Source Rock Characteristics and Maturation of Palaeogene Coals, Northeast India

Abstract A large number of coal samples from the Palaeogene coal deposits of Northeast India were subjected to detailed chemical (proximate, ultimate and Rock-Eval pyrolysis) and petrographic (maceral, microlithotype and vitrinite reflectance) analyses to examine their source rock characteristics and to explore their participation in hydrocarbon generation. The results show that these coals are sub-bituminous ‘C’ to high volatile bituminous ‘C’ in rank and have requisite petrographic characteristics to act as a potential source for the generation of significant amount of normal hydrocarbons. The values of vitrinite reflectance, particularly of the coals of Meghalaya and Assam, suggest a maturation close to the ‘top oil window’ (birth line). This indicates the possibility of expulsion of oil and condensates in the basin. However, this contention needs to be supported by organic geochemical data, maturation modelling and time of hydrocarbon generation.