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The AAPG/Datapages Combined Publications Database

Indonesian Petroleum Association


Proceedings of an International Conference on Petroleum Systems of SE Asia and Australasia, 1997
Pages 175-190

Palaeozoic Source Rock Facies and Maturation History of the Southern Merlinleigh Sub-Basin, Carnarvon Basin, Western Australia

K. A. R. Ghori


The widespread, organic-rich shales of the Artinskian Wooramel Group are the best source rocks of the southern Merlinleigh Sub-basin. They have very good to fair, predominantly gas-generating potential in the northern part of the sub-basin, and this source potential gradually decreases southwards. The next best source rocks within the Lower Permian are organic-rich shales of the Artinskian Byro Group. This gaseous source facies equates with regional and global gas source deposited during the marine regressions.

The Upper Devonian Gneudna Formation contains the best quality oil source beds with good to fair generating potential and equates with regional and global source facies deposited during a marine transgression. Source potential within the Gneudna Formation varies considerably both vertically and laterally.

The thermal maturity of Lower Permian and Upper Devonian source rocks in the sub-basin range from immature to overmature, depending on the maximum and present-day depths of burial and heat flows. The Wooramel Group is marginally mature in the northwest of the area, mature to overmature in the centre and immature in the south. The Wooramel Group has abnormally high thermal maturity in Kennedy Range 1, at the centre of the area, probably due to the presence of unpenetrated intrusives. The Gneudna Formation is immature along the outcrop belt on the eastern margin of the sub-basin, but overmature in Quail 1 on the deeply buried western margin.

Maximum burial, maturation, and petroleum generation occurred during the Permian. Petroleum charge peaked during the Early Permian from the Upper Devonian source, and during the Permo-Triassic from the Lower Permian source. Thus, the most favourable traps should be those that developed during the regional Permo-Carboniferous structuring of the sub-basin.

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