Frictional pressure losses of Non-Newtonian fluids in helical pipes: Applications for automated rheology measurements

Abstract

Frequent and accurate drilling fluid measurements are critical to optimum well construction. Proper management of drilling fluid properties such as density and rheology optimizes the fluid's hydraulic and hole cleaning ability while maintaining the fluid in its role as primary well control barrier. In current practice, these measurements are typically done only once or twice a day using the methods described by American Petroleum Institute (API) standards. Moreover, taking the measurements is labor-intensive, and the data quality and reliability are highly dependent on the practicing engineer. An automated, continuous, and practical way of measuring and monitoring drilling fluid properties is therefore needed.In this paper, we introduce a novel helical pipe viscometer system for automated and continuous drilling fluid measurements. A flow-loop was constructed to measure frictional pressure losses of aqueous solutions with various concentrations of xanthan gum in water, generating a non-Newtonian fluid that is best described by a Yield-Power Law (YPL) rheological model. Flow tests were performed simultaneously in two straight- and two helical-pipe test-sections. Flow rate, density, and temperature data were obtained using a Coriolis flow meter. Pressure loss data was obtained using side by side differential pressure measurements from each test-section.A delayed transition to turbulent flow and elevated frictional pressure losses was observed in the experiments with the curved pipes. This is attributed to secondary flow driven by centrifugal forces in the helical pipe system. The results of the experimental data were compiled and used to build an empirical correlation for friction factor predictions using the Dean number. CFD analyses were also performed to validate the accuracy of pressure loss measurements and to obtain a better understanding of the helical velocity profiles. The proposed equation was compared with theoretical equations previously reported in the literature. The results from the analyses show that the equations previously derived for Newtonian and Power Law (PL) fluids are not applicable to YPL fluids in the tested geometries.An algorithm was developed and tested using the experimental data to prove the applicability of the helical system for rheological property calculations. Good accuracy was observed in mud rheology characterization tests. The helical system, which can be fully automated, provides significant practical advantages over standard linear pipe viscometers by offering improved accuracy and smaller footprint. The results of the study are also of importance for the hydraulic design and evaluation of coiled tubing drilling and well completion operations, where the pressure loss is a limiting factor for the maximum flow rate that can be used in such operations.