A microvisual study of solution-gas-drive mechanisms in viscous oils

For coalescence of two gas bubbles into a single bubble, the liquid lens separating the bubbles must drain. Experimental results in micromodels and triangular capillary tubes indicate that when oil-phase viscosity is high, the rate of coalescence of gas bubbles is slow. Capillary tube experiments are modeled exactly with no adjustable parameters. It is shown that the period of time for drainage is at least linearly proportional to the liquid viscosity. The implication for recovery of viscous oil is that the produced gas-oil ratio and gas-phase relative permeability remain relatively low because gas bubbles remain dispersed. Correspondingly, oil-phase relative permeability remains high contributing to relatively efficient oil recovery despite high oil-phase viscosity.