Development of a new scaling model for asphaltene precipitation in light, medium, and heavy crude oils

Abstract

Asphaltene precipitation adversely affects crude oil recovery and transportation. Hence, a precise determination of asphaltene precipitation is of great importance. Development of a scaling equation by Rassamdana et al. and its modifications have been based on asphaltene aggregation. However, the proposed models/correlations do not consider the contribution of oil characteristics including resin content and API gravity to the precipitation phenomena.The present study aims to propose a modified scaling model for forecasting asphaltene precipitation in three different types of crude oils: light, medium, and heavy oils. The impacts of resin to asphaltene ratio, pressure, dilution ratio, and molecular weight of precipitant (n-alkane) are investigated through conducting experimental and modelling phases. Compared to the previous methods, the key difference of the proposed model is the inclusion of API gravity and resin to asphaltene ratio as additional parameters in the predictive equation, leading to a better estimation. The comparison of the new model with the previously reported models confirms its greater accuracy over a wide range of input parameters for different oil types. The high magnitude of the coefficient of determination (0.98) and low value of mean absolute error (0.06) for all three oil types demonstrate that the proposed model is a robust predictive tool for the estimation of asphaltene precipitation. It was found that a greater amount of asphaltene precipitation in light oil samples is obtained at higher dilution ratio and lower pressure conditions where the lighter diluents are used. In addition, the API gravity and molecular weight of diluents have the greatest influence on asphaltene precipitation.