ConocoPhillips is to farm into three of Cairn Energy’s blogs off the coast of Senegal.

The deal, subject to government approval, will see Conoco taking a 25% stake in three contiguous blocks, with Cairn retaining a 40% stake and ownership.

Terms of the deal have not been disclosed, although Conoco will pay a portion of back costs on the block along with future exploration charges.

“The strategic farm-out means Cairn is able to intensify its plans to explore its acreage offshore Senegal, where the gross prospective block wide resource potential is estimated to be in excess of 1.5 billion barrels,” said Cairn chief executive Simon Thomson.

“The transaction is in line with Cairn’s strategy of balancing material frontier exploration alongside sustainable levels of financial commitment.”

Exploration work is targeting up to 1.5billion barrels on the sites, with a proposed two-well programme. Drilling work by the Cajun Express rig is due to start in the first half of 2014.