Models for Fault Development and Linkage in Extensional Systems and Their Relationship With Sediment Migration and Supply Into Potential Hydrocarbon Reservoirs

Abstract

As a result of extensive hydrocarbon exploration on the NW Shelf, Australia, the acquisition of high quality 3D seismic data has enriched opportunities for research into the structural modelling of extensional systems. Detailed structural analysis of this 3D seismic data, scaled analogue modelling of 3D extensional systems including digital image correlation analyses, and observations made from satellite data of other extensional systems such as those found in East Africa and the Gulf of Suez, Egypt, has allowed comprehensive investigation of the mechanisms for extensional fault system development and their control on sediment supply into potential hydrocarbon reservoirs. Detailed analyses of seismic data utilising modern techniques, in particular volume-based attribute analysis, and of satellite data has been carried out using industry standard software (Landmark, Petrel, TrapTester, and ArcGIS). Multiple phases of extension, including the reactivation of Late Triassic faults, have occurred in the Northern Carnarvon Basin, NW Shelf of Australia. High quality 3D seismic data has permitted mapping of these fault systems in detail. Three general fault arrays have been mapped as well as their linkages and interactions. Detailed fault analysis has provided important insights into the fault development and linkages, which are similar to the architectures formed in scaled analogue models of rift systems. As indicated by Present-Day drainage analyses of digital elevation models from Egypt and East Africa, there is clear evidence that early footwall uplift and development of relay ramps during fault growth and linkage play an important part in the evolution of sediment pathways. Where the rate of footwall uplift exceeds the rate of incision of a sediment pathway the drainage will be diverted around a footwall. Relay ramp structures are able to provide an alternate pathway allowing sediment to be transported across areas affected by footwall uplift. Consequently, it follows that understanding the mechanisms by which fault systems develop is key to understanding the evolution of sediment input points into rift basins and the distribution of clastic reservoirs within the rift. Critical evaluation of the timings and mechanisms of fault system evolution are essential in order to determine whether viable reservoirs may have been deposited in syn-extension basins.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015