Developing a new model for the determination of petroleum fraction PC-SAFT parameters to model reservoir fluids

• A molecular based equation of state, PC-SAFT, is employed to predict the phase behavior of reservoir fluids.
• A new approach to estimate PC-SAFT parameters for petroleum cuts and plus fractions existing in reservoir fluids.
• Proposed model takes only molecular weight and specific gravity of petroleum fractions as input parameters.
• There is no need to perform compositional analysis on petroleum fractions (such as PNA-distribution) for the determination of PC-SAFT parameters.
• A careful comparison is finally carried out between PC-SAFT simulation results and cubic equations of state for several oil samples.

In this work, PC-SAFT, an equation of state based on perturbation theory, is applied to predict the reservoir fluids phase behavior. PC-SAFT parameters for pure components have previously been assessed, but they cannot be determined for petroleum fractions with unspecified components and composition. In order to remove this difficulty and making use of PC-SAFT model in the reservoir fluids simulations, a new approach is studied which leads to appearing generalized correlations for the estimation of PC-SAFT parameters for petroleum cuts and plus fractions using only their molecular weight and specific gravity, without the essential need for the characterization of petroleum fractions in different homologous hydrocarbon families. The proposed technique is then validated with the reliable experimental PVT data of reservoir fluids, including saturation pressure and differential liberation test (oil formation volume factor, soluble gas oil ratio, and liquid phase density) for 10 oil samples. Subsequently, available experimental data are compared to results calculated by PC-SAFT model for all existing samples. Afterwards, a comparison between PC-SAFT model and two widely used cubic equations of state (PR and SRK EOS) was also conducted. The results demonstrated PC-SAFT model estimation capabilities and ease of use as an effective tool for describing the phase behavior of reservoir fluids in a wide range of scales and applications. Moreover, the effect of parameter tuning process on reduction of error values was investigated and acceptable results were obtained.