China's largest oil and gas field, the Changqing oilfield, has produced over 600 billion cubic meters of natural gas, setting a new national record, the country's major oil and gas producer and distributor PetroChina Limited said on Tuesday.

Equivalent to the country's total natural gas consumption for two years, the cumulative production can replace 720 million tonnes of standard coal and reduce carbon emissions by 1.66 billion tonnes, said PetroChina.

Located in northwest China's Ordos Basin, the oilfield has played an important role in optimizing the country's energy structure and improving its ecological environment, it added.

According to the company, around 70 percent of the gas in this field is tight gas –  natural gas trapped within a rock with extremely low permeability, making it extremely difficult to extract.

"We have made breakthroughs in core technologies for gas field exploration and development," said Li Zhanming, executive director at PetroChina Changqing Oilfield Company, adding that they've drilled 14 gas fields under such conditions and increased natural gas production by over 2 billion cubic meters annually.

Researchers used a three-dimensional seismic technology, which is like performing high-precision computerized tomography (CT) scans to discover underground natural gas deposits.

Gas recovery rate at the Changqing Oilfield tight gas reservoir has increased by 15 percent over the past 10 years, and it has become the country's largest natural gas producing region for 12 consecutive years, said Li.

It is estimated that the annual natural gas produced by the oilfield accounts for one fourth of the total domestic gas production, supplying over 40 large and medium-sized cities and meeting the natural gas demand for nearly 400 million people.