China's giant oil and gas conglomerate Cnooc Ltd. said early Monday it will pay $15.1 billion in cash for Canadian oil and gas company Nexen Incorporated (NYSE: NXY), among whose assets are large oil sands and shale gas properties.

Nexen's board, which approved the deal, will call a shareholder meeting for the third quarter to vote on the takeover proposal by China's largest offshore oil and gas producer. Cnooc said in a statement that the acquisition will contribute to the company's long-term, sustainable growth.

Shares of Nexen, which holds properties in western Canada, the Gulf of Mexico, the British North Sea and offshore Nigeria, shot up 56 percent to $26.63 in premarket trading.