Accurate Modeling of Asphaltene Onset Pressure in Crude Oils Under Gas Injection Using Peng-Robinson Equation of State

Asphaltene precipitation is considered a precursor of the plugging of oil wells and subsurface equipment and is a topic of continuous interest among companies and academic institutions. Numerous models to predict asphaltene precipitation at reservoir conditions have emerged over the years, and some have been dropped for several reasons. Several researchers have published work claiming that cubic EOS (e.g. Peng-Robinson and Soave-Redlich-Kwong) cannot accurately capture the asphaltene phase behavior in crude oils under gas injection. However, we have found that after improving the crude oil characterization procedure to obtain a proper set of simulation parameters from the available experimental data, the cubic equation of state can show excellent predictive capabilities in modeling asphaltene onset pressure under gas injection. Several case studies with published data from six crude oils are conducted to assess the predictive capability of the new approach. The modeling results are compared to PC-SAFT EOS to highlight the advantages and disadvantages of each model.