Foams as Mobility Control Agents for Oil Recovery by Gas Displacement

Abstract

Abstract Experimental studies were conducted to facilitate understanding of the behavior of foam flow and its application in gas flooding processes. This paper presents the results of studies that involved: (1) foam flow behavior in smooth capillary tubes and packed glass tubes; (2) effects of changes in injection rates on foam performance; (3) effects of foams on unsteady state gas-liquid relative permeabilities; and (4) effects of foams on improving gas sweep efficiency. The apparent viscosities and mobilities of foams flowing through smooth capillaries and packed glass tubes were measured. The experiments were designed to observe and quantify the behavior of foam under various conditions including foam quality, shear rate, surfactant concentration, and temperature. The bubble size distribution of pregenerated foam was measured to determine the contribution of foam texture to its flow behavior. Experimental results were evaluated using available mathematical models developed for predicting apparent viscosities of foam in smooth capillary tubes and packed glass tubes. Coreflooding experiments were conducted to evaluate effects of variations in injection rates on foam performance as a mobility control agent. Results of the experiments showed that higher injection rates of nitrogen displacing a surfactant solution resulted in foam generation that contributed to a significant increase in sustained pressure gradient across the core. The unsteady state method was used to study the effects of foam injection on gas-liquid relative permeabilities and improving sweep efficiency in Berea sandstone cores. The presence of foam resulted in a significant reduction of the permeability of the core to gas. The ability of a foam of known texture to sustain differential pressures across a core in the absence of flow was also determined. Using a parallel coreflood setup, fluid flow was preferentially diverted from a high-permeability core to a low-permeability core.