Supermajor Shell has spudded what will be a closely watched ultra-deepwater wildcat offshore the West African island nation of Sao Tome & Principe.

The two-island country has previously hosted exploration wells, but these have been drilled in the joint development zone (JDZ) with Nigeria which hosts an extension of the prolific Niger Delta basin.

One non-commercial discovery was drilled 16 years ago in the JDZ — located north-west of the islands — by Chevron and is called Obo.