Asphaltene Precipitation Modeling

Abstract

Once asphaltene concentration exceeds the solubility of the dissolving medium, they are destabilized, and some amount precipitates to form another phase. These precipitated asphaltenes then deposit on the surface of production tubing, introducing a potential flow-assurance problem for oil-producing wells. Asphaltene deposits reduce the efficiency of oil production and often require shutdowns to clean affected piping components. Determining the limits of asphaltene solubility in the bulk oil medium is the first step toward understanding potential deposition problems, and asphaltene solubility can be explained via the principles of phase-equilibrium thermodynamics. In this chapter, the concepts of phase equilibrium are introduced and discussed in the context of the asphaltene-precipitation problem, and then the models for describing asphaltene-phase behavior (including colloidal models, approaches based in regular solution theory, and equations of state with particular focus on PC-SAFT EOS) are presented.