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.
That development consists of a 22-mile tie-back of three subsea wells to the existing Laggan-Tormore production system.
Gas from Laggan-Tormore is exported to the onshore Shetland Gas Plant via a 90 mile long pipeline.
Arnaud Breuillac, president of exploration and production at Total, said: “Glendronach is a significant discovery for Total which gives us access to additional gas resources in one of our core areas and validates our exploration strategy.
“Located on an emerging play of the prolific west of Shetland area, the discovery can be commercialised quickly and at low cost by leveraging the existing Laggan-Tormore infrastructure.”
Total has a 60% operated interest in Glendronach, while partners Ineos and SSE each have 20%.
SSE wholesale director Martin Pibworth said: “This discovery represents a major addition to SSE’s recoverable gas resources. Gas production assets are a natural complement to SSE’s interests in gas-fired power generation and gas supply to business customers.
“They are expected to add to SSE’s earnings from gas production in due course. In the meantime, we will continue to support exploration and appraisal activities around our existing assets.”