The Stabilization of Asphaltenes in Different Crude Fractions: A Molecular Approach

Abstract

The conditions of petroleum extraction may allow asphaltenes to precipitate, causing deposition that clogs wells, pipes and equipment, consequently reducing productivity. In this work, the solubility parameters and precipitation onset of polar fractions of heavy crudes from Brazilian fields were estimated using a simplified system of n-heptane/toluene mixtures. Asphaltenes were extracted by two different methods with regard to pressure and temperature. The samples were physically and chemically characterized, and both density (1053-1159 kg m-3) and molecular weight (1176-5316 g mol-1) were estimated based on the density of diluted asphaltenes in toluene solutions. The solubility of those fractions was studied as well as their solubility parameter (ca. 19-23 MPa0.5) based on regular solution theory, Flory-Hüggins theory and empirical correlation. The influence of asphaltene concentration (between 0.5 and 5.0 g L-1) on the solubility parameter and precipitation onset was studied, and a strong linear correlation between them was not found.