In this study, foam as a circulating fluid was analyzed and discussed in horizontal and highly inclined wellbores. Rheological and hydraulic behaviors of aqueous foam were investigated extensively. Rheological models are developed for estimating generalized consistency index (K?) and generalized flow behavior index (N) for laminar foam flows in pipes and annular geometries. Rheology experiments were conducted to determine foam rheological properties as a function of foam quality. Analysis of the flow curves of the foam used in this study indicated that foam behaves like a pseudo-plastic fluid with a negligible yield stress; and the flow behavior and consistency indices changing non-linearly with foam quality. Wall slip was observed.