Great Eastern Energy Corp (GEECL) will invest up to USD 2 billion over the next 10 years in its Raniganj (south) block in West Bengal to exploit shale gas reserves, its chief executive Prashant Modi said. GEECL's coal-bed methane (CBM) block may hold as much as 6.63 Trillion cubic feet (Tcf) of shale resources, of which about 1.7 Tcf can be recovered, he said. The company expects to start initial shale gas exploration work of drilling core wells in the first half of next year.