Hyperslow drainage

Abstract

We investigate the process of very slow drainage from pore network simulations in relation with the study of the storage of radioactive waste materials in deep geological formation. The process is characterized by a quite low desaturation of the medium. Considering the special case of a constant stabilizing gradient, we first study the sensitivity of the solution given by the classical continuum two phase flow model to the shape of the retention curve. The solution is found to be very sensitive to the evolution of the retention curve in the range of the high wetting fluid saturations. We show how to construct the retention curve so as to minimize the prediction error with the classical two-phase flow model. Then we consider the immiscible displacement of a non-viscous wetting fluid by a viscous non-wetting fluid and study the influence of the non-wetting fluid relative permeability from three dimensional pore network simulations. Similarly as the retention curve, we show how the relative permeability must be specified in the range of the high wetting fluid saturations so as to obtain optimal predictions from the classical two-phase flow model.