Abstract: Architecture of multiphase narrow-channel sand bodies has always been one of the subjects to be urgently defined in development of the Bohai oilfield. Taking the BZ25-1S oilfield as an example, guided by the theory of sand body architecture, available data (e.g. drilling, well logging, seismic and outcrop) were used to ascertain the geologic model of shallow water deltaic sand bodies, and the fine stratigraphic framework was established. By applying three types of single well correlation models (i.e. discontinuous distributary interchannel sandbody, elevation difference of the distributary channel sandbody tops, and difference in scale of distributary channel sandbody deposits) on drilling profiles, together with some seismic response features (e.g. wave amplitude variation and complex wave occurrence), well data and seismic data were combined to analyze the reservoir architecture of single-phase channel sand bodies, and the single-phase channel sand bodies were classified. The study results indicate that the thicknesses of single-phase narrow-channel sand bodies have logarithmic correlation with the widths of these sand bodies, with average width/thickness ratio of 35. The widths of single-phase narrow-channel sand bodies are 200-400 m, and they can extend across the whole study area. These study results have been adopted as effective guidance for oilfield water injection optimization, liquid producing structure adjustment and well pattern arrangement, laying a solid geologic foundation for oilfield development.

Key words: narrow-channel, multiphase channel, single sand body, reservoir architecture, Bozhong sag