致密砂岩储层敏感性及影响因素分析:以鄂尔多斯盆地王家湾东南区长6油层组为例

Analysis of Sensitivity and Influencing Factors of Tight Sandstone Reservoir:A Case Study of Chang 6 Oil Layer in Wangjiawan Southeast Area,Ordos Basin

鄂尔多斯盆地王家湾东南区长6油层组为致密砂岩储层,储层敏感性评价是研究流体对储层伤害的重要手段,对后期的注水开发有着重要的指导意义。基于扫描电镜、铸体薄片、压汞实验和敏感性实验等手段,对储层敏感性及其影响因素进行深入研究。结果表明,研究区主要为长石砂岩,长石、石英、岩屑含量较高,黏土矿物主要为伊利石、绿泥石、伊蒙混层;岩石较致密,孔隙结构较差、孔喉分布不均匀,为低孔低渗储层;敏感性表现为中等偏弱速敏、中等偏弱水敏、中等偏强酸敏、弱-中等偏弱碱敏以及中等偏弱-弱盐敏,黏土矿物的类型和含量影响储层敏感性的主要因素,黏土矿物中的伊蒙混层、伊利石、绿泥石对分别对盐敏、水敏、酸敏影响较大。因此,在注水开发过程中要有针对性地对盐敏、水敏、酸敏采取储层保护措施。

The Chang 6 reservoir group in the southeastern Wangjiawan area of the Ordos Basin is a tight sandstone reservoir.Reservoir sensitivity evaluation is an important means to study fluid damage to reservoirs and has important guiding significance for later water injection development.Reservoir sensitivity and its influencing factors were studied based on a scanning electron microscope,mercury injection test,and sensitivity test.The results show that the study area is mainly feldspar sandstone with high content of feldspar,quartz and rock debris,and clay minerals are mainly illite,chlorite and illite-montmorillonite mixed layer.The rock is dense,the pore structure is poor,and the pore throat distribution is uneven,which is a low porosity and low permeability reservoir.The sensitivity is characterized by medium-weak velocity sensitivity,medium-weak water sensitivity,medium-strong acid sensitivity,weak-medium-weak alkali sensitivity and medium-weak-weak salt sensitivity.The type and content of clay minerals affect the main factors of reservoir sensitivity.The mixed layer of illite and montmorillonite,illite and chlorite in clay minerals have great influence on salt sensitivity,water sensitivity and acid sensitivity respectively.Therefore,in the process of water injection development,targeted reservoir protection measures should be taken for salt sensitivity,water sensitivity and acid sensitivity.