Chinese refiner Sinopec has agreed to buy Canadian oil and natural-gas exploration company Addax Petroleum Corporation for $7.2 billion, gaining access to reserves in West Africa and the Middle East. Addax said Wednesday its board unanimously approved the deal, which is subject to regulatory approval. Sinopec, China's biggest refiner, urgently needs to expand upstream international assets to help protect against spikes in global crude prices that have caused it to post billions of dollars in losses in recent years due to caps on domestic fuel prices. The acquisition by Sinopec, a subsidiary of China Petrochemical Corporation, is the latest effort by Chinese energy firms to expand and diversify overseas assets, as Beijing seeks to secure resources for the country's future growth.