1. n. [Drilling Fluids]

An invert-emulsion mud, or an emulsion whose continuous phase is oil. In the past, the term referred to an oil mud containing less than about 5 vol.% water. This definition, at the time, distinguished mud with less than 5 vol.% water from invert-emulsion oil muds, which had more than 5 vol.% water. Today, this distinction is not practical because most commercial oil muds can be formulated with more or less than 5 vol.% water using essentially the same types of products.

Synonyms: invert-emulsion oil mud

See: aliphatic compound,  aniline point test,  electrical stability test,  invert emulsion,  oil content,  oil mud,  spotting fluid,  syn,  synthetic-base fluid