The Karish field, about 100 kilometers (62 miles) off Israel's coast, was the latest in a series of discoveries in recent years in the eastern Mediterranean, though it is much smaller than the nearby Tamar and Leviathan fields that turned Israel into a potential gas exporter.
It also holds an estimated 12.7 million barrels of condensate, the Israeli partners in the project, Delek Drilling and Avner Exploration, said.
The 1.8 tcf estimate, given in a resources report by petroleum consultants Netherland, Sewell & Associates, is similar to a preliminary estimate made by Texas-based Noble Energy, which is leading the development of the well.
The announcement came as Israel is settling on its export policy. The government last month decided Israel would keep most of its reserves for domestic use and allow 40% to be sold abroad, though some lawmakers are still trying to get the export quota lowered.
"This is further proof of the strength of Israel's energy market and the importance of continued exploration – because if you search, you find," Avner chief executive Gideon Tadmor said.
Noble has a 47.06% stake in Karish, while Avner and Delek Drilling each have a 26.47% share.