Densification and diagenetic facies of Donghetang Formation sandstone reservoir in Bachu-Maigaiti area, Tarim Basin

The reservoir characteristics, diagenesis, densification mechanism and diagenetic facies of the Donghetang Formation in the Bachu-Maigaiti area of Tarim Basin were studied using detrial reservoir and sedimentation research. The Donghetang Formation mainly contains dissolution pores, characterized by extra low porosity and permeability. Through restoring the original porosity, we identified the contribution of main diagenesis to porosity. Compaction is the main reason for reservoir densification, while cementation also works in some wells. There are six types of diagenetic facies in this reservoir, namely strong compaction and strong cementation with weak dissolution facies, strong compaction and medium cementation with weak dissolution facies, strong compaction and medium cementation with medium dissolution facies, weak compaction and strong cementation with weak dissolution facies, medium compaction and strong cementation with strong dissolution facies, and medium compaction and strong cementation with weak dissolution facies. By summarizing the well logging characteristics of the six diagenetic facies reservoirs and analyzing its similarity with the wells in the non-core sandstone segments, we discriminated the diagenetic facies of 23 sandstone segments in 9 wells. The dominant diagenetic facies of the upper sandstone is in the Batan 2 well area while the lower sandstone is in the Bakai 8 well area.