Directional displacement of non-aqueous fluids through spontaneous aqueous imbibition in porous structures

[Display omitted] •Saturation patterns in porous media were analyzed experimentally and numerically.•The two-phase flow pattern is linked to a wettability profile within porous media.•The concept of wettability capacity distribution is introduced.•Two-ends-open cores exhibit different imbibition patterns at boundaries.•Hydromagnesite exhibits a directional saturation pattern for two-phase flow. The concept of the spatial wettability gradient is applied to bulk porous media to passively influence directional spontaneous imbibition flow. The imbibition process in an oil-bearing medium was mathematically modeled and experimentally validated for cores with an induced wettability profile. This was modeled by defining a wettability capacity distribution function (WCD), which is incorporated into the capillary forces term in the transport equation. The performance of the model was verified via experiments varying the interfacial tension, viscosity, permeability, core size, and porous materials. Gypsum, calcite, and hydromagnesite exhibited specific displacement patterns under one-end-open and two-ends-open boundary conditions. Of these materials, calcite and gypsum showed a symmetric saturation pattern. In contrast, hydromagnesite was the only material that exhibited a directional phase displacement under a two-ends-open boundary condition. This behavior has been associated with a WCD. The mathematical model accurately predicted this behavior, reflecting that the main interacting forces have been considered.