Numerical Studies of Unstable Fingering Flow in a Water-Oil System

Summary Fingering behavior is a crucial phenomenon in the improved oil recovery process and significantly influences oil recovery, including heterogeneity channeling and viscous fingering. This study modeled the fingering behavior during the water flooding process and enhanced the simulation method to represent these two phenomena simultaneously. In this study, we employ the Corey correlations to preserve laboratory-measured data on the relative permeability and incorporate the impact of capillary pressure. The Leverett J-function is additionally used to integrate formation heterogeneity and saturation influence on capillary pressure. The method is validated through a comparison with lab-based flat-plate displacement experiments, with authentic measured relative permeability data. our improved model can accurately capture the results of the fingering phenomenon, obtaining similar fingering patterns and quantitatively matching the BHP, water cut, and oil recovery factor. Based on it, we explored the influence of injection rate, water and oil viscosities, and viscosity ratio. The results indicate that increasing the injected water viscosity delays the breakthrough, thus improving the oil recovery. It is worth noting that the same value of viscosity ratio does not obtain the same results. For instance, when the water and oil viscosities are 100m and 1000 mPa·s, 1PV water injection results in a final recovery factor of 54.79%, while 38.02% with viscosities of 1mPa·s and 10 mPa·s respectively. Water injection rates also affect the final oil recovery. These two typical findings cannot be captured in most of previous simulations. By considering the impact of capillary pressure heterogeneity, such physical phenomena are well reproduced in this work. Compared to visualization experiments and micro-scale direct simulation, macro-scale fingering simulation has always been challenging. While some studies can obtain fingering images similar to those observed in laboratory experiments, the relative permeability used deviates significantly from actual conventional laboratory measurements. However, our improved model can simultaneously reproduce both heterogeneity channeling and viscous fingering phenomena with authentic laboratory-measured data.