Seismic Modeling Elastic Grid Shear Wave Attenuation
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Solution Overview
Problem
Seismic modeling using elastic models is computationally intensive due to the need for smaller grid spacings and time steps to avoid numerical dispersion and stability issues, making it challenging to achieve efficient generation of synthetic seismic data, especially in 3D simulations, where it can be 10 to 1000 times more intensive than acoustic modeling.
Innovation Solution
The method involves using an elastic model with a grid spacing larger than conventional limits to introduce numerical dispersion in shear wave data, which is then attenuated, allowing for more accurate and computationally efficient generation of synthetic compression wave data, thereby reducing the computational requirements while maintaining accuracy in reflection coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If elastic modeling is used to improve accuracy of reflectivity and reflection coefficients, then modeling accuracy is improved, but computational intensity increases significantly
Solution Approach 1:
The patent segments the wavefield into compressional wave components and shear wave components. By separating these components, the method can selectively attenuate only the shear wave portions that cause numerical dispersion while preserving the compressional wave data that is essential for accurate reflection modeling. This segmentation allows the use of larger grid spacings without compromising the accuracy of the primary modeling objectives.
Solution Approach 2:
The patent extracts and removes the harmful shear wave components from the elastic model output. By taking out the shear wave data that causes computational problems and numerical dispersion, the method retains only the beneficial compressional wave information needed for accurate reflectivity and reflection coefficient modeling, thereby improving computational efficiency without sacrificing accuracy.
2Productivity
If larger grid spacing is used to reduce computational intensity, then computational efficiency is improved, but numerical dispersion errors increase in shear wave data
Solution Approach 1:
The patent converts the harmful effect of numerical dispersion in shear waves into a beneficial process. By intentionally allowing numerical dispersion to occur in the shear wave components when using larger grid spacings, and then selectively attenuating only those dispersed shear wave portions, the method actually benefits from the larger grid spacing while maintaining overall accuracy. The numerical dispersion that would normally be harmful is confined to the attenuated shear wave component.
Solution Approach 2:
The patent applies partial action by selectively attenuating only the shear wave components rather than the entire wavefield. This partial treatment allows the compressional wave data to retain full accuracy while the shear wave data receives the necessary attenuation to remove numerical dispersion effects. The excessive attenuation of shear waves is acceptable since they are not the primary target for accurate reflection modeling.
3Reliability
If elastic properties are included to model both shear waves and compression waves, then physics accuracy is improved, but the number of field variables and model parameters increases
Solution Approach 1:
The patent extracts only the necessary elastic effects related to compressional waves while removing the complexity associated with full shear wave modeling. By taking out the shear wave components that increase model complexity and computational burden, the method retains the essential elastic properties needed for accurate reflection modeling without the full complexity of complete elastic wave propagation.
Solution Approach 2:
The patent applies local quality by treating different wave components differently. The compressional wave portions are modeled with full elastic accuracy where it matters most for reflection coefficients, while the shear wave portions are attenuated where they cause problems. This localized differential treatment optimizes the balance between physics accuracy and model complexity.
Data Source
AI summary
A method of seismic modeling using an elastic model, the elastic model including a grid having a grid spacing sized such that, when synthetic seismic data is generated using the elastic model, synthetic shear wave data exhibits numerical dispersion, the method including: generating generated synthetic seismic data using the elastic model, wherein the generated synthetic seismic data includes synthetic compression wave data and synthetic shear wave data, and modifying the generated synthetic seismic data to produce modified synthetic seismic data by attenuating at least some of the synthetic shear wave data in order to attenuate at least some of the numerically dispersive data.