Visualization of improved sweep with foam in heterogeneous porous media using microfluidics

We demonstrate the use of foam to divert flow from high permeable to low permeable regions in a PDMS heterogeneous porous microfluidic system. Foam is generated using a flow-focusing microfluidic device with co-flowing gas and aqueous surfactant streams. Foam quality (gas fraction) is modulated by adjusting the flow rate of the aqueous surfactant solution while keeping the gas inlet pressure fixed. The foam is then injected into an aqueous-solution filled heterogeneous porous media containing a high and low permeable region and sweep of the saturated aqueous phase is monitored. Compared with 100% gas injection, surfactant-stabilized foam is shown to effectively improve the sweep of the aqueous fluid in both high and low permeable regions of the porous micromodel. The best performance of foam on fluid diversion is observed in the lamella-separated foam regime, where the presence of foam can enhance gas saturation in the low permeable region up to 45.1% at the time of gas breakthrough. The presented results are useful in understanding and designing foam injection in porous underground formations for aquifer remediation and enhanced oil recovery processes.