Marine Seismic Data Processing Using Sparse Under Streamer Arrays
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Solution Overview
Problem
Marine seismic surveys face challenges in achieving optimal signal-to-noise ratios due to the 'ghost effect,' which varies with streamer depth, leading to poor acquisition of low-frequency data at shallow depths and high-frequency attenuation at deeper depths, and existing compensation methods either require more streamers or suffer from noise issues.
Innovation Solution
The method involves processing seismic data acquired at both shallow and deep streamer depths, combining low-frequency data from deep streamers with high-frequency data from shallow streamers to achieve broad-band data with improved signal-to-noise ratios, using a sparse-under configuration that optimizes mid- and upper-frequencies while reducing the number of required streamers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the streamer is towed at a shallow depth, then the signal-to-noise ratio at higher frequencies is improved, but attenuation at lower frequencies increases
Solution Approach 1:
The invention divides the streamer array into multiple depth layers (first plurality at first depth, second plurality at second depth, third plurality at third depth). Each layer is optimized for different frequency ranges, with shallow streamers capturing high frequencies and deep streamers capturing low frequencies, thereby resolving the frequency-dependent attenuation problem through spatial segmentation.
Solution Approach 2:
The invention transitions from a single-depth streamer configuration to a multi-depth vertical arrangement. By adding the depth dimension to the traditional horizontal streamer array, the system can simultaneously capture a broad frequency spectrum, with each depth layer contributing to different frequency bands without mutual interference.
2Reliability
If the streamer is towed at a deeper depth, then the signal-to-noise ratio at lower frequencies is improved, but attenuation at higher frequencies increases
Solution Approach 1:
The streamer array is segmented into multiple depth groups, with deeper streamers (second plurality) specifically positioned to optimize low-frequency capture while shallower streamers (first and third pluralities) handle higher frequencies. This segmentation allows each subgroup to specialize in particular frequency ranges, eliminating the need to choose a single depth that compromises either low or high frequency performance.
Solution Approach 2:
Different regions of the streamer array (different depths) are assigned different functional qualities optimized for their respective frequency ranges. The deeper streamers are positioned and configured specifically for low-frequency sensitivity, while shallower streamers are optimized for high-frequency capture, creating a vertically stratified system where each layer has specialized local quality for its frequency band.
3Reliability
If over/under acquisition with vertically aligned pairs is used to compensate for ghost effects, then deghosting is achieved, but the number of streamers required increases
Solution Approach 1:
Instead of requiring complete vertical pairs at all locations (excessive action), the invention uses a sparse under-sampler configuration where only selected streamers are positioned at deeper depths. This partial arrangement provides sufficient deghosting capability for the critical low-frequency band without the need for a complete paired streamer array across the entire spread, thereby reducing the total number of streamers required.
Solution Approach 2:
The deeper streamers serve multiple functions: they provide low-frequency data capture and simultaneously enable deghosting for the entire array through their sparse positioning. Rather than requiring dedicated paired streamers for deghosting, these multi-functional deep streamers contribute to both frequency coverage and ghost effect compensation, reducing overall system complexity and streamer count.
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 provides enhanced signal-to-noise ratios across both high and low frequencies, improving data quality and reducing the number of streamers needed, thus increasing acquisition efficiency and reducing noise issues compared to traditional methods.
Implementation Method 1
the 'ghost effect' at a receiver disposed in a water column occurs as a result of interference between a seismic signal arriving at the receiver directly from reflection at a geological feature within the earth and a seismic signal from that geological feature that has travelled to the surface of the water column and has been reflected at the surface of the water column back to the receiver
Implementation Method 2
the deeper is the streamer, the greater is the attenuation at high frequencies
Data Source
AI summary
Embodiments of the invention provide a method of processing marine seismic data, the data having been acquired using a “dense over/sparse under” streamer array having N over streamers disposed at a first depth and M under streamers disposed at a second depth greater than the first depth, where 0<M<N. The method comprises: a) processing seismic data for one of the over streamer target locations and seismic data for one of the under streamer target locations; b) processing seismic data for another of the over streamer target locations; and c) combining the result of (a) and the result of (b). The one of the over streamer target locations and the one of the under streamer target locations may lie in a vertical plane.