Identify a common type of water-based drilling fluid.

Bentonite mud is a common type of water-based drilling fluid, primarily due to its effective properties in maintaining wellbore stability and controlling fluid loss. It is composed mainly of bentonite clay, which, when mixed with water, forms a gel-like substance. This gel helps to cool the drill bit, carry cuttings to the surface, and prevent collapse of the wellbore.

The viscosity of bentonite mud can be easily adjusted by varying the concentration of bentonite, making it versatile for different drilling conditions. Additionally, it has excellent suspension properties, allowing it to keep drilled cuttings in suspension while circulating through the wellbore. This type of drilling fluid is environmentally friendly compared to oil-based muds and is widely used in many drilling applications due to its effectiveness and ease of use.