The contract is for five offshore blocks in waters off the African nation and covers a total area of about 29,000 sq km (11,200 sq miles) with water depths from 500 m to 2,500 m (1,640 ft to 8,202 ft), it said in a statement.
The first phase of the exploration period is four years, with five CNOOC subsidiaries serving as operators in the exploration and development phases, having independent operator rights and interests.
ENH owns the remaining non-operating interests.
CNOOC's gas and power unit Singapore Trading and Marketing in 2019 signed a 13-year sale and purchase agreement with Mozambique LNG1 Company for liquefied natural gas (LNG) from the Mozambique Area 1 onshore LNG plant.
At an earning briefings in March, CNOOC said it planned to focus on increasing reserves and production this year.