Characteristics and petroleum geologic significances of clay rims in sandstones of Mingshui Formation, well Songke 1, Songliao Basin

Clay rim is one of the influencing factors of sandstone properties.The characteristics of clay rims in sandstones from the Mingshui Formation in well Songke 1 in the Songliao Basin have been studied by means of casting thin section observation,XRD,SEM and EDS.The clay rims in sandstones from the Mingshui Formation are composed of montmorillonites with potassium and iron,and the contents of potassium and iron increase as burial depth increases.The clay rims are original ones,and can be further divided into inherited and infiltrated clay rims.They mainly distribute in fine-grained and silt-grained sandstones in shore sand platform,and are poorly developed in fine-grained and medium-grained sandstones in subaqueous distributary channels in delta fronts.The generation of clay rims is mainly controlled by source,climate,granularity and hydrodynamic condition.The genetic type,mineral composition and crystal feature of clay rims all influence the preservation of porosity.As a result,the studies of the composition and distribution of clay rims have an important significance for clastic rock reservoir evaluation.