Seismic Imaging Dual-Expanding Box Method
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Solution Overview
Problem
Current seismic imaging methods, such as reverse time migration and waveform inversion, face significant computational challenges due to the need for simultaneous availability of forward and backward-propagated wavefields at each time step, leading to high computational costs despite existing optimizations like the expanding box method, which only reduces costs by up to 30%.
Innovation Solution
The implementation of a dual-expanding box method that limits the time range for calculating source and receiver wavefields, allowing for efficient seismic wave propagation by calculating wavefields only within a specific time range where they are non-zero, thereby reducing computational costs further.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If forward and backward propagated wavefields are calculated simultaneously at every subsurface point for every time step, then complete wavefield data is obtained for accurate seismic imaging, but computational cost and memory requirements become prohibitively high
Solution Approach 1:
The computational domain is segmented into an expanding box region where wavefields are calculated and an outer region where wavefields are assumed zero. This segmentation allows the method to focus computational resources only on the relevant subsurface volume, reducing computational cost while maintaining image quality in the region of interest.
Solution Approach 2:
The method pre-calculates and stores forward propagated wavefields at selected time steps before backward propagation begins. This preliminary action allows the backward propagated wavefields to be correlated with pre-stored forward wavefields without requiring simultaneous calculation, significantly reducing memory requirements and computational cost.
2Power
If the expanding box method is used to limit wavefield calculations to regions where wavefields are non-zero, then computational cost is reduced by up to 30%, but the computational cost remains very high for large datasets
Solution Approach 1:
Forward propagated wavefields are calculated and stored at selected time steps before backward propagation begins. This preliminary calculation and storage approach allows subsequent correlation to use pre-computed data, avoiding the need to recalculate forward wavefields during backward propagation and significantly improving processing efficiency.
Solution Approach 2:
The method calculates forward wavefields at periodic intervals (selected time steps) rather than continuously at every time step. This periodic sampling approach reduces the total number of calculations required while maintaining sufficient data for accurate correlation during the imaging process.
Data Source
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AI summary
A computer-implemented method, system, and article of manufacture for generating images of a subsurface region are disclosed. The method includes obtaining seismic data and an earth model related to the subsurface region, forward propagating a source wavefield through the earth model for a limited time range dependent on a first travel time and a second travel time, backward propagating a receiver wavefield through the earth model for the limited time range dependent on the first travel time and the second travel time, and applying an imaging condition to the forward propagated source wavefield and backward propagated receiver wavefield to generate images related to the subsurface region.