Sedimentary facies of the lower bitumen-bearing sandstone member of the Silurian Kepingtage Formation in the S1 well area, Tarim Basin

The sedimentary facies of the lower bitumen-bearing sandstone member of the Silurian Kepingtage Formation in the S1 well area, Tarim Basin are discriminated on the basis of core examination, lithology, grain size analysis, sedimentary structures, trace element analysis, well logs and seismic data. The lower bitumen-bearing sandstone member of the Kepingtage Formation is mainly composed of the tidal-influenced braided delta front subfacies, and may be subdivided into the subaqueous distributary channel, interdistributary bay and channel mouth bar microfacies. The planar distribution of the sedimentary facies is delineated in terms of seismic data. The migration and longitudinal and horizontal superimposition of the multistage channels led to the widespread distribution of excellent reservoir rocks, and to the best reservoir quality of the subaqueous distributary channel sandstones. The new insights in this study may provide new geological basic data for the further petroleum exploration and development in the study area.