What role does drilling fluid play in borehole stability?

Drilling fluid plays a crucial role in maintaining borehole stability, primarily by counteracting hydrostatic pressures and stabilizing the wellbore. When a borehole is drilled, the surrounding geological formations exert pressure that can lead to collapse or instability. Drilling fluid, also known as mud, exerts a balancing pressure against these formations. This pressure prevents the walls of the borehole from caving in and can help to manage any influx of fluids from the surrounding rock, which might otherwise destabilize the borehole.

Moreover, drilling fluids are designed to support the integrity of the borehole by creating a filter cake on the walls, reducing fluid loss into the formation, and minimizing erosion. They can also help to cool the drill bit and carry cuttings to the surface, but their primary role concerning borehole stability lies in this pressure-balancing function. This essential aspect of drilling fluid underscores its importance in successful drilling operations and in preventing drilling-related issues like stuck pipe or uncontrolled collapse of the borehole.