HRT suitable for deepwater, ultra-deepwater
Judy Maksoud
International Editor
Offshore
The oil and gas industry is always looking for better production options for deepwater and ultra-deepwater, according to Stéphane Luteyn, project engineer at Doris Engineering. Luteyn presented a new hybrid riser tower (HRT) concept at the Offshore Mechanics and Arctic Engineering conference in Halkidiki, Greece.
Doris based design parameters for its HRT on conditions in GoM deepwater and ultra-deepwater areas (Green Canyon and Garden Banks areas) and in the Gulf of Guinea off West Africa (Girassol field).
Luteyn said in describing the components of the HRT system from the top down. A buoyancy tank sits at the top of the tower, flexible jumpers, which convey fluid to the production unit, hang below the tank. The next segment is a bundle of risers, beneath which the anchoring system and spools connect. The final system components, the flowlines, lie on the seafloor.
Doris based its HRT design principles on the buoyancy tank, bundle design, and foundation design. Each posed unique concerns.
Design issues for the buoyancy tank included the flexible jumper load as well as environmental factors, Luteyn said.
The second analysis segment was bundle design. The core pipe is at the center of the bundle, Luteyn said. "The core pipe is the backbone of this segment of the design."
According to Luteyn, parameters affecting bundle design include:
• Hydrostatic and compression pressures
• Riser arrangements
• The overall diameter of the riser bundle buoyancy arrangements
Parameters affecting the foundation, Luteyn said, are soil conditions and the tower bottom load.
Doris analyzed these and other elements of the HRT design taking into account water, current, and 100-year storm conditions for the Gulf of Guinea. Doris analyzed water, Eddy current, and 100-year storm condition effects for the GoM.
According to Luteyn, Doris' HRT design offers advantages. It features a simple field layout, can be fabricated locally, and can be installed irrespective of a surface production vessel.
06/15/05