Two-phase modelling of the effects of pore-throat geometry on enhanced oil recovery

Abstract

This study presents computational fluid dynamics (CFD) analysis of the effects of wettability, viscosity and interfacial tension (IFT) for enhanced oil recovery (EOR) with varying pore configuration. A more realistic pore-throat geometry is studied which was motivated by oil-containing rock configuration that indicates the importance of pore geometry in EOR. The results are compared with those obtained for a simple geometry. Both saturated and unsaturated conditions are considered while the IFT varies. For both geometries, the saturated condition presents 99% of oil recovery, for the water-wet and intermediate states while it is about 88% for the oil-wet state. However, there is a significant difference in the temporal evolution of the oil recovery factor, as the complex model is 1.4 to 3 times slower than the simplified one to achieve maximum oil recovery factor under the same conditions. For unsaturated conditions, two different initial oil volumes were considered to explore the combined effect of low IFT and change in wettability. Similarly, the oil recovery process is significantly slower for the complex geometric configuration. The study of very low IFT values (10, 35, 65 and 75 µN/m) for the complex configuration in the unsaturated oil condition revealed that highest oil recovery is achieved at the IFT of 75 µN/m. The results confirm that geometric configuration plays an important role in EOR. The impact of pore structure becomes more significant in the unsaturated oil state demonstrating that very low values of IFT slow the oil recovery process.