柴达木盆地西部北区新近系非常规低渗储集层特征及控制因素分析

柴达木盆地西部北区新近系储集层岩石成分复杂，矿物成分包括石英、长石等陆源碎屑，也有较多碳酸盐矿物和黏土矿物，且粒度偏细，通过一般薄片鉴定难以准确进行岩性定名。本文主要对该区南翼山、油泉子、小梁山和咸水泉四个含油构造储集层岩石类型进行分析，基于岩芯观察和薄片鉴定，借助X射线全岩矿物分析，认为该区储集层岩石为陆源碎屑物质和化学成因的碳酸盐混合沉积的岩石类型，按黏土含量、碳酸盐含量和石英长石含量做出矿物三角图，提出岩性分类方案，将储集层岩性划分为泥岩、砂岩、碳酸盐岩和混合沉积类。该区储集层岩石物性普遍较差，孔隙类型包括粒间溶蚀孔隙、微裂缝和微孔隙等。压实作用、溶蚀作用及胶结充填作用是控制储集层性能的主要因素。

Characteristics and Controlling Factors of the Unconventional Low Permeability Reservoir of Neogene in the Northwest of Qaidam Basin

The lithology of Neogene reservoirs in the northwest part of Qaidam Basin is very complex. The rock minerals contain terrigenous materials such as quartz and feldspar as well as lacustrine materials such as carbonate and clay minerals. In addition, the grain size of the sediment is very fine. As a result, the rocks can not be denominated easily by means of thin section examination. This paper mainly discusses four oil structures of the area, including Nanyishan, Youquanzi, Xiaoliangshan and Xianshuiquan. Based on core observation and thin section examination, with the help of X ray diffraction analysis, the sediments of the reservoirs are considered to be mixed deposition which is composed of terrigenous clastic materials and bio chemical carbonate minerals. A triangular graph is drawn according to the contents of clay minerals, carbonate minerals, and quartz and feldspar. So，a lithology classification is put forwards and the rocks can be classified as mudstone, sandstone，carbonatite, and mixing deposited rocks. The physical properties of the reservoirs are poor, and the pore types include intergranular solution pores, micro fractures and micro pores. Compaction，corrosion and cementation are main factors controlling the characteristic of the reservoir. 