The Future for Exploration in the Gippsland Basin

Abstract

The Gippsland Basin is, by Australian standards, mature from a petroleum exploration point of view but retains significant potential for success. The main recognised plays of Top Latrobe porosity, deeper fault blocks and stratigraphic truncations are in various stages of exploitation, with the latter two showing the greater undiscovered potential. Parameters for hydrocarbon accumulations, such as source, seal, structural style and trap timing, are now reasonably well documented and future success in established and untested plays will rely heavily on detailed velocity analysis, deep- penetration high- frequency seismic data and an integrated regional approach to stratigraphic controls.

The Geology of Fluvial Deposits

“…Paleovalleys are, of course, common in other structural settings, but most do not appear to be associated with significant petroleum trapped in fluvial reservoirs. Similarly, the Latrobe Group in the Gippsland Basin contains incised valley fills that are largely mud dominated, but some isolated channel-sand deposits are present which may have future potential as exploration targets, given improvements in seismic methods (Mebberson 1989;Rahmanian et al 1990). .…”

Petroleum system of the Gippsland Basin, Australia

“…Structures in the northwest were not available for early oil migration so these structures have trapped mostly mature gas (Keall and Smith, 1996). Source 20 rocks in the southwestern portions of the basin are still in the oil window (Mebberson, 1989;Rahmanian and others, 1990;Keall and Smith, 1996).…”

“…Better reservoirs and good exploration targets may be defined with an exploration program aimed specifically at rift-basin style stratigraphy and traps. The source-rock potential of the coals and lacustrine shales in the group is poorly known (Mehin and Bock, 1998), although the subsurface edges of the depositional extent of the group appear to be in the oil window along the northern and southern terraces (Ozimic and others, 1987), and methane occurrences at the margins of the basin may have been sourced by the Strzelecki Group (Mebberson, 1989 between the northern and southern terraces, has buried the Strzelecki Group offshore to depths of more than 8 km (Ozimic and others, 1987) and currently into the overmature range.…”

“…5) (the large Cobia-Halibut, Fortescue, Kingfish, Mackerel and Blackback Fields). This distribution is considered to be a result of local subsidence combined with general heatflow producing areas where the source rock is overmature and generating gas, and other areas where it is mature and generating oil (Mebberson, 1989;Rahmanian and others, 1990;Moore and others, 1992). This distribution is further influenced by local versus areal hydrocarbon drainage areas and migration paths (Moore and others, 1992).…”

“…These differences are attributed to oil being generated at different maturities, low reservoir temperatures, and the presence of a fresh-water wedge that extends from the present shoreline east and south into the basin and to depths of as much as 2,400 m (Fig. 5) (Mebberson, 1989;others, 1992: Burns andothers, 1987). Oils in traps at Top Latrobe are not chemically distinct from oils in traps within the Latrobe Group (Clark and Thomas, 1988).…”