High-Temperature, High-Pressure Viscosity Measurements for the Binary System Cyclohexane + n-Hexadecane at Extreme Conditions

Despite the significance of viscosity in the petroleum industry, experimental viscosity data for many hydrocarbons and their mixtures are scarce, particularly at extremely high-temperature, high-pressure (HTHP) conditions reaching up to 530 K and pressures up to 240 MPa. These conditions are typically encountered in ultra-deep formations, such as those found beneath the deepwaters of the Gulf of Mexico. In this study, a windowed, volume-variable, Inconel rolling-ball viscometer is used to collect viscosity data for the binary hydrocarbon mixture cyclohexane + n-hexadecane at elevated temperatures and pressures for different compositions. Because fluid density is required for the determination of viscosity, we are using our group’s recent measurements of the density of this binary mixture at extreme conditions. In order to provide a modeling tool that is amenable to estimating viscosity of multi-component mixtures of changing composition in reservoir simulators, the experimental viscosity data generated in this study are modeled with the free volume theory (FVT) coupled with various equations of state, such as  the Peng-Robinson (PREoS), the volume-translated PREoS (VT-PREoS), and the perturbed chain statistical associating fluid theory (PC-SAFT EoS) and its high temperature-high pressure modification (HTHP PC-SAFT) EoS.