甘泉—富县地区长7致密砂岩储层成岩相的定量识别及其对含油性的控制作用

Quantitative Identification of Diagenetic Facies of Tight Sandstone Reservoirs and Its Control on Oil-Bearing Property:A Case Study of Chang 7,Ganquan-Fuxian

以岩心分析、测井数据为基础,结合薄片鉴定、扫描电镜等分析手段对鄂尔多斯盆地甘泉-富县地区长7致密砂岩储层的岩性、物性以及成岩相进行了研究。长7致密砂岩储层岩性主要以长石砂岩为主,孔隙度主要分布在3%~10%之间,渗透率主要分布在0.05~0.60mD之间。依据成岩作用类型和强度及成岩矿物组合特征,并结合孔隙发育特征,将研究区内岩相划分为中压实绿泥石薄膜胶结原生粒间孔相、中压实不稳定组分溶蚀溶孔相、强压实弱溶蚀微孔相、强压实伊利石胶结致密相和强压实钙质胶结致密相5类。通过对成岩相较为灵敏的自然伽马和声波时差交汇建立成岩相识别标准,利用"优势相"法绘制研究区成岩相平面图。勘探成果显示,成岩相对致密油富集具有一定控制作用。

The lithology,physical property,and diagenetic facies of the Chang 7 tight sandstone reservoirs in Ganquan Fuxian area of Ordos basin were studied by using core analysis,thin section identification,SEM,and logging data.The lithology of the Chang 7 tight sandstone reservoir is mainly feldspar sandstone,with porosity between 3% and 10%,and permeability between 0.05 and 0.60 mD.Five types of digenetic facies were identified based on the type and strength of diagenesis combined with the features of diagenetic minerals,the characteristics of pore development,and its impact on reservoir property.They are medium compacted chlorite cementation native intergranular pore facies,medium compacted corrosion of unstable components solved pore facies,strongly compacted weakly dissolved microporous facies,strongly compacted illite cemented tight facies,and strongly compacted calcareous cemented tight facies.Natural gamma ray and acoustic logging are sensitive to diagenetic facies.A logging identification model was established by using the logging data of the study area,and the"dominant facies"method was used to predict the distribution of diagenetic facies.The result shows that the diagenesis is relatively tight,and plays a controlling role in oil accumulation.