Borehole deformation based in situ stress estimation using televiewer data

Abstract

The knowledge of in situ stress is critical in safe and optimised extraction of minerals and energy resources. In situ stresses are either measured directly (e.g. overcoring) or estimated indirectly (e.g. borehole breakouts). Borehole breakout analysis for in situ stress estimation is considered as a relatively simple and cost-efficient technique. This technique, however, poses certain limitations such as progressive formation of breakouts and requires inputs such as rock failure parameters that are not often available. As a result, significant effort has been made to develop new indirect methods for in situ stress estimation. Borehole deformation analysis using four-arm caliper has been recently proposed for in situ stress estimation and has shown promising results. In this study, we demonstrate a new methodology that analyses the borehole televiewer data with the technique of borehole deformation analysis to estimate the in situ stresses through a field case study. The advantages and challenges of using borehole televiewer data for stress estimation based on borehole deformation analysis are discussed and the best practice to obtain the reliable results is explained. The limitations of using four-arm caliper and borehole deformation analysis for in situ stress estimation are also discussed and it is shown how televiewer data can overcome such limitations. Finally, the in situ stress results obtained from televiewer data and borehole deformation analysis are compared with independent in situ stress measurements to show the robustness and reliability of the proposed methodology.