BOP tethering is a system installed around the wellhead with the purpose of stabilizing laterally the top of the BOP Stack through the action of cables, anchors, and other devices. This system, which significantly reduces loads on the wellhead, have been used in the last decade in operations in the North Sea and other locations around the world to mitigate wellhead fatigue. In Brazil, it was proposed to enable the use of dynamically positioned (DP) drilling rigs in shallow waters, where the loads imposed by the riser-BOP on the wellhead during a drift-off/drive-off event are a stricter restriction to operations than wellhead fatigue. This article describes the process of investigation, homologation, design, construction, and operation of the BOP tethering system in a semisubmersible rig, making feasible important projects for Petrobras using this resource.

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