THE PHYSICAL PROPERTIES OF GIPPSLAND BASIN HYDROCARBONS

Abstract

Since the beginning of offshore drilling in the Gippsland basin, during 1964, hydrocarbon accumulations have been encountered in nine of the eleven exploration wells drilled. Commercial gas fields have been proved at Barracouta and Marlin with estimated total recoverable reserves of 5.3 Tcf wet gas. The Halibut and Kingfish fields are estimated to contain total recoverable reserves of 1,500 million barrels of oil. Minor accumulations of oil have been encountered at Barracouta and Marlin and are presently being evaluated. Other accumulations, presently considered non-commercial, were found in the Dolphin and Perch fields. Recent discoveries in the Snapper, Tuna and Flounder fields are yet to be appraised.

Generally, analyses of gases discovered in the Gippsland area show them to be of good quality with a methane content in the order of 80-85%. Hydrogen sulphide of 45-50 ppm has been found in the Barracouta gas but only a trace has been reported in the Marlin gas. Commonly, the percentage of non-hydrocarbons in the gas is low in the shallower horizons but appreciable quantities exist In accumulations encountered at depth.

Oils are generally of low sulphur content and range in gravity from 40° API to 64° API. Gas-Oil ratios of from 100 to 1,100 cu.ft./bbl have been measured in crudes which range from highly under-saturated to saturated. The oils are of the light variety and yield high proportions of gasoline and kerosenes and small quantities of residues. Wax contents of the crudes range from very low to 27% and pour points from —80° to 75°F.