An important factor in the overall success and cost of an offshore well intervention depends significantly on the choice of the equipment including downhole tools and surface units. Using a conventional workover rig for well intervention is expensive and may not be appropriate in many circumstances. Additionally, intervention of a subsea well can further increase the costs due to the requirements of a floating vessel and subsea systems to access the wellbore. This paper systematically

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... s downhole applications that are performed during well intervention. It reviews techniques such as Wireline, Coiled Tubing (CT) and Hydraulic Workover (HWO) that do not require use of a conventional workover rig and have capability of performing downhole applications in live (under pressure) wells. Included are guidelines for selection of these rigless techniques for the various downhole applications. The rigless techniques are further reviewed in relation to subsea well intervention. The emphasis is placed on selection of a floating vessel along with subsea systems to connect to the well. The paper includes a discussion on market trends that are directed towards either reducing intervention costs or minimizing its frequency.