Print this pageGeochemical Characteristics of Paleozoic Petroleum Systems of the Bonaparte Basin, Australia
SUMMONS, ROGER E., DIANNE EDWARDS, MARITA BRADSHAW and JOHN KENNARD
The integration of biostratigraphy, carbon isotopic analyses and biomarker studies have proven instrumental in defining the Palaeozoic petroleum systems of the Bonaparte Basin. Three Palaeozoic systems have been defined for this basin: Late Devonian Ningbing-Bonaparte (Larapintine 3), Early Carboniferous Milligans (Larapintine 4) and Permian Keyling- Hyland Bay (Gondwanan). The Ningbing-Bonaparte oils occur in mineral and onshore petroleum wells and are characterized by light carbon isotopic signatures (mean delta{13}Csat = -29 o/oo) and biomarker patterns indicating localized generation from marginal marine carbonates. Oils attributed to the Milligans Petroleum System occur at Waggon Creek and in wells immediately offshore, notably at Barnett and Turtle. Characteristic features of these oils include light carbon isotopic values (mean delta{13}Csat = -28 o/oo), pristane/phytane and C[27]/C[29] sterane ratios of around unity and other biomarkers correlating with those in anoxic marine mudstones of the Early Carboniferous Milligans Formation. Burial history modelling suggests that hydrocarbon generation commenced in the mid-Carboniferous (lower Milligans source) and continued throughout the Permian (mid-Milligans source). Gas flows at Fishburn, Penguin and Tern, and gas with minor condensate at Petrel are believed to have been sourced by Permian deltaic source rocks and constitute the Keyling-Hyland Bay Petroleum System. Evidence exists for this system having analogues in Gondwanan continental fragments of Irian Jaya.