Pressure and Composition Effect on Wax Precipitation: Experimental Data and Model Results

Abstract

Summary Wax precipitation is often studied using stock-tank oil. However, precipitation may be very different in well-tubing and production facilities because of the effects of pressure and composition. For example, the cloudpoint temperature may decrease as much as 15 K from atmospheric pressure to a saturation pressure of 100 bar mostly because of the solubility of light hydrocarbons into the oil (i.e. because of composition effect). In this study, the cloudpoint temperature (CPT) at live-oil conditions and the amount of the precipitated wax at stock-tank-oil conditions are provided for four crudes. For one of the crudes, the effect of dilution with C1, C3, n-C5, n-C7, n-C10, n-C12, and n-C15 on the CPT is measured. A modified multisolid-wax model is used to study the effects of pressure and composition on wax precipitation. The experimental data and model results reveal that the CPT rises with the increase of the pressure and decreases when a crude is mixed with light hydrocarbons (such as C1, n-C5, and n-C7).