1. n. [Drilling Fluids]

A small volume or pill of fluid placed in a wellbore annulus to free differentially stuck pipe. Oil-base mud is the traditional stuck-pipe spotting fluid. Speed in mixing and placing the spot is of primary importance to successfully freeing pipe. Because of concern about mud disposal, spots used offshore are either synthetic-based emulsions or benign water-base formulations. Each type is supplied as prepackaged concentrate designed for rapid access and mixing at the rig. A spot frees pipe by covering the stuck region. It presumably breaks up the filter cake, allowing the spot to migrate into cracks in the cake and between the pipe and the cake, reducing the stuck area and allowing pipe to be pulled free.

See: differential sticking,  dynamic filtration,  hydrostatic pressure,  pill,  spot,  spotting,  static filtration,  surfactant,  synthetic-base mud,  water-based drilling fluid