Experimental study on rheological properties of water based drilling fluid and its impact on drilling operations

Abstract

Most encountered problems like fluid loss, wellbore stability, well control, poor capacity of cuttings transport, poor torque performance, increased drag, and stuck pipe can occur during drilling due to the improper design of the drilling mud, which can increase the cost of drilling. This study looks into the rheological properties of ten water-based drilling mud and their impact on drilling operations. A viscometer is used to conduct the analysis in the laboratory. The density of the prepared mud ranges from 8.7 ppg to 10.01 ppg. This experimental study focuses on determining the viscosity, gel strength, and yield point of ten water-based drilling mud which are formulated under different barite concentrations. The plastic viscosity of the ten mud samples ranges from 10 cp to 18 cp, yield point ranges from 5 lb/100ft2 to 12.75 lb/100ft2 and gel strength ranges from 2 lb/100ft2 to 9 lb/100ft2. The effect of density on viscosity, gel strength, and yield point is also observed in this study. Key findings indicate that the viscosity, gel strength, and yield point of the drilling fluid are significantly influenced by the density of mud at constant pressure and temperature. Five drilling mud rheological models such as Newtonian, Bingham plastic, Power law, API, and Herschel-Bulkley are analyzed to select the most suitable fluid model and measure the total frictional pressure drop in the wellbore, considering the suitable model. The error analysis of experimental/measured shear stress and theoretical/modeled shear stress is done to choose the most perfect fluid model. The minimum error indicates the best fitted rheological fluid model. This study found the error between experimental/measured shear stress and theoretical/modeled shear stress maximum for Newtonian model (7% to 18%) and minimum for API model (up to 0.16%). The mud samples are preferable for the API model to calculate the standpipe or pump pressure. Data matching is done to compare the experimental and real pressure loss data, SBHP and FBHP. There is good scope in the future to study the effect of some chemical additives on the rheological properties of water based drilling mud in different pressure and temperature.