Exploration for a suitable underground gas storage target in the Northern Adelaide Plains was initiated in 1964. Prior to the present investigation, four other areas have been examined and rejected as target areas, mainly due to the shallow depth of potential reservoir sands and the lack of adequate confining beds. The history of exploration to 1978 is contained in a report by Cockshell, Nelson and Cooper (1978). Drilling in the Korunye area, north of Two Wells, was undertaken in 1978 to test for the presence and areal extent of the deep Northern Adelaide Plains Aquifer C (which includes the North and South Maslin Sands and the Clinton Formation). Biostratigraphic examination of sediment samples from these wells showed that the sands intersected were younger than Aquifer C sands, and an evaluation of the data led to a new conceptual model for the deposition of Eocene sediments in this portion of the St. Vincent Basin. As a consequence of adopting the new depositional model, further exploration was concentrated in the Port Gawler area, where Observation Bore F, drilled between 1961 and 1964 (Lindsay, 1965), had intersected a thick Cainozoic sequence including all known Tertiary units of the eastern St. Vincent Basin (Lindsay, 1969). In this bore the Clinton Formation comprises mainly clays and lignites which appear to provide good hydrological separation of the North and South Maslin Sands. This indicated that the underlying 19 m thick North Maslin Sands, at a depth of 330 m, would be a good target for further study. Although the porosity and permeability of these sands were not determined during the development of the bore, likely high values of these properties were indicated because contained groundwater flowed to the surface during development, and the sands were blown up the hole during casing operations. Groundwater samples with salinities in the order of 60,000 mg/1 were obtained from these sands.