Russia’s Gazprom Neft has been forced to revise downward its output plateau at the Badra oil field in Iraq, which has proven to be more geologically complex than previously thought, a company executive told Reuters.

Production at Badra started in 2014. It has reached 85,000 barrels per day (bbl/d).

Initially, an international consortium which includes Gazprom Neft, South Korea’s Korea Gas Corp. (KOGAS), Malaysia’s Petronas, Iraq’s OEC and Turkey’s TPAO, planned to reach peak production of 170,000 bbl/d.

However, Denis Sugaipov, head of Gazprom Neft’s department of large projects, said the consortium has proposed to the Iraqi government setting the output plateau for the next few years at around 85,000 bbl/d.

“Now, we are producing 85,000 bbl/d and believe we have achieved an effective plateau,” he said.

So far, investments into the project have amounted to $4.0 billion, including $1 billion for a gas processing plant. By 2030, the consortium will invest an additional $2.5 billion.

Gazprom Neft’s first deputy chief executive Vadim Yakovlev has said Badra had been expected to reach a plateau of 110,000 bbl/d in the future.