Measuring in-situ capillary pressure of a flowing foam system in porous media

In the low-quality regime, a plateauing trend in P was identified. In-situ microscopic visualization of the flowing foam revealed that gas bubbles were convecting with a fine discontinuous texture while P is at the plateau value P. In the high-quality regime, the measured capillary pressures first decreased with increasing quality before increasing again at the driest qualities. These changes in P correlated with foam bubbles becoming coarser with increasing injected gas fractional flow before transitioning to continuous-gas flow at the slowest and driest injection conditions. These findings have been previously unreported for steady-state flow conditions and shall have significant implications for the general physical description of foam flow in porous media.