By Chris Hogg
BBC News, Hong Kong
CNOOC, one of China's largest state-run oil and gas producers, has agreed to buy a stake in a Nigerian offshore oil and gas field for $2.3bn (£1.3bn).
The Niger Delta is an area attracting interest from international firms
It will buy a 45% stake in the license covering the OML 130 field, which is owned by South Atlantic Petroleum and is in deep water near the Niger Delta.
CNOOC is hunting overseas oil and gas assets to supply its domestic market.
China's appetite for commodities such as oil and gas is second only to that of the United States.
The OML 130 field covers almost 500 square miles, and was first discovered six years ago.
It is reported to need billions of dollars of investment before it comes on stream in two years time.
Company chairman and chief executive, Fu Chengyu, said the purchase would give CNOOC access to "an oil and gas field of huge interest and upside potential, located in one of the world's largest oil and gas basins".
CNOOC is one of four big oil companies created when China's oil industry was restructured seven years ago.
Its parent company is controlled by the Chinese government.
CNOOC shares were suspended before the start of trading in Hong Kong on Monday, ahead of the announcement.
The company has bought access to overseas oil and gas resources in a number of countries in recent years, including Indonesia and Australia.
Last year CNOOC failed to buy US firm Unocal following what it called unprecedented political opposition to its plans from US lawmakers.
The deal still needs to be approved by the Nigerian National Petroleum Corporation and the Chinese government.