PEL 53 covering 10,136 square km of the Stansbury Basin, which embraces the southern and central parts of Gulf St Vincent and Yorke Peninsula, was granted to local companies Preview Resources Pty Ltd and Oakman Pty Ltd for 5 years from November 1989. Their primary exploration target was a succession of Early Cambrian limestones, dolomites and sandstones which had been identified by previous exploratory drilling in the region. An offshore seismic survey of 303 line km funded by SADME in 1985 had shown that the sediments buried under the Gulf are thick enough to have generated petroleum from potential source rocks. The seismic also revealed that faulting and folding of the sediments had produced potential traps for petroleum. Preview and Oakman's entry to the Stansbury Basin acreage represented the first interest in the basin by the petroleum industry since the last exploration licence had expired in 1984. The most recent well in the basin was then Stansbury Town 1, drilled by Beach Petroleum in 1967. The new licensees intended to conduct at least 500 line km of seismic and to drill at least 2 new wells, for an estimated minimum cost of $11 million. To meet this commitment, a joint venture was set up in May 1992 with Texas-based independent explorers Cyrus Wagner and Dick Brown (through Canyon Australia Pty Ltd), who by August 1993 had underwritten the costs of the 703 line km, July 1992 Western Atlas Marine Seismic Survey, and of the 226 line km, July 1993 Troubridge Shoals Marine Seismic Survey, besides reimbursing the costs of the original licensee's prior reprocessing of earlier seismic data, and other geological and geochemical basin studies. This expenditure earned for Canyon a 100% transfer of interest in the licence, while leaving one proviso, that of a 4% over-riding production royalty share in favour of Preview/Oakman, should a subsequent successful petroleum discovery be made. Stratigraphic drilling carried out in late 1992 by SADME under the South Australian Exploration Initiative, at two sites on northern Kangaroo Island near Emu Bay and between Stokes Bay and Cape Cassini, revealed a buried sequence of Early Cambrian rocks which had good reservoir potential and which were within the oil window of petroleum generative capability. Shortly after this, a joint government/industry funded 63 line km seismic survey laid out through Backstairs Passage and south-eastwards towards the Otway Basin revealed the existence of a new, un-named Palaeozoic basin containing sediments up to 2500 m thick. These findings enhanced the prospects for oil discoveries on northern Kangaroo Island and below the coastal waters to the north and south-east of the island, so in view of this Wagner and Brown in mid-1993 took out PEL 59 covering Kangaroo Island and extending into the Fleurieu Peninsula. Despite having obtained by early 1994 a systematic, high quality regional seismic coverage of the offshore Stansbury Basin, Canyon encountered difficulties with interpreting its detailed seismic data acquired over the Investigator and Troubridge drilling prospects. Shallow water around the Troubridge Shoals near the south-eastern tip of Yorke Peninsula also prevented complete seismic mapping of this area of interest. Therefore, during March-August 1994 Canyon flew a detailed aeromagnetic survey of approximately 16,000 flight line km (partly funded by MESA under the SAEI) over Investigator Strait and Gulf St Vincent to obtain structural information to help resolve the trap closure of potential drilling locations. Owing to such delays with firming up drillable prospects, and because of continuing difficulties in contracting for the use of a specialised drilling vessel suitable for deployment in the shallow Gulf St Vincent waters, the licensees were twice compelled to apply to the SA government for grant of consent to variations of their licence conditions. This eventually led to the postponement of the PEL 53 drilling commitment to beyond licence year 5, when the requirement for a first partial relinquishment of acreage fell due. In the meantime, during the period 1993-1996, Canyon's staff and technical consultants performed a deal of other supporting studies including source rock geochemistry and thermal maturation determinations, reservoir rock quality assessments and well log petrophysics, magnetic data interpretations and tectonic modelling, and remote sensing of possible submarine petroleum seeps, plus research into the Stansbury Basin's micropalaeontology, sedimentology, burial history, seismic stratigraphic development, and the nature and origins of well hydrocarbon shows and stranded coastal bitumens.