Marine Seismic Ghost Removal Using Variable Sea Surface
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Solution Overview
Problem
Current methods for deghosting in marine seismic data acquisition require continuous measurements of wave height or substantial modifications to the acquisition setup, which is undesirable, and fail to accurately account for the varying sea surface shape caused by factors like wind and earthquakes, leading to degraded seismic data quality.
Innovation Solution
A method that calculates wave height based on new approaches and modifies the deghosting scheme to account for the calculated wave height, allowing for corrected ghost removal without modifying the existing acquisition setup, using techniques such as cross-correlation and iterative wave estimation to align up-going and down-going energy fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional deghosting algorithms assume a constant datum sea surface, then the processing is simpler, but the quality of wave-field separation is degraded due to unknown time delays caused by sea surface variations
Solution Approach 1:
The patent applies preliminary action by estimating the sea surface shape before performing deghosting operations. The method calculates wave height data from the recorded seismic data itself, then uses this estimated sea surface information to correct travel-time delays in the ghost reflection paths. This preliminary estimation allows the subsequent deghosting to account for sea surface variations, improving wave-field separation quality without requiring complex real-time measurements during acquisition
Solution Approach 2:
The patent introduces an intermediary approach by using the recorded seismic data itself as a source of sea surface information. Instead of requiring external wave height measurements or complex acquisition setups, the method extracts wave height data from the ghost reflections already present in the seismic records. This intermediary use of existing data bridges the gap between simple processing and accurate sea surface modeling
2Measurement precision
If continuous wave height measurements are implemented, then the accuracy of deghosting is improved, but the device complexity and operational requirements increase substantially
Solution Approach 1:
The patent applies self-service by enabling the seismic data processing system to generate its own sea surface information from the recorded data. The method uses the ghost reflections already captured by the seismic sensors to estimate wave height and sea surface shape, eliminating the need for separate wave height measurement instruments. The system serves its own information needs using its existing resources
Solution Approach 2:
The patent demonstrates multi-functionality by making the seismic recording system perform multiple functions: it not only records subsurface reflections for imaging but also captures sea surface wave information through the ghost reflections. This dual-purpose use of the same equipment allows accurate deghosting without adding dedicated wave height measurement devices to the acquisition setup
3Ease of operation
If the sea surface is modeled as a flat horizontal plane, then the travel-time calculation is simpler, but the accuracy of ghost reflection timing is reduced due to ignoring sea surface variations
Solution Approach 1:
The patent applies dynamics by transitioning from a static flat sea surface model to a dynamic wave-based model. The method estimates time-varying wave height data from the seismic records and uses this dynamic information to adjust travel-time calculations for ghost reflections. This allows the system to adapt to changing sea surface conditions while maintaining reasonable computational efficiency
Solution Approach 2:
The patent changes the parameter representation of the sea surface from a constant flat plane to a variable wave surface described by time-varying height parameters. By extracting wave height data from the recordings and incorporating these parameter variations into the travel-time calculations, the method achieves more accurate ghost timing correction without excessive computational complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method improves the accuracy of seismic data processing by correctly accounting for sea surface variations, enhancing the quality of subsurface imaging without the need for continuous wave height measurements or setup modifications, thereby improving the resolution and reliability of seismic data.
Implementation Method 1
Since the interface between the water and air is well approximated as a quasi-perfect reflector (i.e., the water surface acts as a mirror for the acoustic waves), the reflected wave 122c is reflected back toward the detector 112
Implementation Method 2
Acoustic wave 122a propagates downward and penetrates the seafloor 124, eventually being reflected by a reflecting structure 126
Data Source
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AI summary
Computing device, computer instructions and method for processing energy at a free-surface reflection relating to an air-water interface. The method includes receiving (2000) input seismic data recorded with seismic sensors; receiving (2002) wave-height data that describes an actual shape of a top surface of a body of water; processing (2004) up-going energy at a receiver and down-going energy following a reflection at the sea-surface, using the input seismic data and a linear operator modified to take into account the wave-height data; and generating (2006) an image of the subsurface based on the up-going energy or the down-going energy or a combination of the input seismic data and one of the up-going or down-going energy.