Three-phase hydrocarbon/water separation and K-values / Michael Kambeez Beladi

Abstract

High-temperature/high-pressure vapor-liquid-liquid equilibrium (VLLE) and three-phase K-value data for heavy hydrocarbon/water and crude oil pseudocomponent/water systems are scarce. The scarceness of the data is associated with the laboratory equipment design limitations for high temperatures (>350 'F) and the high costs associated with such experiments. Nevertheless, compositional reservoir simulators and their EOS packages need such data (three-phase K-values) to adequately describe the phase distribution of the fluids in the reservoir. An approach is required to gather and analyze the data and quantify the three-phase K-values for heavy hydrocarbon/water and crude oil/water systems at high temperature. The analyzed K-values reflect the effect of single component numbers (SCN)and system temperatures at their relative three-phase saturation pressurewith water. In this research a method of laboratory test and three-phase K-value analysis is presented. This approach consists of the following four parts. 1.Three-phase stage-wise isochoric distillation (SWID) tests were developed and performed to obtain the vapor phase compositions of binary, ternary, quaternary, and crude oil systems in the presence of water for the temperature range 250 to 500 'F. 2.Compositional empirical material balance model (EMBM) was developed to calculate pure component mixtures, pseudocomponents and water three-phase K-values using the laboratory vapor phase compositions. 3.Correlations were devised for three-phase K-values of binary systems (C8/H20 through C20/H20) for the temperature range 250 to 500 'F. 4.Ternary, quaternary and crude oil systems multi-component three phase K-values were calculated using EMBM. These three-phase K-values were used to examine the binary three-phase K-value correlations and their applicability to multi-component and pseudocomponent systems. The above approach required a consistent pseudoization technique to calculate pseudocomponents' K-values of crude oil. Also, empirical mutual solubility correlations are proposed for both the hydrocarbon solubility in aqueous phase and the water solubility in the oleic phase. EMBM incorporated the new correlations for mutual solubilities, critical properties, and fluid densities to calculate the three-phase compositions. EMBM compositions were used to calculate the three-phase K-values. We have, also, provided a comparison between EMBM compositions and existing equation of states (EOS) compositions.