Modelagem termodinâmica da viscosidade da mistura de SF6 e óleo mineral

Abstract

Brazil is one of the main oil producers, with prominence in the Pre-salt region. However, extraction in this area faces complex challenges, such as high pressures and high concentrations of CO2, which is a contaminant. CO2 is a dense gas that is typically found in a supercritical state under oil production conditions. The presence of this contaminant triggers various phenomena in the area of multiphase flows, such as a lack of understanding of two-phase flow patterns in its presence. To study these phenomena, several laboratory-scale experiments can be performed, such as tests in two-phase circuits, and also the dynamic modeling of these flows. Due to the high pressures, for safety reasons, fundamental laboratory-scale research usually employs model fluids to mimic the real fluids found in Pre-salt production systems. It is common to use SF6 (which is also a dense fluid) to mimic the behavior of CO2, with the advantage of working at much lower and safer pressures. In this work, SF6 and mineral oil were used to simulate the thermodynamic conditions of the fluids present in the Presalt. Viscosity is an important property for understanding flow during oil production. In this study, the viscosity of the SF6+mineral oil liquid mixture was thermodynamically modeled using the Friction Theory (f-theory) model coupled with the Cubic Plus Association (CPA) equation of state over a temperature range of 15 to 45ºC. Accurate viscosity modeling can be used as input in various multiphase flow models that attempt to simulate the impact of the presence of dense gases (contaminants like CO2) on oil production in the Pre-salt. The results obtained for pure substances were compared with literature data, demonstrating the model’s reliability. However, the lack of mixture experimental data highlights an opportunity for further research.