China National Petroleum Corp., the nation's largest oil producer, agreed to jointly develop an oil refinery with Chad as the world's second-largest energy user strengthens its links with the African country.

China National Petroleum signed an accord with the Chadian government on Sept. 20, the Beijing-based state oil company said in its online newsletter China Oil News today, without giving financial details.

Africa is attracting increasing investment from China's state oil companies as they intensify the search for oil and gas to supply the world's fastest-growing major economy. China aims to double its trade with Africa to $100 billion a year by 2010, President Hu Jintao said in November.

China National Petroleum will design and build the refinery north of the capital N'Djamena. Chad, which started oil production in 2003, has 13 oilfields and no refineries, the Chinese oil company said.

President Hu and his counterpart Idriss Deby witnessed the signing of the agreement in Beijing, it said.

China National Petroleum, parent of Hong Kong-listed PetroChina Co., made a commercial oil discovery during its first test drilling in Chad, it said July 30.

The state-owned oil and gas producer acquired seven sedimentary basins in Chad from Canada's Encana Corp. for about $202.5 million, Calgary-based Encana said Jan. 12.