Petrographic evaluation of the coal seams from Gundala area, Godavari Valley Coalfield, Andhra Pradesh, India

Abstract

Gundala area represents the north-western extremity of Lingala-Koyagudem Coal Belt, Godavari Valley Coalfield. Andhra Pradesh. The sub-surface explorations from the virgin tracts of Gundala area revealed the existence often coal seams. Representative coal samples collected from seams III A, III (Top), III (Bottom), L-1, IV A, V(Top) and V(Bottom), pertaining to Bore Hole No. SGK-124 and III (Top), III (Bottom), L-1, IV A and V seams of Bore Hole No. SGK-128 have been critically analyzed for their maceral constitution and vitrinite reflectance measurements to understand the quality, rank, depositional environment, besides the economic and coal bed methane potentialities.
 Based on the ternary mineral matter free (m. m. f.) maceral plotting, it has been inferred that, various coal seams intersected in Gundala area, in general contain mixed type of coal, barring V Top (Bore hole No. SGK-124) and III Top (Bore hole No. SGK-128) seams, which contain vitric type of coal. However, liptinite rich coal has been recorded from III Bottom seam of Bore Hole No. SGK-124. The vitrinite reflectance (Ro max %) has been recorded between 0.47 and 0.60%, which suggests that the coal has attained high volatile bituminous C stage of rank. Existence of low (8 to 21 %) frequency of mineral matter indicates the better quality of coal, which may find its commercial utility. The maceral constitution suggests that the coal deposits of this basin have evolved with prolonged spell of cold climatic condition, besides a few dry oxidizing spells. The slowly sinking basin has received continuous input of vegetal resource. The facies model based on maceral and mineral matter contents of these coals have shown the development of alternate oxic and anoxic moor at the depositional site.