Study of New Methods To Obtain the n-Paraffin Distribution of Crude Oils and Its Application to Flow Assurance

Abstract

One of the most important problems related to flow assurance is the precipitation of paraffinic waxes present in crude oils. The study of the wax precipitation process is commonly carried out using thermodynamic models to determine the wax precipitation curve (WPC). These models require as input information the molecular weight and the n-paraffin distribution of the crude oil. The n-paraffin distribution of raw crude oils is commonly determined by high-temperature gas chromatography (HTGC), despite this technique shows limitations. In this work, the saturate fraction of two crude oils was extracted using two different methods. The n-paraffin distribution of the raw crude oils and their saturate fractions was determined by both HTGC and differential scanning calorimetry (DSC) analysis. The former showed limitations regarding heavy n-alkane quantification, and the latter yielded distributions shifted toward a higher carbon atom number. Obtained results suggested the possibility of combining both techniques to obtain reliable n-paraffin distributions. WPC of the selected crude oils were calculated using a predictive model. Obtained results greatly varied regarding the n-paraffin distribution used. Experimental and predicted WPC were compared, showing the best agreement when using the n-paraffin distribution from the combination of both techniques.