Cairn Energy and its partners have discovered oil at the FAN-1 exploration well, located about 60 miles offshore Senegal.
Located in the Sangomar Deep block, the FAN-1 well was drilled to a total depth of 16,164ft in about 4,700ft of water.
The Cajun Express semi-submersible drilling unit was used to drill the well, which is the third in Cairn Energy’s North West Africa programme and the first in Senegal.
Several samples indicated that the oil types discovered range from 28 degrees API to 41 degrees API.
Initial gross estimates for the FAN-1 well range from 250 million to 2.5 billion barrels.
Cairn Energy owns a 40% working interest (WI) in three Senegal offshore blocks: Sangomar Deep; Sangomar Offshore; and Rusifique, which cover 7,490 km².
ConocoPhillips holds a 35% WI while FAR and the Senegal national oil company, Petrosen, own 15% and 10% WI respectively.
Cairn Energy CEO Simon Thomson said: "The oil discovered in the FAN-1 prospect is an important event for Senegal and the Joint Venture.
"We have encountered a very substantial oil bearing interval, which may have significant potential as a standalone discovery. Furthermore, this result materially upgrades the prospectivity of the block with a proven petroleum system and a number of deep fan and shelf prospects established.
"Work is already underway with the Joint Venture partners to determine follow up activity, which is targeted for 2015 onwards."