深层致密砂岩储层特征及物性控制因素

基于川东北元坝西地区10口钻井的须二下亚段砂岩物性测试数据，结合铸体薄片、氩离子抛光扫描电镜和压汞测试等手段，分析了致密砂岩储层的特征及物性控制因素。研究表明元坝西须二下亚段砂岩为低孔中低渗储层，孔隙度为0.99%~10.53%，渗透率为（0.003 6~1.41）×10-3 μm2，孔渗关系表现为“分层”特征，根据孔渗关系可划分出低孔中渗储层，低孔低渗储层和特低孔低渗储层3种类型储层。不同类型储层的砂岩物性受沉积条件和成岩作用共同控制，沉积条件决定了砂岩岩石学特征，进而对成岩作用产生重要影响；成岩作用的非均质性最终决定了储层物性的差异。不同类型储层砂岩在垂向上表现出强烈的成岩非均质性，发育岩屑溶蚀段（绿泥石膜胶结段）—硅质胶结段—方解石胶结段的成岩组合序列。优质储层主要分布在发育强烈溶蚀作用河道砂体中部的中粒（长石）岩屑砂岩中。此项研究结果能更好地进行深层致密砂岩甜点预测，指导四川盆地深层致密砂岩气的勘探。

Characteristics of Deep Tight Sandstone Reservoirs and Their Controlling Factors of Physical Properties: A case study of the Xu-2 member in the western Yuanba area of the northeastern Sichuan Basin,China

Based on the sandstone physical property test data of 10 wells in the western Yuanba area， northeastern Sichuan， this paper analyzes the characteristics and physical control factors of tight sandstone reservoirs by means of casting thin sections， scanning electron microscopy， cathodoluminescence， X-ray diffraction analysis， and mercury intrusion testing. The study shows that the sandstone of the Xu-2 Member in the western Yuanba area is a low-porosity and low-permeability reservoir with a porosity of 0.99%?10.53% and a permeability of 0.003 6 ×10-3 μm2 - 1.41 ×10-3 μm2. The porosity-permeability relationship is characterized by “stratification”. According to the porosity-permeability relationship， three types of reservoirs can be classified: low-porosity and infiltration reservoirs， low-porosity and low-permeability reservoirs， and ultra-low-porosity and low-permeability reservoirs. The physical properties for the different types of sandstone reservoirs are controlled by sedimentary conditions and diagenesis. The sedimentary conditions determine the petrological characteristics of the sandstone， which in turn has an important impact on diagenesis. The heterogeneity of diagenesis ultimately determines the difference in the reservoir physical properties. Different types of reservoir sandstones show strong diagenetic heterogeneity in the vertical direction and the diagenetic combination sequence of the developed lithic dissolution section （chlorite film cementation section） - silica cementation section - calcite cementation section. The best reservoir quality is mainly distributed in the middle-grained lithic sandstone in the middle of the sand body where the strong dissolution is developed. The results of this study can better predict the deep tight sandstone desserts and guide the deep tight sandstone gas exploration in the Sichuan Basin.