摘要
Based on studies of carbonate cement characteristics,the distribution and generation environment of carbonate cements in overpressure zone of the Paleogene Anjihaihe Formation in the southern margin of Junggar Basin have been discussed in this paper by means of thin section observation,well-logging interpretation and O-C isotope analysis.The carbonate cements in the study area are mainly composed of sparry ferri-calcite in connected-crystal form,characterized by low AC,high RT and low GR.Vertically,the cemented layers mainly locate in the pressure-released zone and the overpressure transition zone,including the upper and the lower parts of overpressure top surface,the top of sandstone belt in the overpressure zone as well as the lithologic transition belt in thick overpressure mudstone.Most of the carbonate cements have high negative oxygen isotope values.They were formed before or during petroleum migration under high temperature.