The Steam-Foam Process

Summary The steam-foam process was developed to improve the sweep efficiency of the steamdrive and steam-soak processes. Steamdrives that are not stabilized by gravity can have a poor vertical sweep efficiency as a result of (1) gravity overlay in a thick sand with vertical communication and/or (2) channeling in a layered formation with poor vertical communication between sand members. The reduced mobility of steam foam increases the pressure, and gradient in the steam-swept region to displace the heated oil better and to divert steam to the unheated interval. Surfactants reduce the steam mobility by stabilizing the liquid lamellae that cause some or all of the steam to exist as a discontinuous phase. The propagation of surfactant is retarded by ad sorption. In the phase. The propagation of surfactant is retarded by ad sorption. In the case of ion exchange of divalent ions from the clays, the surfactant is also retarded by precipitation and/or partitioning into the oil. The rate of propagation of foam is also determined by the mechanisms that generate and destroy foam. The generation mechanisms include leave-behind, snap-off, and division. The destruction mechanisms include condensation and evaporation, coalescence by a limiting capillary pressure, and coalescence resulting from the presence ofoil. The foam texture can be predicted from a population balance that includes these mechanisms. predicted from a population balance that includes these mechanisms. Introduction Scope. This paper reviews the steam-foam process. It is not an exhaustive survey of the literature, and I apologize to the many contributions that had to be omitted because of length limitations. The types of field application of steam foam are discussed first. Examples are taken from reported pilot results. The remainder of the paper focuses on process mechanisms. Understanding of the mechanisms for foam flow in porous media is still in the formative stage, and many advances can be expected. It is hoped that this paper will help the practicing engineer apply the process more efficiently and will challenge the researcher to advance the knowledge of the process and to develop more efficient formulations.