Coiled Tubing Drilling Case History

Abstract

This case history outlines a recent North Sea Coiled Tubing Drilling Project (CTD). The Project consisted of 2 main phases – Onshore Testing and Offshore Operations. The objective of the Project was to drill a 1000 ft sidetrack from an existing water injection well via a window cut in 7 inch casing. If the operation were to be unsuccessful, the well would be returned to its original configuration. The existing perforations were successfully abandoned using a gel plug and a cement abandonment plug. A separate cement kick off plug was spotted above the cement abandonment plug. A pilot hole was drilled in the kick off plug and a window cut in the casing. Eighty feet of formation was then drilled. Following a bottom hole assembly change access to the window was lost. Subsequent attempts to re-enter the window were unsuccessful. The drilling bottom hole assembly continued past the window into the original wellbore. Attempts were made to re-cement to allow a new window to be cut. These operations were unsuccessful. The Project was terminated after 52 days on location. All cement was underreamed from the well, the perforations treated with an acid wash and the well successfully returned to injection.