LAGOS — Esso Exploration and Production Nigeria, an ExxonMobil affiliate, has started the $1 billion Usan infill drilling project in OML 138 with the arrival of an ultra-deepwater drillship. The project aims to add up to 40,000 barrels per day within 18 months. Separately, regulator data show that local refineries received 53.7 million barrels of crude in the second quarter under the domestic supply obligation.