--> Biological Markers for Discriminating Cainozoic Petroleum Source Rocks in Southeast Asia, by R. E. Summons, A. P. Murray, C. J. Boreham, and L. M. Dowling; #90986 (1994).

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Abstract: Biological Markers for Discriminating Cainozoic Petroleum Source Rocks in Southeast Asia

Roger E. Summons, Andrew P. Murray, Christopher J. Boreham, Lesley M. Dowling

The biomarkers present in Cainozoic oils from, SE Asia, Southern China and New Zealand comprise many source-and environment-diagnostic compounds. As a result, it is possible to recognize many consistencies between oils with different geographical origins and to relate these patterns to specific source rock organofacies. In addition, we have measured the carbon isotopic signatures for individual components of these oils, and some possible source rocks, to provide further diagnostic information.

Oils sourced from fluvio-deltaic or paralic coals/carbonaceous shales are characterized by compounds derived from tropical terrestrial plants and from bacteria and have high pristane/phytane ratios, high oleanane/hopane ratios, moderate to low C27/C29 sterane ratios, negligible or absent 4-methyl steranes and high concentrations of oleanoid triterpanes of varying type and abundance. Trace amounts of 24-n-propyl cholestanes in some of these oils signify some marine influence or co-sourcing from marine and non-marine sediments. Bicadinanes, methyl bicadinanes and related compounds are generally abundant. Oils of this type are found throughout Indonesia, the Philippines, the Taranaki basin of New Zealand and have recently been discovered in Papua New Guinea. The pre ence of bicadinanes in non-SE Asian oils is confirmed for the first time and a new, bicadinane based maturity parameter has been developed.

A transitional freshwater facies, characterized by abundant 4-methyl steranes is the source of seep oils in the Philippines and Southern China but is distinct from the deeper lacustrine facies which has sourced the botryococcane containing oils of Sumatra (Indonesia). Isoprenoids and n-alkanes of these lacustrine oils show major differences in their carbon isotopic signatures and we discuss these issues in terms of what is known about carbon isotopic fractionation in lipids from communities of extant bacteria, algae and higher plants.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994