China National Petroleum Corp, the country's largest oil and gas producer by annual output, said the company will have more than 10 billion cubic meters of natural gas injected in its gas storage tanks by 2021 to ensure sufficient supply.

Its Shuang 6 gas storage facility in Liaoning province started gas injections on April 25, marking the start of the company's gas injection of all its 10 gas storage tanks, the company said in a press release.

The company, which is better known as PetroChina, vows to continue maximizing production at domestic gas fields while ensuring adequate gas imports to guarantee supply.

The company's peak load regulation capacity of its gas storage tanks was up 24 percent year-on-year during the previous heating season. Gas from the storage tanks contributed 10.88 billion cubic meters, up 55.73 percent year-on-year according to the company, the biggest supplier of gas in China.

Last year saw higher storage levels, which also reduced the country's dependency on foreign supplies, said Li Ziyue, an analyst with Bloomberg NEF. The company said earlier the gas imported from abroad also plays a major role in ensuring sufficient supplies of heating fuel. The company has been negotiating with international peers, including Shell and ExxonMobil, to ensure stable gas supply.