HYDRODYNAMICS AND HYDROCARBON MIGRATION — A MODEL FOR THE EROMANGA BASIN

Recent oil discoveries in the Eromanga Basin in sediments ranging in age from Early Jurassic to Early Cretaceous provide strong evidence for an oil source within the basin. A recent study of the thermal history of Eromanga Basin sediments within the licence areas of Delhi Petroleum Pty Ltd and Santos Limited indicates that generation and primary migration of oil within the basin occurred within a period ranging approximately from late Cretaceous to Early Tertiary and that these events pre-dated the artesian system, which developed in Plio-Pleistocene times. Generation is believed to have occurred within deeper basin depocentres; migration toward the shallower marginal areas followed. The present artesian system is unlikely to have flushed oil out of existing traps. However, there is evidence that the artesian flow was stronger previously, and may have influenced secondary migration of oil. A mound spring has furnished evidence of possible migration to the western margin of the basin.