Petrographic analysis and depositional environment of subsurface coal seams of Koyagudem area, Godavari Valley Coalfield, Telangana, India

Abstract

The study area marks the south–eastern extremity of the Mulug Coal Belt of Godavari Valley Coalfield, Telangana. The Bore–hole No. KYG–353, containing Index above Queen and Queen seams, is located in north–western direction from Kothagudem Town of Khammam District. The petrographic analysis has been done to ascertain their rank by random vitrinite reflectance (Ro mean %) measurements and quality estimation through maceral analysis, in order to interpret the environment of deposition as well as economic significance. The Index above Queen Seam has vitrinite group of maceral in dominance therefore, contains vitric type of coal whereas; the top and a band in the middle part of the Queen Seam contain coal which is fusic (inertinite rich) in nature. The bottom part of this seam has shown vitrinite in abundance indicating its vitric nature. The random vitrinite reflectance (Ro mean %) study has revealed that the coals of Index above Queen and the Queen seams have attained high volatile bituminous C stage of rank, except for a coal band located between 161.44 m and 162.44 m depth range, which has reached high volatile bituminous B rank. It is also inferred that the vegetal resource of Index above Queen Seam has been deposited during oxic and anoxic moor conditions; however, a distinct change in the climatic conditions to oxic moor with intermittent moderate to high flood situation occurred in the depositional phase of the Queen Seam. The study also suggests that coal deposits in this region have significantly high economic potentials.