Method and system for laying a marine cable active seismic source considering observation coverage and economy

Abstract

The application discloses a submarine cable active seismic source laying method and system considering observation coverage and economy, and belongs to the technical field of marine geophysical exploration. The method comprises the following steps: performing a sensor effectiveness diagnosis stage, performing a diagnostic excitation on the submarine cable, identifying and screening out sensor points with signal receiving capability, and generating an effective exploration target point set; performing an adaptive path planning stage, taking the effective exploration target point set as a planning target, taking a three-dimensional seabed topography model as a physical constraint, performing acoustic accessibility evaluation, and based on the evaluation result, solving an excitation path capable of avoiding acoustic obstacles and covering the effective exploration target point set. Through the two-stage linkage method of diagnosis and screening first and adaptive planning second, the application solves the problem of resource allocation blindness caused by the disconnection between exploration decision and system physical state in the prior art, and can obtain more complete signal coverage and higher positioning accuracy at a lower cost under complex topography.

Description

Technical Field

[0001] This invention belongs to the field of marine geophysical exploration technology, and specifically relates to a method and system for deploying active seismic sources for submarine cables that balances observation coverage and economy. Background Technology

[0002] Using submarine optical cables (submarine cables) as distributed acoustic sensors (DAS) for seismic exploration and location is a rapidly developing technology in recent years. In active source exploration operations, a survey vessel typically excites an artificial seismic source along a pre-set path, and the submarine optical cable receives the seismic wave signals.

[0003] Existing technologies typically employ fixed patterns such as evenly spaced grids or S-shaped layouts when planning the excitation path of active seismic sources. However, this approach fails to consider two crucial physical realities: first, the obstruction effect of complex seabed topography (such as seamounts and trenches) on sound wave propagation paths, easily creating "acoustic blind spots" behind these topographical features where effective signals cannot be received; and second, the non-uniform physical coupling between the submarine cable and the seabed, with some cable sections potentially becoming "ineffective sensors" with poor signal reception due to suspension or burial in soft sediments.

[0004] Therefore, existing deployment methods suffer from decision-making blindness. To compensate for data gaps, large-scale encrypted excitation is often required, which not only significantly increases operation time and economic costs, but also only adds noise data to the repeated exploration of "invalid sensor" areas, which is not beneficial to the final positioning accuracy and may even be detrimental. How to achieve accurate and efficient deployment of exploration resources (excitation points) to ensure complete coverage of effective signals while taking into account economic efficiency is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] This invention provides a method and system for deploying active seismic sources via submarine cables that balances observation coverage and economy, in order to solve the problem of blind resource allocation caused by the disconnect between exploration decisions and the physical state of the system in the prior art.

[0006] In view of the above problems, in a first aspect, the present invention provides a method for deploying submarine active seismic sources that balances observation coverage and economy, the method comprising: The sensor effectiveness diagnosis stage includes performing diagnostic excitation on the submarine cable, identifying and screening sensor points with signal receiving capabilities, and generating a set of effective exploration target points. The adaptive path planning phase includes using the effective set of exploration target points as the planning target and a three-dimensional seabed topography model as the physical constraint to perform an acoustic accessibility assessment, and based on the assessment results, solving for the excitation path to ensure that the excitation path can avoid acoustic obstacles and cover the effective set of exploration target points.

[0007] Secondly, this invention also provides a submarine cable active seismic source deployment system that balances observation coverage and economy, comprising: A sensor diagnostic unit is configured to perform a sensor effectiveness diagnostic phase of the method as described in claim 1 to generate a set of effective exploration target points; The path optimizer is configured to use the set of valid exploration target points generated by the sensor diagnostic unit as its planning target and receive a three-dimensional seabed topography model as a constraint, and to perform an adaptive path planning phase of the method as described in claim 1 to output an excitation path.

[0008] The technical solution provided in this application, by introducing a sensor effectiveness diagnosis stage before path planning, enables the exploration resources to be precisely focused on effective sensor points with high-quality signal reception capabilities, avoiding redundant exploration of ineffective sensor points, thereby reducing the introduction of noise data at the source and saving exploration costs. By using the selected effective sensor points as targets and combining them with terrain constraints for adaptive path planning, this invention can actively avoid acoustic blind spots caused by terrain, ensuring complete coverage of effective signals. Compared with existing technologies, this invention can significantly improve signal coverage and final positioning accuracy while reducing exploration costs. Attached Figure Description

[0009] Figure 1 A schematic flowchart of the submarine cable active seismic source deployment method that balances observation coverage and economy provided in this embodiment of the invention; Figure 2 Simulation comparison diagram of the technical effects of one embodiment of the present invention; Figure 3 The structural block diagram of the submarine cable active seismic source deployment system provided in this embodiment of the invention, which balances observation coverage and economy. Detailed Implementation

[0010] The above technical solutions will now be described in detail with reference to the accompanying drawings and specific embodiments to provide a better understanding of them. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. It should be understood that the present invention is not limited to the exemplary embodiments used only to explain the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Furthermore, it should be noted that, for ease of description, only the parts related to the present invention are shown in the drawings, not all of them.

[0011] Please see Figure 1 A method for deploying active seismic sources via submarine cables that balances observation coverage and cost-effectiveness, the method comprising: The sensor effectiveness diagnosis stage includes performing diagnostic excitation on the submarine cable, identifying and screening sensor points with signal receiving capabilities, and generating a set of effective exploration target points. The adaptive path planning phase includes using the effective set of exploration target points as the planning target and a three-dimensional seabed topography model as the physical constraint to perform an acoustic accessibility assessment, and based on the assessment results, solving for the excitation path to ensure that the excitation path can avoid acoustic obstacles and cover the effective set of exploration target points.

[0012] The implementation of a method for deploying active seismic sources via submarine cables that balances observation coverage and cost-effectiveness begins with the sensor effectiveness diagnosis stage.

[0013] The sensor diagnostic unit generates a diagnostic excitation sequence operation command based on the geographical information of the target submarine cable segment and sends the operation command to the navigation and excitation control system of the survey vessel. After receiving the operation command, the navigation and excitation control system controls the navigation trajectory of the survey vessel and the excitation timing of the active seismic source. The operation command includes two excitation operations: First, the survey vessel travels along the estimated direction of the target submarine cable segment at a preset speed within a lateral offset distance of 5 to 20 meters and performs parallel excitation at fixed time intervals or distance intervals; then, the survey vessel adjusts its course to cross the target submarine cable segment with a track perpendicular to the estimated direction of the target submarine cable segment, and performs vertical excitation at predetermined points during the crossing process.

[0014] During the diagnostic excitation sequence performed by the survey vessel, the demodulator of the distributed fiber optic acoustic sensing system connected to the target submarine cable segment continuously acquires backscattered Rayleigh light signals along the cable at a high-frequency sampling rate. The synchronization unit of the distributed fiber optic acoustic sensing system ensures that the excitation time of the active source is time-aligned with the acquired fiber optic vibration data stream. The acquired raw vibration data stream is a multidimensional dataset containing time-series vibration information from all sensing points along the fiber. After receiving the raw vibration data stream, the sensor diagnostic unit initiates a data preprocessing process. This preprocessing includes applying a bandpass filter, the passband frequency range of which is set according to the spectral characteristics of the active source, for example, 5-150 Hz. Then, FK filtering or median filtering algorithms can be applied to suppress linear interference or sudden noise pulses in the data, outputting a vibration response dataset.

[0015] After obtaining the vibration response dataset, the sensor diagnostic unit then performs energy calculations on the vibration signals corresponding to parallel and perpendicular excitation within the dataset. For each sensing point i (i from 1 to N) among the N sensing points on the submarine cable, the sensor diagnostic unit performs the following calculation steps: First, starting from the excitation time of parallel excitation, a vibration signal time sequence of a preset time length (e.g., 1 second) is extracted. Then, the absolute or squared value of the time series signal is integrated over the entire time window to obtain the response energy value of the parallel excitation. Secondly, using the same method, starting from the excitation time of vertical excitation, vibration signal time series of equal length are extracted. The response energy value of the vertical excitation is obtained by integrating the result. .

[0016] After completing the numerical calculation of the response energy for all sensing points, the sensor diagnostic unit calculates the response anisotropy ratio for each sensing point i. The calculation process involves calling the corresponding function of sensor point i. and Numerical values, and according to the formula Perform a division operation. The calculated anisotropy ratios of the responses at all sensing points are stored as a one-dimensional array or list corresponding to the sensing point indices.

[0017] After obtaining the response anisotropy ratios of all sensing points, the sensor diagnostic unit performs a step to generate the effective exploration target point set. At the beginning of this step, the sensor diagnostic unit loads a preset response anisotropy ratio threshold, the value of which can be set based on experimental data or geological conditions, for example, 0.5. Then, the sensor diagnostic unit iterates through the response anisotropy ratios of all sensing points. The calculation results are then used to compare each RAR_i value with a preset threshold. When the value is below a preset threshold, the sensor point i is determined to be a valid sensor point. The sensor diagnostic unit stores the indices i of all valid sensor points into a newly created data structure, such as an integer array or list. After traversing all sensor points, this data structure containing only the indices of valid sensor points constitutes the final set of valid exploration target points, which is output by the sensor diagnostic unit to the path optimizer.

[0018] After the sensor effectiveness diagnosis phase is completed, the method enters the adaptive path planning phase. This phase is executed by the path optimizer.

[0019] After initialization, the path optimizer performs acoustic simulations for each target point in the effective exploration target point set to generate its reachable excitation region. The path optimizer iterates through all target point indices in the effective exploration target point set and, for each target point, uses its geographic coordinates as the sound wave receiving point. Then, the path optimizer invokes the built-in acoustic ray tracing engine to emit virtual acoustic rays from the target point into the surrounding water. When simulating ray propagation, the acoustic ray tracing engine reads data from the 3D seabed topography model; when the ray path encounters obstruction caused by topographic undulations, the ray is deemed invalid. The coordinates of all virtual sound wave emission points that can propagate unobstructed to the target point in a straight line or after one or more reflections from the sea surface or seabed are recorded. The set of these coordinate points constitutes the target point's exclusive reachable excitation region and is stored in a data format associated with the target point index.

[0020] After generating the reachable excitation regions for all valid exploration target points, the path optimizer then executes the step of solving the excitation path. First, the path optimizer constructs a set coverage model, in which the set of valid exploration target points output by the sensor diagnostic unit is defined as the entire set, and the reachable excitation region corresponding to each target point is defined as a subset.

[0021] Subsequently, the path optimizer invokes a built-in optimization algorithm solver, such as an integer programming solver. This solver uses the core constraint that "the union of subsets must cover the entire set" and iteratively calculates and compares the total travel costs of candidate paths composed of different combinations of trigger points to find the optimal solution that satisfies this constraint. Finally, the solver outputs a combination of trigger points determined to have the lowest total travel cost; this combination constitutes the initial trigger path.

[0022] During path solving, the path optimizer simultaneously monitors the cost of covering each target point. Coverage cost is quantified by calculating the average travel distance between the trigger point covering a specific target point and that target point. The path optimizer loads a preset cost threshold. When the path optimizer detects that, for a target point in the effective exploration target point set, the travel cost calculated for all trigger point combinations covering that target point exceeds the preset cost threshold, the path optimizer triggers an enhanced calculation procedure for that high-cost target point.

[0023] The triggered augmented computation program utilizes an acoustic ray tracing engine and a 3D seabed topography model to optimize reflector focusing paths for a specified high-cost target point. The program first identifies high-reflectivity topographic features, such as steep trench walls or bedrock surfaces, located around the high-cost target point in the 3D seabed topography model. Then, it treats these topographic features as potential reflectors and performs acoustic ray tracing simulations to calculate the coordinates of all potential excitation points that can propagate sound energy to the high-cost target point after one or more reflections through these reflectors. The set of these potential excitation point coordinates calculated via reflection paths constitutes one or more indirect excitation paths. The augmented computation program adds these indirect excitation paths as new candidate paths back to the solution space of the set cover problem for the path optimizer to recalculate the global optimum.

[0024] After completing optimization calculations for all direct and indirect paths, the path optimizer ultimately determines a sequence of excitation point coordinates that covers the entire set of valid exploration target points and minimizes the total navigation cost. The path optimizer sorts this coordinate sequence according to the navigation order and formats it into a dynamic operational path file that can be directly read and executed by the shipborne navigation system. This dynamic operational path file is the final output of the adaptive path planning phase and is output by the path optimizer.

[0025] In one specific embodiment, after completing all optimization calculations, the path optimizer generates a dynamic job path file as a structured text file, which may be in comma-separated value (CSV) format. This file is intended to be directly parsed and executed by the shipborne navigation and excitation control system. Each line of the file represents an excitation point and contains all the instruction parameters required to perform the operation at that point.

[0026] An example of the contents of a dynamic job path file is as follows: Excitation point number, longitude, latitude, excitation type: {1, 122.12345, 30.67890, direct}, {2, 122.12480, 30.67912, direct}, {3, 122.12855, 30.68050, indirect - reflecting surface A}.

[0027] In this example, the "Excitation Point Number" defines the execution order of the operation. The "Longitude" and "Latitude" fields provide the precise geographic coordinates of the excitation point for the vessel's dynamic positioning. The "Excitation Type" field provides additional information, such as whether the excitation point is used to directly cover the target or indirectly cover it via a specific reflector (e.g., reflector A), which can be used for subsequent analysis of the operation's quality. The shipboard navigation system reads this file line by line in sequence, guiding the survey vessel to the designated coordinates and triggering the active seismic source to perform the excitation operation.

[0028] In another embodiment, the specific implementation process and technical effects of the method of the present invention are further illustrated.

[0029] In a specific implementation scenario, the sensor diagnostic unit receives diagnostic data containing four sensing points (index numbers 101, 102, 103, and 104). After integration, the obtained response energy value is as follows: Sensing point 101: Parallel excitation response energy is 3.2; Vertical excitation response energy is 0.8.

[0030] Sensing point 102: Parallel excitation response energy is 2.9; Vertical excitation response energy is 0.7.

[0031] Sensing point 103: Parallel excitation response energy is 0.4; Vertical excitation response energy is 2.1.

[0032] Sensing point 104: Parallel excitation response energy is 3.5; Vertical excitation response energy is 1.1.

[0033] The sensor diagnostic unit then calculates the response anisotropy ratio (RAR) for these four sensing points: Subsequently, the sensor diagnostic unit loads a preset response anisotropy ratio threshold of 0.5 and performs comparisons. The calculation results show that the RAR values ​​of sensing points 101, 102, and 104 are all below 0.5, and therefore are determined to be valid sensing points. The RAR value of sensing point 103 is much higher than 0.5, and is therefore determined to be an invalid sensing point. Finally, the sensor diagnostic unit constructs and outputs an integer array [101, 102, 104] containing only the indices of valid sensing points. This array constitutes the set of valid exploration target points for this operation.

[0034] To verify the technical effects of the present invention, a set of comparative experiments based on computer simulation were conducted. Figure 2 The scenario setup and final results of this simulation experiment are shown below. The quantitative results of the simulation are explained in detail below with reference to the accompanying figures.

[0035] like Figure 2As shown, the simulation environment is set as a complex terrain containing seabed ridges. A section of simulated submarine optical cable is laid along the seabed, and based on the sensor effectiveness diagnosis results, the sensing points are divided into effective sensing points (represented by legend "o") and invalid sensing points (represented by legend "x").

[0036] Reference Figure 2 Figure (a) illustrates a simulation scenario using existing technology. In this scenario, a uniform excitation path is employed, with excitation points (represented by the legend "+") arranged along a fixed straight line. Figure 2 Numerical calculations in scenario (a) show that a total of 200 excitation points were set up. Due to the obstruction of the underwater ridge topography, an acoustic blind zone was formed as shown in the figure, resulting in a signal coverage rate of only 42% for the effective sensing points. Inversion calculations using the simulation data of this scenario yielded a final root mean square error of 4.8 meters for positioning.

[0037] Reference Figure 2 Figure (b) illustrates a simulation scenario employing the present invention. In this scenario, the system first identifies the valid sensing points in the figure as targets, and then plans an adaptive exploration path (represented by a dashed line). Figure 2 Numerical calculations for the scenario shown in (b) show that, to achieve coverage of all effective target points, the final generated path contains 175 excitation points. As shown in the figure, this path successfully avoids terrain obstacles, ensuring that the acoustic ray (represented by solid lines) covers all effective sensor points, achieving a signal coverage rate of 99%. Inversion calculations using the simulation data for this scenario yield a final root mean square error of 1.1 meters for positioning.

[0038] By comparing the quantitative results of the above simulation experiments, it can be seen that the present invention reduces the number of excitation points by 12.5%, while increasing the effective signal coverage by more than double and reducing the final positioning error by 77%.

[0039] In a specific calibration embodiment, an optical cable can be pre-laid in a section of seabed with known physical properties, containing both well-coupled bedrock sections and poorly coupled mud sections. Diagnostic excitation is performed on this area to collect the RAR values ​​of these two typical cable segments. Experimental data shows that the energy of well-coupled cable segments primarily originates from vibrations transmitted from the underlying strata; therefore, their response to parallel excitation is much stronger than that of vertical excitation propagating laterally into the water, and their RAR values ​​typically range from 0.1 to 0.4. Poorly coupled (especially suspended) cable segments, like cables in water, are more sensitive to lateral water waves, and their RAR values ​​are usually much greater than 1.0. Therefore, setting the decision threshold at 0.5 serves as a reliable distinguishing boundary, effectively differentiating the two types of sensing points while balancing the accuracy of the selection with tolerance for minor coupling differences. In different geological environments, the above calibration experiments can be repeated to determine the threshold that best matches the local environment.

[0040] See Figure 3 The present invention also provides a submarine cable active seismic source deployment system that balances observation coverage and economy, thereby realizing a method for deploying submarine cable active seismic sources that balances observation coverage and economy. This system can be deployed on a hardware combination of a shore-based control center and a survey vessel.

[0041] The system includes a sensor diagnostic unit, a path optimizer, and an exploration execution unit.

[0042] In one embodiment, the sensor diagnostic unit is a software module deployed on a computer. This unit is configured with an input interface to receive raw vibration data streams from a distributed fiber optic acoustic sensing system. Internally, the unit integrates a data preprocessing pipeline and an algorithm module for performing energy calculations. This energy calculation module is configured to perform integral operations on the vibration signal for each sensing point within a preset time window. The unit also includes a calculation module for calculating the response anisotropy ratio and a filtering module for comparing the calculation results with preset thresholds and constructing an indexed data structure. By performing these functions, the sensor diagnostic unit ultimately outputs a set of valid exploration target points.

[0043] In one implementation, the path optimizer is another software module deployed on the same computer as the sensor diagnostic unit. This optimizer is configured with an input interface to receive the set of valid exploration target points output by the sensor diagnostic unit and an interface for loading a 3D seabed topography model. Internally, the optimizer integrates an acoustic ray tracing engine and an optimization algorithm solver for solving the set coverage problem. The optimizer is configured to first invoke the acoustic ray tracing engine to generate reachable excitation regions for the target points in the set of valid exploration target points; then, it invoke the optimization algorithm solver to iteratively calculate and find the combination of excitation points that minimizes the total navigation cost, while satisfying the coverage constraints. The optimizer also includes an enhanced computation module that performs optimization calculations for indirect excitation paths when a specific cost threshold is triggered. The path optimizer ultimately outputs the excitation paths.

[0044] In one embodiment, the exploration execution unit is a combination of hardware and software including a shipborne navigation system, an active seismic source control system, and a distributed fiber optic acoustic wave sensing acquisition system. This unit is equipped with an interface to receive the excitation path output by a path optimizer. The shipborne navigation system controls the ship's navigation based on the coordinate sequence in the received excitation path. The active seismic source control system triggers the active seismic source at designated coordinate points according to the instructions in the excitation path. The distributed fiber optic acoustic wave sensing acquisition system simultaneously acquires vibration data.

[0045] When the system is working, the sensor diagnostic unit first completes the calculation and outputs the set of valid exploration target points. The path optimizer receives the set of points, completes the path calculation, and outputs the activation path. Finally, the exploration execution unit receives the path and executes the exploration operation in the physical world, thus forming a complete operation process.

[0046] The embodiments described above are only some embodiments of the present invention, and not all embodiments. It should be noted that the present invention is not limited to the embodiments described above. Any modifications, equivalent substitutions, variations, or improvements made by those skilled in the art based on the above embodiments without creative effort, within the scope of the concept and principles of the present invention, should fall within the protection scope claimed by the claims of the present invention.

Claims

1. A method for deploying active seismic sources via submarine cables that balances observation coverage and cost-effectiveness, characterized in that, The method includes: The sensor effectiveness diagnosis stage includes performing diagnostic excitation on the submarine cable, identifying and screening sensor points with signal receiving capabilities, and generating a set of effective exploration target points. The adaptive path planning phase includes using the effective set of exploration target points as the planning target and a three-dimensional seabed topography model as the physical constraint to perform an acoustic accessibility assessment, and based on the assessment results, solving for the excitation path to ensure that the excitation path can avoid acoustic obstacles and cover the effective set of exploration target points. The sensor effectiveness diagnosis phase includes: The submarine cable is subjected to parallel excitation parallel to its orientation and vertical excitation perpendicular to its orientation. The ratio between the response energy of each sensing point on the submarine cable to the vertical excitation and the response energy to the parallel excitation is calculated, and a corresponding response anisotropy ratio (RAR) is generated for each sensing point. The value of the i-th sensing point corresponding to the response anisotropy ratio Calculated using the following formula: , Let be the response energy of sensing point i to the vertical excitation. Let i be the response energy of the sensing point i to the parallel excitation; The step of generating a valid set of exploration target points includes... Sensing points with values ​​below a preset threshold are considered valid sensing points; The adaptive path planning stage further includes: when the navigation cost of the directly accessible excitation area for a target point in the set of effective exploration target points is higher than a preset cost threshold, further calculating an indirect excitation path that can focus the acoustic energy on the target point via one or more reflective surfaces in the three-dimensional seabed topography model, and incorporating the indirect excitation path as a candidate path into the process of solving the excitation path.

2. The method for deploying submarine cable active seismic sources that balances observation coverage and economy, as described in claim 1, is characterized in that... The and The calculation includes: for sensing point i, performing integral calculations on the vibration signals responding to the vertical excitation and the parallel excitation within a preset time window respectively; The step of generating a set of valid exploration target points specifically includes constructing a data structure containing an index of the sensor points that are determined to be valid.

3. The method for deploying submarine active seismic sources that balances observation coverage and economy, as described in claim 1, is characterized in that... The acoustic accessibility assessment in the adaptive path planning phase includes: performing acoustic ray tracing simulation for target points in the set of effective exploration target points to determine potential excitation points that can excite the target points without obstruction under the constraints of the three-dimensional seabed topography model, and generating an accessible excitation region for the target point.

4. The method for deploying submarine cable active seismic sources that balances observation coverage and economy, as described in claim 3, is characterized in that... The steps for solving the excitation path include: constructing a set coverage model with the set of effective exploration target points as the whole set and each reachable excitation region as a subset; The optimization algorithm solver is invoked to iteratively calculate and compare the total travel cost of different combinations of trigger points, under the constraint that the union of the subsets covers the entire set, in order to determine the trigger path with the lowest total travel cost.

5. A submarine cable active seismic source deployment system that balances observation coverage and economy, characterized in that, include: A sensor diagnostic unit is configured to perform a sensor effectiveness diagnostic phase of the method as described in claim 1 to generate a set of effective exploration target points; The path optimizer is configured to use the set of valid exploration target points generated by the sensor diagnostic unit as its planning target and receive a three-dimensional seabed topography model as a constraint, and to perform an adaptive path planning phase of the method as described in claim 1 to output an excitation path.

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