Simulation of counter-current imbibition in water-wet fractured reservoirs

Counter-current imbibition, where water spontaneously enters a water-wet rock while oil escapes by flowing in the opposite direction is a key recovery mechanism in fractured reservoirs. Fine grid, one- and two-dimensional simulations of counter-current imbibition are performed and the results are compared with experimental measurements in the literature. The experimental data are reproduced using two sets of relative permeabilities and capillary pressures. One set is derived from a counter-current experiment and one set is computed using pore-scale modelling. Two-dimensional simulations of water flow through a single high permeability fracture in contact with a lower permeability matrix are run. The results are compared with experimental measurements of fracture flow and matrix imbibition in the literature and with one-dimensional simulations that account for imbibition from fracture to matrix using an empirical transfer function. It is shown that with this transfer function the behavior of the two-dimensional displacement can be predicted using a one-dimensional model. (c) 2005 Published by Elsevier B.V.