RECENT EXPLORATION AND PETROLEUM DISCOVERIES IN THE DENISON TROUGH, QUEENSLAND

Four gas fields (Glentulloch, Westgrove, Rolleston and Arcturus) were discovered by AAR Limited in the Denison Trough in the early 1960's. Permian gas reservoirs were encountered in Late Triassic wrench anticlines. The fields were not developed because of low gas prices and exploration technology problems at that time. Exploration activities ceased in 1970.Increased gas prices, the opportunity of an expanded gas market, and improved seismic technology provided the incentive to recommence regional seismic surveying of the basin in 1979. More than 2600 km of multi-fold seismic data have been recorded by the AAR Limited/Oil Company of Australia N.L. Joint Venture. The enhanced seismic resolution resulted in a revision of the structural and stratigraphic interpretation of the basin. Exploration drilling in 1981 was directed initially at deep Early Permian structures; however, reservoir quality of the Lower Permian sequence was poor and gas flow rates minimal.Exploration was therefore redirected towards the definition of prospects which were structurally and stratigraphically similar to the known fields. Five exploration wells have been drilled since November 1981, resulting in the discovery of a further three gas fields — Merivale, Yellowbank and Punchbowl Gully. Appraisal wells were drilled on the Glentulloch, Westgrove, Merivale and Yellowbank Fields, and were cased for future production.It is estimated that nine billion cubic metres (x 109m3) of conventional gas reserves are present within the basin. In addition, tight reservoirs contain large volumes of gas which may be producible by hydraulic fracturing. The basin is being actively explored to realize its full potential and to supply industrial and domestic markets in central and southeastern Queensland.