南黄海盆地白垩系油气赋存特征与2类烃源岩
THE OCCURRENCE AND DISTRIBUTION CHARACTERISTICS OF CRETACEOUS IN THE SOUTH YELLOW SEA BASIN AND THE TWO TYPES OF SOURCE ROCKS
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摘要: 南黄海盆地是中国海域历经54年勘探至今尚未实现工业油气发现的唯一大型含油气盆地,特别是29年前发现的白垩系黑色页岩含轻质油,属于页岩油范畴。分析了南黄海盆地白垩系勘探研究现状,提出白垩系主要分布于盆地北部,有8口井钻遇,K1系红浦口组,K2系黑泰州组,与苏北盆地近似;在最新地震测线上表现为顶蚀,与古/新近系及下伏侏罗系均呈不整合接触,斜层状分布,残留沉积,部分构成次凹的特征。通过近海灵山岛露头调查、剖面实测和包括常规生油岩有机质丰度、类型、成熟度、等离子质谱、U-Pb同位素年龄等测试,发现下白垩统多套深灰黑色含煤泥岩层,发育Ⅰ型和Ⅲ型干酪根,自由烃0.02~0.07 mg/g或为零,生油潜力0.06~0.03 mg/g或为零,残留有机碳1.85%~1.99%或0.70%~0.84%,氧指数4及超过10,属于2类烃源岩,分别生烃和二氧化碳气。总体认为南黄海盆地白垩系具有一定资源前景,值得开展深入分析。Abstract: 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.