Fortescue Field, Gippsland Basin, Offshore Australia: Flank Potential Realized
J. H. Hendrich, I. D. Palmer, D. A. Schwebel, 1992. "Fortescue Field, Gippsland Basin, Offshore Australia: Flank Potential Realized", Giant Oil and Gas Fields of the Decade 1978-1988, Michel T. Halbouty
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The Fortescue field is the last of the "giant" oil fields discovered to date in the offshore Gippsland basin, southeastern Australia. This field is a stratigraphic oil accumulation on the western flank of the giant Halibut-Cobia oil field. The Fortescue field discovery well, West Halibut-1, was drilled in 1978—some 11 years after the Halibut discovery—as a follow-up to the dry Fortescue-1 wildcat. The occurrence of a stratigraphic trap in a sand-prone section is a unique feature of the Fortescue field. Fortescue reservoirs are Eocene sandstones that are interpreted as having been deposited in coastal plain, upper shoreface, and lower shoreface environments. Fortescue reservoirs are stratigraphically younger than, and hydraulically separated from, those in the underlying Halibut-Cobia field. Pressure data have conclusively demonstrated that there are at least three separate hydraulic systems within Fortescue field. Reserves are estimated at 280 MMSTB on the basis of an original oil in place estimate of 415 MMSTB.
Fortescue field was developed by two 21-conductor platforms, Fortescue A and Cobia A, which also developed the underlying Cobia reserves. These platforms were commissioned in 1983. At the conclusion of development drilling in early 1986, 28 productive wells had been drilled into the field.
Peak production of 100,000 BOPD from the combined development facilities was achieved in 1984 and sustained until 1986. Production received a boost in 1989 from two infill wells that were drilled following interpretation of the available reservoir data.
Following these successes, a 3D seismic survey was acquired over Fortescue, Halibut-Cobia, and Mackerel fields in 1990. A revised detailed reservoir description based on these data is expected to allow identification of additional infill and workover opportunities and to help mitigate production declines in these mature fields.
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The success of Memoir 14 and the worldwide interest shown for data on giant fields prompted AAPG to schedule a symposium on giant fields at the end of each subsequent decade. The 1968-78 symposium was held in Houston, Texas, April 1-4, 1979, and the papers were published in AAPG Memoir 30, December 1980.
The Stavanger Conference "Giant Oil and Gas Fields of the Decade: 1978-1988" was held in Stavanger, Norway, September 9-12, 1990, and is a continuation of the Giants of the Decade series.
Scientific studies and projections of future world energy demand indicate that although alternative-energy fuel sources must be actively pursued and developed, there also must be adequate petroleum supplies to bridge the gap. For the international petroleum industry, the years covered by this conference, 1978-88, were complex. They were years of boom and bust. The world's energy consciousness was boosted sharply by the effects of the 1979 Iranian revolution and the resulting embargo, which sent world oil prices to record heights. Global petroleum exploration soon surged, leading to the industry's all-time drilling high in 1981. Then came the oil price collapse in 1985, and the following years were characterized by falling oil prices and drastic budget cuts for exploration and development.
Although exploration dropped sharply during the latter part of the decade, there was a steady flow of giant oil and gas field discoveries. Using the giant field designation criteria of 500 million bbl of oil recoverable for fields in Asiatic Russia, North Africa, and the Middle East,