Wet storage of steel lazy-wave risers

Abstract

A steel lazy-wave riser pre-laid in an empty state is supported while being flooded for hydrotesting during wet storage. A central array of primary buoyancy units 26 supports an elevated section of the riser above the seabed, the elevated section terminating in touch-down points 16a spaced longitudinally along the riser and across the seabed. Auxiliary buoyancy units 34 spaced outboard of respective ends of the central array support sagbends of the elevated section inboard of the touch-down points. The central array and the auxiliary buoyancy units are arranged symmetrically about a central apex of the elevated section. The primary buoyancy units and the auxiliary buoyancy units are attached to the riser before pre-laying and remain attached to the riser after wet storage, when the riser is configured for operation. The primary buoyancy units then support a hogbend of the operational riser.