The amount of oil in volume-percent in a drilling fluid.

A man who has been around the oil field for a long time.

A well completed for the production of crude oil from at least one oil zone or reservoir.

Also called operator.

See operator.

A drilling mud, e.g., oil-base mud and invertemulsion mud, in which oil is the continuous phase.

It is useful in drilling certain formation that may e difficult or costly to drill with water-base mud.

Compare oil emulsion mud.