Shoreface Reservoir Architecture Characterization and Its Impact on Oil–Water Distribution in the HD4 Block, Hudson Oilfield

As the largest deep‐marine clastic reservoir in China, the Hudson Oilfield has entered a high water‐cut development stage. Detailed characterization of reservoir architecture and clarification of oil–water distribution patterns are, therefore, essential for identifying remaining oil and optimizing further reservoir development strategies. In this study, the reservoir architecture of the HD4 block in the Hudson Oilfield was systematically characterized on the basis of core observations, conventional wireline logs, high‐resolution array induction logs, and outcrop analog analysis from the Yuntaishan area, constrained by a depositional genetic model. A deterministic geological model was constructed, and reservoir numerical simulation was conducted to investigate the controlling mechanisms of reservoir architecture on oil–water distribution and remaining oil occurrence. The results indicate that (1) controlled by oscillatory sea‐level fluctuations, argillaceous, calcareous, and calcareous–argillaceous interlayers are extensively developed along architectural interfaces, with their strikes generally perpendicular to the shoreline and dip angles ranging from 0° to 5°; (2) fourth‐order architectural units are classified into composite bar sands, composite beach sands, and composite beach–bar sands, exhibiting a progressive decrease in lateral extent and thickness, whereas third‐order architectural units comprise bar sands, beach sands, and grooves, with their bounding surfaces displaying three geometric types: parallel, oblique, and trough‐shaped architectural surfaces; (3) laterally continuous interlayers developed along fourth‐order architectural interfaces effectively inhibit vertical oil–water migration, whereas the barrier effects of third‐order architectural surfaces restrict fluid communication and result in inclined original oil–water contacts within individual reservoir units; and (4) the absence of barrier layers at marginal architectural interfaces, the development of argillaceous interlayers along architectural interfaces, and the occurrence of calcareous interlayers along architectural interfaces generate three distinct types of remaining oil enrichment patterns, namely, marginal remaining oil, roof‐type remaining oil, and eaves‐type remaining oil. This study establishes the reservoir architecture framework of shoreface reservoirs in the study area and provides geological insights for optimizing remaining oil recovery strategies.