Three Phase K-Values of Heavy Paraffins and Crude Oil Pseudocomponents in Presence of Water
Authors: Wu C.H. , Beladi M.K. , Xue G.P. , Barrufet M. , Chawla I. , Liu K. 
Published: December 2007

A series of laboratory tests is conducted to obtain the basic distillation data needed to determine the three-phase K-values of heavy paraffins (C8-C20) and of crude oil pseudocomponents. The system temperature ranges from 250 to 500 F and the saturation pressures from 28 to 961 psia. Stagewise isochoric distillation (SWID) experiments are conducted to obtain the vapor phase compositions which are used to calculate the phase compositions and phase volumes within the distillation cell. Three-phase K-values are calculated using empirical component property correlations and a material balance model.

A series of binary, tertiary, and quaternary mixtures of heavy paraffins and water is investigated to determine their three phase K-values. Reported are vapor-oleic () and vapor-aqueous () phase K-values of the heavy paraffins. A pseudoization technique (modified Whitson's approach) is used for a consistent lumping of crude oil pseudocomponents for determining three-phase K-values. Pseudocomponent three-phase K-values of four crude oils with API gravity ranging from 10 to 29 are determined. The three-phase K-values should be useful for thermal recovery simulation and process evaluation.

Introduction

Three phases usually coexist in petroleum production and hydrocarbon processing systems where a significant amount of water is present. Although water always coexists with hydrocarbons in oil reservoirs and in improved oil recovery processes, the effects of water on the fluid phase behavior are often neglected for simplicity. In practice, such a simplification may not be recommended when the system temperature is greater than 250 F.

Steam distillation of crude oil is one of the major mechanisms responsible for improved recovery in steamflooding and in in-situ combustion. Steam distills the light components of the crude oil in the steam zone and transports them to the advancing front where they condense and form a light distillate bank. The distillate bank effects a miscible displacement of the enriched oil and mobilizes the oil toward the producing well, Wu and Brown reported that crude oil ultimate steam distillation yields range from 16 to 57 % for 14 to 34 API crude oils. Farouq Ali indicated that 10 percent of the heavy oil recovered and that as much as 60 percent of the light oil recovery by steam flooding can be attributed to steam distillation. Volek and Pryor showed that a very low residual oil saturation of three percent can be obtained in volatile reservoirs by a combination of steam displacement and steam distillation.

The three-phase systems considered in this study consist of a vapor phase, an oleic phase, and an aqueous phase. Three sets of K-values can be defined as:

(1)

(2)

(3)

where:

= vapor-oleic equilibrium ratio of component i

= vapor-aqueous equilibrium ratio of component i

= oleic-aqueous equilibrium ratio of component i

yi = i component composition in vapor phase

xi = i component composition in oleic phase

wi = i component composition in aqucous phase.

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