ONGC Mittal Energy, the joint venture company floated by ONGC and Mittal Steel, has won a highly prospective oil block in Nigeria.The JV company bid $100 million for Nigeria's OPL-246 after the licence of South Atlantic Petroleum (Sapetro) for the block was revoked, industry sources said.The joint venture outbid INC Natural Resources and BG-Sahara at an auction held on October 4 shortly after Sapetro lost a legal challenge against a government decision to revoke the licence.OPL-246 is the relinquished area of the billion-barrel Akpo oilfield of Sapetro, which is part-owned by Theophilus Danjuma, former defence minister of President Olusegun Obasanjo, who fell out with him after opposing a campaign to extend Obasanjo's hold on power.ONGC had, in January, lost out on acquiring Sapetro's 45% stake in Akpo to China's CNOOC after the Indian government disallowed the state-owned firm from proceeding on the transaction where it was the highest bidder.ONGC-Mittal has to pay 25% of the $100 million as signature bonus for OPL-246 this week, failing which it would lose the block to INC, which was designated the reserved bidder.An ONGC official said the company was "studying the prospects" and will take a decision shortly on the issue.