Long-Range Description of Rheological Properties of a High-Pressure High-Temperature Oil-Based Drilling Fluid

Abstract

Drilling teams face several challenges when operating in high-pressure, high-temperature (HPHT) fields, such as lost circulation and difficulties in well control. One way to address these issues is to fully understand the rheological properties of the drilling mud being used at the temperature and pressure conditions observed in the formation. Operationally, this may not only help to increase drilling efficiency and reduce its costs, but also in avoiding wellbore instability and loss of drilling fluids.

Aiming to investigate the behavior and apply novel models that closely describe the rheological properties of an oil-based drilling fluid under larger than previously described HPHT intervals in the literature, this research uses formerly obtained experimental data to develop models for dynamic viscosity, shear stress, 10s gel strength, 10min gel strength, yield point, flow behavior index and flow consistency index as a function of temperature, pressure and, where applicable, shear rate. These models, unlike other works currently available in the literature for HPHT drilling fluid rheology, allow for robust prediction of fluid behavior in virtually any condition in the HPHT section of a wellbore, including shear rate.