川东北地区自流井组陆相页岩岩相类型及储层发育特征

中国陆相页岩气资源潜力巨大，其中川东北部分地区下侏罗统获得了工业性页岩气流。开展页岩岩相划分与储层特征的研究有利于进一步勘探开发陆相页岩气。通过XRD、普通薄片、扫描电镜、高压压汞、N₂吸附及CO₂吸附等实验方法对川东北地区自流井组陆相页岩进行精细研究。以有机质丰度及矿物组成为分类参数将页岩分为12种不同岩相，查明了自流井组页岩主要发育4种岩相，即贫有机质硅质页岩（Ⅰ₃）、含有机质混合质页岩（Ⅳ₂）、含有机质硅质页岩（Ⅰ₂）与富有机质黏土质页岩（Ⅱ₁）。不同岩相的页岩储层特征存在较大差异，富有机质黏土质页岩有机质含量大于2%，生烃潜力最好，有机质孔及黏土矿物晶间孔之间连通性较好且比表面积较大，发育的纹层状构造有利于工业压裂，为最优陆相页岩岩相，是最有利的陆相页岩气勘探开发目标；含有机质混合质页岩（Ⅳ₂）有机质含量大于1%，孔体积较高，储气能力较好，且发育有利于压裂的层状构造，为良好陆相页岩岩相，是较有利的勘探开发目标；而贫有机质硅质页岩（Ⅰ₃）与含有机质硅质页岩（Ⅰ₂）则具块状特征，孔体积与比表面积均较低，为较差陆相页岩岩相，是最不利的勘探开发目标。

Lithofacies types and reservoir characteristics of continental shales of Ziliujing Formation in northeastern Sichuan Basin

The potential of continental shale gas resources in China is abundant and the industrial shale gas has been obtained in shale reservoir in the Lower Jurassic of northeastern Sichuan Basin. The types of lithofacies and reservoir characteristics are essential to exploration and development of continental shale gas. Based on the experiments of XRD, analytical data of ordinary thin section, scanning electron microscope, high pressure mercury pressure, N₂ adsorption and CO₂ adsorption, a study on the continental shale of Ziliujing Formation in northeastern Sichuan Basin is carried out. According to the total organic matter content and mineral composition as classification parameters, the shale is divided into 12 different lithofacies. Four kinds of lithofacies are developed in Ziliujing Formation, which are organic-poor siliceous shale(Ⅰ₃), organic-fair mixed shale(Ⅳ₂), organic-fair siliceous shale(Ⅰ₂) and organic-rich argillaceous shale(Ⅱ₁). The reservoir characteristics of different lithofacies are quite different. The total organic matter content of Ⅱ₁ is more than 2%, and the hydrocarbon generation potential is the best. The pores of organic matter and clay minerals have good connectivity and large specific surface area, and the Ⅱ₁ developed laminar structure which is favorable for artificial fracturing. The organic matter content of Ⅳ₂ is more than 1%. The Ⅳ₂ developed high pore volume and the layered structure. However, the Ⅰ₃ and the Ⅰ₂ have the characteristics of massive, and developed low pore volume and specific surface area.