Drilling deeper, longer and more challenging wells has been made possible by improvements in drilling technologies, including more efficient and effective drilling fluids. Drilling fluids, also referred to as drilling mud, are added to the wellbore to facilitate the drilling process by suspending cuttings, controlling pressure, stabilizing exposed rock, providing buoyancy, and cooling and lubricating.

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Purposes of drilling fluid

During drilling, cuttings are obviously created, but they do not usually pose a problem until drilling stops because a drillbit requires replacement or another problem. When this happens, and drilling fluids are not used, the cuttings then fill the hole again. Drilling fluids are used as a suspension tool to keep this from happening. The viscosity of the drilling fluid increases when movement decreases, allowing the fluid to have a liquid consistency when drilling is occurring and then turn into a more solid substance when drilling has stopped. Cuttings are then suspended in the well until the drill is again inserted. This gel-like substance then transforms again into a liquid when drilling starts back up.

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Drilling mud also help to control pressure in a well by offsetting the pressure of the hydrocarbons and the rock formations. Weighing agents are added to the drilling fluids to increase its density and, therefore, its pressure on the walls of the well.

Another important function of drilling fluids is rock stabilization. Special additives are used to ensure that the drilling fluid is not absorbed by the rock formation in the well and that the pores of the rock formation are not clogged.

The longer the well, the more drill pipe is needed to drill the well. This amount of drill pipe gets heavy, and the drilling fluid adds buoyancy, reducing stress. Additionally, drilling fluid helps to reduce friction with the rock formation, reducing heat. This lubrication and cooling helps to prolong the life of the drillbit.