Persistence of Local Capillary Trapping during Caprock Leakage and Forced Imbibition

A bench scale experiment using a fluid pair analogous to supercritical CO2 and brine in saline aquifer is created, which allows for studying plume migration with physically representative properties but at experimentally convenient ambient conditions. A variety of heterogeneous porous media made of loosely packed silica beads are used to validate and test the persistence of local capillary trapping mechanism. By adjusting the boundary conditions, the capillary pressure gradient across the domain was manipulated. The trapped buoyant phase remained secure beneath the local capillary barriers, as long as the effective capillary pressure exerted by the trapped phase is smaller than the capillary entry pressure of the barrier. The local capillary trapping mechanism remained persistent even under forced imbibition, and the mobile phase trapped even survived a breach of caprock in adjacent region. (C) 2014 The Authors. Published by Elsevier Ltd.