Surfactant concentration and end effects on foam flow in porous media

Foaming injected gas is a useful and promising technique for achieving mobi lity control in porous media. Typically, such foams are aqueous. In the pre sence of foam, gas and liquid flow behavior is determined by bubble size or foam texture. The thin-liquid films that separate foam into bubbles must b e relatively stable for a foam to be finely textured and thereby be effecti ve as a displacing or blocking agent. Film stability is a strong function o f surfactant concentration and type. This work studies foam flow behavior a t a variety of surfactant concentrations using experiments and a numerical model. Thus, the foam behavior examined spans from strong to weak. Specifically, a suite of foam displacements over a range of surfactant conc entrations in a roughly 7 mum(2), one-dimensional sandpack are monitored us ing X-ray computed tomography (CT). Sequential pressure taps are employed t o measure flow resistance. Nitrogen is the gas and an alpha olefin sulfonat e (AOS 1416) in brine is the foamer. Surfactant concentrations studied vary from 0.005 to 1 wt%. Because foam mobility depends strongly upon its textu re, a bubble population balance model is both useful and necessary to descr ibe the experimental results thoroughly and self consistently. Excellent ag reement is found between experiment and theory.