Iran has discovered an oil oilfield in the Caspian Sea for the first time in over a century, the Fars news agency reported.

The deposit was found at a depth of 2.5 kilometers (1.5 miles) during drilling on a natural-gas field and may contain 10 billion barrels of crude, according to the National Iranian Oil Co., the news agency reported.

The discovery is the first in the Caspian Sea for 104 years, Fars noted, citing the National Iranian Oil Company.

While Iran is the second-largest oil producer in the Organization of Petroleum Exporting Countries (OPEC), following Saudi Arabia, most existing fields are in the south and the Arabian Gulf. 

The Islamic Republic does not yet extract crude in the Caspian, where nations including Azerbaijan are tapping large deposits and demarcation lines over territorial claims are disputed.

“Iran has never found anything in its section of the Caspian because it’s deep water, so these would be the first wells ever drilled,” said Robin Mills, head of consulting at Dubai-based Manaar Energy Consulting and Project Management. “Ten billion barrels is certainly something to talk about. The question is whether Iran has the technology to develop it.”

Iran currently has proven crude reserves of about 151 billion barrels, according to the OPEC website.