ABSTRACT: Reservoirs in the Cooper Basin Basement, South Australia

HIBBURT, JACQUE, DAVID GRAVESTOCK, and LES TUCKER, South Australian Department of Mines and Energy, Adelaide, South Australia, Australia

Hydrocarbons were discovered in 1990 by SANTOS and Joint Venture partners in "basement" updip from Permian Cooper basin source rocks.

"Basement" comprises gently dipping to vertical volcanics, carbonates and siliciclastics of the Cambro-Ordovician Warburton basin. The deliberate search for petroleum in Cambrian carbonates has not been successful, but unexpectedly, oil has been found in underlying volcaniclastics (average well production 115 BOPD), and gas in overlying porous sandstones and fractured siltstones (maximum Q = 9.6 MMCFD).

Recognition and regional mapping of pre-Permian rocks is in progress using data from cores, cuttings, wireline logs, gravity, and magnetics. Seismic data are used only in limited areas of gentle dip.

Major objectives center on: determining lithostratigraphy and distribution of volcanic rocks below the southwest Cooper basin; differentiating Mesozoic from subjacent basal Ordovician redbeds in the Merrimelia-Innamincka area; recognizing and mapping stratigraphically distinct sandstones and quartzites; mapping the types and most likely locations of potential Warburton basin reservoirs currently updip from mature Permian source rocks; recognizing structural controls on the distribution of Warburton basin strata.

Warburton basin rocks were deformed and intruded by granite in the Late Devonian-Early Carboniferous Alice Springs Orogeny, and the Cooper-Warburton unconformity (Z-horizon) was further modified by glacial processes. Reconstruction of reservoirs in this ancient basin is challenging but the potential rewards are great.

AAPG Search and Discovery Article #91015©1992 AAPG International Conference, Sydney, N.S.W., Australia, August 2-5, 1992 (2009)