The concept of milling obstructions in wellbores, utilizing electric wireline deployed services, was introduced in 2005. Since that time, oil and gas operators around the globe have used this well intervention technique efficiently and cost effectively. These wireline-conveyed technologies have performed well in both completion and workover programs by providing the means to drilling out stuck valves, remove non-retrievable plugs and re-establish production by removing scale.
The additional cost of lost or deferred production is always unwanted. The deployment of a traditional rig or coiled tubing unit to help restore production comes with considerable cost owing to the equipment and personnel requirements to operate. Consequently, operators continually look to new techniques to minimize this burden. Milling on electric wireline is one such technique since it can be performed in a rig-less environment.
Experience has shown that each and every new milling challenge requires well planned and careful study of the problem along with extensive testing and verification of the technique. Every down hole scenario provides a different characteristic to consider. As a result, many man-hours and research dollars have gone into providing solutions for advanced milling projects.
This paper presents new applications for electric wireline milling. First, a summary of the milling experience to date will be presented followed by the examination of some complex milling challenges through several varied case histories including the milling of isolation valves, cast-iron bridge plugs, glass plugs, nipple profiles as well as scale removal.
