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RiserTec - Independent Engineering  Design Consultancy

RiserTec Concepts

RiserTec is an Independent Engineering Design Consultancy

RiserTec

Tension Leg Riser

Description
This concept utilises a mid-depth buoyancy unit to hang-off the SCR and a flexible jumper to connect to the FPSO. The mid-depth buoyancy unit needs to be tethered to the seabed for the installation condition but not necessarily for the operational configuration.

The SCR is decoupled from the vessel motions. The riser can be installed by traditional J-Lay. The buoyancy unit can accommodate several risers.

TLR

Key Benefits

  • SCR Motions decoupled from vessel which substantially improves fatigue life
  • SCR TDP is stable which allows local weld improvement
  • Extreme environmental loads are reduced
  • System can be installed by J-Lay with substantial cost benefit over tower systems
  • System can be pre-installed prior to FPSO arrival


Vertically Installed Riser Tower

Installation Procedure

This concept utilises a modularised tower system which is installed from a drill rig or J-Lay construction vessel:

  • The central core, including centralisers for the production risers is assembled using TLP tendon type connectors such as the Oilstates Merlin Connector.
  • Buoyancy tanks lowered into top guides
  • Riser tower frame is latched to the base structure and buoyancy tanks de-ballasted to make tower frame buoyant.
  • Further buoyancy tanks added depending on riser service.
  • Once the core has been installed the individual risers can be installed by traditional J-Lay method. Centralisers would allow for thermal coating and centralisers would be preformed urethane cones
  • Each riser has a load shoulder on the final joint and hangs off at the top of the tower.
  • Bottom and top connections made by collet connectors or a flanged system such as the SCS, MATIS system.
  • Flexible can be pre-installed with last joint

Riser Images

Key Benefits

  • Typical small riser footprint of tower system
  • No requirement for large local fabrication facility
  • Avoids tow and upending
  • All risers and buoyancy tanks can be removed and re-run at any stage during field life
  • Riser utilisation and service can be varied through life. Spare slots can be left for expansion
  • All critical parts of the system are able to be inspected and repaired
  • System can be installed by J-Lay with substantial cost benefit over tower systems
  • System can be pre-installed prior to FPSO arrival
  • Tower can be disassembled, recertified and reused if required
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