Sedimentary microfacies characteristics within the high-resolution sequence framework of the Fuyu oil layer in the New North region

The Xinbei Oilfield has gone through decades of exploration and development, and lithological oil and gas reservoirs with stronger concealment are currently the focus of research. It is urgent to implement the sedimentary microfacies and sand body distribution characteristics of the Fuyu oil layer in the Xinbei area, providing a new theoretical basis for predicting the "sweet spot" of facies control in the area. Using core, logging, and logging data from the study area, a high-resolution sequence stratigraphic framework of the Fuyu oil layer was established. The distribution characteristics of sedimentary microfacies within the sequence framework were analyzed. The study showed that the Fuyu oil layer in the study area was divided into one long-term base level cycle of rising half cycle, four medium-term base level cycles, and 13 short-term base level cycles; In the area, river controlled shallow water delta plains and front sediments are developed, and a total of 10 types of sedimentary microfacies have been identified. Among them, the (underwater) distributary channel sand body, as the dominant reservoir sand body, extends along the southwest to northeast direction. As the A/S value increases, four stacking styles are developed vertically, including vertical shear stacking, staggered shear stacking, horizontal shear stacking, and isolated distribution. In the horizontal, the locally developed wide channel sand body composite zone gradually transitions into a single channel.