Chinese state-owned oil company Cnooc Ltd. said it will pay $3.1 billion for a 50% stake in a unit of Argentina's Bridas Energy Holdings Ltd. in a move to boost its production and reserves. The deal highlights China's growing thirst for energy resources globally. The Chinese government is encouraging state-owned energy companies to buy assets abroad to power the country's booming economy. The deal is structured as an oil and gas production joint venture. The Beijing-based oil company's unit, Cnooc International Ltd., and Bridas Energy Holdings will each hold a 50% stake in Bridas Corp., which has exploration and production...