Simulation of Phase Behavior of Crude Oil using Different Equations of State (EOS)

The knowledge and understanding of the phase behavior of crude oil is
essential in order to know the changes of fluid behavior with respect to changes of
temperature and pressure. Phase behavior of hydrocarbon mixture can be modeled using
equation of state (EOS). It offers the advantage of an improved fluid property prediction
over conventional black oil model and can be used to predict behavior of the entire
composition path and pressure range of the process. The purpose of this study is to
investigate the modeling of crude oil phase behavior using four different EOS which are
Peng-Robinson (PR), Redlich-Kwong (RK), Soave-Redlich-Kwong (SRK), and
Zudkevitch-Joffe-Redlich-Kwong (Z.TRK). The phase behavior of crude oil are examined
and compared among three commercial softwares which are PVTi (ECLIPSE), PVTx
(TEMPEST) and PVTp (Petroleum Expert). This work investigated the equation that
best simulated the experimental Pressure, Volume and Temperature (PVT) data and
described the phase behavior of crude oil accurately. Adjustment on the parameters of
the chosen EOS, known as tuning or regression, is made to improve the prediction of
chosen EOS model to match a variety of experimental fluid data. The work focused on
the comparison using different EOS cross checked using three commercial PVT
simulation softwares to test for the accuracy. Statistical error analysis along are used to
evaluate the accuracy and applicability of the result generated. The results indicated PR
EOS is the most accurate EOS in describing the phase behavior of crude oil. It fitted good
and provided good representation of PVT experimental data. The tuning of the equation
further resulted in greater accuracy. An efficient way of tuning strategy has been
developed in this work which emphasis on the critical importance of sequence. It is
concluded that the sequence of tuning which started with critical properties followed by
BIC and omega properties resulted in greater accuracy.