Maximum horizontal stress orientations in the Cooper Basin, Australia: implications for plate-scale tectonics and local stress sources

Abstract

SUMMARY Borehole breakouts and drilling‐induced tensile fractures (DITFs) were interpreted in 61 wells in the Cooper Basin indicating an average maximum horizontal stress orientation of 101°N. A total of 890 borehole breakouts and 608 DITFs were interpreted in the Cooper Basin. The approximately east–west maximum horizontal stress orientation is consistent over much of the basin, except in the Patchawarra Trough where maximum horizontal stress rotates to a northwest–southeast orientation. This rotation in maximum horizontal stress orientation is consistent with in situ stress data to the northwest of the Cooper Basin. The stress field in the Cooper Basin appears to mark the apex of a major horseshoe‐shaped rotation in maximum horizontal stress direction across central eastern Australia. Finite element modelling of the in situ stress field of the Indo–Australian Plate (IAP) using a range of plate‐scale tectonic forces is able to match the regional maximum horizontal stress orientation over most of Australia reasonably well, including the mean east–west maximum horizontal stress orientation in the Cooper Basin. However, plate boundary–scale modelling does not adequately match the horseshoe‐shaped stress rotation across central eastern Australia. The average east–west maximum horizontal stress orientation in the Cooper Basin indicates that stresses from tensional forces acting along the Tonga–Kermadec subduction zone are not transmitted into the interior of the Australian plate. The majority of the tensional forces associated with the Tonga–Kermadec subduction zone are most likely accommodated along the numerous spreading centres within the Lau–Havre backarc basin. A number of more localized stress anomalies have also been identified. These cannot be explained by plate‐scale tectonic forces and are possibly a result of geological structure and/or density contrasts locally perturbing the stress field.

The relationship between closure pressures from fluid injection tests and the minimum principal stress in strong rocks

“…The orientation of the maximum horizontal stress in the Cooper Basin can be determined using breakouts and drilling-induced tensile fractures (DITFs) observed on image logs and/or caliper logs [15]. The orientation of S Hmax is predominantly east-west (0901N) throughout the Cooper Basin although there appears to be some local stress rotation adjacent to faults (Fig.…”

“…Several studies have been undertaken to determine the in situ stress tensor in the Cooper Basin [13][14][15]. Here we summarise previous relevant studies to constrain the magnitudes of the minimum horizontal stress, vertical stress and the orientation and magnitude of the maximum horizontal stress in the Cooper Basin.…”

Uncovering Seismic HTI Anisotropy of the Cooper Basin

“…Cooper Basin in situ stress is strike-slip at shallow depth and transitions into reverse fault regime at depth (about 3km) while the principal maximum horizontal stress (S H ) direction is consistent at approximately N100°E (King, et al 2011, Reynolds, et al 2005). In our study area, the target Permian tight gas sand is at a depth of about 2.2 -2.4km depth.…”

Magnetotelluric monitoring of hydraulic fracture stimulation at the Habanero Enhanced Geothermal System, Cooper Basin, South Australia

“…The Cooper and Eromanga sedimentary basins (~3.6 km thick) act as an insulating cap over the granitic EGS reservoir (Holl and Barton 2015). The project area is characterized by a compressive stress field oriented approximately in E-W direction (Reynolds, et al 2006, Reynolds, et al 2005. In November 2012, the Habanero-4 well was stimulated by injecting 36.5 ML of near-surface aquifer-sourced water (13 Ωm at 25°C) over 14 days (Hogarth, et al 2013, Holl and Barton 2015, McMahon and Baisch 2013.…”