Publication Name: The Cooper & Eromanga Basins Australia
Authors: S.M. McIntyre, F.G. Jamal, C.L. Pidcock and M.I. Kabir
Date Published: June 1989
Number of Pages: 25
Reference Type: Book Section
Abstract:
The Gidgealpa Field, discovered in 1963, is located in the South Australian portion of the Cooper Basin about24 km (15 miles) north-west of the Moomba Gas Plant. The Field produces dry gas from the Late Permian Toolachee Formation, rich gas from the Early Permian Patchawarra Formation and Tirrawarra Sandstone and oil
from the Jurassic Namur, Birkhead, Hutton and Poolowanna Formations. The hydrocarbons are located in two structural traps- the North and South Domes. The majority of the oil is contained within the South Dome while the majority of the gas is in the North Dome Toolachee Formation.
Continued production and additional drilling have made it possible to identify areas of undrained oil and gas
and to predict sand trends with increased confidence. The Gidgealpa Field has been appraised continually and this has allowed increased oil and gas reserves from the oldest producing field in the Cooper Basin. The Gidgealpa Gas Field was first brought on line in 1969. With the Moomba Field it is the oldest producing gas field in the Cooper Basin and is over 70 per cent depleted. The Gidgealpa North Dome Toolachee Formation contains approximately 78 per cent of the total gas-in-place in the Gidgealpa Field. Field-wide pressure surveys in the North Dome Toolachee Formation have been conducted regularly since 1971. The reservoir pressure/gas
deviation factor established material balance estimates of gas-in-place match well with the volumetric estimate.
It was not until 1985, sixteen years after gas was first brought on line, that oil production commenced from the
Gidgealpa Field oil reservoirs subsequent to the discovery of oil in Gidgealpa-17 which was drilled in 1984. The
reservoir drive mechanism in the Jurassic reservoirs is predominantly water drive with the exception of the
Birkhead Formation where oil production is primarily due to volumetric expansion. The majority of the current oil
production is from the Hutton Sandstone with an average oil production of 270 m3Jd (1700 BOPD) during 1988.
The reserves in the various Jurassic reservoirs are determined by estimating the reserves of the individual wells based on the oil-cut history. The potential for methods such as waterflooding in the Birkhead reservoir and enhanced oil recovery through miscible gas injection in the Namur and Hutton Sandstones are currently being evaluated: their implementation would be strongly influenced by the world oil prices.