UPDATE, 7/24/12, 6:00 p.m. EDT: Legal Week reports that Herbert Smith is advising CNOOC on UK and European Union aspects of the deal, with a team lead by competition head James Quinney and energy partner Simon Tysoe. Also, additional Stikeman Elliott partners have been added to the article in the seventh paragraph.

China National Offshore Oil Corporation (CNOOC), the state-owned energy giant, said Monday that it will pay $15.1 billion to acquire Canadian oil and gas company Nexen Inc. CNOOC will also assume $4.3 billion of Nexen debt.