Flow-unit classification in an example of compound sand-body architecture was carried out in a delta in the W oilfield, Weixinan Sag, Beibuwan Basin to further describe reservoir heterogeneity and also to summarize the remaining oil distribution pattern. Combining well logging, seismic, production dynamics and a geological knowledge database with similar sedimentary characteristics, the compound sand-body architecture was analyzed using sparse well network data in W oilfield. The porosity, permeability and flow-zone index were adopted to divide the reservoir into four types of flow units. Their distribution was well described within compound sand-body architecture constraints, and their distribution pattern was summarized. The study revealed a complex internal architecture for the delta front compound sand-body for W oilfield in the third member of the Weizhou Formation. Geological factors （compound sand-body architecture, flow units and faults） had significant influence on the flooding characteristics and the distribution of remaining oil. In-depth analysis of the waterlogged properties of the water-flooded zone of the adjustment wells revealed three main distribution patterns of the remaining oil： （i） differential displacement patterns due mainly to flow units only; （ii） complex blocking patterns controlled by flow units combined with mud interlayers; and （iii） fault⁃flow unit patterns controlled by flow units and faults. These results provide an important reference for tapping the full potential of the oilfield.