PetroChina's largest oil discovery in a decade boasts more reserves than estimated, it was confirmed yesterday - a shot in the arm for both the company and the country's energy security.

Jidong Nanpu Oilfield in the Bohai Bay has combined proven, probable and possible reserves of as much as 1.18 billion tons of oil equivalent, the Ministry of Land and Resources of China certified yesterday.

The proven reserves are certified at 445 million tons oil equivalent.