Borehole Sonic Anisotropy for Maximum Horizontal Stress Estimation
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Solution Overview
Problem
Current methods for estimating maximum horizontal stress in geological formations are associated with significant uncertainty, and there is no direct correlation or model available to interpret vertical and minimum horizontal stresses into maximum horizontal stress.
Innovation Solution
The method involves using borehole sonic anisotropy measurements to compute maximum stress σH by determining anisotropic shear moduli C44, C55, and C66, and employing a stress regime factor Q, which characterizes the in-situ stress state, allowing for accurate estimation of σH from sonic log data in three dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional correlations (pore-elastic strain correlation) or approximations (equating maximum horizontal stress to multiple of minimum horizontal stress) are used to estimate maximum horizontal stress, then the estimation can be performed, but the uncertainty is big
Solution Approach 1:
The patent replaces conventional mechanical correlation methods with acoustic wave propagation theory. By measuring sonic log data (acoustic wave velocities) and using elastic wave mechanics to relate wave properties to stress state, the method achieves direct physical measurement-based estimation rather than indirect statistical correlations, thereby reducing uncertainty and improving reliability
Solution Approach 2:
The patent changes the approach from using stress ratios or multiples to using absolute stress values derived from acoustic wave velocities. By transforming the problem into the acoustic parameter domain (measuring wave speeds and converting to stress values through elastic wave theory), the method obtains more reliable stress estimates that are not constrained by uncertain correlation relationships
2Measurement precision
If no direct correlation or model is available to interpret vertical and minimum horizontal stresses to maximum horizontal stress, then the estimation process becomes complex, but accuracy improves
Solution Approach 1:
The patent introduces acoustic wave propagation as an intermediary mechanism to connect measurable quantities (sonic log data) to the target parameter (maximum horizontal stress). The elastic wave theory serves as a bridge that directly relates acoustic measurements to stress state, providing a straightforward physical model rather than a complex multi-step interpretation process
Solution Approach 2:
The patent uses sonic log data (acoustic wave measurements) to simultaneously determine multiple stress parameters (vertical stress, minimum horizontal stress, and maximum horizontal stress) through a unified elastic wave theory framework. This multi-functional approach allows a single measurement type to provide comprehensive stress characterization without requiring separate specialized measurements for each stress component
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 more accurate and reliable estimation of maximum horizontal stress, reducing uncertainty and enabling better prediction of geo-mechanical issues in the petroleum industry.
Implementation Method 1
measuring the formation rock anisotropic wave velocities induced by in-situ stress anisotropy
Implementation Method 2
formation rock anisotropic wave velocities
Data Source
AI summary
Methods and systems for analyzing subterranean formations in-situ stress are disclosed. A method for extracting geological horizon on-demand from a 3D seismic data set, comprises receiving sonic log data; computing the anisotropic shear moduli C44, C55 and C66; determining in-situ stress type and selecting an in-situ stress expression corresponding to the in-situ stress type; computing stress regime factor Q of the formation interval; and computing and outputting the maximum stress σH by using the stress regime factor Q, Vertical stress σv and Minimum horizontal stress σh.