Fundamental Discrimination Between Fluids Originating From Source Rocks of Jurassic Age versus Triassic Age in the Dampier Sub-Basin

Abstract

The North West Shelf of Australia is a world class petroleum system but multiple uncertainties remain about the origin of the fluids, which has been assigned on limited fluid-source correlation data. The fluids in the basins are very light and arise from mixed marine/terrigenous sources. The very low concentration of key organic compounds and alteration processes (e.g. biodegradation, evaporative fractionation, and water washing) create challenges for fluid-source correlation and limit the differentiation available using traditional biomarker and isotope methods. An example is the Dampier sub-Basin petroleum system, where the source rock for some of the fluids in the Rankin Platform remains uncertain. Therefore, a fundamental discrimination is required to improve our understanding of fluid families and properties, both within the known reservoirs and those yet to be identified, enabling explorationists to evaluate new plays in the region. To generate new insights in this respect, this research addresses two problems: discrimination between Triassic and Jurassic origin fluids and, within the latter, between Upper Jurassic vs Middle Jurassic contributions to the Rankin Platform accumulations. State of the art techniques such as comprehensive two dimensional gas chromatography coupled to time-of-flight mass spectrometry (GCxGC-TOFMS) and compound specific isotope analysis (CSIA) are proposed as the main tools (amongst others) in generating new data which may provide more effective discrimination of fluid origins.

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