Foam-flow behavior in porous media: Effects of flow regime and porous-medium heterogeneity

Foam is used in enhanced oil recovery (EOR), matrix acidization and environmental remediation because it can lower the mobility of the fluids injected into the reservoir. Modeling foam in porous medium is vital to understanding foam mechanisms to increase the efficiency of foam processes. Much of the current foam knowledge is based on the P_c* model. However, recently Osterloh and Jante (1992) found that foam flow in porous media can be divided into two regimes: a high-quality regime described by the P_c* model, and a low-quality regime with very different behavior. Their results were presented as plots of contours of constant pressure gradient as a function of flow rates of gas and liquid. The transition between the two regimes was defined by a foam quality f_g *. Rossen and Wang (1997) conjectured a model based on fixed bubble-sizes to explain foam behavior in the low-quality regime.; Laboratory coreflooding experiments performed with either Berea or Antolini cores or a sandpack were used in this study to evaluate the effect of surfactant type, surfactant concentration, permeability, flow rate and heterogeneity on the shape of the contour plots and in the value of f_g *. A new model is proposed, which describes foam behavior in the two flow regimes and the transition between them. These results show that any parameter affecting foam strength shifts the f_g* value. Permeability also influences f_g*; the lower the permeability the lower the value of f_g*. Additionally, experimental data supporting the fixed-bubble-size model is presented.; An NMR apparatus was used to evaluate water-saturation profiles and changes in water saturation between layers in foam flow in heterogeneous porous media. Coreflooding experiments performed in either cored cores (composite cores of coaxial layers of sand and Berea sandstone) or Antolini sandstone found that heterogeneity effects were more important than gravity override in determining sweep efficiency in these cores. Foam was slow to sweep all layers of the Antolini sandstone cores. Some evidence of capillary crossflow was observed in one of the experiments.