Two-Dimensional Visual Experimental Investigation of Interlayer Effects on Thermal Recovery in Bottom-Water Heavy Oil Reservoirs.

This study presents a systematic experimental investigation of heat and mass transport behaviors in bottom-water heavy oil reservoirs with interlayer heterogeneity using a two-dimensional visual physical model. The presence of bottom water and geological barriers introduces complex coupling between fluid flow, heat transfer, and displacement stability, which remains insufficiently quantified. Comparative experiments, including natural energy depletion and cyclic steam stimulation, were conducted under homogeneous and interlayer conditions. The evolution of displacement fronts, oil saturation distribution, and production dynamics was analyzed using visualization and resistance-based monitoring. To enable quantitative evaluation, a displacement uniformity index and an apparent heat utilization efficiency were introduced to characterize spatial sweep stability and thermal effectiveness, respectively. The results indicate that thermal recovery modifies the flow regime by reducing oil viscosity and altering mobility contrast, leading to an expanded heated region and delayed bottom-water intrusion. Interlayers act as flow barriers that redistribute both fluid and heat transport: they promote lateral heat spreading and suppress direct heat loss to bottom water, while simultaneously inducing localized unswept regions due to shielding effects. The role of interlayers is found to be stage-dependent, governed by the transition from confined flow to edge-dominated bypass and subsequent flow reorganization. These findings provide a physically interpretable framework for understanding coupled thermal-hydrodynamic processes in heterogeneous heavy oil systems and offer quantitative tools applicable to the evaluation of thermal recovery performance.