Publication Name: PESA's Eastern Australasian Basin Symposium II
Authors: J.J. Draper, C.J. Boreham, K.L. Hoffmann and J.L. McKellar
Date Published: December 2004
Number of Pages: 39
Reference Type: Book Section
Abstract:
Devonian, marine, sedimentary rocks are common throughout Queensland, but petroleum potential is restricted to the Adavale Basin system (grouping of the Adavale Basin, Warrabin Trough and Barrolka Trough), the Belyando Basin (newly named) and the Burdekin Basin. All three basins are structural remnants of larger basins and contain both carbonate and siliciclastic rocks. The structural history of the Adavale Basin system is complex involving initial rifting, widespread downwarping and subsequent thrusting and uplift. The sole discovery, the Gilmore gasfield, had reserves of 115 BCF of gas. Oil recovered from PPC Gilmore-2 has been geochemically and isotopically correlated with other Australian Devonian-sourced oils. Its geochemistry indicates that the source rock was deposited under mildly evaporitic, restricted marine conditions. The Gilmore gas is a mixture of late stage wet gas and gas from deep over-mature source rocks. This under-explored basin system is considered to contain all the elements of a petroleum system. The rift-sag Belyando Basin, underlying the western Drummond Basin, is postulated on geological and geophysical grounds to contain marine Devonian rocks. Oil in ENL Lake Galilee-!, from the younger Galilee Basin, has a prominent marine Devonian geochemical signature. Isolated remnants of marine Devonian rocks on the adjacent Anakie Inlier provide evidence for the types of rocks that may be present in the Belyando Basin. The Burdekin Basin formed by back-arc extension with subsequent sag. Mid Carboniferous folding resulted in reactivation of existing faults and large, tight folds. Minor traces of oil have been observed, potential source rocks are present and suitable reservoir rocks exist. Conodont colour alteration indices indicate that some parts of the basin are still within the oil and gas window. Both the Belyando and Burdekin Basins contain speculative petroleum systems.