Effect of Injection Rate on Oil Water Relative Permeability Accounting for Capillary Pressure and Outlet end Effects

Abstract

Two-phase immiscible drainage experiments are performed on strongly water-wet sandstone sample to assess and illustrate capillary end effects at different rates on relative permeability. All the experiments were done under unsteady state conditions with oil displacing brine in fully brine saturated cores. First, relative permeability curves are calculated using the Johnson–Bossler–Naumann (JBN) method (Johnson et al. 1959). Then, modified JBN model is defined to account for capillary pressure. Lastly, numerical simulator is used to generate relative permeability curves based on history matching. Results of the experiments show that as the rate increases (higher capillary number), the water relative permeability increases while the irreducible water saturation decreases. With high rate, less water saturation is being accumulated at the outlet hence less irreducible water and higher relative permeability. Moreover, the oil relative permeability curves are getting higher with higher rates confirming CEE impact on the tests. The calculated irreducible water saturation based on the core weights re-affirms the JBN calculation and decreases with higher rates. This paper proves capillary end effects on relative permeability curves at low rates which have low capillary numbers on water-wet sandstone cores.