Drilling operations began towards the end of 1902 in Chiah Surkh, a likely oil-bearing area near the border with Iraq.

With only one third of Colombia's oil-bearing area explored, Ecopetrol will accept a new round of exploration bids in October.

Initial negotiations are understood to have begun but much of the violence that has flared before, during and after the Jan. 9-15 referendum, occurred in oil-bearing areas like the hotly disputed Abyei region, which straddles the border.