The effect of pore throat size and injection flowrate on the determination and sensitivity of different capillary number values at high-capillary-number flow in porous media

This study examines the effect of pore throat size and injection flowrate on the values of the pore-scale capillary number, the Newtonian-fluid capillary number and the apparent capillary number ( N c 1 , N c 2 and N c 3 , respectively) and their sensitivity to change in high-capillary-number flow through porous media, which occurs in polymer-assisted dilute surfactant flooding (PADSF). Additionally, the influence of pore throat size and injection flowrate on oil recovery at breakthrough and at the end of displacement (ultimate) and the relationship between the effective shear rate γ eff and the porous medium-dependent shift factor α are discussed. The results indicated that N c 2 was the smallest and N c 3 was the largest value. The difference between N c 2 and N c 3 is due to the increase in apparent viscosity of the polymer-contained surfactant solution during the flow through porous media and the change in N c 3 should be utilized to characterize the macroscopic behavior of the PADSF. Generally, the decrease in pore throat size and the increase in injection flowrate caused an increase in the ultimate oil recovery and N c3 . Moreover, the oil recovery at breakthrough decreased with an increase in pore throat size and injection flowrate. Finally, the rate of change of γ eff , with change in α, increased almost uniformly with a decrease in pore throat size and an increase in injection flowrate.