What are drilling fluids primarily used for in rotary drilling?

Drilling fluids, also known as mud, play a crucial role in the process of rotary drilling. Their primary function is to circulate down the borehole, which achieves several important tasks.

One of the primary functions is to remove cuttings created as the drill bit penetrates the earth. This circulation helps to bring these solid particles back to the surface, ensuring that the borehole remains clear and reducing the chances of the drill bit becoming stuck or slowed down by debris.

Additionally, drilling fluids contribute to cooling the drill bit. As drilling generates heat due to friction, the fluid helps to dissipate this heat, allowing for more efficient drilling operations and prolonging the life of the drilling equipment.

Stabilization of the borehole is another essential function of drilling fluids. By maintaining pressure within the wellbore and providing support to the walls, drilling fluids help to prevent collapses or the unwanted influx of water or other fluids, making it safer and more efficient to drill.

While other options touch on specific components of the drilling process, they do not encompass the multifaceted role that drilling fluids play within rotary drilling. Thus, the answer highlighting the circulation, removal of cuttings, cooling of the bit, and stabilization of the hole accurately reflects the primary use