AN ALTERNATIVE VIEW ON INDO-AUSTRALIAN COALS AS A SOURCE OF PETROLEUM

Abstract

Numerous studies have argued that coals are the primary source for much of the petroleum in the Indo-Australian region. These studies have invoked this genetic relationship because of similarities in n-alkane distributions among coal extracts and oils and the apparent absence of conventional sources. Others have suggested that the ability of southern hemisphere coals to source oil is a result of differences in the nature of their precursors compared to their gas-prone northern hemisphere counterparts.

Suggested genetic relationships are challenged through several independent approaches. Organic geochemical data reveal that these coals display characteristics similar to their northern hemisphere, gas-prone counterparts. They appear capable of generating large volumes of heavy hydrocarbons but are incapable of expelling them within the oil-window. Other data reveal that many of the region's proposed oil-source rock correlations are internally inconsistent. And finally, data are becoming available which indicate that conventional lacustrine or marginal marine source rocks are present.

This alternative view of the petroleum potential of coals is significant in that it alters exploration concepts and mass-balance calculations of reserves.