Russia’s Rosneft and ExxonMobil began drilling Russia’s northernmost well Monday.
The joint-venture project, named Karmorneftegaz, will drill at the Universitetskaya-1 block in the Kara Sea for two months.
The Kara Sea is part of the Arctic Ocean and is located north of Siberia.
The block covers 49,000 sq mi (126,909 sq km) and could contain up to 9 billion barrels of oil, Bloomberg said.
Universitetskaya-1 could be worth as much as $900 billion.
The project is expected to cost upwards of $600 million.
Official estimates put Kara Sea reserves at around 36 billion barrels of oil.
The West Alpha rig will drill in the Universitetskaya-1 block up to a maximum depth of 4.35 mi (7 km).
The West Alpha is a semi-submersible owned and managed by Norway-based North Atlantic Drilling.
Exxon currently operates the rig.
The Universitetskaya-1 block is only the first in of many planned joint ventures between Exxon and Rosneft.
Exxon will take on exploration and development costs and recoup its expenses once production starts.