Study on The Spatial Distribution of Single Sand Bodies in Subaqueous Distributary Channels and Their Impact on Remaining Oil

Subaqueous distributary channel sand bodies are an important sedimentary type in the delta front facies and serve as high-quality reservoirs in oil and gas development. Compared to subaerial sedimentary types such as floodplains and distributary plains, subaqueous distributary channel sand bodies are smaller in scale, exhibit rapid facies changes, and have poor continuity. However, they still consist of composite sand bodies formed by the vertical and lateral stacking of single sand bodies from multiple channel phases. The development and contact relationships of single sand bodies from different phases directly influence the internal heterogeneity of composite sand bodies, thereby affecting the distribution of remaining oil. This study employs methods such as “sedimentary phase guidance,” “log facies analysis,” and “well-seismic combined prediction” to conduct a detailed dissection of composite subaqueous distributary channel sand bodies in the northern S area of Daqing Placanticline. It identifies the developmental characteristics and contact relationships of four types of single sand bodies: migratory, stacked, regressive, and transgressive. Based on this, the study analyzes fluid flow patterns under different contact relationships, identifies the locations of remaining oil enrichment, and lays a geological foundation for improving the development efficiency of subaqueous distributary channel sand bodies.