Secrets from the Past: The Stepwise Fill History of Petroleum Reservoirs Revealed By Fluid Inclusions
Peter Eadington, Richard Kempton, and Herbert Volk
Division of Petroleum Resources, CSIRO, Kensington, WA, Australia
Fluid inclusions within sedimentary grains track many aspects of the stepwise fill history of petroleum reservoirs and integrate with other disciplines to provide diverse kinds of information used in exploration.
Attributes of oil inclusion assemblages, including fluorescence colours and location, identify interactions of oil with water and gas. In the Jabiru oil field, Vulcan Sub-basin oil inclusion assemblages in residual zone have attributes that differ from those in the oil zone. This suggests oil was modified during increasing water saturation consistent with the current OWC being the depth for loss of oil by transient fault leakage. Oil inclusion assemblages in palaeo-oil zones within gas zones of wells may have variable and correlated fluorescence colour and proportion of gas bubble. This is interpreted as interactions during displacement of oil by gas.
In the Laminaria High, Timor Sea, the depth of palaeo-oil water contacts determined by the GOI technique was important input into a structural analysis that identified leakage points and a favourable juxtaposition of faults with reservoir for preservation of oil.
At the Blackback oil field in the Gippsland Basin, biomarkers indicate that the inclusion oil is less mature and derived from a marine source rock whereas the MDT oil has a terrestrial source rock. No indication of marine source in the recovered MDT oil is attributed to dilution; however the oil inclusion data indicate a new petroleum system in the basin.
Seismic data from the Bremer Basin, with no exploratory wells, indicate reservoirs in anticlines and fault blocks with potential for hundreds of millions of barrels, but the risk is unproved hydrocarbon charge. Samples dredged from incised canyons contain oil inclusions in low abundance indicating that oil had migrated in the reservoir.
AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery