An evaluation of oilfield drilling fluid rheological properties at low shear rate ranges for hydraulic flow models

Abstract

The hydraulic calculation requires the selection of a best fit model from some models used in petroleum industry. Especially, at low shear rate. This study is based on the data taken from ten wells to evaluate five models- Bingham plastic, Power Law, Casson, Herschel-Bulkley, and Robertson-Stiff for hydraulic optimization. In the course of optimizing, statistical method was used to evaluate all the data using linear regression and least square methods. Calculations were made to determine the rheological parameters, correlation coefficients and relative errors. Comparison was also made to the correlation coefficients and relative errors for selecting the best model for optimizing the hydraulics of specific drilling fluids. In order to verify the optimized results, the pressure losses both inside the drillpipe and the annulus and the Equivalent Circulating Density (ECD) were calculated by using these five models. Data obtained from Herschel-Bulkley model presented the most accurate results.