The high-pressure capillary viscometer is a tool designed to determine the viscosity of fluids under varying pressures and temperatures. Knowledge of viscosity under operating conditions is crucial for the design and optimization of processes in the petroleum, petrochemical, and geothermal industries. Viscosity measurement is not limited to pure phases but also applies to gas-saturated liquids. This is particularly useful when dealing with subsurface fluids such as oils or formation water, which contain dissolved gases. The high-pressure viscometer operates based on laminar flow through cylindrical channels. The system consists of a coiled capillary tube with specific dimensions tailored to the respective range of dynamic viscosity. The pressure at both the inlet and outlet of this tube is measured, and the resulting pressure difference is used in the Hagen-Poiseuille equation, along with a calibration parameter, to determine the dynamic viscosity.

• Villablanca, R., Jaeger, P., von Reinicke Laredo, D., 2023. Inline method for measuring gas and salt solubility in liquid phases. Erdoel Erdgas Kohle/EKEP 139, 25–34. https://doi.org/10.19225/200203