A critical review of Roof snap-off as a mechanism of steady-state foam generation in homogeneous porous media

Foams are used worldwide to divert acid in well-stimulation treatments and on a pilot basis to divert gas or liquid flow in improved-oil-recovery projects and environmental remediation. Optimizing foam performance requires predictive foam modeling for use in design of field applications. Central to many mechanistic foam models is the concept of repeated snap-off creating foam lamellae at ‘germination sites,’ pore throats upstream of wide pore bodies. This mechanism is based on the classic study of Roof on the breakup of oil droplets passing through pore throats into water-filled pores. This paper calls into question whether this mechanism applies to foam generation at steady-state in homogeneous porous media.