Better understandings are made on the basic petroleum geologic settings of petroliferous basins on the Chinese offshore continental shelf as a result of extensive exploration done in last decade. Indicated by more and more available data, there does exist conditions for forming major oil/ gas provinces on the Chinese offshore continental shelf, and four major oil/gas rich provines. Foreseeing the future of Chinese offshore petroleum industry, it is of optimistic prospects and gives more confidence.
GENERALS OF CHINESE OFFSHORE PETROLIFEROUS BASINS
China has traditional territory sea of 4.73 million square kilometers, and the offshore continental shelf covers about 1.3 million square kilometers. Eight petroliferous basins lie from the North to the South, Le. Bohai Gulf basin, Yellow Sea basin, East China Sea basin, S-W Taiwan basin, the Pearl River Mouth basin, S-E Q iong basin, Yinggehai basin and Beibu Gulf basin, offering an effective are for exploration of about 600,000 square kilometers (Figure 1 &2).-
They are all different types of Tertiary developed rift basins, characterized by large basin size, thick sedimentary section, multiple cycles, massive lacustrine and swamp source beds and multiple reservoir - cap associations, and various trap plays. As indicated by exploration results, these basins are all of good petroliferous potential (Figure 3 & 4).
As evaluated many times by foreign petroleum geologists, the total oil and gas resource potential offshore China is estimated to be in the range of 12-49 billion tons. Chinese geologists have also done evaluations in 1980s, giving an estimated resource potential ranging from 9 - 14 billion tons (Figure 3).
Since 1979, China began with the cooperative exploration activities with foreign oil companies in Bohai Sea, Yellow Sea, the Pearl River Mouth, S-E Qiong and Beibu Gulf areas, and launched concurrently the self financed exploration programmes in Liaodong Bay and Beibu Gulf. By the end of 1988, a total of 390,000 km seismic lines have been shot, 153 wildcat wells drilled, and 48 oil/gas bearing structures discovered, giving a success ratio of 31%.
Up till now, three offshore oil fields have been onsream and 13 fields are under development or feasibility study for development. Among which, two oil fields have reserve greater than 200 milloin tons each, and one large size natural gas field.
FOUR POTENTIAL MAJOR OIL/GAS PROVINCES
Based on the excellent petroleum geological conditions offshore China and the exploration results, it is certain that there are conditions forming large oil/gas provinces on Chinese offshore continental shelf. And four major oil/ gas provinces are possibly existing.
1. Ying-Qiong gas province
The region surrounds Hainan Island, and subordinates Yinggehai basin and S-E Qiong basin, having excellent geological conditions for a large gas province (Figure 5).