西湖凹陷花港组深部储层特征及控制因素

Study of deep reservoirs characters and main control factors of Huagang Formation in Xihu sag,East China Sea

探讨东海陆架盆地西湖凹陷深部(>3.5km)低孔渗背景中优质储层的发育控制因素。以岩心与薄片观察为基础,结合扫描电镜、物性测试及压汞分析、X射线衍射、碳氧同位素分析等技术手段,对渐新统花港组砂岩低孔渗储层及优质储层成因进行分析,认为压实作用是本区深层低孔渗储层形成的主要原因,含铁方解石及伊利石等胶结物的发育导致储层质量变差。而深部花港组优质储层发育受控于有利沉积相带和异常高压,导致后期储层压实作用较弱;绿泥石矿物的大量发育阻止了硅质胶结作用的发生;成岩阶段有机酸、大气淡水及热液等造成的溶蚀作用共同形成了深部优质储层。西湖凹陷深部优质储层发育的控制因素:沉积是基础,成岩是关键,超压是重要原因。

Based on detailed observations of cores and thin sections, com bined w ith the application offield em ission scanning electron m icroscopy （F E S E M ）, physical property and m ercury intrusionanalysis, X -ray diffraction, carbon and oxygen isotope analysis, the causes of low porosity andperm eability sandstone and favorable reservoir in the H uagang Form ation of Xihu sag in E ast ChinaSea are analyzed. It reveals that the sandstones in the H uagang Form ation m ainly consist of detritusfeldspar sandstone and feldspar detritus sandstone w ith dom inant secondary pores. T he cause of deepreservoirs is discussed based on research of sedim entary facies, digenesis of rocks and abnorm alpressure and it is considered th at the m ain reason for the low porosity and low perm eability in deeplyburied reservoirs is the late stage com paction and cem entation. T he form er is responsible for the lowporosity and low perm eability of reservoirs. Developm ent of ferrocalcite and illite cem entation leads todeterioration of reservoir quality, w hile silk thread shaped illite occurred in pore throat is alsodecreasing the perm eability of reservoirs. It show s that the sedim entary facies, digenesis and overpressure are main controlling factors on deeply buried reservoirs of high quality. Uncompactionresulted from corrosion and overpressure, organic acid, meteoric water and hydrothermal liquid aremain factors for the formation of deeply buried high-quality reservoirs. In general, deposition is thebasis, diagenesis is the key and overpressure is the important reason for the development of favorablereservoir in the Xihu sag.