Study on Microscopic Seepage Characteristics and Oil Displacement Effect of Heterogeneous Composite Flooding

In response to the problems of high water content, low recovery rate, and ineffective circulation of injected displacement fluid in heavy oil reservoirs with extremely high water content, this study systematically explores the micro seepage characteristics and oil displacement effects of heterogeneous composite flooding through micro visualization experiments, clarifies its mechanism of action under different crude oil viscosity, system concentration, and component conditions, and provides theoretical basis for improving chemical flooding recovery rate. This study adopts a microscopic visualization model combined with high-speed dynamic image acquisition technology to design multiple experimental schemes. Through three-stage displacement experiments of water flooding, heterogeneous composite flooding, and subsequent water flooding, the remaining oil occurrence state, changes in sweep coefficient, and seepage laws are quantitatively analyzed. Heterogeneous composite flooding significantly improves the micro residual oil utilization efficiency by reducing interfacial tension, regulating flowability ratio, and dynamically plugging large pores. Compared with water flooding, after composite flooding, the proportion of remaining oil area in thin film and corner shapes decreased by 45% and 38% respectively, and the remaining oil in cluster shapes decreased by 72%; The subsequent water drive sweep coefficient was further increased to 94.34%. The increase in crude oil viscosity leads to a decrease in water flooding efficiency, but composite flooding inhibits viscosity fingering through the thickening effect; System concentration and component optimization (such as PPG plugging) can selectively regulate the seepage field, further improving the sweep coefficient. This study, based on microscopic visualization technology, reveals the triple mechanism of synergistic emulsification, flowability control, and plugging in heterogeneous composite flooding, providing a quantitative design basis for the development of heavy oil reservoirs in the ultra-high water cut stage, and has significant technical and economic value.