Summary
Foamy-oil flow has been successfully demonstrated in laboratory experiments and site applications. On the basis of solution-gas-drive experiments with Orinoco belt heavy oil, the effects of temperature on foamy-oil recovery and gas/oil relative permeability were investigated. Oil-recovery efficiency increases and then decreases with temperature and attains a maximum value of 20.23% at 100°C. The Johnson-Bossler-Naumann (JBN) method has been proposed to interpret relative permeability characteristics from solution-gas-drive experiments with Orinoco belt heavy oil, neglecting the effect of capillary pressure. The gas relative permeability is lower than the oil relative permeability by two to four orders of magnitude. No intersection was identified on the oil and gas relative permeability curves. Because of an increase in temperature, the oil relative permeability changes slightly, and the gas relative permeability increases. Thermal recovery at an intermediate temperature is suitable for foamy oil, whereas a significantly higher temperature can reduce foamy behavior, which appears to counteract the positive effect of viscosity reduction. The main reason for the flow characteristics of foamy oil in porous media is the low gas mobility caused by the oil components and the high viscosity. High resin and asphaltene concentrations and the high viscosity of Orinoco belt heavy oil increase the stability of bubble films and prevent gas breakthrough in the oil phase, which forms a continuous gas, compared with the solution-gas drive of light oil. The increase in the gas relative permeability with temperature is caused by higher interfacial tensions and the bubble-coalescence rate at high temperatures. The experimental results can provide theoretical support for foamy-oil production.
