柴西地区古、新近系页岩气储层微观特征研究

Study on microscopic features of Paleogene and Neogene System shale gas reservoir in western Qaidam Basin

通过X衍射、氩离子抛光-扫描电镜、纳米CT、氮气吸附法等分析测试,研究了柴西地区古、新近系不同类型页岩气储层微观特征。研究表明,古、新近系页岩发育多种储集空间类型,主要为残余的原生孔隙或微裂缝、有机质生烃形成的微孔隙、黏土矿物转化形成的孔隙、长石和方解石等溶蚀形成的孔洞等,这些微孔隙以及裂缝的存在,为页岩气的赋存提供了空间。古、新近系泥页岩微孔隙发育,且连通性较好,从泥质粉砂岩→泥岩→灰质泥岩孔隙连通性具有逐渐减小的趋势。上、下干柴沟组泥页岩中的泥质粉砂岩夹层是优质的页岩气储层,而灰质泥岩是最不理想的页岩气储层。研究成果可为下一步的页岩气勘探开发提供基础支撑。

Study on microscopic features of shale gas reservoir in the shale gas reservoir of Paleogene and Neogene System in western Qaidam Basin was carried out using X-ray diffraction（XRD） analysis,argon ion polishing-scanning electron microscope（SEM） analysis,nanometer CT analysis,nitrogen adsorption analysis.The comprehensive evaluation showed that many types of reservoir space was developed in Paleogene and Neogene System shale,such as residual original pores and micro-cracks,microporosity due to hydrocarbon formation,clay mineral transformation and dissolution of feldspar and calcite.The microporosity was well developed in Paleogene and Neogene System shale with good connectivity,but the connectivity decreased gradually from argillaceous siltstone to shale to lime mudstone.Argillaceous siltstone interlayer in Upper and Lower Gancaigou Formation shale is the ideal high-quality reservoir while the lime mudstone is the poor quality reservoir.The study result can be used as a reference for the future shale gas exploration.