In Hainan offshore area, there are three Cenozoic sedimentary basins distributed Beibuwan, Yinggehai and Qiongdongnan, being as an exploration perspective area for oil and gas resources with a total coverage of 12 X 104 km2. By the end of last century, an OGIP 113 X 108m3 in total had been proven in Hainan offshore area, accounting for about 33% of the proven natural gas reserves in China.
Yacheng13-1 gasfield is the first large offshore gas field in China, which is located in the southern offshore of Hainan island, 100km south of Shanya city. It was discovered at about 100m deep subsea in Aug.1983. In the total area of 349.04 km2 for development, a proven gas bearing area of 45.2 km2 and a proven OGIP 884.96×108m3 have been verified. Arco as the operator has 15% equity holding, Kuwait National Petroleum Corp. 15% and China Offshore Petroleum Corporation 51%. Yacheng13 became the first offshore gas field in China when put into production. With its yearly gas production 34X108m3, 9X108m3 are transported to the sales terminal in Lanjiaozui, HK through 778 km submarine pipeline and 5X108m3 transported to Nanshan base in Shanya through 97km submarine pipeline.
Development in Yacheng gas field is an unprecedented project in China since treatment facilities both onshore and offshore as well as gas transmission pipelines to Hainan island and Hong Kong were to be constructed. A 480 km submarine pipeline to be laid for gas transmission to Hong Kong is the second longest submarine pipeline in the world.