内蒙古二连盆地阿南凹陷腾格尔组一段下部特殊岩性段储集性能

Reservoir property of the special lithologic section in the lower Tengger Formation of A'nan depression,Er'lian basin

二连盆地阿南凹陷油气资源的勘探开发程度较高,但岩性油藏的勘探尚未取得突破。下白垩统腾格尔组一段下部的特殊岩性段是潜在的油藏储集层。通过岩矿鉴定、电子探针、扫描电镜等研究了该层段的岩石学特征和储集性能。结果表明,该岩性段由深灰色云质泥岩、灰色泥质云岩、钙质沉凝灰岩、钙质细砂岩构成,夹有薄层灰绿色块状凝灰岩,钙质胶结和泥质胶结为主要胶结类型。对凝灰岩和沉凝灰岩的元素地球化学分析发现,受成岩流体的影响,钙质沉凝灰岩中硅酸盐矿物和火山碎屑的溶蚀现象较普遍,导致更显著的重稀土元素亏损和粒间孔、溶蚀孔发育,这些次生孔隙和微裂缝能提供油气储集空间和运移通道。

Although A’nan depression has been well prospected in past years,no lithologic reservoir has been discovered.The special lithologic section of the Tengger Formation is the potential reservoir strata.Based on lithologic characterization,scanning electronicmic roscopy,and electron probe measurement,the authors investigated the reservoir properties of the special lithologic section.The lithologic section is mainly composed of gray dolomitic mudstone,argillaceous dolomite,calcareous sedimentary stuff and calcareous fine sandstone intercalated with gray green massive tuff.The calcareous cementation and clayey cementation are the main types of cementation.The tuff and sedimentary tuff elemental geochemical analysis shows that,with the alteration of diagenesis fluid,the silicate and sedimentary tuff dissolved significantly,which led to abundant secondary pores and strong depletion of heavy rare earth elements.These secondary pores and intergranular pores together with micro-fracture constitute the main potential reservoir space and the migration paths of the hydrocarbon.