Soil Gas Alkane Survey EP 9 Pedirka Basin, N.T.

Abstract

A helicopter supported soil gas survey was carried out from widely spaced lines over EP9 to assess the petroleum potential of the permit. Throughout the survey area ethane, propane and butane concentrations are low with no anomalous samples present. Methane concentrations are low to moderate with one zone of anomalous concentrations and one zone of elevated concentrations, both located in the central region of the permit.

The ratios of the alkane concentrations suggest a gas-rich source for the hydrocarbons. However, it is possible that high methane concentrations observed in some samples may be derived from a remote source. Also heavy rain during July and August 1986 may have preferentially removed the heavier alkanes as it moved downwards through the soil suggesting that potentially anomalous areas would not be as gas rich as the ratios indicate.

The results of the soil gas survey indicate the permit to have a low prospectivity for the discovery of large oilfields.