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ABSTRACT: Evidence for a rift related heating event around the Alpha Arch, Barrow Sub-basin, Western Australia

Kaiko, Alexander R. , Curtin University of Technology, Perth, Australia

Examination of the match between calculated and measured vitrinite reflectance maturity profiles (from simple 1D burial history modelling) from one well on the Alpha Arc (Bowers-1, and one from the Exmouth Sub-Basin Region (Jurabi-1) indicates that the Triassic sediments intersected by these wells have experienced higher palaeo-temperatures. Higher palaeo-temperatures are indicated when the measured maturity data are significantly higher than the calculated maturity profile determined from present-day formation temperature data. The divergent nature of the calculated and measured maturity profiles indicates that these higher palaeo-temperatures are most likely to be due to increased thermal gradients. The elevated gradients are related to the Jurassic rift event noted in this region. Rifting heat flow was modelled using the rifting heat flow option in BasinMod® 1D with initiation occurring at approximately 205 Ma and final break-up at approximately 160 Ma. The b stretching factors, determined for Bowers 1 and Jurabi 1, were 2.3 and 1.4 respectively. For both the wells the application of a rifting heat flow model was found to provide a good match between the calculated and measured maturity profiles within the Triassic section. The application of the rifting heat flow model from Bowers 1 to nearby wells on the Alpha Arch, such as Chinook 1 and Griffin 1 has reduced the amount of missing section which can be modelled from approximately 2500 m to approximately 1000m which is more consistent with seismic data.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia