Fu earlier told reporters that the company would focus on "cooperation" to boost its overseas output.

"A cooperation with Ghana National Petroleum Corp would help CNOOC reduce risks in the deal," said Han Xiaoping, a veteran energy analyst.

CNOOC is reportedly bidding for 6 billion barrels of oil, equivalent to one in six barrels of proven reserves in Nigeria, the second largest oil producer in Africa.

The overall value of the offer has not been disclosed, although some details suggest a figure of about $30 billion, the Financial Times reported.

The company's potential bid came after Nigeria's oil licenses were set for renewal. Global oil giants including Shell, Chevron, Total and ExxonMobil control or partially control 23 oil blocks in Nigeria, among which 16 licenses are set to expire.

CNOOC, together with China's second largest oil company Sinopec, in July agreed to buy a stake in an Angolan oil block from US oil major Marathon Oil. The Chinese companies would form a 50-50 venture and pay $1.3 billion for a 20-percent stake in the highly prospective block, which has already yielded 12 discoveries.

According to a report by China National Petroleum Corp (CNPC), State-owned companies had successfully made seven acquisitions of overseas oil and gas assets cumulatively worth 82 billion yuan by September this year.

This represents an 80-percent increase compared with the same period last year, it said.