BEIJING, Feb. 7 (Xinhua) -- China's domestically developed submarine oil drilling equipment has been put into operation in the waters near Zhanjiang in south China's Guangdong Province, China National Offshore Oil Corporation (CNOOC) announced Tuesday.

The subsea Christmas (Xmas) tree, a core piece of equipment used in subsea production systems in the petroleum industry, can efficiently increase oil output in mature oilfields.

It is used to connect oil from deep in the formation to external oil and gas transport pipelines. By injecting filtered seawater with a maximum pressure of about 17 MPa into the reservoir, the pressure pumps oil out of deep layers.

The subsea Xmas tree measures 3.5 meters in length, 3.2 meters in width and 3 meters in height, with an overall weight of almost 22 tonnes, according to the CNOOC.

Compared to overseas products, CNOOC's Xmas tree, operating in Zhanjiang's Weizhou Oilfield, reduces weight by 40 percent and cuts costs by 60 percent. It is expected to increase annual output by 50,000 tonnes in shallow waters.

The operation of the new system has validated the safety and reliability of the domestically manufactured equipment, which is crucial for promoting the development of offshore oil and gas-related technologies.