Marine Seismic Source Segmentation for Low-Frequency Data
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Solution Overview
Problem
Marine seismic surveys face challenges in enhancing low-frequency content without increasing source vessel capacity or air compressor size, and in maintaining acceptable shotpoint intervals when using larger-volume airguns, which result in sparse data due to prolonged filling times.
Innovation Solution
The use of large-volume seismic sources in conjunction with standard-volume sources, where the large-volume sources are activated at longer shotpoint intervals, allowing for improved low-frequency data acquisition while maintaining efficient survey operations, and utilizing multiple smaller airguns to enhance low-frequency content and penetration depth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If larger-volume airguns are used to enhance low-frequency content, then low-frequency data quality is improved, but filling time increases and shotpoint intervals become too long
Solution Approach 1:
The patent divides a single large-volume source into multiple smaller-volume sources (e.g., four 250 cubic inch airguns instead of one 1000 cubic inch airgun). Each smaller source can be filled independently and more quickly, allowing for shorter shotpoint intervals while collectively providing sufficient low-frequency energy through the combined response of multiple sources.
2Measurement precision
If larger-volume airguns are used to produce lower-frequency signals, then low-frequency content is enhanced, but data sparsity increases due to reduced number of shotpoints
Solution Approach 1:
By segmenting one large source into multiple smaller sources, the system can deploy more shotpoints along the survey line. Each smaller source contributes to the low-frequency signal, and the increased number of shotpoints ensures adequate spatial sampling and data density throughout the survey area.
Solution Approach 2:
The patent combines the responses from multiple smaller-volume sources to achieve the low-frequency content that would otherwise require a single large-volume source. The constructive interference of signals from multiple sources at low frequencies provides the desired enhancement while maintaining higher shotpoint density.
3Length of stationary object
If larger-volume airguns are used to enhance low-frequency penetration, then subsurface imaging depth is improved, but source vessel capacity requirements increase
Solution Approach 1:
Instead of requiring a single large-volume source that would demand increased source vessel capacity, the patent uses multiple smaller-volume sources that can be accommodated within existing vessel constraints. Each smaller source is filled with compressed air from the vessel's existing supply, and their combined effect achieves the necessary penetration depth for deep subsurface imaging.
Data Source
AI summary
A method and apparatus for marine surveying. A system includes: a standard-volume source element; a large-volume source element comprising an airgun having a volume greater than 1200 cubic inches; and a long-offset survey streamer. A method includes: towing a standard-volume source element; and towing a large-volume source element; activating the large-volume source element at large shotpoint intervals; and activating the standard-volume source element at standard shotpoint intervals, wherein the large shotpoint intervals are at least twice as long as the standard shotpoint intervals. A method includes: obtaining geophysical data for a subterranean formation; and processing the geophysical data to produce an image of the subterranean formation. A method includes: obtaining a firing plan for a plurality of seismic sources, wherein: a first seismic source of the plurality comprises a large-volume source element, and a second seismic source of the plurality consists of standard-volume source elements.