GEOCHEMICAL EVIDENCE OF MULTIPLE HYDROCARBON CHARGES AND LONG DISTANCE OIL MIGRATION IN THE VULCAN SUB-BASIN, TIMOR SEA

Abstract

Hydrocarbon accumulation and migration processes in the Vulcan Sub-basin, Timor Sea, were investigated using the Total Scanning Fluorescence (TSF) technique and phenol and carbazole abundances in both reservoired and inclusion oils. The TSF spectral signatures have delineated multiple groups of oils within the Vulcan Sub-basin, largely identifying with the different oil families previously identified by biomarkers and isotope data. An apparent correlation between diminishing carbazole concentration and increasing distance from the source kitchen was found in reservoired oils within the Vulcan Sub-basin, providing evidence for long distance oil migration of up to 80 km. In the southernmost part of the Vulcan Sub-basin a possible light hydrocarbon charge rich in benzene and other low-molecular-weight aromatic hydrocarbons is believed to be responsible for the observed anomalously high phenol concentrations in oils from the surrounding wells. A previously unknown, possibly a Cretaceous-or-younger, source kitchen may be present along the eastern margin of the Vulcan Sub-basin and was probably responsible for the palaeo oil accumulations in the Tancred and Osprey structures as revealed by the TSF spectral signatures and biomarkers from the fluid inclusion oils.