The Golden Beach-Latrobe Petroleum System, Gippsland Basin, Australia
The Golden Beach-Latrobe petroleum system in the Gippsland Basin, Australia covers a relatively small area of 15,000 sq km2. It is the source of approximately 4.2 billion barrels of oil and 9.1 tcf of gas reserves. The main source rocks are nonmarine shales and coals of Late Cretaceous age, which were deposited during the rifting and passive margin phases of basin development. Reservoir rocks range in age from Late Cretaceous to Eocene but about 80% of hydrocarbon reserves occur in good quality quartzose sandstones of Eocene age which were deposited in an upper shoreface environment. Regionally extensive marine shales and marls provide excellent seals.
Most of the hydrocarbons are reservoired in structural or combined structural-stratigraphic traps which formed during a compressional phase in the Late Eocene to Mid Miocene. Geochemical modelling results indicate that hydrocarbons were first generated and expelled from the deepest parts of the basin during the Paleocene but the main phase of generation has been in the last 20 Ma. In the northwest of the basin, structuring occurred too late to capture much of the early-generated oil which passed through the system prior to trap formation and the fields in this area contain mainly gas. In the southeast, however, the main source rocks still lie within the oil window and the fields contain mostly oil.
AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California