Experimental Study of Hysteresis Behavior of Foam in Porous Media

Abstract

Foam EOR improves the sweep efficiency by reducing gas mobility and creating a stable displacement front. In the field application, the surfactant concentration and flow rate vary in the reservoir, influencing dramatically the foam mobility. However, the variations of surfactant concentration and flow rate do not relate monotonously to the foam properties. In some cases, the foam properties depends on the history of the flow, i.e., a hysteresis effect. But hysteresis in foam flood has not been well characterized and understood. This study aims to understand hysteresis behavior of foam in porous media. To this end two series of experiments have been conducted: 1) Hysteresis behavior due to flow rate variations and 2) Hysteresis behavior due to surfactant concentration variations. In the flow rate experiments, several shear-thinning experiments at different volume fractions of gas (foam quality) are conducted in order to understand the effect of gas fraction and total velocity on foam generation mechanisms. In the surfactant concentration experiment, experiments have been performed at different surfactant concentrations and at different volume fractions of gas (foam quality). Results showed that a transition from weak to strong foam is more pronounced in high-quality regimes (gas fractional flow above 90%) than low-quality regimes (gas fractional flow below 80%). Remarkably, no hysteresis behavior has been observed in low-quality regimes, while hysteresis behavior occurred in high quality regimes. Furthermore, the effect of surfactant concentration on hysteresis behavior has been also investigated at high- and low-quality regimes. Contrary to some previous works, hysteresis behavior does not occur for surfactant variation. Remarkably, the apparent viscosity remains almost constant in low-quality regime for different surfactant concentrations. These results have important implications of the injection strategy and the economics of foam EOR. The surfactant concentration could be decreased and less gas could be injected, and in the same time, the foam performance could be maintained.