The long-term contract will see Cairn engage the rig in multi-well campaign in off Senegal.
According to Cairn, the semi-submersible drilling rig would be used for an initial one-year period on a frontier exploration programme in Senegal, Morocco and potentially other areas.
It will commence work off Morocco on the Foum Draa licence in the second half of this year.
The Cajun Express is designed to drill in deep water but has shallow mooring capabilities, and a 15,000 psi blowout preventer stack.
It had been working on a development well in the pre-salt Lula field off Brazil for state-owned oil company Petrobras.