Soil Gas Alkane Survey - OP238, Pedirka Basin, NT

Abstract

A detailed helicopter supported soil gas alkane survey over four seismic grids and two regional lines in OP 238 resulted in the detection of five zones containing anomalous concentrations of methane, ethane, propane and butane.

These zones are present over two seismic grids and one regional line in the central and western parts of the permit where clusters of anomalous samples occur. Samples over the two seismic grids in the east of OP 238 have anomalous concentrations of only one or two of the light alkanes and do not form clusters. No samples with anomalous concentrations of the light alkanes are present on the second regional line.

The ratios of methane to ethane, propane and butane concentrations suggest an oil-rich source for the hydrocarbons in Zones B, D and E. However, the ratios of the light alkanes in Zones A and C suggest a source for the hydrocarbons that is gas rich. It is possible that some of the methane may be derived from a remote gas source and migrated to traps within the vicinity of Zones A and C.