Organic maturation study of Permian coal seams, Rajmahal Basin, Bihar

The coals are sub-bituminous to high volatile bituminous in rank and show evidences of "bituminization" stage of. maturation. They have distinctive petrographic characteristics being rich in secondary liptinites such as exsudatinite (nil to 7.66%), bituminite (0.94 to 28.88%) and fluorinite (nil to 0.99%). The rock-eval data suggest that they are hydrogen-rich and have immature organic matter-kerogen type III. The study corroborates the earlier contention regarding the onset of 'oil window' at Rom of 0.5% and suggests that the paleodepth of burial of the coal bearing horizon in the Rajmahal basin was from 1890 to 2970m. The loss of cover has been estimated to range from 1440 to 1720m.