Measurement of imbibition rate of surfactant solution into fractured oil-wet porous media using CT scanning

Imbibition of surfactant solution into the matrix of fractured oil-wet reservoirs is a complicated process which involves gravity, capillary, viscous, diffusive, and compositional gradients. The standard experiments for testing imbibition of surfactant solution involves an imbibition cell, where the core is placed in the surfactant solution and the recovery is measured versus time. Although these experiments prove the effectiveness of surfactants, little insight into the physics of the problem is achieved. Here we study the imbibition by flowing surfactant vertically through an artificially fractured core. We monitor the imbibition fronts along the core using CT scanning. We perform the experiments with cores of different sizes and permeability and various flooding solutions and visualize the front position using CT scanner. We also propose a simple analytical method to explain our observations. Simplified experiments of imbibition of surfactant into oil-wet capillary tubes are also performed to better understand the controlling physics. We find that imbibition front moves faster in high permeability zones. In addition, the imbibition rate depends on the surfactant solution viscosity. We show how these results lead to insight of the physical processes that take place during surfactant mediated imbibition.