Zero-Offset Seismic Trace Construction via Near-Field Acquisition
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Solution Overview
Problem
Current marine seismic acquisition methods face challenges in accurately determining zero-offset seismic data due to the distance between seismic sources and receivers, leading to missing data that can only be estimated through numerical extrapolation, which is less accurate and limited to deep water seismography.
Innovation Solution
A method that involves obtaining near-field acoustic signals from locations close to the seismic source, muting direct arrivals, and using the remaining signals to estimate a zero-offset data set, which is then deconvolved and shaped to match non-zero-offset data sets, allowing for improved interpolation and extrapolation to fill data gaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If near-field receivers are placed close to the seismic source to directly measure zero-offset data, then measurement precision of zero-offset data is improved, but device complexity and logistics difficulty increase due to the complex arrangement of sources and receivers
Solution Approach 1:
The receiver array is segmented into multiple sub-arrays, with at least one sub-array positioned in the near-field of the seismic source. This segmentation allows direct measurement of zero-offset data while maintaining manageable complexity through modular arrangement. The near-field sub-array specifically captures signals for determining source signature and zero-offset traces, separating this function from the main far-field receiver array.
Solution Approach 2:
Near-field receivers act as intermediaries between the seismic source and far-field receiver array. These receivers directly measure the seismic signals in the near-field zone, providing intermediate data that bridges the gap between source and distant receivers. This intermediary measurement enables accurate determination of source signature and zero-offset data without requiring complex direct positioning of all receivers at zero-offset locations.
2Device complexity
If numerical extrapolation methods are used to estimate zero-offset data from non-zero-offset data, then device complexity is reduced, but measurement precision and reliability of zero-offset data deteriorate
Solution Approach 1:
The near-field receivers perform preliminary measurement of zero-offset data directly at the source location, before the seismic waves propagate to far-field receivers. This preliminary action of capturing zero-offset signals in the near-field eliminates the need for subsequent numerical extrapolation from non-zero-offset data, providing accurate baseline measurements for source signature and zero-offset traces that can be used in further processing.
3Measurement precision
If near-field receivers are used to measure source signature, then measurement precision of source signature is improved, but sea bottom reflections interfere with accurate measurements in shallow water
Solution Approach 1:
The near-field receiver system extracts and isolates the direct source signature signals from the total recorded wavefield. By positioning receivers in the near-field zone and using appropriate signal processing, the direct arrivals from the air gun array are separated from reflected and scattered signals. This extraction of the primary source signature component allows accurate characterization of the source while minimizing the influence of sea bottom reflections through selective signal isolation.
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 accuracy of seismic data by directly obtaining zero-offset data, improving data interpolation and extrapolation, and enabling more precise seismic signal processing, including matching receiver characteristics and removing source effects, thus facilitating better earth interior representation.
Implementation Method 1
generate seismic pulses or waves from at least one seismic source and to measure or record the produced wavefield
Implementation Method 2
measure or record the produced wavefield... reflections, interactions or the like of the seismic pulses with earth formations may be analyzed
Data Source
AI summary
Described are methods for obtaining seismic signals representative of properties of the earth's interior, including the steps of obtaining near-field acoustic signals recorded in the vicinity of a seismic source (13), muting from the near-field acoustic signals at least partly signals representing direct arrivals from the seismic source (13), and using a remaining part of the obtained signals as estimate of a zero-offset data set. The zero-off set data set can then be used to interpolate data from conventional acquisition location, such as streamers (11), to locations closer to the source (13).