Beneath the Atlantic's surface off Nigeria's coast, a billion-dollar wager is being placed on the enduring value of what lies beneath. NNPC Limited and ExxonMobil have renewed their deepwater partnership after nearly a decade of dormancy, launching the Usan Infill Project to recover oil left behind by earlier wells and add 40,000 barrels per day to a nation whose energy fortunes have long promised more than they delivered. The meeting in Abuja between the two companies' leaders was less a beginning than a recommitment — a signal that Nigeria's deepwater frontier, battered by underinvestment an