Variable-Depth Streamer Shape Determination for Ghost Reduction
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Solution Overview
Problem
Current marine seismic survey methods face challenges in achieving accurate subsurface imaging due to ghost waves, which degrade bandwidth and resolution, and existing streamer configurations are impractical for deep water depths, leading to detector failure or impractical deployment.
Innovation Solution
A method for determining the shape of a streamer to be towed underwater, using a variable-depth configuration that optimizes ghost removal and bandwidth by calculating residual ghosts and spectra, allowing for improved seismic data acquisition across a broader frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a slanted streamer configuration is used to increase time gap between primary and ghost reflections, then deghosting is facilitated, but detector depth exceeds current operational capabilities (requiring depths >50m while detectors are designed for ≤50m)
Solution Approach 1:
The streamer configuration transitions from a static slanted arrangement to a dynamic variable-depth configuration where detectors are positioned at different depths along the streamer body. This allows the system to adapt detector depths to match operational capabilities (≤50m) while still achieving sufficient time gaps between primary and ghost reflections through strategic depth variation rather than uniform slanting.
Solution Approach 2:
The invention changes the depth parameter distribution along the streamer from a uniform slanted configuration to a variable-depth configuration. By varying detector depths strategically, the system achieves the necessary time gap for deghosting without requiring any single detector to operate beyond its depth capability, thus resolving the contradiction between deghosting requirements and detector reliability.
2Measurement precision
If ghost waves are present in seismic data, then bandwidth and resolution are degraded, but removing ghosts requires complex deghosting processes that affect data quality
Solution Approach 1:
The system performs preliminary action by configuring the streamer depths before data acquisition to optimize the time gap between primary and ghost reflections. This pre-configuration reduces the strength and impact of ghost waves at the source, making subsequent deghosting processes simpler and more effective, thereby improving seismic image quality without requiring overly complex processing.
Solution Approach 2:
The invention incorporates feedback mechanisms where the streamer depth configuration is optimized based on calculated ghost characteristics and residual ghost spectra. By using feedback from ghost analysis to adjust detector positioning, the system minimizes ghost interference iteratively, reducing both the need for complex deghosting and improving final image quality.
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 approach enhances the quality of subsurface imaging by minimizing ghost interference and expanding the frequency range, enabling sharper wavelets and clearer images of the subsurface, even in challenging geological environments.
Implementation Method 1
The acoustic wave 22a propagates downward and penetrates the seafloor 24, eventually being reflected by a reflecting structure 26
Implementation Method 2
The reflected acoustic wave 22b propagates upward and may be detected by detector 12
Implementation Method 3
the interface between the water and air is well approximated as a quasi-perfect reflector (i.e., the water's surface acts as a mirror for the acoustic waves), the reflected wave 22c travels back toward the detector 12
Data Source
AI summary
A method for determining a shape of a streamer to be towed under water for collecting seismic data. The method includes receiving a velocity model for the subsurface; selecting a first profile for a streamer to be used to survey the subsurface; calculating ghosts and/or residual ghosts and/or residual ghost spectra for a plurality of reflectors of the subsurface; and determining that the first profile is appropriate for surveying the subsurface when at least one criterion, related to the ghosts, residual ghosts and/or residual ghost spectra is met.