Geohistory, Thermal Maturation And Migration In The Barrow Sub-Basin, Western Australia, With Emphasis On Gazettal Blocks W96-17 And W96-18.
Honours Degree, 1996
University of Adelaide
Geohistory and thermal modelling was undertaken within and surrounding permits W96-17 and W96-18 in the Barrow Sub-basin, North West Shelf, Western Australia. Sixteen wells were analysed using the 1-D basin modelling software package BasinMod version 5.0. Four of these 16 wells are "synthetic", representing sites in the deep basinal areas that were chosen to give information about the deep "kitchen" areas.
A particular level within the Jurassic Dingo Claystone, the W. spectabilis dinoflagellate zone, was used throughout this study as the main source interval. Geochemical evidence suggests that 16 of the 25 crude oils and condensates in this area were sourced from sediments from the W. spectabilis age range. The maturity of this source rock horizon was plotted with respect to the present day oil window and that estimated at 55 Ma. This allowed the migration direction of the oil window to be determined.
From the study it is apparent that the present day oil window lies beneath Barrow Island and at 55 Ma it lay further to the west. The oil window, with respect to the W. spectabilis age range, has migrated up the continental shelf in an easterly direction, away from the areas of interest within the permits. It is possible that the oil window once lay along the eastern side of the Alpha-Arch, but any oil in the permit areas would have a high risk of gas displacement and at worst, gas displacement including carbon dioxide and inert gas.