Influence of salt contamination on the rheological and filtration properties of bentonite-based mud

Abstract

Bentonite-based mud has been widely used in petroleum, geotechnical and civil engineering to lubricate the drill bit, maintain wellbore stability, and lift the drilled cuttings up to the surface during drilling operations. Understanding salt contaminants influences the quality of bentonite-based mud is necessary to create a suitable formula for drilling mud to achieve a successful drilling process in deep formations and coastal regions. In this paper, several experiments were carried out on bentonite-based muds with different types of salt (NaCl and CaCl2) and various concentrations of salts (NaCl - 0.5, 1, 1.5, 2 wt%; CaCl2 - 0.1, 0.2, 0.3, 0.4 wt%). The properties of mud were examined by laboratory equipment, including an 8-speed viscometer, and American Petroleum Institute (API) Filter Press. The findings indicate that salt contamination impairs the characteristics of drilling fluid. The rheological parameters of mud, such as viscosity, yield point, and gel strength, drop dramatically as the concentration of salt increases. Furthermore, the filtration test indicated that the bentonite-based mud encountered severe water loss into the formation with increased salt concentration.