The exploratory wells confirming existence of natural gas reserves were drilled in 1972–1974.
[4] Before production started in 1982, recoverable reserves of natural gas were estimated about 60 trillion cubic feet (1.7×10^12 m3).
[2] In 1992, its estimated recoverable reserves were 48.7 trillion cubic feet (1.38×10^12 m3) of natural gas.
[1] In 1997, the United States independent consultancy DeGolyer and McNaughton certified recoverable reserves at about 25 trillion cubic feet (710×10^9 m3).
[2] In 2005, the Asian Development Bank estimated gross reserves 49.5 trillion cubic feet (1.40×10^12 m3).