Sedimentary Microfacies and Sand Body Characterization of Lower Section of He 8 Member in the X Area, Northern Ordos Basin

The study area is located in Ordos City, Inner Mongolia Autonomous Region, China, and one of its main gas producing layers is the lower section of He 8 Member of Lower Permian Lower Shihezi Formation. Mainly utilizing core, well logging, drilling and other data, and integrating theories and methods of sedimentary petrology, sedimentology, reservoir geology and development geology, sedimentary microfacies types such as central bar, channel fill, interchannel and abandoned channel are identified in the braided river delta plain of the lower section of He 8 in the study area; On the plane, the microfacies of central bar are surrounded by the channel, and together with the channel fill microfacies control the distribution of sand bodies, forming the sedimentary microfacies distribution pattern of the braided channel controlled sand bodies. The spatial distribution characteristics of sand bodies are analyzed by analyzing vertical overlay styles and Lateral contact relationships of sand bodies. On this basis, it is considered that the vertical superimposition of overlay cutting style between sand bodies is more common, and the lateral contact is mainly replacement type and side shear type between sand bodies, which reflect the good connectivity of sand bodies in the lower section of He 8 Member. This study provides new insights into sedimentary microfacies and sand body characterization for the fine description of He 8 tight sandstone gas reservoir in the northern Ordos Basin.