Abstract: Geochemical Typing of Crude Oils from the Gulf of Thailand and the Natuna Sea
C. Schiefelbein, H. L. Ten Haven
The geochemical characteristics of approximately thirty oils from the Gulf of Thailand and Natuna Sea have been measured, viz., sulfur, vanadium and nickel content, density, 13C isotopes of the isolated aliphatic and aromatic hydrocarbon fractions, capillary gas chromatography of the whole oil, and gas chromatography-mass spectrometry (GC-MS). The GC-MS analysis included the classical monitoring of specific ions (SIM mode) as well as sophisticated multiple reaction monitoring (MRM) measurements (MRM mode). These latter analyses are of key importance for the detection of 24-propylsteranes, a prerequisite for the discrimination between lacustrine/deltaic oils vs. marine crude oils. Classification of the different types of oil families encountered in this region was based on v sual inspection of the data, supported by multivariate statistical analysis.
In the Gulf of Thailand, which includes oils from the Pattani trough and the northern part of the Malay basin, essentially three different types are recognized, generated by lacustrine, resinous, and carbonate source rocks. The situation encountered in the Natuna sea, including oils from the southern part of the Malay basin (Indonesia), the Penyu basin, and the west and east Natuna basins is almost similar to the same suite of different oil types. Although the geochemical characteristics of the resinous-derived oils is more or less similar in all basins, the lacustrine-derived oils exhibit large variations especially expressed in their isotopic signature. Interestingly, the carbonate-sourced oils from the east Natuna basin show characteristics that resemble those of the main oil famil found offshore northwest Palawan.
AAPG Search and Discovery Article #90982©1994 AAPG International Conference and Exhibition, Kuala Lumpur, Malaysia, August 21-24, 1994