The approval from the authorities means the firm will double its interest in licence 0010, and planning for a well on the Delta prospect offshore Namibia can now begin.
Tower's chief executive, Graeme Thomson said today that Repsol was one of the foremost experts in West African offshore exploration.
"Planning for drilling the Welwitschia well on the Delta prospect, which our CPR [competent person's repot] indicates has multi-billion barrel potential, can now progress in earnest," he said.
Given market conditions it is now expected that the tender and procurement processes for the long-lead items could take around a year, he added.
Tower's Namibian licence is targeting the giant Delta structure with five targets estimated to contain 9.3 billion barrels of recoverable oil and 14.5 trillion cubic feet of gas.
Tower shares rose 5.15% to 2.55 pence in early deals.