Distillation of oil at the steam-oil interface has long been recognized as an important mechanism for oil recovery during steam flooding, particularly in light-oil reservoirs. However, the heat and mass transfer mechanisms at the interface are not well understood.
This paper describes an experimental study conducted to shed more light on these mechanisms. The apparatus used consisted of a vertical sand pack containing a three-component liquid mixture, namely, cyclohexane, n-octane, and water. Cyclohexane has a boiling point lower than that of the steam introduced at the top of the sand pack, so that this hydrocarbon component will be predominantly distilled off. Data obtained included produced hydrocarbon and water volumes, sand-pack temperature profiles, and steam front velocity as measured with the aid of the CT scanner.
Analysis of the data indicates that, contrary to the usual assumption, steam distillation does not occur at equilibrium conditions. Moreover, oil recovery by steam distillation is largely dependent on the steam saturation point and injection rate. Based on these findings, an analytical steam displacement model has been developed. Temperature profile, steam front velocity, and hydrocarbon production based on the model agree satisfactorily with the experimental results.