沁水煤田石炭系—二叠系煤系地层页岩气开发潜力评价

通过对采集自沁水煤田27口钻孔695块山西组-太原组泥页岩岩心样品开展总有机碳含量(TOC)、岩石热解、有机质成熟度和全岩X-射线衍射等实验,分析了煤系泥页岩的有机地球化学及矿物组成特征。结果表明:海陆交互相煤系泥页岩TOC平均值大于2.0%,中-好等烃源岩主要集中在第Ⅱ层段;泥页岩以Ⅲ型干酪根为主,热演化程度主要处于过成熟阶段,转化率程度高;沁水煤田泥页岩主要为黏土质泥页岩,矿物组成以高黏土、低硅质矿物为特征,黏土矿物中高岭石富集;基于矿物组成法计算泥页岩脆性指数主要分布在30%~50%之间,平均大于40%,脆性指数Ⅱ>Ⅲ>Ⅳ>Ⅰ(第Ⅰ层段为K8-3^#煤,第Ⅱ层段为3^#煤-K4灰岩,第Ⅲ层段为K4灰岩-15^#煤,第Ⅳ层段为15^#煤-铁铝岩段);气测异常层、含气层和气层厚度比例分别为4.78%、33.38%、61.83%,气测显示以气层为主,气测显示级别Ⅱ>Ⅲ>Ⅳ>Ⅰ。综合煤系泥页岩厚度、有机质丰度、脆性特征和含气性特征等评价了各层段页岩气的勘探开发潜力有利顺序依次为Ⅱ>Ⅲ>Ⅳ>Ⅰ。

Development potential of Carboniferous-Permian coal measures shales gas in Qinshui coalfield

The organic geochemistry and mineral composition characteristics of shale in coal measures are analyzed through the experiments of total organic carbon content(TOC),rock pyrolysis,maturity of organic matter and rock X-ray diffraction of 695 shale core samples collected from 27 wells in Qinshui coalfield. The results show that the average TOC value of marine-terrigenous facies shale in coal measures is more than 2.0%,and the middle-good source rocks are mainly concentrated in the second interval. The shale is mainly composed of Type Ⅲ kerogen,and its thermal evolution is mainly at the over-mature stage with high conversion rate. The shale in Qinshui coalfield is mainly clayey shale. Its mineral composition is characterized by high clay and low silica minerals,and kaolinite is enriched in clay minerals. The rock brittleness index based on mineral composition is mainly distributed between 30% and 50%,with an average of more than 40%,and the brittleness index is Ⅱ>Ⅲ>Ⅳ>Ⅰ(The first interval is K8-3^# coal,the second interval is 3^# coal-K4 limestone,the third interval is K4 limestone-15^# coal,and the fourth interval is 15^# coal-the Fe-Al-Bearing Rock Members). The ratio of abnormal layer,gas-bearing layer and gas layer thickness is 4.78%,33.38% and 61.83%,respectively. Gas layer is dominant,and the gas measurement shows the level is Ⅱ>Ⅲ>Ⅳ>Ⅰ. Based on the comprehensive analysis of the thickness,organic matter abundance,brittleness and gas-bearing characteristics of shale gas in coal measures,the favorable sequence of the exploration and development potential of shale gas in each interval is Ⅱ>Ⅲ>Ⅳ>Ⅰ.