Core scale analysis of low viscosity oil injection in enhancing oil recovery of heavy oil reservoirs

In this study, static tests and core experiments were carried out to evaluate heavy oil (high viscosity oil) production performance using low viscosity oil as a potential injection, as well as the coupling effects of viscous fingering and viscosity reduction on the displacement efficiency. Results show that 30% was the optimal maximum dilution ratio when considering economy and efficiency. With the low viscosity oil injecting, the displacement front came to breakthrough around 0.3 pore volume (PV), and then the effluents' viscosity and the viscosity distributions along the core came to a sharp decline, indicating that low viscosity oil has already mixed thoroughly with heavy oil. The low viscosity oil displacements and heavy oil reverse displacements revealed a key instruction for the field application: The final total recovery of heavy oil was up to 65%, while it was almost 100% near the injection port. The injected low viscosity oil could be almost 100% retrieved for recycle, the larger displacement rate facilitated the faster growth of viscous fingering, further assisting low viscosity oil better dissolving into heavy oil and reducing the flow resistance. The study demonstrated a promising and practical strategy of low viscosity oil injection on enhancing heavy oil recovery.