In this study, the ensemble Kalman lter is used to characterize threephase flow in porous media through simultaneous estimation of three-phase relative permeabilities and capillary pressures from production data. Power-law models of relative permeability and capillary pressure curves are used and the associated unknown parameters are estimated by assimilating the measured historical data. The estimation procedure is demonstrated on a twin numerical setup with two dierent scenarios, in which a synthetic 2D reservoir under three-phase flow is considered. In the rst scenario, all the endpoints are assumed to be known and only the shape factors are estimated during the assimilation process. In the second, all the endpoints and shape factors are estimated by assimilating observed data. Accurate estimation of the unknown model parameters is achieved by assimilating oil, water, and gas production rates of the producers and bottom-hole pressure
of the injector. Moreover, sensitivity analysis of the observations with respect to the parameters dening the relative permeabilities and capillary pressures shows that for the most sensitive parameters, better estimation and lower uncertainty are obtained at the end of the assimilation process.