Surrogate models to predict initial shear stress of clay bentonite drilling fluids incorporated with polymer under various temperature conditions

The use of water-based muds (WBMs) in the drilling industry has increased over the past decades because of their environmentally-friendly features. In addition, natural polymers are in demand for controlling yield stress and viscosity of bentonite drilling fluids instead of conventional additives. This study experimented with and analyzed experimentally and analytically investigated bentonite and natural polymer concentrations on non-Newtonian fluid parameters, including initial shear stress and fluid resistance to flow (viscosity) under high-temperature conditions. The shear stress and shear strain rate relationships for water-based drilling fluids (WBMs) were simulated using Weibull and Vipulanandan rheological models. The modeling results were compared with the Herschel-Bulkley (HB) model. Hence, 208 data of water-based drilling fluids were collected from the published articles, and 64 data were obtained experimentally in this investigation considering the concentration of bentonite, polymer, and temperature range which were 0 to 14 wt.%, 0 to 3 wt.%, and 25 to 150 °C, respectively. The results show that the nonlinear model is stronger than the linear model in predicting the shear stress of WBMs as a function of bentonite, polymer, and temperature. Meanwhile, according to several statistical tests, the Weibull rheological model was more effective in predicting the initial shear stress than other rheological models.