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Summary. High-temperature crude-oil/water/vapor separation takes place in steamflooding and in-situ combustion processes. It also takes place in hydrocarbon recovery from deep volatile oil and condensate reservoirs. A practical procedure that uses the Holland and Welch method and simulated practical procedure that uses the Holland and Welch method and simulated distillation data was developed to calculate crude-oil/water/vapor separations at 387 and 456 deg. F [197 and 236 deg. C]. The overhead yields obtained from the calculations were expressed as a function of the steam distillation factor. The Vw/Voi results were compared with laboratory crude-oil steam distillation data. The approach satisfactorily predicted the overhead yields of 13 out of 16 crude oils with an average predicted the overhead yields of 13 out of 16 crude oils with an average error of 12% (+/-3.6% in yield). This is within experimental error of crude-oil steam distillation. Twelve pseudocomponents of crude oils were selected and characterized with simulated distillation data for the calculations. The physical properties of the pseudocomponents were determined from existing properties of the pseudocomponents were determined from existing correlations and from matching laboratory steam distillation data. The use of simulated distillation data eliminates the uncertainty and assumptions normally involved in the selection of crude oil pseudocomponents with U.S. Bureau of Mines distillation data, and thus improves the reliability of the proposed computational approach. proposed computational approach. The proposed approach eliminates the need to conduct experimental steam distillation tests if simulated crude oil distillation data are available. It is easy and fast to calculate the overhead yields and densities without use of the equation of state (EOS) and uncertain pseudocomponent critical properties and interaction parameters. The pseudocomponent critical properties and interaction parameters. The proposed approach will provide useful information for the numerical proposed approach will provide useful information for the numerical simulation and design of thermal recovery processes and for the prediction of hydrocarbon recovery from high-temperature volatile oil and condensate reservoirs.

Introduction

Methods for calculating liquid-hydrocarbon/water/vapor separations have been reported in the literature. Lee et al. and Hseuh et al. used the Peng-Robinson EOS to calculate high-temperature three-phase separations that would take place in in-situ combustion or steamflood processes. Because of limited high-temperature three-phase processes. Because of limited high-temperature three-phase separation data and critical properties of crude oil fractions, the approach using the EOS required many uncertain assumptions. Holland and Welch developed a method for calculating multicomponent hydrocarbon/water/vapor separation in steam distillation. The Holland and Welch method is applicable for separations at saturated steam temperatures where the mutual solubility of hydrocarbon and water is negligible. In a steam distillation study, Moreno recommended that the Holland and Welch approach be used for crude oil steam distillation calculations. Rhee extended the Holland and Welch approach to consider the condensation effect on steam distillation yield in steam-flooding. Rhee synthesized the crude oil composition in twelve components on the basis of U.S. Bureau of Mines routine distillation data and laboratory steam distillation data. His work significantly contributed to the use of the Holland and Welch approach for predicting crude-oil steam distillation yields. Laboratory data on high-temperature crude-oil/water/ vapor separations have appeared in the literature. Recently, Wu and Elder reported steam distillation data for 16 crude oils selected from different producing regions of the U.S. They discovered that crude-oil steam distillation yields can be nicely correlated with simulated distillation yield and temperature. It was interesting to see whether simulated distillation data can be used advantageously to better Rhee's approach for crude-oil steam distillation calculations. This paper attempts to provide a practical approach to apply the modified Holland and Welch method modified by Rhee for calculating high-temperature crude-oil/water/ vapor separations. Laboratory steam distillation data on a hexane/decane system and on 16 crude oils were extensively analyzed in this study.

Holland and Welch Approach

The Holland and Welch approach applies to liquid-hydrocarbon/water/vapor separation of multicomponent systems such as those shown in Fig. 1. Its major assumptions are (1) constant steam throughput, (2) constant saturated steam temperature, (3) negligible mutual solubility between hydrocarbon and water, and (4) the use of vaporization efficiency to account for deviation of dynamic separation from equilibrium and/or ideal separation.

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