塔木察格盆地南贝尔凹陷塔Ⅱ油层组火山碎屑岩储层特征研究

Characteristics of volcaniclastic rock reservoirs of Ta Ⅱ Formation of South Buir Sag in Tamtsag Basin,Mongolia

蒙古国塔木察格盆地南贝尔凹陷下白垩统塔Ⅱ油层组的主要岩石类型为岩屑长石砂岩和凝灰质砂岩,其储层物性、成岩作用特征与正常沉积岩相比具有独特性。应用偏光显微镜、扫描电镜及X射线衍射分析等测试手段,对研究区储集层的岩石学特征、物性特征、成岩作用及演化等进行了详细研究。结果表明:粒间孔、杂基间微孔、粒间溶孔等是塔木察格盆地南贝尔凹陷塔Ⅱ油层组的主要孔隙类型;塔Ⅱ油层组储层成岩阶段以中成岩阶段A期为主,压实作用和胶结作用是造成储层孔隙度降低的主要因素,长石和凝灰质物质的溶蚀溶解作用有利于次生孔隙的形成。

A set of volcaniclastic rocks were developed in the Lower Cretaceous Ta Ⅱ Formation of South Buir Sag in Tamtsag Basin of Mongolia. The main rock types are lithic arkose and tuffaceous sandstone,of which the reservoir physical properties and diagenesis are different from normal sedimentary rocks. Detailed studies were carried on the petrology,physical properties,diagenesis and evolution of reservoirs,using polarizing microscope,scan electron microscope and X ray diffraction. The results indicate that intergranular pore,micropore among matrix and intergranular dissolution pores are the main pore types of Ta Ⅱ Formation. The main diagenetic phase belongs to stage A of middle diagenesis phase. Compaction and cementation were the main factors reducing reservoir porosity,and the secondary porosity zone was developed because of erosion-dissolution of feldspar and tuffaceous material.