Aberdeen-based Faroe said a well drilled near the Pil discovery had also found oil, boosting hopes that the find could be bigger than expected.
Chief executive Graham Stewart said: "We are very pleased to announce the results of this successful side-track appraisal well on the Pil discovery, which proves further resource potential in this already significant discovery."
The successful well result on this Pil appraisal side-track adds further value to Faroe's already substantial position in this prolific part of the Norwegian Sea, and we aim to unlock further potential in this exciting core area."
Faroe plans to start drilling a separate side-track well in coming days to test the Bue prospect, which it said could add further volumes to the Pil discovery.
Faroe said initial results from the appraisal well indicate a hydrocarbon-bearing reservoir section with approximately 80-metres of oil.
In March, the company said the Pil discovery well encountered a hydrocarbon-bearing reservoir section with approximately 135-metres of oil and 91-metres of gas.
The company has a 25% interest in the Pil licence, which is operated by VNG Norge AS with 30%.
Shares in Faroe Petroleum closed up 0.75p at 139p.