Abstract
This paper details a case history of a recent HPHT CT well intervention operation to gain access to a suspended subsea well, in order to finally abandon the well including wellhead removal from seabed. There was a need to mill out the shallow set environmental cement plug to allow section milling and cement plug setting on well that had been originally suspended in 1997. The absolute worst case predicted pressure trapped below the shallow set cement plug was 12,500psi. This paper will take the reader through the full life cycle of the CT well intervention project. Starting with the initial feasibility study that lead to the selection of CT as the most viable option, moving onto the two sets of trials on test wells verifying the milling parameters and BHA selection. There will then be details on the 15,000psi live well intervention landing string that had to be manufactured to act as a conduit for the milling operations and also having the capability to shear the 2″ QT1000 0.203″ CT. The paper covers a review of the actual versus planned operations and captures high level lessons that would benefit future similar operations. The requirement to enter old wells that have been previously suspended / abandoned to fully abandon to current standards is an area of increasing interest. The use of CT to re-enter a HPHT subsea well has proven its versatility in comparison to alternatives such as costly relief well or HP interface equipment to allow jack up operations that could facilitate a snubbing unit.
