Experiments and phase-field simulation of counter-current imbibition in porous media with different pore structure

Spontaneous imbibition is relevant to many processes in nature and industry. In this work, the effect of pore structure of porous media on counter-current imbibition is studied. The one-dimensional counter-current imbibition experiments were conducted in packed porous media with different pore structure. Experimental results showed that counter-current imbibition can only proceed for a short time in homogeneous porous media for all fluids. In heterogeneous porous media, counter-current imbibition can only proceed a short time for water–air experiments as well. However, imbibition can proceed continuously until the imbibition front reaches the end of packed porous media for water–oil experiments and the mass of water infiltration is proportional to the square root of time. The efficiency of water infiltration behind the imbibition front decreases with increase in viscosity of non-wetting phase fluid. In addition, the numerical simulation of counter-current imbibition in porous media with different pore structure were conducted using phase-field method. Simulation results showed that very little oil was produced in homogeneous porous media and more oil was produced in heterogeneous porous media. It is indicated that the difference between capillary driving pressure and capillary back pressure, which are closely related to pore structure and pore size distribution of porous media, has important influence on counter-current imbibition. Furthermore, the snap-off of oil or gas production channels in narrow pore throats may lead to termination of imbibition when the water saturation behind the imbibition front is higher.