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A model of one-dimensional steam displacement of residual oil has been developed. The quasi-steady model considers the capillary pressure gradients due to the simultaneous flow of the oil, water, and steam to be the dominant factors in oil bank mobilization. The effects of gravity on steam displacement were also included in the model. Semi-analytical calculations of saturation and pressure distributions are presented to illustrate the mechanisms. It was shown that under most conditions, the Buckley-Leverett displacement velocity is significantly faster than the steam condensation front velocity. This result and conservation of oil mass required the use of the steam condensation front velocity as the characteristic velocity in the problem formulation. An expression for a limiting oil saturation at the steam zone interface was thus derived. Experiments were conducted to examine steam displacement of volatile, partially volatile and nonvolatile nonaqueous phase liquids at a residual saturation of 2.5%. Complete displacement of all low viscosity, partially volatile liquids was observed. Displacement of a high viscosity, nonvolatile oil was not observed. These experiments were in reasonable agreement with the model. Introduction Thermally enhanced oil recovery by steam injection has been demonstrated to be particularly effective in terms of increased resource recovery and overall profitability. Thus, a great deal of analytical, computational, and experimental effort has been placed on the description of the steam displacement process. Due to the extreme complexity of the thermally driven transport process, numerical simulation based on finite differencing has emerged as the primary reservoir level predictive technique. Nevertheless, such techniques lack the necessary spacial resolution to provide the details of the small scale interactions representative of the steam displacement of a multicomponent hydrocarbon liquid, particularly near the condensation front where capillary pressures dominate the multiphase flow process.

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