China's first set of subsea capping stack Photo: courtesy of CNOOC

China's first set of subsea capping stacks have been successfully tested in deep water in the South China Sea, with measured performance output meeting international advanced levels.

The trial marked a major breakthrough and filled the technical gap in the field of deep-water oil and gas emergency equipment development in China. 

The development means that China's offshore oil equipment manufacturing sector has entered world-class levels, according to a document sent to the Global Times from China National Offshore Oil Corp (CNOOC) on Wednesday.

The subsea capping device is a major type of offshore well control equipment, which integrates mechanical, hydraulic, sealing, acoustic and information technology, according to an industry report.

China's first set of subsea capping stack made trial run at the South China Sea. Photo: courtesy of CNOOC

Zhang Chong, a senior engineer of the device at CNOOC, said that the subsea capping stacks can operate at a water depth of 3,000 meters and weigh more than 130 tons, equivalent to the combined weight of three modern battle tanks.

The device will be stored in the offshore oil and gas exploration logistics base located in China's coastal areas. The operating cost is 40 percent less than that of similar equipment used in foreign countries, and boasts a superior emergency response time as well as enhanced equipment support for the efficient disposal of domestic offshore oil and gas blowout emergencies.

"Blowouts are the most serious accidents in oil and gas exploration and development. The environment of the offshore oil industry, especially deep-water exploration, is more complex than the onshore environment. The challenge of handling blowout accidents is greater, and the need for special treatment methods is more urgent,�?said Liu Shujie, deputy general manager of CNOOC's Hainan branch.

The Deepwater Horizon oil spill in the Gulf of Mexico in 2010, the largest marine oil spill in history, was handled effectively by the use of the most advanced subsea capping device, Liu noted.

The use of a capping stack to control a flowing well has been part of the industry's response tool kit for some time. The capping stacks have flanges and intervention adapters installed to either shut in the well while a relief well is drilled, or to have intervention equipment rigged up to stop the flow, according to a report by the International Association of Oil & Gas Producers published in February 2020.