RECENT INFORMATION AND PROSPECTS IN THE KIDSON SUB-BASIN

Abstract

A deep sedimentary depression, the Kidson Sub-basin, has been indicated within the southern Canning Basin by gravity and aeromagnetism. The wells, Sahara 1, Kidson 1 and Wilson Cliffs 1, showed that at least 15,000 feet of Phanaerozoic sediments were present. This paper aims to summarise information given by these wells and to indicate prospects and techniques for further exploration in the sub-basin.

Previous surface geology had indicated Mesozoic and Permian sediments in the area bordered by Proterozoic outcrop. Geomorphological mapping techniques have been successfully used by Aquitaine to indicate possible structures for seismic work.

Seismic results from Wapet and Aquitaine indicate gentle diastrophism within the sub-basin with the existence of a palaeogeographic limit to pre-Permian sediments in the east.

The western Canning Basin had previously shown a Mesozoic and Permian sequence overlaying Ordovician shales, limestones and sandstones on igneous and metamorphic basement.

Sahara 1, and later Kidson 1 and Wilson Cliffs 1, proved the presence of a Middle and pre-Middle Devonian limestone — red bed — evaporite sequence in the sub-basin: the Mellinjerie

Limestone, Tandalgoo Red Beds and Carribuddy Formation. The underlying Ordovician shales and tight sandstones in Wilson Cliffs 1 can be correlated with the Horn Valley to Pacoota Formations in the Amadeus Basin. In Wilson Cliffs 1 these sandstones overlie Proterozoic shales.

The only show noted was minor wet gas associated with Ordovician dolomites in Wilson Cliffs 1. A major petroleum prospect of the sub-basin could be sought in improvement in the reservoir capabilities of the Ordovician sandstones along the palaegeographic eastern margin of the basin.

Favourable pinchout forms of these Ordovician sandstones have been found by recent refraction seismic. Refraction, combined with gravity, geomorphology and detailed seismic techniques, can outline drillable prospects along the Kidson Sub-basin.