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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 55 (1971)

Issue: 2. (February)

First Page: 333

Last Page: 333

Title: Halibut Field, Gippsland Basin, Southeastern Australia: ABSTRACT

Author(s): B. B. Clifton, E. H. Franklin

Article Type: Meeting abstract

Abstract:

Australia's first offshore production, in the Gippsland basin of southeastern Australia, was discovered in 1965. Further exploratory drilling in the area has led to the discovery of additional oil and gas fields.

The Halibut oil field, currently being developed, is considered as a field case history of this Australian offshore operation. The field was discovered, by drilling only 1 exploratory well, in August 1967. It is 40 mi offshore in 238 ft of water and encompasses an area of 11 sq mi. At this early stage, the confidence factor on the seismic interpretation was sufficient to construct a 24-conductor drilling platform.

Oil, associated with a common oil-water contact, is found at the top of the Latrobe complex of Paleocene rocks between depths of 7,400 and 7,856 ft subsea. Stratigraphically the reservoir is composed of braided stream sandstones with some point bar and stream mouth bar sandstones that have been subdivided and mapped as 8 units separated by impermeable breaks. These strata, dipping monoclinally westward, are truncated by a post-Eocene angular unconformity. Closure in excess of 500 ft is provided at the unconformable surface by the combination of erosion and post-Oligocene tilting.

The field is being developed by drilling deviated wells, some in excess of 45° and 6,000 ft from the centrally located platform. With an available maximum of only 24 conductors, optimum drainage points must be selected with care. The number of wells to be drilled to any specific sandstone unit is based on its respective percentage of total reserves. The optimum drainage position is then determined from structure and isopach maps where individual sandstone units are in their highest nontruncated structural position.

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