The Impact Of Diagenetic Changes On Chang6 Reservoir In Huaqing Region

Huaqing region is located in the southwest of the Ordos basin.Sand bodies are highly developed in Chang 6 oil-bearing bed of Yanchang formation and the oil-bearing property is one of the best there.So the study on diagenesis in this area has great impact for further exploration and exploitation.Based on previous foundation,the way of scanning electronmicroscope,casting microsection,cathodoluminescence,XRD and other physical property analysis are used to research on the control of diagenesis over pore evolution,meanwhile,pore types of sandstone and diagenesis of Chang6 are also summed up in this paper.The main diagenesis types of Chang 6 oil reservoir set are compation,cementation,metasomatic alteration and dissolution.The Diagenesis in study area is markedly divisional.Authigenic chlorite is well developed in northern area,where illite coexists with chlorite.The main pore type in the north is primary intergranular pore;illite cements are dominant in the south and main pore type of the reservoir is secondary porosity.Ferrocalcite cements and ankerite cements are well developed.This study shows that compaction and cementation are the main destructive digenesis and it led to great decrease in Pores.To a certain degree,chlorite cementation can protect pores.Dissolution is the main constructive digenesis and it contributes to the favorable reservoir quality.After comprehensive analysis,it is concluded that Chang-6 reservoir in study area is at late diagenesis A.And a formula,which proposed by Beard and Weyl,was used to calculate porosity at all stages of diagenesis in Chang-6 reservoir.