Improved Rheology Model and Hydraulics Analysis for Tomorrow&s Wellbore Fluid Applications

Abstract

Abstract Wellbore fluid applications continue to expand in complexity, necessitating more versatile rheological and hydraulics models amenable to efficient real-time data analysis. Substantial recent advancements have been made by numerous workers, applying the Herschel-Bulkley model to drilling fluids, highlighting the underlying importance of fluid rheology. However, this classic model alone does not fully describe the complexity of oilfield fluids. Therefore, this paper presents a Generalized Herschel-Bulkley (GHB) rheological model and hydraulic analytical method that accommodate a broader spectrum of wellbore fluids, whether of simple character, or having the complex properties of multiphase fluids such as foamed cement and high-density cements in addition to drilling fluids. The GHB model offers several advantages: (1) it readily reduces to several popular conventional models (Newtonian, power-law, Bingham-plastic, Casson, and Herschel-Bulkley), (2) it can provide additional flexibility for characterizing apparent viscosity functions of current and future multiphase fluid systems such as lightweight cements, foams, and high-density slurries, and (3) it can provide an effective generalized framework for developing friction prediction equations. A highly accurate numerical simulator for the comprehensive family of fluids modeled by the GHB model was developed for predicting laminar flow-friction loss in pipes and annuli. The computational method, based on several exact integrals of motion, could be made as accurate as desired by decreasing mesh size. While the simulator itself is not ideal for real-time application, the results of comprehensive calculations using it were incorporated into field-usable software by developing "generalized explicit functions" that encapsulated all the physics correctly. These practical functions are in turn used for accurately and rapidly predicting friction loss of the GHB family of fluids in pipes and annuli (concentric and eccentric) for laminar, transitional, and turbulent flow.