Analysis of Primary Safety Barrier on Workover Operations Using MCD on Deepwater Scenarios – Design and Execution

Abstract Intelligent completion installed in Brazilian pre-salt wells presents some challenges for workover. Pre salt ultra-deep-water wells are commonly equipped with two or three zones of integral intelligent completion, where severe fluid losses after acid stimulation, in depths is present on all wells. The usual methods to remove the intelligent completion string requires controlling fluid losses to the reservoir or installing a mechanical barrier to isolate the reservoir. Both options have a high risk of non-productive time and safety risks. A new approach is to remove the completion string in a single trip while dealing with losses. The reservoir would be communicated with the drilling riser while pulling the completion string. Clamps and flatpacks will be in front of the BOP during this trip. To control the risks, the project team developed tools and procedures to use MPD equipment and Mud Cap techniques during the critical parts of the operation. One of the challenges faced was to prove that ALARP (As Low as Reasonably Practicable) was achieved in non-normative operations. This article will describe the concept and equipment used on the successful intervention. The objective is to present a new use of current MPD techniques for well maintenance operations. There will be special focus on the primary safety barrier during the operations and contingencies since there is no similar operation reported in the industry.