Simulador termodinâmico para fluidos de petróleo com associação molecular

Abstract

In this work, we develop a software that can be used for simulating both P V T properties and asphaltene onset pressure envelope of a reservoir fluid and estimating parameters for fitting both Peng-Robinson and Cubic Plus Association (CP A) equations of state to experimental data from downhole samples. The aforementioned software can describe acuratelly the complex liquid-liquidvapor equilibrium (VLLE) at high pressures and can be used for parameter estimation, with PVT properties calculated by combining the two liquid phases and asphaltene onset pressures used as input as well. Some commercial softwares can perform three-phase flash calculations but can only calculate PVT properties for VLE and are not able to use asphaltene onset pressure for parameter estimation. P V T calculations (VLE) were validated against a commercial software and two real reservoir fluid samples of high CO2 content susceptible to asphaltene precipitation were used to test the software. The performance of both equation of state on reproducing the PVT properties as well as asphaltene onset curves was compared after the optimization of the set of parameters for each EoS. PR EoS, when ajusted to the experimental data available, was capable of reasonably reproducing the upper onset curve for one of the samples. We noticed, however, that the consideration of the association term influences the values of some parameters in the cubic part (specially the binary interaction coefficients matrix), bringing their values to a more reasonable range compared to those needed for reproducing experimental data by taking into account solely the attraction and repulsion term of Peng-Robinson’s equation of state.