Barite sag is a well recognized, but poorly understood phenomenon in the drilling industry. Industry experts have offered a variety of measuring parameters, based upon empirical data that only partially correlate with the occurrence of barite sag. The development and introduction of robust, standardized well-site techniques to predict the onset of barite sag in dynamic flow has evaded the industry. The effect of shear rate and viscosity on dynamic barite sag has been studied and quantified using new and advanced technology. Changes in the potential for dynamic barite sag as a function of shear rate, hole angle, annular velocity and eccentricity correlate with ultra-low shear rate viscosity.
Field-proven technology has been developed to predict the potential for barite sag and to provide remedial measures through ultra-low shear rate viscosity modification. This technology was originally developed and validated in the field with invert-emulsion drilling fluids. Subsequent verification and validation work showed the technology was equally valid for water-based drilling fluids. This innovative technology is well-suited for use with a variety of commercially-available field viscometers and therefore lends itself towards widespread industry use. The paper will discuss the theoretical basis for this barite sag management technology and present the viscosity levels, with corresponding shear rates, required to manage dynamic barite sag. A case is made for use of this technology as an industry standard for barite sag management and is accompanied by full disclosure of the technology for peer review. Lastly, case histories are presented demonstrating the suitability of this technology in the field and ease-of-use at the well-site.