Abstract

Geochemical characteristics of oil reveal important information on the age of the source rock and the palaeoenvironmental conditions of source rock deposition. With this premise in mind, almost 200 oils, covering the majority of the sedimentary basins of Indonesia, have been analysed by geochemical methods. These analyses include the measurements of bulk parameters (API, S, V and Ni content), stable carbon isotopes, whole oil gas chromatography, and biomarker fingerprinting by mass spectrometry either in the selected ion monitoring mode or in the multiple reaction monitoring mode. The analytical data were statistically compared to each other with commercial programmes, such as clustering and principal component analysis. With this approach, a number of general petroleum system are identified, differing from each other in the age and type of depositional environment of the source rocks.

In West Indonesia, the two main petroleum systems are lacustrine and terrigenous, both of Tertiary age. Only in the North Sumatra Basin and the East Natuna Basin, an additional marine petroleum system has been encountered. Subdivisions within the two main systems could be made, especially in those basins for which a large number of oil samples are available. In East Indonesia, the three main petroleum systems are Tertiary marine carbonate, Mesozoic marine carbonate and Mesozoic marino silicoclastic. As only a limited number of oils from East Indonesia (16) have been analysed, the existence of other petroleum systems is not excluded.