GEOLOGY OF THE JACKSON OIL FIELD

Abstract

The Jackson oil field was discovered late in 1981 with the drilling of Jackson 1, which was programmed as an exploration well designed to test the Jurassic-Cretaceous Eromanga Basin sequence and the Permian Cooper Basin sequence, if present. The well tested oil from three formations.

The first test to produce oil was carried out across a sand in the Early Cretaceous Murta Member of the Mooga Formation. The zone produced 47° API gravity oil at the rate of 338 barrels (53.7 kilolitres) of oil per day. This was followed by two tests which produced 41° API gravity oil at the rates of 188 and 1165 barrels (29.9 and 185.2 kilolitres) per day respectively from thin sands in the Late Jurassic Westbourne Formation. As a fitting conclusion, the well intersected a 100ft (30 m) oil-saturated section in the Jurassic Hutton Sandstone which on testing flowed 41° API gravity oil at a maximum rate of 2616 barrels (415.9 kilolitres) per day.

Four appraisal wells subsequently drilled in the Jackson Field confirmed the initial belief that development of the field was a viable proposition.

Compared to the Hutton and Westbourne accumulations, the size of the Murta accumulation is relatively insignificant. The accumulation in the Murta is primarily controlled by structure. On the other hand, the Westbourne accumulation appears to have a strong component of stratigraphic control. In the Hutton accumulation, there is a fair amount of variation in the geometry of the sand bodies at the top of the reservoirs. The accumulation is, however, dominantly controlled by structure.