Petrographic studies to delineate suitable coal seams for coal liquefaction and their palaeo-environmental analysis: A case study from the Ib river and Mand-Raigarh coalfields of the Mahanadi valley coalfields, India

Abstract

A systematic approach has been carried out to delineate the coal seam zones from the Ib river coalfield, Odisha and the Mand-Raigarh coalfield, Chhattisgarh for the conversion of coal to oil as well as to establish the peat-forming environment of the mire and determine the depositional facies analysis of the coal seams. Zone R-I of Raniganj formation and Belpahar, Parkhani and Lajkura of Barakar formation from the Ib river coalfield and Seam nos. VII, VI, III and I of the Barakar formation from the Mand-Raigarh coalfield are identified based on their high percentage of liptinite and reactive content as well as their suitable maturity (mostly sub-bituminous rank) as potential for coal-to-oil conversion. The palaeo-depositional environment for peat formation has been constructed using the tissue preservation index and gelification index following coal facies analysis which shows that the peat formation in the Ib river coalfield took place under limnic to limno-telmatic conditions with prolonged wetness in the mire, whereas in the Mand-Raigarh coalfield, peat evolved under a clastic to an open marsh limnic environment with intermittent wet and dry spells. The microlithotype composition indicates that both the coalfields evolved under lower to upper deltaic settings.