Fluid Inclusions as from Exploration Tool for Petroleum Systems: Studies from the Perth Basin, Australia

Richard Kempton¹, Peter Eadington¹, and Herbert Volk^2
1Petroleum, CSIRO, Kensington, WA, Australia
²Petroleum, CSIRO, North Ryde, NSW, Australia

Oil-filled fluid inclusions are hidden oil shows with unique properties for characterising elements of petroleum systems that augment the information available from conventional techniques. Studies from the northern Perth Basin are presented for exploration applications.

At Cliff Head a palaeo oil-water contact, established from fluid inclusions, is above the current contact and now inclined to it, indicating structural growth during oil accumulation. Spectra of the inclusion and production oil are similar and plot in the yellow region of the visible spectrum. Both have a geochemical signature of basal Kockatea Shale source that calibrates the spectra for mapping petroleum systems.

Palaeo-oil zones in non-productive offshore wells with oil inclusions sharing the Cliff Head spectral signature occur in both Permian and Jurassic reservoirs. This suggests the petroleum system sourced from the basal Kockatea Shale is widespread and that future exploration success will depend on understanding the factors required for preservation of oil.

Inclusion oil from Leander Reef-1 has evidence for another petroleum system. The molecular and compound specific isotope analysis data indicate a mixed Early-Permian and basal Kockatea Shale source. Some prospects may have received oil or gas from more than one petroleum system and this is a factor for prognosis of fluid type.

In the onshore region of the Perth Basin, oil-filled inclusions with white to blue fluorescence colours within the gas-cap of the Dongara Field indicate an early oil charge. These fluorescence colours differ from the basal Kockatea Shale derived inclusion oil raising the prospect that this fluid-inclusion oil at Dongara has a source other than the Kockatea Shale, and differ from the current reservoir oil.

AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery