(623c) Probing the Effect of Oil Type and Saturation on Foam Flow in Porous Media: Core-Flooding Coupled with Nuclear Magnetic Resonance (NMR) Imaging

Foam efficiency in the Enhanced Oil Recovery (EOR) processes mainly depends on its stability which is generally reduced by the presence of crude oil. In this study, we experimentally investigate the effect of oil type and saturation on foam rheology in Berea sandstone using coreflooding and nuclear magnetic resonance (NMR) imaging. From the results of foam quality scan, we showed that the calculated apparent viscosities were higher in the presence of remaining hexadecane compared to the oil-free case. This was because the relative permeability reduction and generation of oil-in-water emulsions prevailed over the foam destabilizing impact of oil. Additionally, from the oil saturation profiles we quantified the relative significance between the increased capillary number and the micellar solubilization as the two identified oil displacement mechanisms. We further correlated the foam strength with the oil saturation from the foam-oil co-injection tests. With the increase in synthetic oil saturation, foam apparent viscosity first decreased because of foam destabilization with oil; and then it was increased due to emulsification of oil with the surfactant solution. The observed trend was similar between octane and hexadecane, even though octane had more weakening effect on foam and less emulsification with the surfactant solution. Results of this study suggest that, even with detrimental effect of oil on foam stability, foam apparent viscosities could be much larger than the viscosity of the oil in place. Therefore, favorable mobility ratios could be achievable during the oil-displacement processes.