conventional mud

1. n. [Drilling Fluids]
A term that, in the past, referred to a mud containing bentonite clay, water, caustic soda and perhaps barite (as needed for density) usually with lignite or lignosulfonate present. Modern drilling does not necessarily recognize this as a conventional mud because polymer muds, special drill-in fluids and synthetic-base muds are now in common use. There may not be a "conventional mud" today.