Diagenesis and Reservoir Evaluation of Chang4+5 Reservoir in Jianyucha iol field,Ordos Basin

The reservoir rock in Chang4+5 of Jianyucha area has been studied on lithology characteristic,diagenesis and property texture with testing methods of casting thin section,X-ray diffraction,scanning electron microscope analysis, etc..It shows that there reservoir rock consists of grayish-white fine arkose and siltstone,whose clastic granule appears subangular,compositional maturity is low,textural maturity is moderate-better and its particle sorting is better. The sandstone reservoir has experienced from late diagenesis A stage to late diagenesis early of B stage and a series of complex diagenesis as compaction,cementation,metasomatism and dissolution;Pore types are dominated by intergranular pore,and secondary dissolution pore,main minimal-fine throat and fine throats are caused by low permeability,ultimately formed the extra-low permeable and ultra-low permeable reservoir.According to the division scheme of ultra-low permeable reservoir of Yanchang formation,Chang4+5 reservoir is divided into three categories by multi-parameters and kinds of analysis methods,evolution result shows there is mainly medium-low pore reservoir and ultra-low permeability-ultra-low permeability type Chang 4+5 reservoir in studied area.