Statoil is to buy a 30 percent interest in block 47, on undisclosed terms, joining Royal Dutch Shell Plc
London-based Tullow will retain a 70 percent stake.
Tullow has bought exploration rights to large swathes of territory offshore French Guiana, Suriname and Guyana, hoping to replicate its success in finding big fields offshore West Africa.
The company believes the regions have shared geology stemming from when Africa and South America were still connected many millions of years ago.
In September, the theory was boosted when Tullow announced its Zaedyus well, in which Shell and Total have stakes, struck oil offshore French Guiana.
Analysts welcomed the 'farm-down'.
A very sensible move by Tullow to capitalise on the Zaedyus success/ growing interest in the Guyanas Trend by introducing a larger partner, Phil Corbett, analyst at Royal Bank of Scotland, said in a note to clients.
Tullow shares traded down 0.8 percent at 0804 GMT, in line with the STOXX Europe 600 Oil and Gas index <.SXEP>, while Statoil was down 0.6 percent.
(Reporting by Tom Bergin; Editing by Jon Loades-Carter and Erica Billingham)