China extracted 861,400 cubic meters of natural gas from combustible ice during a one-month trial production in the South China Sea, the Chinese Ministry of Natural Resources announced on Thursday.

The trial mining was conducted at a depth of 237-304 meters undersea in the Shenhu sea area, about 320 kilometers southeast of Zhuhai City in Guangdong Province, from February 17 to March 18.

China has set two world records in terms of the total gas output in a month and the daily gas production of 28,700 cubic meters.

The latest test adopted a horizontal well drilling technique, the first time it has been used in the natural gas hydrate extraction, which has greatly increased the gas production, according to the ministry's China Geological Survey.

Qin Xuwen, deputy director of the Guangzhou Marine Geological Survey, said Chinese scientists have achieved gratifying results after two years' efforts and made new breakthroughs in key technologies and core equipment.

"We have overcome the worldwide problem of using a horizontal well drilling technique in deep sea's shallow soft layer, developed 32 key technologies including the horizontal well drilling in deep sea's shallow soft layer and 12 pieces of core equipment including the deep sea's wellhead suction anchor," said Qin, who is also deputy commander of this year's natural gas hydrate extraction mission.

Qin said an environmental monitoring and warning system was introduced during the whole exploitation process to protect the undersea structure and marine ecology. The monitor results show there had been neither methane leakage, nor environment pollution or geological disaster, he said.

Combustible ice is a natural gas hydrate trapped in ice crystals formed under high pressure and low temperatures in permafrost or under the sea. It can be ignited like solid ethanol, which is why it is called combustible or flammable ice.

Combustible ice that contains 88 percent to 99.9 percent of methane is an efficient, abundant and clean energy. Like natural gas, it can be used for household gas consumption, motor fuel supply, chemical industrial production, city heat supply and electricity generation.

Mining of combustible ice started in the 1960s, but China began research in 1998. China found flammable ice in the South China Sea in 2007 and conducted its first experimental gas extraction in 2017.

The first exploitation test succeeded in producing a total of 309,000 cubic meters of natural gas in a 60-day period.

"Compared with the exploitation test in 2017, we adopt a brand-new drilling technique that enables the one-month trial gas production to be 2.8 times the two-month output in 2017 and has greatly improved the daily gas production," said Qin.

The combustible ice reserve in China's waters is equal to around 80 billion tons of oil and boasts a bright future. The improvement in gas scale and efficiency will bring China's combustible ice mining on to a fast track.