THE HUTTON SANDSTONE - TWO SEPARATE RESERVOIRS IN THE EROMANGA BASIN, SOUTH AUSTRALIA

Abstract

The Hutton Sandstone in the South Australian portion of the Eromanga Basin consists of two units, one Early to Middle Jurassic, the other Middle to Late Jurassic in age. The younger unit may conformably overlie the older in areas of persistent subsidence but either may be thin or absent in areas of complex structure.

Siliceous and calcareous authigenic cements at the top of the older unit and within the younger unit indicate surficial weathering in a warm arid to humid climate, supported independently by palaeofloral and faunal evidence. Duricrusts of Middle to Late Jurassic age have been recorded in outcrop from the southwest Eromanga Basin margin and the Surat Basin region.

Both units have disconformity trap potential and the younger unit has additional poor to excellent stratigraphic trap potential. Exploration strategies will be enhanced by mapping each unit as a separate reservoir and by recognizing the downflank stratigraphic trap potential of the younger unit.