Petroleum Systems Modelling of the Perth Basin, Western Australia

Abstract

Petroleum geochemistry of over 4000 rock and oil samples identified source beds within the: a) Permian Irwin Coal Measures and Carynginia Formation, which are predominantly gas prone, and sourced petroleum to the Whicher Range gasfield, southern Perth Basin; b) Triassic Kockatea shale, which are oil prone, and sourced petroleum to the Dongara, Erregulla, Mount Horner, and Yardarino oilfields, northern Perth Basin and; c) Jurassic Cattamarra Coal Measures, which are gas and oil prone, and sourced petroleum to Walyering gasfield, central Perth Basin. Organic petrology and Apatite Fission Track Analysis (AFTA) of 15 samples from Arranoo South 1, Cataby 1, and West Erregulla 1 identified two regional paleothermal events, the first during the Cretaceous (135–56 Ma) and the second in the Tertiary (30–0 Ma). These events differ locally. Petroleum system modelling of over 60 wells with source rock data indicates major subsidence and burial occurred during the Permian–Jurassic. Source rock maturities and time of petroleum generation were influenced by the Cretaceous and Tertiary paleothermal events. These models were used to calibrate measured data in order to predict the regional distribution of Rock-Eval and other parameters: potential yield S2, hydrogen index, production index, transformation ratio, temperature, and %Ro for the Permian, Triassic, and Jurassic source rocks. The Triassic Kockatea Shale contains the best source units of the northern Perth Basin; their maximum organic richness is 11% TOC, potential yield is 81 S2 mg/g, and hydrogen index is 800 mg HC/g TOC. In the central Perth Basin, the Jurassic Cattamarra Coal Measures contain the main source beds; their maximum organic richness is 50% TOC, potential yield is 76 S2 mg/g, and hydrogen index is 760 mg HC/g TOC. The Permian Irwin River Coal Measures and Carynginia Formation contain the most important source rocks of the southern Perth Basin; their maximum organic richness is 47% TOC and 31% TOC, potential yield is 20 S2 mg/g and 15 S2 mg/g, and hydrogen index is 150 mg HC/g TOC and 200 mg HC/g TOC, respectively. The timing of petroleum generation–expulsion–accumulation was spread over the Cretaceous–Tertiary interval within the northern Perth Basin, varying from Early Cretaceous in the Erregulla area to Late Cretaceous-Tertiary in the Jingemia area.

AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017