Marine Seismic Source Signature Estimation via Direct Arrival Processing
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Solution Overview
Problem
Current methods for estimating the far-field signature of a marine seismic source are costly and technically complex, often resulting in unreliable source signature estimates, especially for frequencies below 30 Hz, due to the need for deep water measurements and three-dimensional positioning of detectors, which can introduce noise and artifacts in seismic data.
Innovation Solution
The method involves utilizing direct arrivals recorded by a production marine streamer to generate a reliable source signature estimate by summing, filtering, and compensating direct arrivals from common shot gathers or common receiver gathers, which can be used to create a mathematical operator for collapsing the air gun source signature, especially effective in naturally band-limited subsurface regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If deep water measurements and three-dimensional positioning of detectors are used to estimate far-field signature, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent creates a virtual far-field signature by mathematically processing near-field measurements from production streamers. Instead of physically placing detectors in deep water at far-field positions, the system copies the far-field signature information through signal processing operations including spherical divergence correction and deconvolution, eliminating the need for complex deep-water measurement setups
Solution Approach 2:
The patent replaces the mechanical/physical system of deep-water far-field measurements with a computational signal processing system. By applying mathematical operations (spherical divergence correction, deconvolution) to near-field data, the system substitutes physical measurement complexity with computational processing to achieve the same far-field signature estimation goal
2Measurement precision
If deep water measurements are used to obtain far-field signature, then far-field signature accuracy is improved, but loss of time and productivity decrease
Solution Approach 1:
The patent makes the production streamers serve dual purposes: they both acquire seismic reflection data and simultaneously provide the near-field measurements needed for far-field signature estimation. This self-service approach eliminates the need for separate dedicated signature measurement operations, allowing continuous acquisition without additional time loss
Solution Approach 2:
The far-field signature estimation is performed continuously during the seismic survey using real-time or near-real-time processing of recorded data. By preparing and computing the signature estimate concurrently with data acquisition rather than as a separate preliminary or post-processing step, the system maintains productivity while achieving accurate signature estimates
3Device complexity
If near-field or mid-field measurements are used to generate far-field signature estimate, then device complexity is reduced, but measurement precision deteriorates due to spatial extent effects
Solution Approach 1:
The patent applies spherical divergence correction to transform the near-field measurements into far-field equivalent data. By mathematically adjusting for the amplitude decay and phase changes that occur with distance, the system compensates for the near-field/mid-field position limitations and recovers the true far-field signature characteristics
Solution Approach 2:
The patent introduces mathematical processing operations as intermediaries between the near-field measurements and the final far-field signature estimate. These processing steps (spherical divergence correction, deconvolution) act as mediators that transform the imperfect near-field data into accurate far-field signature information
4Measurement precision
If traditional far-field measurement methods are used, then source signature estimate is obtained, but object-generated harmful factors increase due to noise and artifacts
Solution Approach 1:
The patent uses the readily available near-field measurements from production streamers—which traditionally would be insufficient for far-field signature estimation—as the basis for computing the far-field signature. By applying appropriate mathematical transformations, the system converts what would normally be inadequate near-field data into accurate far-field signature information, eliminating the need for separate deep-water measurements that could introduce additional noise
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 a reliable source signature estimate up to 70 to 80 Hz, enhancing seismic imaging by reducing noise and improving the accuracy of seismic data processing, particularly in deeper zones where low-frequency content is critical.
Implementation Method 1
The acoustic signals created by these high pressure air impulses travel through the water and the earth
Implementation Method 2
The acoustic signals arriving at the seismic detectors in the streamer cable are a summation of energy
Data Source
AI summary
Method for estimating source signature of a marine seismic source array in a naturally band-limited subsurface region, for designature processing of resulting seismic data. Direct arrivals identified in the streamer receivers' records (131) provide a far-field estimate of the source signature, provided that the subsurface naturally limits frequencies to below the first notch frequency in the amplitude response of the seismic streamer receiver array. Processing of the direct arrivals may include move out or alignment correction (132), signal enhancement (133), summing of direct arrival traces over all offsets (134), windowing or tapering of direct arrivals (135), and deterministic corrections to the combined direct arrivals to compensate for ghosting and streamer array effects (136).