鄂西-渝东地区下侏罗统东岳庙段泥岩地球化学特征及有机质富集模式

Geochemical Characteristics and Organic Matter Enrichment of the Dongyuemiao Member Mudstone of Lower Jurassic in the Western Hubei-Eastern Chongqing

我国不同地区页岩非均质性研究是亟待解决的基础地质问题,且四川盆地陆相页岩气的研究十分薄弱.通过对鄂西-渝东地区下侏罗统自流井组东岳庙段剖面和钻井岩心的岩石学特征、地球化学等方面的精细分析,结合测井曲线,查明了该层段地球化学垂向变化特征及有机质富集模式.结果表明,东岳庙段脆性矿物含量高,粘土矿物含量较少,下部有机质含量高于上部.地球化学指标所反映的古气候、古生产力、古氧化还原、古盐度表明东岳庙段垂向上具有明显差异;东岳庙段下部为干旱炎热古气候、贫氧-偏咸化水体和高古生产力,而东岳庙段上部为温暖湿润古气候、淡化水体和低古生产力,故东岳庙段下部更有利于有机质富集.

The shale heterogeneity in different regions of China is the basic geological issue to be addressed urgently.However,the study of continental shale gas in the Sichuan basin is very weak.Based on analysis of the petrology and geochemistry of the Dongyuemiao member of lower Jurassic Ziliujing Formation in western Hubei-eastern Chongqing area,and combined with the logging curve,the vertical variation of geochemical characteristics and organic matter enrichment have been discussed.The results show that the Dongyuemiao member has high brittle mineral content and low clay mineral content,and higher organic matter content at the lower part than that at the upper part.Geochemical index,such as paleoclimate,paleoproductivity,paleoredox,paleosalinity has obvious vertical differences in the Dongyuemiao member.The lower part of Dongyuemiao member shows dry paleoclimate,dysoxic water column,saline water and high paleoproductivity,but the upper part of Dongyuemiao member shows warm and humid paleoclimate,low salination water and low paleoproductivity.It is concluded that the lower part of Dongyuemiao member has been more favourable for organic matter enrichment.