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

A. Chauhan, F. Salehi, S. Jalalifar and S.M. Clark Applied Nanoscience https://doi.org/10.1007/s13204-021-01791-x (2021).

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.

Fig. 1 Simple (a) and more complex (b) geometries considered

Fig. 3 A mesh snapshot for the pore region

Fig. 4 Volume fraction of cases at (1.1) Water-wet, (1.2) Intermediate-wet and (1.3) Oil-wet states at diﬀerent ﬂow times a 1 ms; b 20 ms; and c 45 ms

Fig. 5 Volume fraction of cases at (2.1) Water-wet, (2.2) Intermediate-wet and (2.3) Oil- wet state at diﬀerent ﬂow times a 1 ms; b 12 ms; and c 30 ms

Fig. 9 Volume fraction of the wettability and IFT combined eﬀect on Case 1 unsaturated oil state (2-droplets (1.4) 15 μm dia and (1.5) 9 μm dia.) at diﬀerent ﬂow times a 1 ms; b 25 ms; and c 70 ms

Fig. 10 Volume fraction of the wettability and IFT combined eﬀect on Case 2 unsaturated oil state (3-droplets (2.4) 15 μm dia and (2.5) 9 μm dia.; surface tension 52 μN/m) at diﬀerent ﬂow times a 0.1 ms; b 20 ms; and c 120 ms