Lightweight risers increase rigs’ water depth ratings ///
As water depths increase, risers for drillships and semisubmersibles become some of the most critical components of the drilling operation. Risers must be strong enough to maintain integrity during deployment and operation; be light enough to be handled and supported by the floating drilling unit; and be constructed of materials that resist corrosion while exposed to seawater. Lightweight, alloy risers provide a means of increasing the water depth rating of floating rigs by as much as 50% without requiring expensive upgrades, Fig. 1. Because of their lightweight construction, alloy risers are easier to handle, require fewer buoyancy devices, and can enable floating rigs to increase their water depth capabilities, when compared to conventional steel risers. The first generation of lightweight deepwater (DW) risers has been used successfully for nearly a decade on two drillships and a semisubmersible rig in Brazil, while drilling in water depths as great as 7,200 ft.
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