Horizon-based splitting intensity inversion for anisotropic characterization
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Solution Overview
Problem
In azimuthally-anisotropic media, shear wave splitting (SWS) complicates seismic data processing by degrading amplitude and resolution, and existing methods for analyzing SWS are prone to errors when dealing with multiple layers, especially in shallow formations where anisotropic parameters are difficult to estimate.
Innovation Solution
A method for seismic processing that inverts interval values of splitting intensity (SI) to estimate anisotropic parameters varying with time or depth, allowing for layer stripping to be avoided and enabling more accurate analysis of SWS without relying on layer-by-layer estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If layer stripping procedure is used to analyze SWS in multiple layers, then anisotropic parameters can be estimated layer by layer, but errors accumulate to unmanageable levels when the number of layers increases
Solution Approach 1:
The patent inverts the traditional layer stripping approach by using surface measurements of SWS to directly infer subsurface anisotropic properties through inversion algorithms, avoiding sequential layer-by-layer estimation and its associated error accumulation
Solution Approach 2:
The patent introduces splitting intensity as an intermediary parameter that linearly relates to anisotropic perturbations at depth, allowing direct inference of subsurface properties from surface measurements without sequential layer stripping
2Productivity
If traditional SWS analysis methods are used in shallow layers, then processing can be performed, but anisotropic parameters are difficult to estimate with sufficient accuracy
Solution Approach 1:
The patent changes the measurement parameter from traditional SWS parameters to splitting intensity, which provides a linear relationship with anisotropic perturbations and enables accurate estimation even in shallow layers where traditional methods fail
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 robust measurement of anisotropic properties within geological formations, improving the accuracy of seismic data processing and facilitating the application of SWS analysis, especially in shallow layers where anisotropic parameters are challenging to estimate.
Implementation Method 1
In azimuthally-anisotropic media, the propagation velocity of shear waves varies with azimuth. This is a result of unequal sub-horizontal stresses or sub-vertical fractures. In these cases, shear waves naturally polarize into a fast wave parallel to the fractures and a slow wave perpendicular to the fractures. This is a phenomenon known as shear wave splitting ('SWS').
Data Source
Figure 1A~1D
Figure 2
Figure 3A
AI summary
A method for seismic processing includes receiving seismic data representing a subsurface volume. The seismic data includes a first horizontal component and a second horizontal component. The first and second horizontal components are rotated such that the first horizontal component is substantially aligned with a source of a seismic wavefield and the second horizontal component is substantially transverse to the source of the seismic wavefield. A splitting intensity is determined at a boundary of the subsurface volume using the first and second horizontal components after the first and second horizontal components are rotated. An anisotropic parameter is determined for a portion of the subsurface volume as a function of time using the splitting intensity.