THE GIPPSLAND BASIN
Llanberis Energy has selected the Southern Margin of Australia’s most petroliferous basin, the Gippsland Basin, as the place most likely to contain significant quantities of undiscovered hydrocarbons.
- The 46,000 km² Gippsland Basin in south-eastern Victoria has been one of Australia’s major crude oil and natural gas provinces since the first discovery in 1965. Seventy percent of the basin lies offshore.
- The commercial oil and gas fields contained recoverable reserves of more than four billion barrels of oil and more than nine trillion cubic feet of sales gas. More than 86% of the current estimates of total original 2P oil reserves and 49% of the total original 2P sales gas in the developed fields have been produced to date.
- The Gippsland Basin oil fields still produce 39.6% of Australian oil and condensate. Liquid production peaked at about 500 kbd in 1985 and has gradually declined since then. Production recovered from a low of 205 kbd to a plateau of about 230 kbd but has been steadily declining in recent years.
- Oil and gas are mainly produced from structural and structural/stratigraphic traps within the Oligocene, Eocene, Palaeocene and Late Cretaceous marine, marginal marine and continental clastic sequences of the Latrobe Group. The petroleum is largely of terrestrial plant origin.
- The distribution and migration pathways of oil and gas can be explained by variations in maturation of several similar source rock intervals, the influence of fresh water bio-degradation and the variable quality of internal stratigraphic and fault seals.
- The crude oils are generally very light and paraffinic, generally ranging from 40° to 60° API, to biologically degraded 26° API in shallow nearshore fields. The condensates range from 48° to 63° API.
Present acreage holdings in the offshore Gippsland Basin reflect the location of the producing fields (orange), and surrounding exploration permits (yellow). The Llanberis Energy permit VIC/P71 is shown in purple in the south at the bottom of the image.
The tectonic elements map of the Gippsland Basin shows that most of the existing oil and gas fields are located in the centre of the basin (shaded blue) with some gas fields located on the Northern Terrace (shaded green). The major oil fields are located in the southeast of the central deep. To date, there are no discoveries on the Southern Margin of the Basin.
THE SOUTHERN MARGIN OF THE BASIN
Llanberis Energy has identified the Southern Margin of the Gippsland Basin as a place most likely to contain significant quantities of undiscovered hydrocarbons.
Almost every study of the hydrocarbon generation, expulsion and migration in the Gippsland Basin shows migration pathways radiating in all directions from the source kitchen located in the Central Deep. It is logical that hydrocarbons would have migrated to the south just as they have migrated to the north. In fact, this is the most probable scenario. The only difference between the southern and northern margins of the basin is that the southern margin is less structured and that exploration in the south has been severely curtailed by the disappointing results of some poorly located wells drilled there in the 1960s and 1970s.
Mapping by Llanberis Energy has identified a large number of structural and stratigraphic traps extending over the entire Southern Platform of the Gippsland Basin. The largest of these traps has potential to contain billions of barrels of oil or trillions of cubic feet of natural gas. Because of the subtle nature of some of these traps and the rugged basement topography, modern seismic data needs to be acquired to properly delineate and de-risk them.
Llanberis Energy has focused its immediate attention on the area of permit VIC/P71, which is seen as a focal point and first trapping opportunity for hydrocarbons migrating southwards out of the basin centre.