French oil major Total said today that its Glendronach prospect could contain one trillion cubic feet (tcf) of gas.
The Stena Don semi-submersible rig started drilling the well in May and encountered a 140 ft gas column.
One tcf equates to about 175 million barrels of oil equivalent.
Initial tests showed good reservoir quality and well production deliverability, Total said.
The company intends to develop Glendronach using infrastructure from the nearby Edradour field.