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通过对柴北缘九龙山地区侏罗系致密砂岩储集层的普通薄片、铸体薄片、压汞曲线等化验资料分析研究,明确储集岩类型主要以岩屑砂岩和长石岩屑砂岩为主,其次为岩屑长石砂岩和长石砂岩。孔隙类型主要以粒间溶孔为主,其次为残余粒间孔和粒内溶孔,平均孔隙度为9.07%,平均渗透率为1.71×10-3μm2,属于典型的低孔特低渗储集层。通过镜下鉴定和扫描电镜对致密砂岩储层的胶结物类型及自生黏土矿物进行了分析,主要有方解石、铁方解石、白云石和铁白云石4种碳酸盐胶结物类型,黏土矿物主要以伊利石、绿泥石和伊/蒙混层为主。致密砂岩储层形成的主控因素—是储集岩粒度偏细,分选中等—差,磨圆以次棱角状为主、岩石类型主要为岩屑砂岩和长石岩屑砂岩、岩屑成分主要为抗压实能力较弱的塑性岩类;其次是由于侏罗系地层曾经经历过深埋藏,强烈的压实作用大大降低了储层的物性条件。但后期碳酸盐胶结物和易溶颗粒的溶蚀作用在一定程度上改善了储层的物性条件。
Based on the analysis of the laboratory test data of ordinary thin slices, cast thin slices and mercury intrusion curves of the Jurassic tight sandstone reservoirs in Jiulongshan, northern Qaidam, it is clear that the types of reservoir rocks are dominated by lithic sandstones and feldspathic lithic sandstones , Followed by lithic feldspar sandstone and feldspar sandstone. The pore types are dominated by intergranular dissolved pores, followed by residual intergranular pores and intragranular dissolved pores with an average porosity of 9.07% and an average permeability of 1.71 × 10-3 μm2, which is typical of low porosity and low permeability reservoirs Floor. By means of microscopic identification and scanning electron microscopy, the types of cements and the authigenic clay minerals in the tight sandstone reservoirs are analyzed. There are four types of carbonate cements: calcite, iron calcite, dolomite and iron dolomite. The main clay minerals are Erie Stone, chlorite and Iraq / mixed layer. The main controlling factors for the formation of tight sandstone reservoirs are the fine grain size of the reservoirs, moderate-poor sorting and rounding with sub-angular shapes. The rock types are mainly lithic sandstone and feldspar lithic sandstone, The main reason is the plastic rock with weak compaction resistance. The second reason is that the Jurassic strata once experienced deep burial, and the strong compaction reduced the physical and chemical conditions of the reservoir greatly. However, the dissolution of later carbonate cements and soluble particles improved the physical properties of reservoirs to a certain extent.