The Incoloy Alloy 925 flapper from a damaged tubing retrievable safety valve (TRSV) was blown downhole using a wireline conveyed cannon. A downhole video survey revealed the flapper to be deformed but intact, lodged above a PBR at 11,902 ft md RKB. Attempts to fish the flapper were unsuccessful and a CT milling operation was planned to reduce the size of the flapper to facilitate its recovery. Consideration of the material properties and the location of the fish indicated that milling could be challenging. Reported industry experience of similar operations was sparse and BHA selection and job design required very close co-operation between the operator, coil tubing and through tubing services providers. The flapper was successfully milled using a combination of crushed carbide and fine diamond grit dressed burning shoes and recovered with an alligator grab on slickline. In addition to presenting the case history of the operation this paper will give an overview of the planning and design considerations which contributed to a successful outcome. The paper will also demonstrate how extensive use of downhole video helped guide development of the intervention programme.

You can access this article if you purchase or spend a download.