MUD is mud, right?

Well, no, not really. Certainly when it comes to the sort of MUD you find around oil and gas platforms at sea. Drilling mud or drilling fluid as it’s commonly called is a viscous fluid mixture that’s used in drilling operations performing a wide range of functions including carrying rock cuttings to the surface and lubricating the drill bit. The recipe for these compounds is varied but the 3 main types are Oil-Based Muds or Non-aqueous Muds, Water Based Muds and, Gaseous Drilling Fluid.

As early as the third century BC, the Chinese were using drilling fluids, in the form of water mixed with actual mud, to help soften the ground when drilling for hydrocarbons. It is said that the term “MUD" was adopted at an oil field in Texas when drillers moved a herd of cattle through a partially flooded field and used the resulting MUD to lubricate the drill.

In general, water-based muds are suitable for the less-demanding drilling of conventional vertical wells at medium depths, whereas oil-based muds are better for greater depths or in directional or horizontal drilling, which place greater stress on the drilling tools. Synthetic-based muds were developed in response to environmental concerns over oil-based fluids, though all drilling muds are highly regulated in their composition, and in some cases specific combinations are banned from use in certain environments.

Depending on the location of the well, the drilling-fluid system can be exposed to:

• Saltwater
• Carbon dioxide and hydrogen sulphide
• Oil or gas
• Extreme temperatures at both ends of the scale
• All of these