4D fracture distribution in the Cooper Basin

Abstract

The Cooper basin is located in central Australia and is made from non-marine sedimentary rocks which were formed in the Late Carboniferous to Middle Triassic period. The basin was formed due to thermal subsidence, and it can be attributed to prior granite emplacement and uplift due to high heat flow. 4D Fracture Distribution is used to identify the effect of stress orientations caused by different tectonic events in the study area by interpreting fractures and faults from image log data. This study focuses on the section of Cooper Basin in South Australia where an intra-cratonic basin is located and, specifically, where it is entirely overlain by the Eromanga Basin and partially underlain by the Warburton Basin. Stress influences tectonic orogeny in this study area from the Warburton Basin stratigraphy (Pando formation) to the Eromanga Basin (Bulldog Shale) section. The image log data provides information on fractures and faults which indicate that fractures and faults were created by different stress mechanisms through time. Firstly, these fractures are interpreted by stereonet and separated to different sets according to the different formations and stress regimes created. Secondly, these fracture and fault interpretations are related to tectonic events in the Cooper Basin. The tectonic events stress influences are shown in wells location map after data cooperation. In conclusion, tectonic events can be seen which include (listed in older of age) Ross-Delamerian Orogeny, Alice Springs Orogeny, Kanimblan Orogeny, Sakmarian uplift, Hunter-Bowen Orogeny, Late Eocene Oilgocene, Mid Miocene Orogeny and an unknown stress which indicate stress directions and time in the area studied. In some events, stress directions are not unitive because well location may lie near fault belts which could obstruct stress conduction.