Coal Petrography and Rock-Eval Pyrolysis of Coals of Barakar Formation of Kothagudem and Godavari Sub-Basins, Pranhita-Godavari Basin, India: Implication to Depositional Environment

ABSTRACT Understanding the depositional environment of coals is crucial for determining the geological history and potential resource assessment. This study employs coal petrography and Rock-Eval pyrolysis to analyse the coals of the Barakar Formation in the Kothagudem and Godavari Sub-Basins, within the Pranhita-Godavari Basin, India. By interpreting the organic composition and thermal maturity of these coals, this study aims to provide valuable insights into their depositional conditions and hydrocarbon potential. The physicochemical and reflectance (0.30% and 0.44%) investigations indicate that the coal samples are sub-bituminous and of low rank. In the Kothagudem and Godavari sub-basins, vitrinite (26.7–70.6%) is the predominant maceral, followed by liptinite (10.7–14.7%) and inertinite (5.3–30.0%). The materials have a high total organic carbon (TOC) content (43.37 to 68.43%) and the capacity to generate hydrocarbons, as indicated by the results of Rock-Eval pyrolysis and analysis. Tmax interpretations (415°C to 427°C) suggest that the samples are primarily immature for oil production. The type II and type III kerogens that make up the majority of the coals in the sub-basins are produced mostly by terrestrial plants, which are the main source of organic matter. This kerogen is typically gas-prone and has minimal potential for oil generation. However, the primary phase was wet moor with intermittent moderate to severe floods and a few alternative dry spells that resulted in oxic and anoxic moor conditions.