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NTNU Norwegian University of Science and Technology Department of Marine Technology Scope of work M.Sc. thesis 2013 for Stud. tech. Arild Grønevik SIMULATION OF DRILLING RISER DISCONNECTION – RECOIL ANALYSIS Drilling risers may have to disconnect in situations with large waves or due to unexpected events. The elastic energy in the riser that is linked to the tension at lower end will lead to stress waves immediately after disconnecting. This stress wave may lead to compression and even beam buckling. Another issue is that the heave compensator must be able to adjust upper end tension in order to avoid an uncontrolled and dramatic pull-­‐in that may lead structural damage. Another problem of importance is the motions of the free end. It is of outmost importance that the end does not hit the blow-­‐out preventer, but is given a controlled uplift to a safe position. Dynamic analysis of drilling risers after disconnecting is mandatory when planning drilling operations. This type of analysis is often referred to as “recoil analysis”. The purpose of this project is to describe a typical disconnection procedure, identify critical events and carry out recoil analyses by the use of the computer program Riflex. The work might be divided into tasks as follows: Literature study and selection of risers and cases to be subjected to analyses. Part of this task was carried out as a pre-­‐project during fall 2012, but some additional work might still be relevant Apply RIFLEX to simulate various disconnection situations by varying time for disconnection relative to the dynamic position of the platform. Parameters like water depth and riser tension may also be varied. Further details should be agreed with the supervisor during the execution of the project. The work may show to be more extensive than anticipated. Some topics may therefore be left out after discussion with the supervisor without any negative influence on the grading.