The Diagenesis in Sequence Stratigraphic Framework of the Upper Paleozoic，Ordos Basin

Key words: 
• rock type /
• diagenetic stage /
• diagenetic facies /
• reservoir predication

Abstract: In the Ordos Basin, the Upper Paleozoic could be divided 5 types of sandstone, mainly including quartz sandstone, lithic sandstone, graywacke, "felty" sandstone, black quartz sandstone, etc. These types of sandstone have some characteristics as that the compositional maturity of the sandstone are relatively high; the textural of the sandstone are relatively medium to low; normal grading; grain size is Coarse and Medium Grains, tuff fillings in the reservoir have multitype, and their concentrations vary greatly. The reservoir experienced three important diagenesis phases that early compaction phaseseriously damaged and losing primary pore phase, intermediate diagenetic A phaseoganic acids corrosionSecondary Porosity development phase, intermediate diagenetic B phaseburial, pressolution and secondary cementation diagenesis phases. The main diagenesis of SQ8 are pressure solution,kaolinite corrosion and quartz overgrouth, et al.The ones of SQ11 are siliceous cementation and carbonate cementation. The diagenetic facies are divided into three grades and five types: the first is strong pressure solutionquartz overgrouth facies;the second is pressure solutioncarbonate corrosionkaolinite metasomatic facies and corrosionweak matrix filledkaolinite metasomatic facies;the third is strong compactionclay cemented facies and strong compaction-carbonate cemented ,metasomatic facies. The main reservoir of studying region is low porosity, low peremeability sandstone,and mostly develops secondary pores,which include intergranular corrosion pores, and kaolinite intercrystal pores. few primary pores were preserved. Through multidisciplinary analysis of sand body distribution, reservoir diagenetic facies types and reservoir property, to predict the favorable reservoir distribution zone.