A fast simulation method for time series of frequency-domain controlled source electromagnetic measurement

Abstract

This invention provides a rapid simulation method for frequency-domain controllable source electromagnetic measurement timing. This method constructs a frequency-domain controllable source electromagnetic timing function, calculates the amplitude and phase of electromagnetic field components and transmitter-receiver distance data based on the observation system and geoelectric model, converts the time axis to the transmitter-receiver distance axis based on observation system information, and completes the timing data using cubic spline interpolation, effectively improving computational efficiency. It replaces the electromagnetic field amplitude attenuation constant and phase shift constant with the frequency domain response, avoiding the complex process of directly calculating these constants, thus achieving rapid simulation of frequency-domain controllable source electromagnetic measurement timing. This method can simulate time-drift noise, noise at the same frequency as the transmitter and noise at different frequencies, white noise, etc. Compared with traditional methods, this method is simple, efficient, and can simulate noise that is difficult to simulate using traditional methods. This invention provides a technical solution for analyzing the influence of specific noise on effective timing signals and for evaluating and verifying processing techniques, and has practical application value.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic simulation technology, specifically relating to a fast simulation method for electromagnetic measurement timing of a frequency-domain controllable source. Background Technology

[0002] Frequency-domain controlled-source electromagnetic (CSEM) methods for the ocean often employ fixed-source observations and mobile excitation techniques. Typically, a horizontal electric dipole towed several tens of meters above the seabed serves as the transmitter, emitting electromagnetic signals of a specific frequency towards an electromagnetic acquisition station located on the seabed. These signals propagate through the seawater and seabed medium, ultimately being received by the acquisition station. The amplitude and phase of these signals depend on the resistivity of the seabed medium. Due to the electrical characteristics of seawater and the seabed medium, the amplitude of the electromagnetic signal excited by the transmitter decays continuously during propagation, and its phase changes with the transmitter-receiver distance.

[0003] During marine CSEM (Conductivity, Semiconductor, and Electromagnetic) measurements, the transmitter is connected to the research vessel's laboratory via a communication cable, enabling real-time GPS timing. However, due to seabed observations, the receiving station cannot receive GPS signals for real-time timing. If prolonged observation leads to a power outage in the receiving system, preventing the station from being retrieved for GPS time synchronization and drift correction, a time difference may exist between the transmitter and receiver systems. In shallow waters, electromagnetic field observations are hampered by strong induced electromagnetic noise caused by seawater movement, including noise signals of the same and different frequencies as the transmitter, as well as relatively strong white noise. The impact of these signals on the timing signals of marine electromagnetic measurements is not yet fully understood. The effectiveness of processing techniques for marine CSEM data and noise suppression needs to be effectively evaluated and verified. However, the effective and noise components in the measured electromagnetic signals are unknown, making it impossible to verify the processing techniques. Therefore, simulated data that closely approximates the actual data is necessary for these tasks. Summary of the Invention

[0004] The purpose of this invention is to provide a rapid simulation method for electromagnetic measurement timing of a frequency-domain controllable source. This method uses the frequency-domain forward modeling response to replace the electromagnetic field amplitude attenuation constant and phase shift constant, thereby realizing rapid simulation of electromagnetic observation timing of a frequency-domain controllable source. The synthesized data can include various types of noise, and can analyze the influence of specific noise on the effective timing signal, and provide a way to evaluate and verify the processing technology.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A fast simulation method for electromagnetic measurement timing of a frequency-domain controllable source includes the following steps:

[0007] S1. Constructing the electromagnetic timing function of a frequency-domain controllable source:

[0008]

[0009] in, For the time of the launch source, The electromagnetic field components emitted by a controllable source. This is the amplitude of the emission source for that component; The electromagnetic field amplitude attenuation constant is The phase shift constant; The angular frequency of the emission source, The time drift length between the receiving station and the transmitting source. This is the initial phase of the emission source; and They are respectively those with the same frequency as the transmitting source The amplitude and initial phase of the noise. Indicates frequency as The noise signal is from It is composed of a combination of noises with different amplitudes and initial phases; and These are the amplitude and angular frequency of the frequency-characteristic noise, respectively. Other noise;

[0010] S2. Set simulation parameters, including measurement time length, sampling rate, signal-to-noise ratio, geoelectric model, observation system, quantity of noise at the same frequency as the emission source and noise at different frequencies, amplitude and phase information, and other noise information;

[0011] S3. Generate the time series corresponding to the data points based on the sampling frequency and measurement time length;

[0012] S4. Calculate the real and imaginary parts of the electromagnetic field components based on the observation system and geoelectric model, and calculate the amplitude and transmit / receive distance data (MVO) and phase and transmit / receive distance data (PVO).

[0013] S5. Based on the observation system, the time axis is transformed, and the amplitude and phase response of all time series are completed using cubic spline interpolation.

[0014] S6. Replace the electromagnetic field amplitude attenuation constant and phase shift constant with amplitude and phase response respectively, thereby updating the timing function;

[0015] S7. Calculate the measurement timing under noise-free conditions;

[0016] S8. Use Fourier transform to convert from the time domain to the frequency domain and compare it with the calculated MVO and PVO data. If the accuracy is not met, go to S2 and densify the observation system. If the accuracy is met, go to S9.

[0017] S9. Add noise components with the set signal-to-noise ratio according to the simulation parameter settings. The noise includes time-drift noise, noise with the same frequency as the transmission source, noise with a different frequency than the transmission source, white noise, measured noise, etc.

[0018] S10, synthesize simulation data and output it.

[0019] The electromagnetic field emitted by the controllable source described in S1 is the total electromagnetic field component of the controllable source in the frequency domain, specifically including the orthogonal three components of the electric field. Orthogonal three components of the magnetic field .

[0020] The geoelectric models described in S2 include one-dimensional, two-dimensional, and three-dimensional models.

[0021] The observation system-based time axis conversion described in S5 is based on the initial position of the emission source. Speed ​​of movement By calculating the positions of the transmitter and receiver at different times Distance between Implement the conversion from the time axis to the transmit / receive distance axis.

[0022] Compared with the prior art, the beneficial effects of the method provided in some embodiments of the present invention are as follows:

[0023] This invention primarily addresses the rapid simulation of electromagnetic measurement timing sequences for controllable sources, proposing a fast simulation method for such sequences in the frequency domain. This method constructs a frequency-domain controllable source electromagnetic timing function, calculates the real and imaginary parts of the electromagnetic field components based on the observation system and geoelectric model, and calculates amplitude-to-transmit / receive distance (MVO) and phase-to-transmit / receive distance (PVO) data. Based on the initial position and velocity of the transmitter, it calculates the distance between the transmitter and receiver at different times to achieve the transformation from the time axis to the transmit / receive distance axis. It uses cubic spline interpolation to complete the amplitude and phase responses across all time series, and replaces the electromagnetic field amplitude decay constant and phase shift constant with the frequency-domain forward modeling response, avoiding the direct calculation of the amplitude decay constant. and phase shift constant This invention addresses the complex process of electromagnetic measurement timing of a frequency-domain controllable source, enabling rapid simulation. It can simulate various noise types, including time-drift noise, noise at the same frequency as the transmitter, noise at a different frequency than the transmitter, white noise, and measured noise. Compared to traditional timing synthesis methods, this method is simpler and more efficient, and can simulate noise that is difficult to simulate using traditional methods, such as noise caused by time drift. This invention provides a technical approach for analyzing the impact of specific noises on effective timing signals and for evaluating and verifying processing techniques, thus possessing practical application value. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

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

[0026] Figure 2 For synthesizing the geoelectric model of the observation time series;

[0027] Figure 3 The Ey component represents the synthesized horizontal electric field.

[0028] Figure 4 The vertical electric field Ez component is the synthesized electric field.

[0029] Figure 5 The horizontal magnetic field component Hx is the synthesized component.

[0030] Figure 6 The amplitude and comparison results are obtained by processing the synthesized electromagnetic field components.

[0031] Figure 7 The phase and comparison results are obtained by processing the synthesized measured electromagnetic field components; Detailed Implementation

[0032] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0033] This invention primarily addresses the simulation of controllable source electromagnetic measurement timing sequences, proposing a rapid simulation method for frequency-domain controllable source electromagnetic measurement timing sequences. This method constructs a frequency-domain controllable source electromagnetic timing function, calculates the real and imaginary parts of the electromagnetic field components based on the observation system and geoelectric model, and calculates amplitude-to-transmit / receive distance (MVO) and phase-to-transmit / receive distance (PVO) data. Based on the initial position and velocity of the transmitter, the time axis is transformed to the transmit / receive distance axis by calculating the distance between the transmitter and receiver positions at different times. Cubic spline interpolation is used to complete the amplitude and phase responses on all time series, and the frequency-domain forward modeling response replaces the electromagnetic field amplitude attenuation constant and phase shift constant, thereby achieving rapid simulation of frequency-domain controllable source electromagnetic measurement timing sequences. This method can simulate signals such as time-drift noise, noise at the same frequency as the transmitter, noise at a different frequency than the transmitter, white noise, and measured noise. Compared to traditional timing synthesis methods, it is more efficient and can simulate noise that is difficult to simulate using traditional methods, such as noise caused by time drift. This invention provides a technical approach for analyzing the impact of specific noise on effective time-series signals and for evaluating and verifying processing techniques, thus having practical application value.

[0034] This invention provides a fast simulation method for electromagnetic measurement timing of a frequency-domain controllable source. See the detailed calculation flowchart below. Figure 1 The specific steps include:

[0035] S1. First, construct the frequency-domain controllable source electromagnetic timing function according to the design requirements:

[0036]

[0037] in, For the time of the launch source, This refers to the electromagnetic field components emitted by the controllable source. These components constitute the total electromagnetic field components of the controllable source in the frequency domain, specifically including the orthogonal three components of the electric field. Orthogonal three components of the magnetic field ; This is the amplitude of the emission source for that component; The electromagnetic field amplitude attenuation constant is The phase shift constant; The angular frequency of the emission source, The time drift length between the receiving station and the transmitting source. This is the initial phase of the emission source; and They are respectively those with the same frequency as the transmitting source The amplitude and initial phase of the noise. Indicates frequency as The noise signal is from It is composed of a combination of noises with different amplitudes and initial phases; and These are the amplitude and angular frequency of the frequency-characteristic noise, respectively. Other noise.

[0038] S2. Set simulation parameters according to design requirements. The parameters include measurement data parameters, model parameters, and noise parameters. Measurement data parameters include the total measurement time, sampling rate of the measurement equipment, and signal-to-noise ratio. Model parameters for the observation location include the ocean geoelectric model and the observation system. The observation system specifically involves information such as the initial position of the transmitter, towing speed, transmission frequency, and the position of the receiving station. Noise parameters include the quantity, amplitude, and phase information of noise at the same frequency as the transmitter and noise at different frequencies, as well as other noise information.

[0039] S3. Generate the time series corresponding to the data points based on the sampling frequency and measurement time length;

[0040] S4. Assume the launch source starts from the initial position. With speed The location of the emission source is shifted. It can be represented as

[0041]

[0042] Assuming the receiving station is located Transmit / receive distance It can be represented as

[0043]

[0044] Due to the amplitude decay constant of the complex model and phase shift constant This is difficult to obtain. This method directly calculates the amplitude of a specific model using a frequency-domain controllable source electromagnetic forward modeling algorithm. and phase The data shows a curve of change in the transmit / receive distance, and the amplitude is... and phase Data replacement amplitude decay constant and phase shift constant This avoids the need to directly calculate the complex amplitude attenuation constant. and phase shift constant Based on the observation system and the geoelectric model, which includes one-dimensional, two-dimensional and three-dimensional models, the real and imaginary parts of the frequency domain electromagnetic field components are then calculated using a controlled-source electromagnetic simulation algorithm, and the amplitude-to-transmit / receive distance (MVO) and phase-to-transmit / receive distance (PVO) data are further calculated.

[0045] S5. Generate the time series corresponding to the data points based on the sampling frequency and measurement time length. Since the horizontal axis of the time series is the time axis, while the horizontal axis of MVO and PVO data is the transmit / receive distance, a direct correspondence cannot be established. Therefore, according to the above formula, the time axis is converted to the transmit / receive distance. Because the emission sources in the observation system are usually obtained by multiple superpositions of emission source information at a certain distance, while the measurement time series involves continuous dense sampling, it is necessary to unify the data volume of both. This method uses cubic spline interpolation to complete the amplitude and phase response on all time series.

[0046] S6. Replace the electromagnetic field amplitude attenuation constant and phase shift constant with amplitude and phase response respectively to update the timing function.

[0047] S7. Calculate the measurement timing sequence without noise based on the updated time function.

[0048] S8. Use Fourier transform to convert from the time domain to the frequency domain, and compare it with the calculated MVO and PVO data. If the accuracy is not met, encrypt the observation system and regenerate a new measurement time series. If the accuracy is met, add noise components with the set signal-to-noise ratio according to the simulation parameter settings.

[0049] S9. Add noise components with the set signal-to-noise ratio according to the simulation parameter settings. The noise includes time-drift noise, noise with the same frequency as the transmission source, noise with a different frequency than the transmission source, white noise, measured noise, etc.

[0050] S10. Finally, synthesize the simulation data and output it.

[0051] See Figure 2 This is a schematic diagram of a typical one-dimensional geoelectric model. To verify the correctness of the algorithm, noise parameters are not set initially. The Fourier transform results of the obtained measurement time series are compared with the actual frequency domain electromagnetic response to verify the algorithm's correctness. It is assumed that the isotropic seawater layer has a depth of 1 km and a resistivity of 0.3. The 100m thick high-resistivity thin layer is buried at a depth of 1km, and its resistivity is... The resistivity of both the overburden and the bedrock is [missing information]. Assuming the survey line and The axes coincide, and the transmitter is located 50m directly above the seabed, with an initial position of (0, -15000, 950)m. It moves to its final position (0, 15000, 950)m at a speed of v = (0, 0, 950)m / s. The transmission frequency is 0.25Hz. The receiver is located on the seabed at coordinates (0, 0, 1000)m. The sampling frequency is set to 100Hz, and the sampling duration is 30000s. Since the direction of the transmitter is consistent with the direction of the survey line, and the receiver is located on the towed line of the transmitter, the receiver can only receive the horizontal electric field Ey component, the vertical electric field Ez component, and the horizontal magnetic field Hx component.

[0052] See Figures 3 to 5 respectively using Figure 1 The steps shown calculate the observation time series of the horizontal electric field Ey component, the vertical electric field Ez component, and the horizontal magnetic field Hx component. As can be seen from the figure, the field values ​​of all three components are at their maximum at 15000 s, i.e., when the transmitter passes directly above the receiving station, and then rapidly decay as the transmitter moves away. (Comparison...) Figure 3 , 4 It was found that the electric field component Ez had the smallest amplitude, while the horizontal magnetic field component Hx had the largest amplitude.

[0053] See Figures 6 to 7 , respectively Figures 3 to 5 The observed time series shown is the result after Fourier transform to the frequency domain and time axis conversion. To verify the correctness of the algorithm, the frequency domain responses of the actual horizontal electric field Ey component, vertical electric field Ez component, and horizontal magnetic field Hx component are also plotted. The dotted line represents the result obtained from the synthesized observed time series, and the solid line represents the actual calculated frequency domain result. As can be seen from the figure, the two results are completely consistent, which demonstrates that the algorithm proposed in this invention can obtain an observed time series consistent with the frequency domain, and also verifies the correctness of the algorithm.

[0054] Based on this, response noise components can be added as needed to further obtain noisy observation time series. By adding noise of different properties, the influence of specific noise on the effective time series signal can be analyzed; by processing data with known noise components, the effectiveness of specific processing methods can be evaluated and verified.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A fast simulation method for electromagnetic measurement timing of a frequency-domain controllable source, characterized in that, Includes the following steps: S1. Constructing the electromagnetic timing function of a frequency-domain controllable source: ,in, For the time of the launch source, The electromagnetic field components emitted by a controllable source. This is the amplitude of the emission source for that component; Let f be the electromagnetic field amplitude attenuation constant. The phase shift constant; The angular frequency of the emission source, The time drift length between the receiving station and the transmitting source. This is the initial phase of the emission source; and They are respectively those with the same frequency as the transmitting source The amplitude and initial phase of the noise. Indicates frequency as The noise signal is from It is composed of a combination of noises with different amplitudes and initial phases; and These are the amplitude and angular frequency of the frequency-characteristic noise, respectively. Other noise; S2. Set simulation parameters, including measurement time length, sampling rate, signal-to-noise ratio, geoelectric model, observation system, quantity of noise at the same frequency as the emission source and noise at different frequencies, amplitude and phase information, and other noise information; S3. Generate the time series corresponding to the data points based on the sampling frequency and measurement time length; S4. Calculate the real and imaginary parts of the electromagnetic field components based on the observation system and geoelectric model, and calculate the amplitude and transmit / receive distance data (MVO) and phase and transmit / receive distance data (PVO). S5. Based on the observation system, the time axis is transformed, and the amplitude and phase response of all time series are completed using cubic spline interpolation. S6. Replace the electromagnetic field amplitude attenuation constant and phase shift constant with amplitude and phase response respectively, thereby updating the timing function; S7. Calculate the measurement timing under noise-free conditions; S8. Use Fourier transform to convert from the time domain to the frequency domain and compare it with the calculated MVO and PVO data. If the accuracy is not met, go to S2 and densify the observation system. If the accuracy is met, go to S9. S9. Add noise components with the set signal-to-noise ratio according to the simulation parameter settings. The noise includes time-drift noise, noise with the same frequency as the transmission source, noise with a different frequency than the transmission source, white noise, and measured noise. S10, synthesize and output simulation data.

2. The method for rapid simulation of electromagnetic measurement timing of a frequency-domain controllable source as described in claim 1, characterized in that, The electromagnetic field emitted by the controllable source described in S1 is the total electromagnetic field component of the controllable source in the frequency domain, specifically including the orthogonal three components of the electric field. Orthogonal three components of the magnetic field .

3. The method for rapid simulation of electromagnetic measurement timing of a frequency-domain controllable source as described in claim 1, characterized in that, The geoelectric models described in S2 include one-dimensional, two-dimensional, and three-dimensional models.

4. The method for rapid simulation of electromagnetic measurement timing of a frequency-domain controllable source as described in claim 1, characterized in that, The observation system-based time axis conversion described in S5 is based on the initial position of the emission source. Speed ​​of movement By calculating the positions of the transmitter and receiver at different times Distance between Implement the conversion from the time axis to the transmit / receive distance axis.

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