical polarization field; Step S50, Data overlay: Perform time window overlay processing on the corrected and rotated data to suppress random noise, reduce data redundancy, and simultaneously estimate data error; Step S60, Navigation data merging and positioning: Filter the navigation data from the transmitter and acquisition station to remove abnormal "flying points"; project the filtered navigation data onto a preset 2D profile orientation by coordinate rotation; align the navigation data with the time series of electromagnetic acquisition data through interpolation, calculate the transmit / receive distance at each time point, and finally generate amplitude-transmit / receive distance and phase-transmit / receive distance curves for inversion.

2. The method for batch processing of seabed-based marine controllable source electromagnetic data according to claim 1, characterized in that, In step S10, key data information includes: signal acquisition time, duration, excitation frequency, and signal-to-noise ratio distribution.

3. The method for batch processing of seabed-based marine controllable source electromagnetic data according to claim 2, characterized in that, In step S20, the method for converting the time-domain observation data to the frequency domain is as follows: For discrete signals, a Fourier transform with the period of the transmitted waveform as the window length is adopted, and the least squares method is used to solve for the real part A and the imaginary part B of the frequency domain amplitude, thereby obtaining the initial spectrum data.

4. The method for batch processing of seabed-based marine controllable source electromagnetic data according to claim 3, characterized in that, Step S30, normalization and system calibration includes: Step S31, Source normalization: Normalize the observed electromagnetic signal to the source dipole moment; Step S32, receiver station calibration: For the electric field channel, normalize the potential difference to the electric field strength using the length of the receiving antenna; for all channels, eliminate the influence of circuit gain; for the magnetic field channel, perform sensor sensitivity conversion. Step S33, Clock Drift Correction: Based on the synchronization information of the recorder's built-in clock and GPS before deployment and after retrieval, assuming that the clock drift is a linear change, the drift amount at each acquisition moment is calculated, and the phase of the electromagnetic field signal is accurately corrected to restore the true phase.

5. The method for batch processing of seabed-based marine controllable source electromagnetic data according to claim 4, characterized in that, In step S40, the method for rotating the electromagnetic field vector to the principal axis direction of the elliptical polarization field is as follows: Based on the two orthogonal electric field components E x With E y Based on the waveform data and the phase difference between them, the elliptic polarization equation is constructed, and the major axis a, minor axis b, and polarization angle θ of the ellipse are calculated; the electromagnetic field energy is projected onto the direction of the major axis of the ellipse.

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