AIM: The 1988 Gambier Seismic Survey of semi-detailed and regional data acquisition was shot principally to upgrade the prominent Glenburnie lead in the northeast of PEL 28 into a drillable prospect. This lead, identified 1n 1986 by the Burrungule Detail coverage, lies on the northern, upthrown side of the Tartwaup Fault in a similar structural setting to the undrilled Honan prospect to the west. Additional Gambier Survey programme was acquired in the east of the licence area, both north and south of the Tartwaup Fault, to attempt to further resolve complex deep structuring evident throughout the respective Cretaceous sections. METHODS: Survey dates: 18 January - 18 February 1988. Energy source: Vibroseis. CDP coverage: 6000%. Recording mode: 120 channel digital - MDS-14 recorder. SP interval: 25.0m; group interval: 25.0m. 14 lines totalling 159 line km were acquired in an area 20 km northeast of Mount Gambier city by Party 6824 of Petty-Ray Geophysical, and were processed in Perth, WA by Simon Horizon Australia. Interpretation was performed in Melbourne, Vic. by licence operator Beach Petroleum. RESULTS: Besides the Glenburnie Prospect, the latest seismic interpretation has delineated a number of smaller anticlinal leads lying within half-graben troughs developed parallel to the Tartwaup hingeline. The interpretation embraced 248 line km of data, including reprocessed lines from the 1985 and 1986 Burrungule, Wanwin Gorae Detail and Burrungule Detail surveys. From the new mapping the Glenburnie Prospect appears to be a valid drilling target, based on its relatively large areal extent (8.2 square km at near base Pebble Point Formation level), ideal position for entrapping hydrocarbons migrating updip out of the Voluta Trough along the Tartwaup Fault, unique (for this area) and well-defined northerly stratigraphic dip, possibility for evaluating both near base Pebble Point and near base Upper Cretaceous - Waarre plays in the one well, and the existence of deeper structural closure below these objective levels as indicated by a seismic velocity low coinciding with the prospect. A maximum vertical relief of approximately 30 metres is observed at base Tertiary level, with structural growth inferred from isochore values to have occurred during deposition of the Pebble Point Formation. However, the more mature Compton prospect, lying in the west of PEL 28 on the downthrown side of the Tartwaup Fault, is due to be drilled first to investigate a probably more prospective, fully developed sequence of Tertiary and Upper Cretaceous reservoirs.