Pore-scale studies of spontaneous imbibition into oil-saturated porous media.

Spontaneous imbibition phenomenon was modeled using the lattice Boltzmann method (LBM). The model was validated using silicon-etched micromodel and sandpack visualization experiments. The strongly water-wet model saturated with oil (kerosene or mineral oil) was exposed to distilled water in order for a capillary interaction to take place under static conditions. These experiments mimic the transfer between rock matrix and fracture during any wetting phase flow in fractures while the matrix contains a nonwetting phase as encountered in oil, gas, and geothermal reservoirs as well as during the application of subsurface CO2 sequestration or waste disposal reservoirs. Despite the vast amount of research work on this common process, pore-scale investigations and modeling are limited especially at small time scales. The results showed that the LBM captures the physics of the process at pore scale for low viscosity values of nonwetting phase for any type of (cocurrent or countercurrent imbibition) interaction.