Solubility of Gaseous Hydrocarbon Mixtures in Water

Abstract

Abstract At present no reliable theoretical or empirical method exists by which the solubility of gaseous hydrocarbon mixtures in water can be determined. Based on the experimental data of this work, an empirical correlation was developed by which solubility of gaseous hydrocarbon mixtures, using pure component solubilities, could be predicted. pure component solubilities, could be predicted. The effect of mixture composition on the solubility was also studied. Solubility of the following binary and tertiary hydrocarbon mixtures in water were experimentally determined as (1) methane-ethane mixtures at temperatures of 100 degrees to 220 degrees F and pressures of 700 to 8,000 psi; (2) methane-propane pressures of 700 to 8,000 psi; (2) methane-propane mixtures and ethane-propane mixtures at 220 degrees F and pressures of 700 to 8,000 psi; and (3) methane-ethane-propane mixtures at temperatures of 160 degrees to 220 degrees F and pressures of 700 to 5,000 psi. We found that:the solubility of hydrocarbon mixtures increases with an increase in pressure and shows a minimum with an increase in temperature;solubilities of the binary and ternary hydrocarbon mixtures are greater than the solubilities of the pure components at the same temperature and pressure; andhydrocarbon-water solutions tested in this work show a positive deviation from Raoult's law. Introduction Quantitative information concerning the behavior of gaseous hydrocarbon-water mixtures under reservoir conditions is valuable to the petroleum and chemical industries. A thorough understanding of hydrocarbon-water systems A necessary because water is present in all steps of hydrocarbon gas handling processes. More experimental investigations have been reported for the formation of gas hydrates and gas water content than the determination of the solubility of hydrocarbon mixtures in water. Solubilities of pure light hydrocarbons and natural gas in water at various pressure and temperature ranges have been published. The information available concerning the solubility of binary hydrocarbon mixtures is fragmentary and data for ternary hydrocarbon mixtures are even more scant. The solubility of an ideal gas in an ideal solution, in equilibrium with each other, can be determined using Henry's law. At high pressures, both the gas and liquid will behave nonideally. The theories pertaining to solubility and the different kinds of nonideal solutions have been presented by Hildebrand and Scott. In analyzing presented by Hildebrand and Scott. In analyzing the solubility of hydrocarbons in water, Shinda and Fujihira state, "Enthalpy and entropy of solution of non-polar solutes in water diverge strikingly from the normal behavior established for regular solutions. This abnormality has been considered mostly due to the iceberg formation around solute molecules in water." There is no reliable method for predicting the solubility of a gaseous mixture in water, under nonideal conditions. This paper describes an experimental determination of the solubilities of gaseous hydrocarbon mixtures in water. Based on the experimental results, we developed an empirical correlation by which the solubility of hydrocarbon mixtures can be predicted. Results indicate that the solubility of the hydrocarbon mixture increase with an increase in pressure and show a minimum at around 160 degrees F. pressure and show a minimum at around 160 degrees F. Solubilities of the mixtures are greater than their pure constituents under the same conditions. pure constituents under the same conditions. Calculated values, using the empirical correlation developed in this work, compare well with the experimental data obtained by McKetta. EXPERIMENTAL WORK APPARATUS The experimental apparatus (Fig. 1) consisted of an equilibrium cell made of stainless steel with a volume of approximately 77 cc. SPEJ P. 21