Azimuthal Gradient Estimation via Windowed Statistical Correlation
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Solution Overview
Problem
Conventional methods for estimating azimuthal amplitude gradient in seismic data are limited by noise, data misalignments, and ambiguity between gradient polarity and symmetry azimuth, making it difficult to accurately determine the orientation and magnitude of reservoir fractures and geologic stress fields.
Innovation Solution
A method that computes the azimuthally-varying component of seismic amplitudes using a windowed statistical approach, involving linear regression and joint correlations of seismic traces within a sliding volume, to stabilize estimates and resolve ambiguity, allowing for more accurate detection of subsurface heterogeneities like fractures and geologic stress fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If point-wise estimation method is used for azimuthal amplitude gradient, then computational simplicity is maintained, but measurement precision and reliability deteriorate due to noise and data misalignments
Solution Approach 1:
The patent combines multiple seismic traces within a time window to perform joint correlation analysis, merging information from different azimuths and offsets to estimate azimuthal amplitude gradient. This integration of multiple data sources improves measurement precision by averaging out noise and reducing the impact of individual trace misalignments.
Solution Approach 2:
The patent transitions from point-wise (1D) estimation to a volumetric approach by incorporating time windows and multiple offsets, effectively adding temporal and spatial dimensions to the analysis. This dimensional expansion allows for more robust gradient estimation through joint correlation of Bcos and Bsin traces across a volume of seismic data.
2Productivity
If point-wise estimation is used, then processing speed is maintained, but reliability deteriorates due to ambiguity between gradient polarity and symmetry azimuth
Solution Approach 1:
The patent merges Bcos and Bsin trace correlations within a time window to simultaneously determine both gradient magnitude and symmetry azimuth. By combining these correlated traces and analyzing their joint statistics, the method resolves the polarity ambiguity that plagues point-wise estimation, improving reliability while maintaining computational efficiency through vector-based analysis.
Solution Approach 2:
The patent introduces joint correlation of Bcos and Bsin traces as an intermediary step between raw seismic data and final symmetry azimuth determination. This intermediary correlation analysis provides additional constraints that resolve the ambiguity between gradient polarity and symmetry azimuth, acting as a mediator that transforms ambiguous point-wise estimates into reliable directional information.
3Quantity of substance
If conventional point-wise method is used, then data requirements are minimal, but measurement precision worsens due to noise and misalignments at different azimuths
Solution Approach 1:
The patent merges seismic traces from multiple offsets and azimuths within a defined time window, combining their correlations to estimate azimuthal amplitude gradient. This merging of multiple data sources improves precision by utilizing the redundancy and complementary information contained in traces from different geometries, while the time-windowing approach selectively integrates only the relevant coherent signals.
Data Source
AI summary
Method of estimating azimuthal amplitude gradient is disclosed. This method uses a correlation of seismic attributes within a sliding volume of data to obtain azimuthal gradient.