چكيده به لاتين
Asphaltene is the heaviest and most polar fraction that exists in the crude oils. Any change in the thermodynamic properties of the crude oil, such as pressure variations and composition alteration, can disturb its thermodynamic equilibrium and lead to Asphaltene precipitation. Asphaltene can precipitate in different parts of the production system, either downstream or upstream, and cause many irreparable operational problems. In this study, we aim to investigate the Asphaltene precipitation in liquid-like framework and with a focus on crude oil characterization.
Cubic Equations of State cannot effectively predict the phase behavior of crudes containing complex fractions, like Asphaltene, and therefore, in this study, we have employed the PC-SAFT EOS for phase behavior calculations. Fluid characterization plays a prominent role in identifying the properties of the crude oil, particularly the equilibrium conditions. Detailed fluid description gains importance in miscible gas injection projects, as it can take into account the effect of heavy hydrocarbon components of the injected gas on Asphaltene behavior. Therefore, in this study, we first implement the detailed characterization to four crude oils to investigate this effect. Thereafter, the lumped characterization is employed to predict the phase behavior of the live oils of two Mexican wells, as well as the Asphaltene yield from their dead oils. Dead oil modeling is carried out by assuming a polydisperse nature for Asphaltene, as different Asphaltene sub-fractions tend to precipitate under different conditions.
Examining the results of our study, one can conclude that the detailed characterization has led to better predictions of Asphaltene instability conditions, and it also is able to capture the actual pressure and temperature trends within the reservoir. The detailed description can also differentiate between different degrees of richness of the injected gas. On the other hand, the lumped characterization can satisfactorily predict the Asphaltene instability conditions and saturation pressures during the pressure and temperature variations of the original live oil. Moreover, integrating the lumped description with Asphaltene polydispersity can generate the Asphaltene yield from the dead oil, due to the addition of n-Pentane, with high precision.
