The influence of viscosity on stability of foamy oil in the process of heavy oil solution gas drive

Primary production from some heavy-oil reservoirs in the process of solution gas drive exhibits high primary recovery. This is because the formation and flow of foamy oil which indicated that gas was dispersed in the heavy oil and flow with oil phase when formation pressure was lower than bubble pressure. The stability of foamy oil was influenced by many issues including oil viscosity, the contents of dissolved gas, temperature and the pressure depletion rate. We mainly researched the influence of oil viscosity on stability of foamy oil in the process of heavy oil solution gas drive. Through sand-pack experiment, we researched foam quality and half-life period of foamy oil for different oil viscosity under atmosphere pressure and temperature of 25 °C, neglecting pressure depletion rate. Results indicated that as oil viscosity increased, the stability of foamy oil became better. Large solution viscosity plays an important role in retarding the transport of gas from solution to the growing bubble in the foamy oil because bubble volume increases much more slowly in viscous oils, coalescence is slowed dramatically. The curve between half-life period and oil viscosity had an inflection point and its corresponding oil viscosity can be used as proper viscosity suitable for heavy oil solution gas drive and sand-carrying cold production.