Manoj Kumar Sarmah
Oil India Limited, India
Title: Geochemical significance of petroleum asphaltenes as maturity and source indicator of oil
Biography
Biography: Manoj Kumar Sarmah
Abstract
In the last few years asphaltenes have become of immense interest for exploration techniques, since it was reported that they possess structural features of the related source rock kerogens. This is because the use of asphaltenes from crude oils may help to overcome the lack of source rock samples in basin analysis when reliable predictions for the generation of hydrocarbons are required. Asphaltenes separated from two different crude oils from upper Assam basin, India having different geological origins, namely DK (Eocene) and JN (Oligocene-Miocene) were pyrolysed at 6000C in a PY-2020iD double shot pyrolyzer and the products were analyzed by gas chromatography-mass spectrometry (GC/MS). Both the asphaltenes produces aliphatic as well as aromatic compound classes. Aromatic compounds like Methylnaphthalenes, Methylphenanthrenes and Methyldibenzothiophenes generated as a result of pyrolysis of the asphaltenes were used to assess thermal maturity of the oils. The ratios of β-substituted to α-substituted isomers of Methylnaphthalenes, Methylphenanthrenes and Methyldibenzothiophenes revealed higher maturity of the JN oil than that of the DK oil. For both the asphaltenes the abundance of 1-methylphenanthrene dominates over that of 9-methylphenanthrene showing the terrestrial nature of the organic matter. The biomarkers present in saturated and aromatic fractions of oils plays an important role in determination of maturity and source of oils. However, it is very difficult to determine maturity of severely biodegraded oils due to bacterial removal of some of the biomarkers in these types of oils. Therefore, asphaltenes should be a better choice for maturity calculation in severely biodegraded oils.
