Shallow Delta Sand Body Characteristics of Chang 6 Oil Layer in Zichang Area, Northern Shaanxi

Based on the coring data of 48 wells and the logging data of 213 wells, this paper comprehensively analyzes the shallow water delta sedimentation and sand body stacking characteristics of the Yanchang 6₁-6₂ sub-member of the Triassic in the Zichang area of northern Shaanxi, as well as the corresponding relationship with reservoir physical properties. According to the accommodation space and sediment supply flux, the single sand bodies in the study area are distributed in an isolated manner in the high accommodation space, and are not connected to each other. The low accommodation space is superposed in a multi-stage vertical connection type and a multi-stage superimposed shear type. The physical properties of reservoirs with different sand body stacking types are different. According to statistical analysis of data, the separated sand bodies in the study area are the thinnest in thickness, and the sand bodies are distributed in an isolated manner. Individual sand bodies are separated by thick interlayer, and there is no connectivity between individual sand bodies. Multiple vertical cut sand bodies are separated by thin interlayer, resulting in weak connectivity between the two sand bodies. The average thickness of multiple vertical cut sand bodies is the thickest. There is no interlayer between the upper and lower single sand bodies, and the connectivity between the two single sand bodies is strong. The lateral contact of sand bodies is comprehensively affected by paleoclimate, hydrodynamic strength, and supply, and is divided into butt contact, lateral shear contact, and inter-bay contact. The connectivity between butt contact sand bodies is strong. The sand bodies in lateral shear contact and inter-bay contact are affected by gravity diversion during development, and the remaining oil is often enriched in the upper sand bodies at relatively high positions.