PETROCHINA Co, the nation's largest oil producer, has developed technology to exploit more than one billion metric tons of oil reserves at Daqing, its largest and oldest field, its parent said.

The so-called "well-fracturing" method will help PetroChina drill reserves at Changyuan in Daqing, in Liaoning Province, parent China National Petroleum Corp said in a statement in its newsletter China Oil News yesterday.