In-situ stresses in the Southern Perth Basin at the GSWA Harvey-1 well site

Abstract

Knowledge of orientations and magnitudes of present-day stresses is important for different applications including fault reactivation, borehole stability and CO2 injection studies. As part of the West Hub Carbon Capture and Storage project, the GSWA Harvey-1 well was drilled in early 2012. It is located ~115 km south of Perth and is used to assess the suitability for CO2 underground storage. The aim of this study is to estimate the mechanical properties and state of stress fields in the Southern Perth Basin. The analysis is based on the newly acquired log and VSP data and results of a rock mechanical model including vertical profiles of elastic and strength properties as well as identified breakout zones. The results indicate that the stress regime in the region is dominantly strike-slip. It changes to a reverse faulting system at shallow depths of below ~900 m. Stress field orientation is obtained from borehole breakout analysis. The average azimuth of the maximum horizontal stress is 106 degrees and the standard deviation is 10 degrees. This direction of the maximum horizontal stress is broadly consistent with the east–west direction earlier reported for the Perth Basin.