The petroleum geology in China has been reported by several authors and the outline of the geologic conditions of the oil and gas fields in China can be understood through the published papers. It was reported that more than 50% of the Chinese petroleum production was from the Ta-ch'ing oilfield
in the Sung-liao basin, Northeast China, in which the non-marine sediments of the Mesozic and Tertiary ages were deposited. Thus, the non-marine sedimentary basins rated highest in petroleum production in China. However, it is considered by the present author that the marine and paralic sediments of the Paleozoic and Mesozoic ages are of importance to the future petroleum exploration in China, especially in the inland regions of the continent. From this standpoint, the geological and geochemical aspects on the following items are described.
1) 382 oilfield in Tibet.
This oilfield is located on an elevation of about 4, 000 meters and some 300km north of Lasa. Petroleum has probably been produced from the marine sediments of the Paleozoic and Mesozoic ages or the Tertiary lacustrine sediments.
2) Newly discovered oil and gas reservoirs in the Southwest Tarim basin.
In the new oilfield located in between Aksu and Kashgar, Sowthwest Tarim basin, petroleum is probably produced from the marine and paralic sediments of the Mesozoic and Tertiary ages.
3) Geologic horizons of oil and gas reservoirs in the Central-Eastern China.
The commercial petroleum production in the Jen-ch'iu and Sheng-li South oilfields was reported from the marine Paleozoic reservoirs. In the Szechwan basin, hydrocarbons have been produced from the marine Permian and Triassic reservoirs and from the non-marine Jurassic ones. In the Ch'ien-chang oilfield
in the Tung-t'ing basin, the petroleum production is from the Devonian and Carboniferous reserviors. Thus, in the sedimentary basins along Yang-tze River, the marine Paleozoic and Mesozoic sediments including carbonate rocks, sandstones and shales probably are of importance to hydrocarcon exploration, bec-
ause, it was reported by the Chinese exploration geochemists that in China even the Sinian carbonate rocks still keep up the potential for petroleum generation.
4) Natural gas in the coastal areas along the East China Sea.
Many gas producing locations were found in the area. In the sedimentary basin near Shang-hai, the thickness of sediments ranges from 4 to 6km or more. It is considered by the author that the marine Paleozoic and Mesozoic sediments, the probable continental and paralic Tertiary sediments and the paralic
Quaternary sediments are the main targets for hydrocarbon exploration in the Shang-hai area. In addition to this, in the South-East China, small but many sedimentary basins filled with the Mesozoic lacustrine deposits of only from several ten to several hundred meters thick are the economic exploration targets.
As a conclusion, it is supposed that the marine and paralic sediments of the Paleozoic and Mesozoic ages in China have higher potential in hydrocarbon resources than have been estimated.
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