Effects of salinity alternation on relative permeability and capillary pressure as determined from steady-state-transient test

Abstract

This paper aims the development of a new laboratory method for the simultaneous determination of phase relative permeability (Kr) and capillary pressure (Pc) for low salinity (LS) waterflooding. The proposed method is based on the so-called steady-state-transient (SSTT) method that uses steady-state and transient coreflood data, which allows calculating Kr and Pc from the same coreflood. A novel mathematical modelling is developed to determine Kr and Pc for two-phase multicomponent transports, where these parameters also depend on component concentrations, i.e. kr(s,c) and pc(s,c).Two sister cores from the same outcrop are used for the SSTT and wettability measurement experiments. The SSTT is performed using a sequence of HS injection → core re-initialization → LS injection to enable comparison of Kr and Pc curves for the same initial conditions. The modelling resultsusing a well-posed inverse algorithm - indicate a significant decrease in relative permeability for water, an insignificant increase in relative permeability for oil, a slight reduction in residual oil saturation, and a negligible downward shift in the Pc curve after LS water injection. This is explained by the formation damage caused by the mobilization of fine particles and the consequent pore-scale flow diversion due to pore plugging.