Seismic Imaging Using Higher-Order Reflections and Wavefield Separation
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Solution Overview
Problem
Geophysical surveys, particularly in marine environments, face challenges with deploying and maintaining large numbers of seabed sensors due to high costs and complexity, limiting the effectiveness of 4D surveying and requiring sparse sensor arrays, which can reduce survey accuracy and increase noise sources.
Innovation Solution
The implementation of geophysical analysis techniques that include switching source and receiver definitions based on reciprocity, using higher-order reflections, separating up-going and down-going wavefields, and deconvolution, allowing for sparse sensor arrays and increased survey flexibility while reducing noise and processing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If large numbers of seabed sensors are deployed to improve survey accuracy and reduce noise, then measurement precision is improved, but device complexity and equipment costs increase
Solution Approach 1:
The patent creates virtual sources and virtual receivers by mathematically processing seismic data from sparse physical sensors. These virtual elements are copies that simulate the response of additional physical sensors, enabling high-resolution imaging without deploying large numbers of actual seabed sensors. The virtual source at the seabed location replicates what a physical source would produce, and virtual receivers replicate sensor responses.
Solution Approach 2:
The patent replaces the mechanical system of deploying numerous physical seabed sensors with a computational system that processes data from sparse sensors. Instead of physically adding more sensors to improve accuracy, the invention uses mathematical operations (wavefield separation, reciprocity-based processing) to achieve the same effect computationally, thereby reducing device complexity while maintaining measurement precision.
2Device complexity
If sparse sensor arrays are used to reduce equipment costs and deployment complexity, then device complexity is reduced, but survey accuracy and illumination area decrease
Solution Approach 1:
The patent transitions from a spatial dimension problem to a temporal and mathematical dimension solution. Instead of adding sensors in space to improve illumination and accuracy, the invention uses time-domain processing and mathematical transformations to extract additional information from the sparse sensor data. Wavefield separation in the time domain and reciprocity-based virtual source creation in the mathematical domain compensate for the spatial sparsity.
Solution Approach 2:
The patent changes the parameters of the seismic data processing by applying wavefield separation techniques that distinguish between up-going and down-going waves. This parameter change in the data domain allows the system to extract more information from the same sparse sensor inputs, effectively improving survey accuracy without increasing sensor density.
3Loss of time
If traditional seismic processing is used with sparse arrays, then processing time is reduced, but noise levels increase and survey quality decreases
Solution Approach 1:
The patent applies wavefield separation as a preliminary action in the processing workflow, separating up-going and down-going waves before subsequent imaging steps. This preliminary separation removes noise and unwanted wave components early in the process, preventing them from interfering with later steps. By addressing the noise problem upfront rather than requiring extensive post-processing, the method maintains quality while controlling processing time.
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
These techniques enhance survey accuracy, reduce equipment costs, and increase the illumination area, enabling more efficient and flexible geophysical surveys, particularly for 4D applications by utilizing sparse sensor arrays and minimizing noise sources.
Implementation Method 1
Seismic geophysical surveys are based on the use of acoustic waves
Implementation Method 2
Acoustic waves generated by the survey source may be transmitted to the earth's crust and then reflected back and captured at the towed and/or seabed geophysical sensors
Data Source
AI summary
Techniques are disclosed relating to geophysical analysis. In one embodiment, a method includes receiving seismic data for a geophysical formation recorded during a seismic survey using one or more seabed sensors and one or more sources. In this embodiment, the method includes determining a seismic gather for a location in the geophysical formation, modifying the seismic gather by interchanging source-receiver definitions for the seismic gather, and imaging the location using the modified gather. In this embodiment, the imaging uses higher-order reflections recorded in the seismic gather. In some embodiments, the method includes separating up-going and down-going wavefields and separately imaging using the up-going wavefield and the down-going wavefield.