Unsaturated flow in fractured media: role of liquid splitting dynamics at fracture intersections

Abstract:

We present a quasi-static model to predict the liquid splitting behavior at a T-junction, as a simplified representation of a fracture intersection and consisting of a main channel and a branch channel. The proposed model is validated against carefully controlled flow visualization experiments. It is found that a critical initial slug length exist at which the splitting behavior shifts from flow dominated by the main channel to that dominated by the branch. We systematically investigate the influence of key parameters, including the inclination angle of the junction, the channel widths, and the dynamic contact angles, on the splitting dynamics is systematically investigated. It is also demonstrated that the splitting ratio depends non-monotonically on the relative width of the branch channel to the main channel. The obtained understanding of liquid splitting behavior is further applied to study of unsaturated flow in fracture networks. The flow focusing behavior at the network scale is quantified and discussed.