Diagenetic processes and environments of the reef shoal dolostones from the Changxing Formation in the Daxian-Xuanhan region,northeastern Sichuan

The diagenesis of the reef shoal dolostones from the Changxing Formation in the Daxian-Xuanhan region includes compression,pressure solution,cementation,dolomitization,neomorphism,dissolution,fracturing and infilling-cementation,of which dissolution,neomorphism and fracturing serve as most important ones in the study area.Judged from abundant solution openings,intercrystal solution openings,intercrystal pores and fissures and cracks in the reservoir rocks,the good physical properties of the reef shoal dolostone reservoirs should be formed in the moderately and deeply buried environments.