The scenario of having drill string or work string cemented up in plugging or squeezing operations is a real occurrence and if the right procedures are not followed, then the intervention process can be lengthy, time consuming with increased costs to the operator. The intervention techniques for drill pipe or work string can be either washing over or milling it out. During wash-over operations when the cemented tubular is eccentric to the casing, and little progress is made, milling the cemented tubular is the best option. Using conventional junk mills, the rates of penetration (ROP) achieved are significantly lower and the over-all mill life is between 10-50 ft before the mill cores out. This paper describes a new cemented tubular mill designed and ruggedly constructed to mill wellbore tubulars that are internally and externally cemented. With its enhanced geometry, this mill has exceeded the rate-of-penetration performance of standard crushed-carbide and/or insert-dressed mills. This paper also describes real field results in details - both with correct application as well as results of incorrect applications.

As always, the objective of this paper is to disseminate technical information within the SPE guidelines.

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