AQUEOUS SOLUBILITY OF CRUDE OIL TO 400°C AND 2,000 BARS PRESSURE IN THE PRESENCE OF GAS*

Abstract

This study reports aqueous solubilities of crude oil distillation fractions over the carbon number range C1‐C34as a function of: temperature (100° to 400° C), pressure (100 to 2,000 bars), NaCl concentration, and gas in solution (N2, CO2, CH4). Experimental parameters were designed so that conditions within a petroleum basin would be duplicated. Increases in temperature increased crude oil solubility, and the higher molecular weight species were affected more positively than lower molecular weight species. Increases in pressure or salinity decreased solubility. The presence of gas in solution increased the solubility of high molecular weight hydrocarbons (> C24) over all temperatures, and increased the solubility of lower molecular weight hydrocarbons at high temperatures (> 180–260°C). Gas decreased the solubility of low molecular weight hydrocarbons at low temperatures.Hydrocarbon solute compositional changes were also examined as a function of the above parameters. At high temperatures, both increasing gas concentration and increasing temperature caused hydrocarbon solutes to become compositionally more similar and eventually identical to the original distillation fraction. The high molecular weight hydrocarbons and saturated hydrocarbons, especially the n‐paraffins, were taken into solution in progressively greater concentrations over the aromatic and low molecular weight hydrocarbons. Thus, the strong preferential uptake of low molecular weight and aromatic hydrocarbons into solution at lower temperatures was reversed.