China’s CNOOC Ltd. said it has agreed to buy Canadian oil and gas producer Nexen for $15.1 billion in cash.

CNOOC, one of China’s three major state-owned oil producers, said Monday the deal will expand its currently limited presence in Canada, Nigeria and the Gulf of Mexico.

The offer of $27.50 a share is a premium of 60 percent to Nexen’s closing price Friday on the New York Stock Exchange.

CNOOC said it expects the takeover to be finalized in the fourth quarter of this year.