The impact of wettability and core-scale heterogeneities on relative permeability

The objectives of this work were to evaluate the effects of several key parameters (e.g., wettability, saturation history and measurement methods) on the water-oil relative permeability in a mixed-wet reservoir rock. Relative permeability was first measured at its initial wettability along with its hysteresis. Wettability was altered and its impact on relative permeability was assessed. Steady-state and unsteady-state methods were compared. The relative permeabilities of the composite core were compared to those of individual plugs. A CT scanner was used to characterize the core heterogeneity and to monitor three-dimensional in situ fluid distributions during steady state and unsteady state experiments. Numerical simulation was conducted with separately characterized lithologies to describe the flow mechanism in mixed-wet porous media. Results show that an increase in oil-wettability increases the water relative permeability and decreases the oil relative permeability. A decrease of initial water saturation produces an increase in relative permeability hysteresis. Three-dimensional in situ saturations help characterize regions of different lithology and flow mechanisms. The low flow rate unsteady-state experiment can be modelled by the steady-state relative permeabilities if the heterogeneities and the capillary pressures of the composite core are considered.