Experimental viscosity monitoring in complex pipe systems for flows of drilling muds based on the energy dissipation rate

Abstract

This study aimed to measure the viscosity of non-Newtonian fluids (xanthan gum solution and drilling muds) in-situ during complex pipe flows using pressure drop and flow rate data without sampling. This method of viscometry can be applied to various inelastic non-Newtonian fluids and pipe systems of general geometries, including shear-thinning fluids (such as xanthan gum) and viscoplastic fluids with yield stress (drilling mud), as long as the flow rate and pressure drop within the system can be measured in-situ. The method employs two flow numbers (energy dissipation rate coefficient and effective shear rate coefficient) that are mainly determined by the flow geometry, nearly independent of the rheological behavior of a fluid. The representative effective shear rate for a given system is determined by the effective shear rate coefficient and flow rate; and the relationship between effective viscosity and material viscosity was found to be identical. The method was validated with three different non-Newtonian fluids in three different lab-scale complex pipe systems, including a straight circular pipe with connectors, a pipe system with an intermediate branch, and a 3D pipe system with height and slope variations. The accuracy assessment of viscosity measurement and pressure drop prediction showed no more than an 18.7% error in all the cases. The in-situ viscosity measurement method presented in this study can be used for process monitoring and process quantification of non-Newtonian fluid flows in various types of pipe flows used in industrial processes.