PEL 12 covering an area of approximately 24,320 square km in the northern Officer Basin region (as a continuation of former OEL 28 and PELs 10/11 held by the same licensees) was granted to Exoil NL and Transoil NL for five years, with renewal rights, from 11/2/1971. These companies had resumed tenure with the main objective of drilling a second, deeper well on the Munyarai structure to search for a possible Ordovician sequence not fully penetrated by Munyarai 1. It was thought that such a section might be analogous to the rocks hosting the newly discovered Mereenie Oilfield in the neighbouring Amadeus Basin of the Northern Territory. The envisaged well entailed rotary drilling to around 16,500 feet depth at an estimated cost of $250,000. Of this amount the PEL 12 licensees were prepared to fund only 10%, and meet the remaining cost through attracting a farm-in partner. Regrettably, the proposed well never eventuated for several reasons: the continuing very low world crude oil price of about US$2/bbl, the perceived absence of local markets for additional supplies of natural gas, the search area's extreme remoteness, the Australian Commonwealth Labor government's interference in the process of licence administration which undermined the ongoing farm-in offer (the Rex Connor era nationalisation scheme for the upstream petroleum industry), and early difficulties with organising access to newly proclaimed Aboriginal homelands. In fact, by the middle of licence Year 4 some $3,000 only had been spent on direct exploratory work in PEL 12, meaning that the licensees were $1 million underspent on their commitments. The only licence activity had been office geological and geophysical studies, the Rb/Sr dating of bottomhole core from Munyarai 1 which had confirmed the mid-Palaeozoic age determined previously by Conoco using palynology, seismic stratigraphic correlations made between Munyarai 1 and SADM Cartu Hill area seismic lines then being shot, and the sedimentological sampling of Cambrian and ?Ordovician outcrops at Mount John and Cartu Hill on the edge of the basin, to determine depositional environments and sandstone porosity. Luckily, in late 1974 Exoil succeeded in gaining the oil major company Shell as a farminee to a 49% interest in PEL 12, under an agreement whereby at Shell's sole risk it would undertake enough additional seismic work to mature the Munyarai prospect, and then after 6 months elect whether to withdraw from the licence or continue earning its share by drilling Munyarai 2 to at least 14,000 feet depth or prior economic basement. Accordingly, Shell acquired the Everard Seismic Survey during Oct-Nov 1974, which comprised 99.5 line km of digital 6-fold detailed profiling over the Munyarai structure, plus a regional dip tie line of 54.5 line km connecting Munyarai 1 to SADM seismic line FK in the Cartu Hill locality. They also carried out seismic data reprocessing tests on regional seismic survey analogue data from the 1964 Mabel Creek and 1967 Namco surveys, and performed clay mineral determinations on 13 Munyarai 1 core samples to look for trends in clay properties (i.e. the degree of illite crystallinity) which might indicate the degree of burial metamorphism and tectonic aging of the well sequence. Unfortunately, the outcome of this preliminary work by Shell was a decision that in its view Munyarai 1 had adequately tested the basin prospectivity after all. Shell withdrew from the farm in agreement, without further obligation, on 28/8/1975. Thereafter the licensees continued in a hopeless and desultory way for another year to seek other farminees, until it became obvious that continuing tenure of the licence was impossible without incurring legal penalties or cancellation. PEL 12 was relinquished in very poor standing in the middle of renewal Year 6, on 11/8/1976.