Catenary risers are potentially the most attractive form of deepwater riser wherein the flowline is ‘simply’ extended up to the vessel in a catenary configuration. However, experience shows that such systems are extremely technically challenging due to complex structural response and in steel pipe risers fatigue and internal corrosion are critical design and fabrication driver leading to high installed costs.
In such catenary configurations where its flexibility, fatigue capacity and corrosion (H2S) resistance are critical, m-pipe® greatly simplifies the design and installation process giving benefits of reduced payload and longer fatigue lives.
Due to the lightweight of m-pipe® it is often necessary to add external weight to the m-pipe to control the response of the catenary. In some applications where the riser may be attached to a high motion vessel such as an FPSO, a chain weighted catenary can provide a simple solution. This uses a chain in a catenary configuration attached at approximately 20% of the water depth to control both the tension distribution along the riser and manage riser corridors. This is a similar geometry to pliant waves used in non bonded flexible pipe but eliminating the costly buoyancy material.