What is the primary role of bentonite in drilling fluids?

The primary role of bentonite in drilling fluids is to improve viscosity. Bentonite is a type of clay that, when mixed with water, swells and forms a gel-like substance. This property is essential for drilling operations as it increases the viscosity of the drilling mud, allowing it to effectively carry cuttings from the borehole to the surface.

An increase in viscosity helps to stabilize the borehole walls, prevents the collapse of the formation, and provides better lubrication for the drill bit. The thickened fluid also enhances the suspension of drilling cuttings, making it easier to manage and optimize the drilling process.

The other options may address certain aspects of drilling fluid properties but do not encapsulate the primary function of bentonite. For example, while bentonite can contribute to the density of the fluid, its effect on viscosity is significantly more pronounced and essential for the operational performance of the drilling fluid.