Research On Sedimentary Facies And Reservoir Diagenesis Differences Of The Silurian Kepingtage Formation From The Southern Slope Of Tabei To Tazhong Area

This study takes the reservoir in the Silurian Kepingtage Formation（S₁k）from the Southern Slope of Tabei to Tazhong Area in Tarim Basin as the research object.The single well facies and continuous well facies analysis are conducted by using the identification marks and characteristics of the sedimentary facies to clarify the sedimentary facies of different layers in different regions and study the characteristics of the plane distribution of sedimentary facies.The reservoir petrological characteristics and diagenesis facies are also analyzed by using petrographic thin sections,scanning electron microscopes,cathodoluminescence,and X-ray diffraction.BP neural network is applied to identify and predict the appearance of different diagenesis facies and to help understand the regularities of the longitudinal and plane distribution of different diagenesis facies.The prediction results are then used to establish a sedimentary-diagenetic difference modeland and identify the distribution of favorable areas.The research results have guiding significance for the oil and gas exploration in marine clastic rock reservoirs in the southern slope of Tabei-Tazhong Area in Tarim Basin.Results show that there are 6 types of sedimentary facies,11 types of sedimentary subfacies and 18 types of sedimentary microfacies in the Kepingtage Formation.The main sedimentary facies is tidal flat-delta.S₁k¹ has various types of sedimentary facies,with estuarine bays,tidal deltas and river-dominated deltas developed in the southern slope of Tabei,and large river-dominated deltas and tidal flats developed in the Shuntuo area.As for S₁k^3-1,tidal flats are developed in the southern slope of Tabei.The river-dominated deltas are developed in the Shuntuo area,but its scale is smaller than that of S₁k¹.The tidal flats are developed in Tazhong area.As for S₁k^3-3,river-dominated deltas and tidal flats are developed in the southern slope of Tabei.Tidal flats are developed in the Shuntuo and Tazhong areas.Generally speaking,the sedimentation of the Kepingtage Formation is a process of overall regression from bottom to top.The Kepingtage Formation is dominated by fine-grained lithic sandstone and feldspar lithic sandstone,which are all well-sorted and medium-sorted,and sub-circular shape rounding.The diagenesis of the Kepingtage Formation is mainly controlled by compaction,carbonate cementation and dissolution.Based on different types of diagenetic minerals and diagenesis,the diagenesis facies are divided into four types:unstable component dissolution facies,carbonate cementation facies,rigid grain compacted compaction facies,and ductile grain compacted compaction facies.Based on the results of diagenesis facies logging identification,it is found that there are differences in the distribution of stratigraphic profiles and regional differences in planes.S₁k¹ develops all the four types of diagenesis facies in the southern slope of Tabei,and is dominated by carbonate cementation facies in the Shuntuo area.S₁k^3-1 develops all the diagenesis facies except for the unstable component dissolution facies in the southern slope of Tabei.In the Shuntuo and Tazhong areas,the carbonate cementation facies and the rigid grain compacted compaction facies are the main diagenesis facies.S₁k^3-3 is dominated by carbonate cemented facies and rigid grain compacted compact facies in the southern slope of Tabei and Shuntuo areas.In Tazhong area,all the diagenesis facies are developed except for the ductile grain compacted compaction facies.Under the control of sedimentary facies,the aforementioned four types of diagenesis facies sandstones have undergone differential evolution.Different types of diagenesis facies are developed in different sedimentary facies.The other three diagenesis facies are all developed in the river-dominated delta facies except for the ductile grain compacted compaction facies.The tidal flat intertidal zone is dominated by the carbonate cemented facies and the ductile grain compacted compaction facies.In the subtidal zone,three diagenesis facies are all developed except for the ductile grain compacted compaction facies.The favorable area can then be determined based on the study of sedimentary facies and diagenesis facies.