Gujarat Chief Minister Narendra Modi claims that Gujarat State Petroleum Corporation (GSPC) has made India's largest-ever gas discovery, but the firm's Canadian partner firm - Geoglobal Resources - downplayed the find saying it was premature to quantify reserves."Testing has proved gas is present at good production rates, but it is premature to quantify the amount of proved and probable natural gas reserves," Geoglobal, a US-based publicly traded oil and gas company, said in its filing to the bourses.Geoglobal holds 10%stake in the shallow water Krishna Godavari basin block KG-OSN-2001/3 where, according to Modi, more than 20 trillion cubic feet of gas reserves has been struck. GSPC is the operator of the block with 80% stake."Additional testing and technical evaluation must be completed, and more exploratory wells must be drilled in order to establish the extent of the field and to estimate the natural gas reserves discovered," Geoglobal said.V K Sibal, director general of the Directorate General of Hydrocarbons, too had opined that estimation of reserves based on just one well was premature.Geoglobal said its interpretation of 3D seismic indicates that the KG-8 (the well that has found to be containing gas and thereafter named Deendayal) may cover a 100 sq km area. "Further exploratory drilling over the coming months at about 4 km stepouts to the east of the KG-8 well is intended to delineate the extent of the structure."