Reservoir characteristics and diagenetic evolution of Kukebai Formation in Kekeya area, Southwest Depression of Tarim Basin

In order to explore the favorable reservoir characteristics and diagenetic evolution laws of the Cretaceous Kukebai Formation in the Kekeya area of the southwestern Tarim Basin, and provide theoretical basis for oil and gas exploration and development in the study area, comprehensive data such as core, cast thin sections, and carbon and oxygen isotopes were used to carry out the classification of diagenetic facies types and the study of diagenetic evolution models. The results indicate that the reservoir of the Kukebai Formation in the study area is mainly composed of feldspar lithic sandstone and lithic feldspar sandstone, with mainly developed diagenetic processes such as compaction, cementation, and dissolution. The diagenetic stage is in the middle diagenetic stage A. The Kukebai Formation reservoir mainly develops four types of diagenetic facies: moderately compacted dissolution facies, moderately compacted cementation facies, strongly compacted compaction facies, and strongly cemented facies. Among them, the strong compacted phase becomes a dense reservoir due to mechanical compaction in the early stage of diagenesis, and is mainly distributed in the sand mud interbedded layers of sedimentary microfacies between river channels and estuarine dams; The strongly cemented phase is densified in the early diagenetic stage due to the precipitation of a large amount of carbonate cement, mainly developed in the sand mud interbedded layers near the mud end of underwater distributary channels and the sedimentary microfacies of estuarine dams; The dissolution effect of medium compacted dissolution phase sandstone is strong, and the reservoir properties are the best, mostly appearing in the upper part of distributary channel sand bodies with strong sedimentation and water accumulation dynamics; The medium compacted and cemented sandstone has moderate compaction, and the reservoir properties are relatively good. It mainly develops in the lower part of distributary channel sand bodies with strong hydrodynamics. There are two types of favorable reservoirs in the study area, namely the medium compacted cementation phase and the medium compacted dissolution phase sandstone.