THE OCCURRENCE AND DISTRIBUTION CHARACTERISTICS OF CRETACEOUS IN THE SOUTH YELLOW SEA BASIN AND THE TWO TYPES OF SOURCE ROCKS

The South Yellow Sea Basin is the only large petroliferous basin in China, in which no industrial discovery has been made since the first finding in the Cretaceous shale 27 years ago. It's proposed that the Cretaceous mainly in the northern part of the basin after the analysis of the South Yellow Sea Basin Cretaceous exploration and research status.So far, there have been a total of 8 wells approached the Cretaceous in the basin. The Taizhou Formation of upper Cretaceous consists of dark-grey deposits, while the Pukou Formation of lower Cretaceous is dominated by red rocks in a sequence similar to that in the Subei Basin. The latest seismic line shows that there are erosional tops indicating disconformity between the Neocene and Paleocene, inclined layers and residual deposits, and some secondary concaves. Though the field survey around the Lingshan Island and the abundance, type, maturity of organic material in oil source rock and LA-ICP-MS and U-Pb, we found that there are many sets of dark grey or black coal-bearing mudstone, in which the free hydrocarbon accounts for 0.02 to 0.07 (mg/g) or zero, the oil genetic potential is 0.06 to 0.03 (mg/g) or zero, the residual organic carbon ranges from 1.85% to 1.99% or from 0.70% to 1.99%, the oxygen index is 4 or more than 10. Upon the data, we can recognize two kinds of source rocks, one for generation of hydrocarbon and the other for generation of CO₂. In conclusion, the Cretaceous in the South Yellow Sea Basin has great hydrocarbon potential. Further investigation is required.