(Yicai Global) March 19 -- State-owned China National Petroleum Corp. plans to invest CNY21 billion (USD3.3 billion) to build seven new gas storage facilities in southwest China as it looks to increase its working capacity to meet rising demand.

Two of the gas holders, one in Tongluoxia, Chongqing, and another in Mingyuexia, Sichuan, are undergoing feasibility studies and should start being built this year, Ma Xinhua, general manager of CNPC unit PetroChina Southwest Oil & Gas Field Co., told online business news agency Jiemian in an interview.

During periods of low consumption, energy firms extract natural gas and store it in underground facilities to meet rising demand during peak times and emergencies. The working capacity of China's gas reservoirs make up only 3 percent of the country's total consumption, compared with a global average of 12 percent.

CNPC and fellow state-owned energy giant China Petroleum and Chemical Corp. (Sinopec) have a combined 25 gas storage sites in China. The two firms can produce 11.7 billion cubic meters of gas during peak production times, but national demand can reach between 21 billion and 27 billion cubic meters.

The new facilities will take the country's working capacity to 21 billion cubic meters, Ma said, adding that under plans from the National Development and Reform Commission, China's top economic planner, it should reach 36 billion cubic meters by 2020 and 45 billion by 2025.