Transport in Porous Media, Vol.64, No.3, 301-313, 2006
Coupling of foam drainage and viscous fingering in porous media revealed by X-ray computed tomography
We investigate the development foam in granular porous media and the subsequent flow of the surfactant solution, where the fluid fraction variations are visualized and quantified using X-ray computed tomography. It is found that foam flows in a front like manner leading to a residual liquid fraction of 0.18 +/- 0.01, far from the inlet surface of the porous sample. A desaturation backward wave is also observed during foam development. We provided direct evidence that the flow of surfactant solution in porous media containing foam gives rise to superposition of a drainage wave and a characteristic viscous fingering pattern. In the wave the liquid fraction ranges from the above residual value to nearly 0.25 +/- 0.01. The liquid fraction associated with the viscous fingering decays as a function of distance but the inlet value increases up to 0.06 +/- 0.01. Certain ideas about the physics of foam flow in porous media are revised in the light of our findings.