Comparative rheology measurement of potential gel-forming base fluids over a controlled temperature range

The application of polymer-based drilling fluids in the drilling process involves gel formation; therefore, before gelation, such fluid samples must possess injectability, pumpability, and stability in different ranges of shear stress and temperature. At present, there is no comparison study of commercial polymer drilling fluids under similar rheological conditions. The rheological performance of five water-soluble polymers, namely, AN 105 (1.5 wt%), AN 125 VHM (0.75 wt%), AN 125 VLM (2 wt%), polyacrylamide (3 wt%), and hydroxyethyl cellulose (2 wt%), was determined with a rotational viscometer over a wide temperature range of 25-90 °C. For comparative analysis of the rheological behavior of the considered drilling fluids, two dimensionless screening parameters, i.e., shear thinning index (STI) and thermal stability index (TSI), were chosen. It was established that all selected polymers demonstrated non-Newtonian behavior, being shear thinning. However, a significant difference in the ability to maintain low-shear viscosity in high-temperature mode was detected. The best results in terms of rheological performance were obtained for AN 125 VHM.