TANAMI-1 OIL DISCOVERY: BARROW SUB-BASIN

Abstract

The Tanami oil discovery was made in 1991. The discovery well was drilled from an onshore location on Varanus Island and deviated into the offshore area. A small, 6.8 m oil column was intersected at the top of the Lower Cretaceous Flag Sandstone Member of the Barrow Group. Beneath the moveable oil, a residual zone of 19.8 m was encountered.

Petrophysical, petrological and core analysis data indicate different reservoir properties in the moveable oil, residual oil and water zones. These results show that the oil in place has retarded diagenesis and associated reduction in porosity and permeability values.

The residual oil column is interpreted to be a result of northward structural tilting in the early Tertiary, causing oil previously trapped to be spilled to the south.