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1. n. [Drilling Fluids]

Placing a small volume or pill of fluid 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 stickingdynamic filtrationhydrostatic pressurepillspotstatic filtrationsurfactantsynthetic-base mudwater-base drilling fluid

2. n. [Well Workover and Intervention]

Accurately placing a fluid, or fluid interface, at a given position within the wellbore. Treatment fluids such as cement slurries and stimulation fluids for localized treatment often require accurate placement. Correctly calculating and pumping the appropriate volume of displacement fluid while taking account of well production, wellbore returns and fluid-density variations are key factors in achieving accurate placement of fluids.

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