Petrographic appraisal of coals of sub–surface seams from Belampalli Coalfield, Godavari Valley, Andhra Pradesh

Abstract

The present paper incorporates a detailed information about the maceral composition and the rank (reflectance Ro mean %) assessment of eight sub–surface coal seams, viz. IB, IA, I, IIB, II, III, IV and V encountered in Bore–hole No. 561 from Belampalli Coalfield of the Godavari Valley. The mineral matter free (m.m.f.) maceral study has suggested that the seam IB contain vitrinite rich coal or vitric type of coal where as, the seam IIB has inertinite affluent or fusic coal. However, the seams IV and V have shown almost similar proportion of vitrinite and inertinite maceral groups, thus their coal is of mixed type. The seams I and III are represented by vitric and mixed coal types, whereas, IA and II seams are marked by the presence of vitric, fusic and mixed coal types. Most of the coal seams in general have reached high volatile bituminous C rank, barring the basal portion of the seams IV and V which have reached high volatile bituminous B stage. Similarly, a wide range of variation in vitrinite reflectance (Ro mean%) 0.53–1.1% has been recorded in seam II and thus the coal is of heterogeneous nature, having reached high volatile bituminous C, B and A stage of rank. The facies model (based upon the maceral and mineral matter association) drawn for these coal seams has indicated that the depositional site has primarily experienced alternate oxic and anoxic moor conditions. Since the seams in Belampalli Coalfield have consistency in thickness, vitrinite and inertinite rich constitution, low mineral matter association and has shown wide range of rank (reflectance) variation, therefore, the study area has potential to emerge as a productive centre of economically viable and commercially exploitable Coalfield of the Godavari Valley in near future.