下扬子地区下寒武统黑色页岩地球化学特征

 通过露头观测、样品采集、有机地化分析等方法,研究了下扬子地区下寒武统黑色页岩的地质特征与油气资源意义.研究表明,黑色页岩沉积厚度大,主要分布在皖南的石台-泾县-宁国、全椒、苏北的高邮-海安地区,厚度介于100~400 m;岩石矿物成分中石英含量较高,有利于页岩的压裂改造;有机碳含量主要分布在1.0%~4.0%,黑色页岩沉积厚度中心有机碳含量普遍大于2.0%;有机显微组成、干酪根碳同位素、Pr/Ph 比值和饱芳比表明,该页岩有机质类型为Ⅰ型,母质来源为低等浮游生物,具有较强生烃潜力;热演化程度较高,等效镜质体反射率主体分布在2.0%~4.0%,普遍处于高成熟-过成熟阶段.综合认为,该区黑色页岩沉积厚度大、有机碳含量较高、有机质类型好、热演化程度高,具备页岩气形成的地质条件,是中国南方页岩气有利勘探区块之一.

Geochemical characteristics of black shale of the lower Cambrian in lower Yangtze area

The geologic characteristics and their hydrocarbon implication of black shale of the lower Cambrian in lower Yangtze area are analyzed by outcrop observation, sampling and geochemical analysis. The following conclusions are drawn. The black shale of lower Cambrian in lower Yangtze area has great thickness between 100 to 400 meters, and is mainly distributed in Shitai, Jingxian, Ningguo, Quanjiao, Gaoyou and Haian. It has high content of quartz in the mineral composition in this set of black shale, which is good for fracturing. The content of organic carbon ranges from 1% to 4% in lower Yangtze area, and is greater than 2.0% at depositional thickness center. The analysis of microscopic organic composition, carbon isotope of kerogen, Pr/Ph and saturated HC/ aromatic HC indicate that the kerogen type is Ⅰ. The origin of parent materials is aquatic organisms with high potential for hydrocarbon generation. The vitrinite reflectance is in the range of 2.0%~4.0%, in the stage of maturity to over-maturity. The black shale of lower Cambrian in lower Yangtze area has great thickness, high content of organic carbon, good kerogen type and high thermal maturity, which suggests promising exploration prospects.