Aberdeen-based Bridge Energy said it estimates the Asha find contains between approximately 30 and 100 million barrels oil equivalent recoverable resources within licence PL457.
When the find was announced in December, the company said it was estimated to contain between 25 million boe and 35 million boe. The AIM and Oslo-listed Bridge Energy said the revised estimate took account of additional information obtained by the operator of the licence, Wintershall.
It said the Asha discovery well encountered "good-quality oil in excellent reservoirs".
Tom Reynolds, chief executive of Bridge Energy, said: "I am very pleased to announce this positive development on the Asha oil discovery, which shows increased commercial resources situated close to the other significant developments in the area."
Bridge, which has a 20% interest in licence PL457, said an external auditor was evaluating the Asha resource numbers.
The company also has a 4% stake in the Taqa-operated Cormorant East field in the UK North Sea. The field was shut on January 15 as a precaution after hydrocarbons were detected inside one of platform's legs.
Shares in Bridge closed up 15.5p at 120p.