Hydroxyethyl cellulose as a rheology modifier for water-based drilling fluids formulated with Algerian bentonite

Under the different geological conditions of wells and during the drilling operation, some of the water-based drilling fluid compositions are sometimes not efficient for the drilling success of the oil and gas wells (case of the Algerian oil and gas wells). In the use of bentonite in drilling fluid applications, the addition of hydroxyethyl cellulose (HEC) is recommended to obtain good rheological properties of the fluid. In this research, we investigate the rheological behaviour in steady state, and dynamic shear rheology of drilling fluids formulated based on an Algerian bentonite with a fixed concentration of 3wt% and a water-soluble polymer HEC of high molecular weight (similar to 9.5x10(5)g/mol) at different concentrations ranged from 0.02 to 0.2%. All the results obtained by a controlled stress rheometer have been commented by taking the interaction between the clay and the polymer molecules into consideration, to highlight the effect of HEC on the rheological properties of bentonite suspensions. Herschel-Bulkley (H-B) model was used to fit and interpret the experimental data. A significant increase in the rheological properties of the mixture bentonite-HEC with the increase in HEC concentration has been shown. These properties reached the maximum at HEC concentration of 0.1wt%; beyond this value, they decreased. X-ray diffraction test performed on the different samples also allowed understanding the rheological behaviour of the system bentonite-HEC. Indeed, the HEC could intercalate the bentonite interlayer and formed link bridges between bentonite particles below a critical concentration of 0.1wt%. Based on the results of the study, it is recommended to choose the optimum concentration of HEC to be added to the bentonite suspension to ensure the optimum rheological characteristics of the drilling fluids.