Forecasting the impact of formation damage on relative permeability during low-salinity waterflooding

Abstract

Low-salinity waterflooding is considered to be an advanced oil recovery method, but the main mechanism behind the increase in oil recovery factor is still under investigation. Fines migration has been recognized to be one of the mechanisms responsible for the increase in oil production. In this case, the increase in oil recovery happens as a result of increased sweep efficiency and consequent reduction of residual oil. The release of particles due to reduction of electrostatic forces results in flux diversion to previously unswept areas in the reservoir, increasing oil recovery. This paper provides a better understanding of the effects of formation damage during low-salinity water injection in Berea sandstones and proposes a methodology to forecast its effects on water relative permeability. We have performed one- and two-phase flow coreflood experiments with varying salinity of the injected solution. The effluent was analysed for salinity, pH and particle concentration. The laboratory data was treated using a mathematical model that accounts for permeability impairment during low-salinity waterflooding due to fines detachment, migration and capture in small pore throats. The parameters of the model were used to predict the impact of formation damage on the water relative permeability during two-phase flow. The mathematical model matched the laboratory data for pressure drop and particle concentration in the outlet with great accuracy. A methodology to predict the impact of formation damage in two-phase flow using one-phase flow data was proposed. A good agreement between the predicted and the measured water relative permeabilities was obtained. The forecasted water relative permeability curve was able to reproduce the non-monotonic behaviour of water relative permeability due to low-salinity water injection.