There is typically a bit of confusion when one speaks of drilling fluids and drilling mud. Drilling fluids are what is combined with mud to make drilling mud. Drilling mud is typically a mixture of dirt, clay and the drilling fluid chemicals that are pumped down hole to flush out the cuttings that the drill bit produces as it bores into the various sediments it encounters. The drilling fluids typically within stand high pressures and act to also cool the drill bit. The mud also supports the casing on the outside of the drill pipe and provides support between the drill casing and hole. Click here bit drilling for more details.
Fluids are typically a combination of various chemicals and lubricants. These chemicals are usually sold in 55 gallon drums and 265 gallon totes, although these sizes may vary depending on the company by a small amount. The fluids must provide sufficient lubrication while still providing some friction and not breakdown easily. Fluids that break down too quickly under high pressure and high temperatures put additional wear on the bit and pipe, which ultimately leads to ruining the drill bit. When a drill bit is ruined and has to be changed all drilling is stopped. The goal of a good driller is make the bit last as long as possible since changing the bit is costly and time-consuming from the resulting delays of having to bring the pipe back up to the surface to change the drill bit. Drill lubricants also help prevent differential sticking or seizing in horizontally drilled wells which sometimes become stuck where the pipe bends at an angle.
As drilling mud, which is infused with drilling fluids, circulates through the system the mud engineer will examine the mud continually to make sure the mud is maintaining desired properties. This is often done by testing the shavings in the mud. If the drill bit is wearing out prematurely, this will show in the tested mud composition and it is necessary to make appropriate changes to the mud, which usually involves an infusion of more drilling fluids or other chemical additives. The primary goal of drilling mud is to keep everything operating within a set of defined parameters, preserve the drill head and prevent any interlocked pipes from seizing, resulting in costly delays.