1School of Earth and Environmental Sciences, University of Queensland, QLD, 4072, Australia
Present-day stresses are of extreme importance for understanding both natural processes (e.g. neotectonics deformation, earthquake cycle and seismic hazard assessment) and anthropogenic activities of underground usage (e.g. petroleum exploration and production, geothermal energy extraction, CO2 sequestration, and mine stability).
This paper presents the updated version of the Australian Stress Map that includes over 2,500 in-situ stress data records in >20 sedimentary basins across Australia. Analysis of stress provinces throughout the continent reveals four major trends for the orientation of maximum horizontal stress, including NE-SW in northern, northeastern Australia as well as Bonaparte and Canning basins in northwestern Australia, E-W in most part of Western Australia and South Australia, ENE-WSW in most parts of eastern Australia and NW-SE in southeastern Australia. In addition, high density datasets in several sedimentary basins of eastern Australia reveal substantial stress perturbations at both basin (10-200 km) and field (0.1-10 km) scales owing to the influence of various geological structures, including basement structures, faults, fractures and lithological contrasts.
Large scale geomechanical-numerical models for the Australian continent reveals that all the stress sources, acting from the tectonic plate to the wellbore scales, are inter-related to each other, so that the in-situ stress at any given point is the resultant of all these different stress sources. However, it should be noted that large scale stress analyses do not necessarily represent the in-situ stress pattern at smaller scales. Similarly, the analyses of just a couple of borehole measurements in one area might not be a good representation of the regional stress pattern.
Dr Mojtaba Rajabi has over 12 years of experience in crustal stress analysis, reservoir geomechanics, geomechanical-numerical modelling and petrophysics. Since 2012, Dr Rajabi has worked on the Australian and World Stress Map projects, and currently is the Deputy-Head of the World Stress Map project.