Insights into the tectonic stress history and regional 4-D natural fracture distribution in the Australian Cooper Basin using Etchecopar's calcite twin stress inversion technique, 2-D/3-D seismic interpretation and natural fracture data from image logs and core

Abstract

A robust understanding of natural fractures can provide valuable information on subsurface fluid flow through optimally oriented fractures relative to the present day stress regime, and can be used as a tool to infer the stress orientation and regime of structural events that have affected a given area. The first part of the research utilises the fundamental principles of rock failure, combined with structural and stratigraphic seismic interpretation of two- and three-dimensional (2D and 3D) seismic data as well as pore pressure data, to investigate the potential relationship between fluid pressure and fracture/ fault distribution and density in Copper Basin. Secondly, and for the first time in Australia, the application of a new approach using the Etchecopar’s calcite twin stress inversion technique (CSIT), along with rock mechanics and fault/fracture data, we will attempt to provide the complete stress tensors of individual structural events that affected the study area. These results will enhance the understanding of the complex structural history of the Cooper Basin, the largest onshore oil and gas province in Australia. Highly desirable information will be presented on the relationship between the timing of natural fracture development, complete natural fracture geometry, and structural event responsible for the development of the different fracture sets. In addition, the complete field scale fault geometry, timing of fault cessation, and geomechanical modelling of fault reactivation potential will be explored. This new approach that we apply to obtain a much more thorough understanding of the tectonic history of the region can also be beneficial in other complex basins around the world that have been affected by poly-phase structural events.