A step frequency control method, system and device for marine controllable vibrator

Abstract

The present invention relates to the field of marine seismic exploration technology, and specifically to a step frequency control method, system and device for marine controllable seismic sources. First, a linear sweep frequency signal is obtained, and the linear sweep frequency signal is divided into a plurality of sub-band signals according to a preset step frequency, wherein the plurality of sub-band signals are used to excite a plurality of controllable seismic sources, and echo signals of the sub-band signals are received, and the echo signals carry formation information of different depths, and the echo signals are phase corrected in real time, and the detection signal is synthesized by step frequency. The technical solution of the present invention divides the linear sweep frequency signal into a plurality of sub-band signals, improves the frequency band utilization rate of the seismic source system, reduces the excitation time of the controllable seismic source, and performs real-time phase correction on the echo signal, thereby improving the signal-to-noise ratio of seismic exploration acquisition data and reducing the phase noise of the acquisition signal.

Description

Technical Field

[0001] The present invention relates to the technical field of marine seismic exploration, and in particular to a stepping frequency control method, system and equipment for a marine controllable vibrator. Background Art

[0002] In order to obtain higher-resolution seismic exploration data in marine controllable vibrators, the elastic wave frequency generated by the source equipment is required to be wider and the excitation time is shorter, but this is a set of contradictory parameters. The wider the excitation frequency, the longer the excitation time. At the same time, the longer the excitation time, the exploration cost increases exponentially. Therefore, a controllable vibrator control method with a shorter excitation time is needed, while ensuring that the seismic exploration signal has a relatively wide frequency range. This requires a controllable vibrator control method.

[0003] In the actual exploration process, the source excitation signal adopts a linear swept frequency signal. The elastic waves excited by the source will have different forms of signal distortion in the low-frequency band and the high-frequency band. Therefore, the source signal can be divided into multiple sub-band signals with stepped frequency, and the sub-width signals are synthesized at the receiving end to obtain the detection signal.

[0004] In a related technology, it is proposed to use image contrast as a criterion for synthetic aperture radar focusing, and continuously adjust the phase error estimate to obtain the high-order phase error in the distance with the maximum contrast function. The conjugate gradient algorithm is used for iterative solution to obtain the phase error that maximizes the contrast.

[0005] This method needs to solve the contrast of the entire radar image in each iteration. The amount of computation for a single iteration is large, and the number of iterations is large. For the volume of marine seismic exploration data, it is inefficient.

[0006] In another related technology, it is proposed to calculate a high-resolution one-dimensional range profile (HRRP) in an iterative process, use a quasi-Newton method to calculate the HRRP, and when the HRRP entropy value reaches a minimum, the phase error is considered to be found.

[0007] This method reduces the amount of computation in a single iteration and improves efficiency to a certain extent, but the number of iterations is still large, the computational efficiency is low, and it is difficult to apply in engineering practice.

[0008] In summary, the existing controllable seismic sources cannot be directly applied to marine controllable seismic sources, and the exploration time is long and the accuracy is low. The existing algorithms have large computational complexity and low efficiency. Summary of the invention

[0009] In view of this, the purpose of the present invention is to provide a step frequency control method, system and equipment for a marine controllable seismic source, so as to solve the technical problems that the efficiency and accuracy of existing marine geophysical exploration development are contradictory and there are random phase differences between sub-band signals, resulting in inaccurate synthesized detection signals.

[0010] According to a first aspect of an embodiment of the present invention, there is provided a step frequency control method for a marine vibroseis source, comprising:

[0011] Acquire a linear frequency sweep signal, and divide the linear frequency sweep signal into a plurality of sub-band signals according to a preset step frequency, wherein the plurality of sub-band signals are used to excite a plurality of controllable vibrators;

[0012] receiving an echo signal of the sub-band signal, wherein the echo signal carries formation information of different depths;

[0013] The echo signal is subjected to real-time phase correction, and a detection signal is synthesized by stepping frequency.

[0014] Preferably, the linear frequency sweep signal is divided into a plurality of sub-band signals according to a preset step frequency, specifically:

[0015] Divide the linear frequency sweep signal bandwidth B, starting frequency f0, into N sub-band signals;

[0016] Furthermore, the overlapping rate of the sub-band signals is r, where r>0;

[0017] Then, the subband signal bandwidth

[0018] Time Width

[0019] The starting frequency of subband n is f n =f0+(n-1)(1-r)b.

[0020] Preferably, the calculating the phase error of the echo signal comprises:

[0021] Performing time shift and phase correction on the received multiple echo signals;

[0022] Furthermore, the received multiple echo signals are coherently superimposed in the time domain to obtain a spliced ​​detection signal.

[0023] Preferably, the time shifting of the received multiple echo signals is specifically:

[0024] The received multiple echo signals are time-shifted, and the time-shift amount is the time width T of the sub-band signal. sub .

[0025] Preferably, the performing phase correction on the received multiple echo signals comprises:

[0026] The phase of the echo signal A or the echo signal B is shifted by c+π to minimize the variance of the echo signal A and the echo signal B.

[0027] Preferably, the performing phase correction on the received multiple echo signals is specifically:

[0028] Phase shift the echo signal A or the echo signal B by c+π, and select a sampling point s between the echo signal A and the echo signal B, calculate the variance of the echo signal A and the echo signal B within a sampling window of length w from the sampling point s to the sampling point after the sampling point, and take the inverse of the maximum variance as the variance of the phase shift amount c.

[0029] Preferably, the performing phase correction on the received multiple echo signals further comprises:

[0030] Calculate the coordinate error of the sampling point in the echo signal, specifically:

[0031] Determine a starting position and select a direction phasor, add the direction phasor to the starting position to obtain a vector of detection point A, and add a vector opposite to the direction phasor to the starting position to obtain a vector of detection point B;

[0032] Calculate the variance of the detection point A and the detection point B, take the detection point with the smaller variance as the first current position, calculate the variance of the first current position, store it, select the minimum value in the iteration result as the current optimal position 1, and determine whether the current optimal position converges;

[0033] If converged, output the minimum value and select the optimal position;

[0034] If it does not converge, redefine the starting position and select the direction phasor.

[0035] Preferably, the performing phase correction on the received multiple echo signals further comprises:

[0036] Solve n Levy solution coordinates according to the Levy flight algorithm, where n is much smaller than the number of solutions m in the vector space, and select the second current position;

[0037] Calculating the variance of the second current position and storing it;

[0038] Determine whether the Levy solution is to be discarded with probability Pa, and calculate the random solution of the solution to be discarded between the lines connecting the two Levy solution spaces;

[0039] Compare the size of the Levy solution and the random solution. If the Levy solution is smaller than the random solution, take the Levy solution as the result of this iteration; otherwise, take the random solution as the result of this iteration;

[0040] The result of this iteration is compared with the minimum value of the previous iteration results to determine whether the current optimal position has converged;

[0041] If converged, output the minimum value and select the optimal position;

[0042] If it does not converge, redetermine the coordinates of the Levy solution.

[0043] According to a second aspect of an embodiment of the present invention, there is provided a stepped frequency control system for a marine vibroseis source, comprising:

[0044] A division module, used for acquiring a linear frequency sweep signal, and dividing the linear frequency sweep signal into a plurality of sub-band signals according to a preset step frequency, wherein the plurality of sub-band signals are used for exciting a plurality of controllable vibrators;

[0045] A receiving module, used for receiving the echo signal of the sub-band signal, wherein the echo signal carries formation information of different depths;

[0046] The correction module is used to perform real-time phase correction on the echo signal and synthesize the detection signal through stepped frequency.

[0047] According to a third aspect of an embodiment of the present invention, there is provided a stepped frequency control device for a marine controllable vibroseis, comprising: the above method.

[0048] The technical solution provided by the embodiments of the present invention may have the following beneficial effects:

[0049] The present invention first obtains a linear swept frequency signal, and divides the linear swept frequency signal into a plurality of sub-band signals according to a preset step frequency, wherein the plurality of sub-band signals are used to excite a plurality of controllable seismic sources, and echo signals of the sub-band signals are received, and the echo signals carry stratigraphic information of different depths, and the echo signals are phase corrected in real time, and the detection signal is synthesized by a step frequency. The technical solution of the present invention divides the linear swept frequency signal into a plurality of sub-band signals, improves the frequency band utilization rate of the seismic source system, reduces the excitation time of the controllable seismic source, and performs real-time phase correction on the echo signals, thereby improving the signal-to-noise ratio of seismic exploration acquisition data and reducing the phase noise of the acquisition signal.

[0050] In addition, the beetle whisker algorithm or cuckoo algorithm is used to search for the minimum phase error and obtain the optimal splicing position, so that the synthesized phase is more accurate, and the algorithm's computational complexity is greatly reduced and efficiency is improved.

[0051] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0053] Figure 1 is a flow chart of a step frequency control method of a marine vibroseis according to an exemplary embodiment;

[0054] Figure 2 is a flow chart showing an overall step frequency control method of a marine vibroseis according to an exemplary embodiment;

[0055] Figure 3 is a schematic diagram showing dividing the linear frequency sweep signal into a plurality of sub-band signals according to a preset step frequency according to an exemplary embodiment;

[0056] Figure 4 is a flow chart showing step frequency synthesis of an echo signal according to an exemplary embodiment;

[0057] Figure 5 is a flowchart of calculating errors of two sub-band signals according to an exemplary embodiment;

[0058] Figure 6 is a phase shift-sampling-error trend diagram shown according to an exemplary embodiment;

[0059] Fig. 7A is a flow chart of searching errors of a beetle whisker algorithm according to an exemplary embodiment;

[0060] Figure 7B is a graph of the number of iterations corresponding to the beetle whisker algorithm according to an exemplary embodiment;

[0061] Fig. 8A is a flow chart of a cuckoo algorithm search error according to an exemplary embodiment;

[0062] Figure 8B is a schematic diagram showing Levi's flight according to an exemplary embodiment;

[0063] Figure 8C is a graph of the number of iterations corresponding to the cuckoo algorithm according to an exemplary embodiment;

[0064] Fig. 9 It is a schematic diagram of a stepped frequency control system of a marine controllable vibrator according to an exemplary embodiment. DETAILED DESCRIPTION

[0065] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are merely examples of devices and methods consistent with some aspects of the present invention as detailed in the appended claims.

[0066] Embodiment 1

[0067] See also Figure 1 , Figure 1 is a flow chart of a step frequency control method of a marine vibroseis according to an exemplary embodiment. Figure 1 As shown, the method includes:

[0068] Step S11, obtaining a linear frequency sweep signal, and dividing the linear frequency sweep signal into a plurality of sub-band signals according to a preset step frequency, wherein the plurality of sub-band signals are used to excite a plurality of controllable vibrators;

[0069] Step S12, receiving the echo signal of the sub-band signal, wherein the echo signal carries stratum information of different depths;

[0070] Step S13: perform real-time phase correction on the echo signal and synthesize the detection signal through stepped frequency.

[0071] It should be noted that the technical solution provided in this embodiment is applicable to the field of marine seismic exploration technology.

[0072] It can be understood that the technical solution provided in this embodiment obtains a linear swept frequency signal, divides the linear swept frequency signal into multiple sub-band signals according to a preset step frequency, and excites multiple controllable seismic sources with the multiple sub-band signals, receives echo signals of the sub-band signals, performs real-time phase correction on the echo signals carrying formation information of different depths, and synthesizes the detection signal through the stepped frequency. The technical solution of the present invention divides the linear swept frequency signal into multiple sub-band signals, improves the frequency band utilization of the seismic source system, reduces the excitation time of the controllable seismic source, and performs real-time phase correction on the echo signal, thereby improving the signal-to-noise ratio of seismic exploration acquisition data and reducing the phase noise of the acquisition signal.

[0073] In addition, the beetle whisker algorithm or cuckoo algorithm is used to search for the minimum phase error and obtain the optimal splicing position, so that the synthesized phase is more accurate, and the algorithm's computational complexity is greatly reduced and efficiency is improved.

[0074] In specific practice, in step S11, "dividing the linear frequency sweep signal into a plurality of sub-band signals according to a preset step frequency" may be implemented in a variety of ways, one of which may be:

[0075] Specifically, see Figure 2 , Figure 2 The flowchart of the step frequency control method of a marine vibrator according to an exemplary embodiment is shown. After the linear sweep frequency signal is obtained, the linear sweep frequency signal is divided into a plurality of sub-band signals according to a preset step frequency, wherein the unused sub-band signals are used to excite different vibrators, such as Figure 2 As shown in , the linear frequency sweep signal is divided into sub-band signal 1, sub-band signal 2, sub-band signal 3, etc. This embodiment only briefly lists three sub-band signals, but there can be multiple sub-band signals here, and they are excited by a controllable vibrator.

[0076] It should be noted that, since there is only one formation channel, when the receiving device receives the echo signal, the echo signals are mixed together, and the mixed echo signals are classified and extracted by filtering, for example: the frequency is divided into three segments of high, medium and low, and echo signal 1, echo signal 2, echo signal 3, etc. can be obtained, where the number of echo signals is the same as the number of sub-band signals. The echo signal contains the formation information of different depths of the formation, but due to the great differences in underground structures, the phase of the echo signal presents a random characteristic, and the echo signal needs to be corrected in real time, and the detection signal is obtained by step frequency synthesis until the detection is completed.

[0077] The preset step frequency is the step frequency division algorithm, and the step frequency division algorithm here is equal division and redundant division.

[0078] Specifically, it can be determined according to the number of receiving devices and the size of the frequency. For example, if there are 4 receiving devices, 100Hz can be divided into 0-20Hz, 20-40Hz, 40-80Hz, and 80-100Hz. In addition, it can also be set as a redundant split frequency method. If there are 9 receiving devices, 100Hz can be divided into 0-20Hz, 10-30Hz, 20-40Hz, 30-50Hz, 40-60Hz, 50-70Hz, 60-80Hz, 70-90Hz, and 80-100Hz. The number of receiving devices here can be customized according to actual conditions, and the range of the step frequency can also be customized to be 2, 4, 8 or 10 frequency ranges. The more frequency ranges, the more equipment is required, the higher the complexity, and the greater the difficulty in performing step frequency synthesis. Different redundant frequencies have different effects on the step frequency synthesis effect. The more redundant frequencies are split, the lower the efficiency of the step frequency synthesis. However, the better the detection signal effect is, the closer it is to the actual situation of the formation.

[0079] It should be noted that the step frequency listed in this embodiment is only an example and does not limit the present invention. The frequency division can also be other division methods. Division methods similar to those of the present application are within the protection scope of the present invention.

[0080] It should be noted that the technical solution of the present invention divides the linear sweep signal into many sub-band signals and transmits them. In the prior art, it takes 10 seconds from the transmission of the linear sweep signal to the reception of the detection information. By adopting the technical solution of the present invention, the time can be shortened to 2 seconds, thereby improving the frequency band utilization of the source system and greatly reducing the excitation time of the controllable seismic source, which is of great significance for the engineering application of the controllable seismic source.

[0081] Specifically, see Figure 3 , Figure 3 is a schematic diagram showing how the linear frequency sweep signal is divided into a plurality of sub-band signals according to a preset step frequency according to an exemplary embodiment, wherein the signal bandwidth B and the starting frequency f0 of the linear frequency sweep signal are divided into N sub-band signals;

[0082] And, the overlap rate of the sub-band signals is r, where r>0;

[0083] Then, the subband signal bandwidth

[0084] Time Width

[0085] The starting frequency of subband n is f n =f0+(n-1)(1-r)b.

[0086] In specific practice, the "real-time phase correction of the echo signal" in step S13 may be implemented in a variety of ways, one of which may be:

[0087] Performing time shift and phase correction on the received multiple echo signals;

[0088] Furthermore, the received multiple echo signals are coherently superimposed in the time domain to obtain a spliced ​​detection signal.

[0089] Specifically, see Figure 4 , Figure 4 A flow chart of synthesizing the step frequency of an echo signal according to an exemplary embodiment. First, the echo signals of different sub-band signals received by the receiving device need to be time-shifted accordingly, and the time shift amount is the time width of the sub-band signal. The phases of different sub-band signals are corrected, and finally the echo signals generated by different sub-band signals are coherently superimposed in the time domain to obtain a spliced ​​detection signal.

[0090] The performing phase correction on the received multiple echo signals comprises:

[0091] The phase of the echo signal A or the echo signal B is shifted by c+π to minimize the variance of the echo signal A and the echo signal B.

[0092] Specifically, see Figure 5 , Figure 5 According to a flowchart of calculating the error between two sub-band signals shown in an exemplary embodiment, the error here is phase correction, that is, finding the phase difference between the echo signals of the two sub-band signals.

[0093] Two echo signals are selected from echo signals 1, 2, 3, ... and named as echo signal A and echo signal B. When the echo signal of one of the sub-band signals is phase shifted by c, the variance of echo signal A and echo signal B is minimized, that is, the phase error of echo signal A and echo signal B is obtained.

[0094] It should be noted that the variance of echo signal A and echo signal B is the variance of the echo part, not the variance of the noise part. According to the principle of signal coherence, when the phase difference between the two coherent signals is π, the two signals interfere with each other destructively. At this time, the variance between the two signals is the largest. When the phase difference is 0, the two signals are coherently superimposed. Therefore, a complete signal time width should be used as the sampling window. If it is necessary to ensure that there is an echo signal in the sampling window and its error is required, the phase shift with the largest superimposed error in the sampling window - π should be found as the phase shift with the smallest error. The error in this window must be the error of the signal, not the error of the noise. And this phase shift -π is the minimum variance phase shift.

[0095] Therefore, the error process after the phase shift c between the two signals is:

[0096] 1. Phase shift is c, sampling window is w, sampling is s

[0097] 2. Perform a phase shift of c+π on one of the echo signals A or B.

[0098] 3. Get all sampling points between echo signal A and echo signal B

[0099] 4. For each window of length w from each sampling point to the next sampling point, calculate the variance of the two signals of echo signal A and echo signal B.

[0100] 5. Take the opposite of the largest variance in the result as the variance of the phase shift c.

[0101] Among them, the relationship between phase shift, sampling and error is simulated in MATLAB software. It can be seen that within one cycle, at different sampling positions, the stronger the echo signal, the greater the fluctuation of the error in the phase shift direction. The global error has a maximum point, and the phase shift amount at this maximum point -π is the minimum point of the signal error. For details, please refer to Figure 6 , Figure 6 is a phase shift-sampling-error trend diagram according to an exemplary embodiment.

[0102] In specific practice, the "real-time phase correction of the echo signal" in step S13 may be implemented in a variety of ways, wherein another implementation may be:

[0103] Calculate the coordinate error of the sampling point in the echo signal, specifically:

[0104] Determine a starting position and select a direction phasor, add the direction phasor to the starting position to obtain a vector of detection point A, and add a vector opposite to the direction phasor to the starting position to obtain a vector of detection point B;

[0105] Calculate the variance of the detection point A and the detection point B, take the detection point with the smaller variance as the first current position, calculate the variance of the first current position, store it, select the minimum value in the iteration result as the current optimal position 1, and determine whether the current optimal position converges;

[0106] If converged, output the minimum value and select the optimal position;

[0107] If it does not converge, redefine the starting position and select the direction phasor.

[0108] Specifically, see Fig. 7A , Fig. 7Ais a flow chart showing a method of searching for errors using a beetle whisker algorithm according to an exemplary embodiment.

[0109] 1. First, randomly determine a starting position, that is, a random phase shift and a random sampling point;

[0110] 2. Calculate the variance of the current position and store it;

[0111] 3. Randomly select a direction vector and add it to the starting position according to a certain length as the vector of the detection point A;

[0112] 4. Add the opposite direction of the direction vector to the starting position with the same length as the vector of the detection point B;

[0113] 5. Calculate the variance of the positions of detection points A and B;

[0114] 6. If the variance of detection point A is less than the variance of detection point B, the position of detection point A is used as the new current position;

[0115] 7. If the variance of detection point B is less than the variance of detection point A, the position of detection point B is used as the new current position;

[0116] 8. Calculate the variance of the current position and store it, and take the minimum value among the iteration results as the current optimal position;

[0117] 9. Determine whether the optimal position result converges, that is, whether the optimal position remains unchanged in a certain number of iterations.

[0118] 10. If converged, end. If not, redefine the starting position and select the direction phasor.

[0119] For the results, see Figure 7B , Figure 7B is a graph of the number of iterations corresponding to the beetle whisker algorithm according to an exemplary embodiment.

[0120] In specific practice, the "real-time phase correction of the echo signal" in step S13 may be implemented in a variety of ways, wherein another implementation may be:

[0121] Solve n Levy solution coordinates according to the Levy flight algorithm, where n is much smaller than the number of solutions m in the vector space, and select the second current position;

[0122] Calculating the variance of the second current position and storing it;

[0123] Determine whether the Levy solution is to be discarded with probability Pa, and calculate the random solution of the discarded solution between the lines connecting the two Levy solution spaces;

[0124] Compare the size of the Levy solution and the random solution. If the Levy solution is smaller than the random solution, take the Levy solution as the result of this iteration; otherwise, take the random solution as the result of this iteration;

[0125] The result of this iteration is compared with the minimum value of the previous iteration results to determine whether the current optimal position has converged;

[0126] If converged, output the minimum value and select the optimal position;

[0127] If it does not converge, redetermine the coordinates of the Levy solution.

[0128] Specifically, see Fig. 8A , Fig. 8A is a flowchart of searching errors using a cuckoo algorithm according to an exemplary embodiment.

[0129] 1. Initialization;

[0130] 2. Use Levy flight to select n Levy solutions, n<<m (m is the number of possible solutions in the vector space). For details, please refer to Figure 8B , Figure 8B is a schematic diagram showing Levi's flight according to an exemplary embodiment;

[0131] 3. Calculate the variance of the current position and store it;

[0132] 4. Discard each solution with probability P;

[0133] 5. Find a new random solution for each abandoned solution by randomly selecting a new spatial position between the spatial lines connecting two other random Levy solutions as the random solution;

[0134] 6. Compare each solution. If the Levy solution is smaller than the random solution, the Levy solution is used as the result of this iteration. Otherwise, the random solution is used as the result of this iteration.

[0135] 7. Among the solutions of this iteration, select the minimum value as the result of this iteration;

[0136] 8. Select the minimum value from all iteration results as the currently found minimum value;

[0137] 9. If the currently found minimum value converges, that is, whether the optimal position remains unchanged in a certain number of iterations;

[0138] 10. If convergence occurs, the process ends. If not, use the Levy flight again to select n Levy solutions.

[0139] For the results, see Figure 8C , Figure 8Cis a graph of the number of iterations corresponding to the cuckoo algorithm according to an exemplary embodiment.

[0140] Embodiment 2

[0141] See also Fig. 9 , Fig. 9 FIG. 1 is a schematic diagram of a step frequency control system of a marine controllable vibrator according to an exemplary embodiment. Fig. 9 As shown, the step frequency control system 900 of the marine controllable vibrator includes:

[0142] A division module 901 is used to obtain a linear frequency sweep signal and divide the linear frequency sweep signal into a plurality of sub-band signals according to a preset step frequency, wherein the plurality of sub-band signals are used to excite a plurality of controllable vibrators;

[0143] A receiving module 902, configured to receive an echo signal of the sub-band signal, wherein the echo signal carries formation information of different depths;

[0144] The correction module 903 is used to perform real-time phase correction on the echo signal and synthesize the detection signal through stepped frequency.

[0145] It should be noted that the technical solution provided in this embodiment is applicable to the field of marine seismic exploration technology.

[0146] It can be understood that the technical solution provided in this embodiment is used to obtain a linear swept frequency signal through a division module 901, and divide the linear swept frequency signal into multiple sub-band signals according to a preset step frequency, wherein the multiple sub-band signals are used to excite multiple controllable seismic sources, and the receiving module 902 is used to receive the echo signal of the sub-band signal, and the echo signal carries stratigraphic information of different depths, and the correction module 903 is used to perform real-time phase correction on the echo signal and synthesize the detection signal through a stepped frequency. The technical solution of the present invention divides the linear swept frequency signal into multiple sub-band signals, improves the frequency band utilization of the source system, reduces the excitation time of the controllable seismic source, and also performs real-time phase correction on the echo signal, thereby improving the signal-to-noise ratio of seismic exploration acquisition data and reducing the phase noise of the acquisition signal.

[0147] In addition, the beetle whisker algorithm or cuckoo algorithm is used to search for the minimum phase error and obtain the optimal splicing position, so that the synthesized phase is more accurate, and the algorithm's computational complexity is greatly reduced and efficiency is improved.

[0148] Embodiment 3

[0149] A stepped frequency control device for a marine controllable vibroseis according to an exemplary embodiment includes: the above method.

[0150] It can be understood that the technical solution provided in this embodiment first obtains a linear swept frequency signal, and divides the linear swept frequency signal into multiple sub-band signals according to a preset step frequency, wherein the multiple sub-band signals are used to excite multiple controllable seismic sources, receive echo signals of the sub-band signals, and the echo signals carry stratigraphic information of different depths, perform real-time phase correction on the echo signals, and synthesize the detection signals through the stepped frequency. The technical solution of the present invention divides the linear swept frequency signal into multiple sub-band signals, improves the frequency band utilization of the seismic source system, reduces the excitation time of the controllable seismic source, and performs real-time phase correction on the echo signals, thereby improving the signal-to-noise ratio of seismic exploration acquisition data and reducing the phase noise of the acquisition signal.

[0151] In addition, the beetle whisker algorithm or cuckoo algorithm is used to search for the minimum phase error and obtain the optimal splicing position, so that the synthesized phase is more accurate, and the algorithm's computational complexity is greatly reduced and efficiency is improved.

[0152] It can be understood that the same or similar parts of the above embodiments can be referenced to each other, and the contents not described in detail in some embodiments can refer to the same or similar contents in other embodiments.

[0153] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention belong.

[0154] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0155] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0156] In addition, each functional unit in each embodiment of the present invention may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0157] The storage medium mentioned above can be a read-only memory, a magnetic disk or an optical disk, etc.

[0158] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0159] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A step frequency control method for a marine vibroseis source, characterized in that: include: Acquire a linear frequency sweep signal, and divide the linear frequency sweep signal into a plurality of sub-band signals according to a preset step frequency, wherein the plurality of sub-band signals are used to excite a plurality of controllable vibrators; receiving an echo signal of the sub-band signal, wherein the echo signal carries formation information of different depths; Performing real-time phase correction on the echo signal and synthesizing the detection signal through stepped frequency; The real-time phase correction of the echo signal comprises: Performing time shift and phase correction on the received multiple echo signals; And, coherently superimposing the received multiple echo signals in the time domain to obtain a spliced ​​detection signal; The performing phase correction on the received multiple echo signals comprises: Phase shifting the echo signal A or the echo signal B by c+π to minimize the variance of the echo signal A and the echo signal B; comprising: phase shifting the echo signal A or the echo signal B by c+π, selecting a sampling point s between the echo signal A and the echo signal B, calculating the variance of the echo signal A and the echo signal B within a sampling window of length w from the sampling point s to the sampling point after the sampling point, and taking the inverse of the maximum variance as the variance of the phase shift amount c.

2. The method according to claim 1, characterized in that The linear frequency sweep signal is divided into a plurality of sub-band signals according to a preset step frequency, specifically: Divide the linear frequency sweep signal bandwidth B, starting frequency f0, into N sub-band signals; Furthermore, the overlapping rate of the sub-band signals is r, where r>0; Then, the subband signal bandwidth is Time Width The starting frequency of subband n is f n =f0+(n-1)(1-r)b.

3. The method according to claim 2, characterized in that The time shifting of the received multiple echo signals is specifically: The received multiple echo signals are time-shifted, and the time-shift amount is the time width T of the sub-band signal. sub .

4. The method according to claim 3, characterized in that The performing phase correction on the received multiple echo signals further includes: Calculate the coordinate error of the sampling point in the echo signal, specifically: Determine a starting position and select a direction phasor, add the direction phasor to the starting position to obtain a vector of detection point A, and add a vector opposite to the direction phasor to the starting position to obtain a vector of detection point B; Calculate the variance of the detection point A and the detection point B, take the detection point with the smaller variance as the first current position, calculate the variance of the first current position, store it, select the minimum value in the iteration result as the current optimal position 1, and determine whether the current optimal position converges; If converged, output the minimum value and select the optimal position; If it does not converge, redefine the starting position and select the direction phasor.

5. The method according to claim 4, characterized in that The performing phase correction on the received multiple echo signals further includes: Solve n Levy solution coordinates according to the Levy flight algorithm, where n is much smaller than the number of solutions m in the vector space, and select the second current position; Calculating the variance of the second current position and storing it; Determine whether the Levy solution is to be discarded with probability Pa, and calculate the random solution of the discarded solution between the lines connecting the two Levy solution spaces; Compare the size of the Levy solution and the random solution. If the Levy solution is smaller than the random solution, take the Levy solution as the result of this iteration; otherwise, take the random solution as the result of this iteration; The result of this iteration is compared with the minimum value of the previous iteration results to determine whether the current optimal position has converged; If converged, output the minimum value and select the optimal position; If it does not converge, redetermine the coordinates of the Levy solution.

6. A step frequency control system for a marine vibrator, characterized in that: include: A division module, used for acquiring a linear frequency sweep signal, and dividing the linear frequency sweep signal into a plurality of sub-band signals according to a preset step frequency, wherein the plurality of sub-band signals are used for exciting a plurality of controllable vibrators; A receiving module, used for receiving the echo signal of the sub-band signal, wherein the echo signal carries formation information of different depths; A correction module, used for performing real-time phase correction on the echo signal and synthesizing the detection signal through a stepped frequency; The real-time phase correction of the echo signal comprises: Performing time shift and phase correction on the received multiple echo signals; And, coherently superimposing the received multiple echo signals in the time domain to obtain a spliced ​​detection signal; The performing phase correction on the received multiple echo signals comprises: Phase shifting the echo signal A or the echo signal B by c+π to minimize the variance of the echo signal A and the echo signal B; comprising: phase shifting the echo signal A or the echo signal B by c+π, selecting a sampling point s between the echo signal A and the echo signal B, calculating the variance of the echo signal A and the echo signal B within a sampling window of length w from the sampling point s to the sampling point after the sampling point, and taking the inverse of the maximum variance as the variance of the phase shift amount c.

7. A step frequency control device for a marine vibrator, characterized in that: include: The method according to any one of claims 1 to 5.

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