An oil and gas field off Guyana’s coast and owned by Tullow, Total and Eco Atlantic has about 3.9 billion barrels of oil equivalent (Bboe), a third more than announced in an estimate released in September, Eco said March 18.

The Orinduik Block is located next to an Exxon Mobil field, which has an estimated 4 Bboe. The Exxon discovery made Guyana one of the world’s most closely watched oil basins.

Tullow, the operator of the Orinduik Block, has a 60% stake, Total has 25% and Eco Atlantic Oil and Gas has 15%.

Eco said the Orinduik Block contained 3.5 billion barrels of recoverable oil and 2.84 trillion cubic feet of associated gas, based on a metric called unrisked prospective resources P50 (best). The company said the upgrade followed additional 3-D processing and interpretation of seismic data.

The company said first well would be drilled in June and partners in the project were in the process of approving a second well.

“We hope to confirm drilling plans for well number two in the near future to take advantage of the economics of our rig on the block,” Eco said.