The present study has been carried out for fresh estimation of Gondwana and Tertiary coal reserves in India from mineable and unmineable point of view as per their depth of occurrence. The re-estimated coal reserves are about 467 billion tonnes (bt), which are more than double the presently known coal reserves of about 213 bt estimated by Geological Survey of India (GSI). Further, the re-estimated reserves are segregated into shallow (mineable) and deeper (unmineable) categories of 161 bt and 306 bt, respectively. An interesting point emerging out of this study is that much more than the Gondwana coal reserves of 213 bt, are the reserves of Tertiary coals re-estimated at about 254 bt down to the depth of 1500 m. Gondwana coals of 213 bt have been further sub-divided into shallow (mineable) of 149 bt and deeper (unmineable) of 64 bt. The Tertiary coals of 254 bt have also been further sub-divided into shallow (mineable) of 12 bt and deeper (unmineable) of 242 bt. Out of the 242 bt deeper (unmineable) Tertiary coals, 123 bt occur in Gujarat, 100 bt in Rajasthan and 19 bt in Tamilnadu. Out of 467 bt of reserves, 66% are deeper (unmineable), which need to be tapped by alternate means. Three pronged strategy for their exploration and exploitation is suggested. (1) Mining; of shallow coals/ lignites occurring at the depth of less than 300 m for power generation and industrial uses. (2) Underground Coal Gasification (UCG); of low rank coals (lignite to sub-bituminous) occurring at moderate unmineable depths of 300-600m, where seams are relatively thicker (>3m), persistent with competent overburden strata and without much aquifer interference, and (3) Coalbed Methane (CBM) Extraction; from deeper (600-1500 m) unmineable coals of sub-bituminous to bituminous rank.
