Foam mobility control and novel oil displacement mechanisms were observed in a microfluidic device representing a porous media system with layered permeability. Foam was pre-generated using a flow-focusing microfluidic device and injected into an oil-wet, oil-saturated 2-D PDMS microfluidic device. The device is designed with a central fracture flanked by high-permeability and low-permeability zones stratified in the direction of injection. A 1 : 1, 1% blend of alpha olefin sulfonate 14-16 (AOS) and lauryl betaine (LB) surfactants produced stable foam in the presence of paraffin oil. The oil saturation and pressure drop across the microfluidic device were measured as a function of time and the injected pore volume, indicating an increase in apparent viscosity for foam with an accompanying decrease in oil saturation. In contrast to the control experiments, foam was shown to more effectively mobilize trapped oil by increasing the flow resistance in the fracture and high-permeability zones and by diverting the surfactant solution into adjacent low-permeability zones. The foam was observed to separate into gas-rich and aqueous-rich phases depending on matrix permeability, suggesting that it is not appropriate to treat foam as a homogeneous dispersion of gas and liquid.

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The effect of polymer composition and polymerization parameters such as comonomers, crosslinking ratio, and polymerization method, on the surface characteristics, surface chemistry, and swelling response of crosslinked 2-(diethylaminoethyl methacrylate) (DEAEM) and polyethylene glycol monoethyl ether monomethacrylate (PEGMMA) nanogels was studied. A novel inverse-emulsion polymerization method was developed, which formed latex nanoparticles on the order of 100-400 nm. The properties of these nanogels were compared to microparticles synthesized via solution polymerization. The new polymerization method allowed the incorporation of PEG surface tethers of lengths 400 Da up to 2000 Da. Surface tethers successfully decreased the ζ-potential of these nanogels from 70 mV to 30 mV in acidic conditions and from −60 mV to 2 mV in basic media. Nanogels swelled from 100 nm in basic media to 800 nm in acidic media due to the protonation of the tertiary amine on DEAEM.