China National Petroleum Corp. (CNPC), one of China's leading oil companies, announced on Tuesday the completion of drilling and exploration off the Xisha Islands in the South China Sea.

Signs of oil and gas were found in the operation, known as the Zhongjiannan Project, and the company will assess the data collected and decide on the next step, a CNPC statement read.

CNPC started drilling two wells in May and completed the work on May 27 and Tuesday respectively. The company has been exploring the area since 2004.

The drilling rig provided by China Oilfield Services Ltd. will be relocated to operations in the Hainan Islands.

Qiu Zhongjian, a geologist from the Chinese Academy of Engineering, said that the drilling was well organized, as the CNPC fully considered geological hazards, engineering issues and possible typhoons.

He said he was firmly opposed to Vietnam's disruption during China's drilling operation as the project area lies in the undisputed sea area of China's Xisha Islands.

Preliminary analysis of the geological data acquired has shown that the area, or Zhongjian Sag as it is called, has the basic conditions and potential for oil exploration, but extraction testing cannot begin before a comprehensive assessment of the data, said Wang Zhen, deputy director of CNPC Policy Research Office.

For safety reasons, the test operation was not arranged immediately, because July is the beginning of the typhoon season.

While the project may help improve understanding of the engineering and geological issues in the South China Sea, the development of "deep-sea drilling technology" will also benefit, said Wang.