THERMAL HISTORY MODELLING AND TRANSIENT HEAT PULSES: NEW INSIGHTS INTO HYDROCARBON EXPULSION AND 'HOT FLUSHES' IN THE VULCAN SUB-BASIN, TIMOR SEA

Abstract

Thermal history data from wells in the Vulcan Sub- basin and adjacent platforms show clear evidence that many reservoir sections have experienced relatively shortlived, high- temperature flushes during the Late Tertiary. These transient heat pulses are related to slow migration of hot fluids and hydrocarbons from adjacent depocentres, or rapid flow of deep-seated brines during Late Miocene- Early Pliocene tectonic reactivation. The hot fluids have been focussed into structured reservoir sections via high- permeability pathways and reactivated faults. As a consequence, most exploration wells are not truly representative of the thermal regime of nearby source kitchens.

In order to constrain the regional thermal and expulsion history of the region, and to address the issue of thermal pulses, burial history analysis of 44 wells and 18 depocentre sites was carried out. This analysis utilises a simplified transient heat pulse model developed as part of the WinBury™ burial and thermal geohistory modelling software. The transient and steady-state thermal history models are constrained by reflectance and fluorescence maturity data, together with apatite fission track analysis and fluid inclusion palaeo-temperature data.