Phase behavior analysis of heavy oil containing asphaltene

A thermodynamic asphaltene precipitation model was developed based on the model of Nghiem et al. using the Peng-Robinson equation of state (PR EOS). This model calculates the amount of asphaltene precipitation based on changes in temperature and pressure. The effects of asphaltene precipitation on rock properties were investigated by observing changes in porosity and permeability. In this model, phase equilibrium was achieved by repeatedly reducing the amount of the asphaltene component, in contrast to the model of Qin et al. using the secant method. The results of this model were compared with experimental data of measured precipitation, based on changes in pressure, and agreed more closely than the model of Qin et al. Our results also confirmed that the maximum precipitation of asphaltene occurred at the bubble-point pressure. Thus, using the model, we verified that the precipitation pattern of asphaltene depended on temperature and pressure, and it is expected that changing patterns in reservoir productivity can be analyzed using asphaltene precipitation in heavy oil-containing asphaltene.