Thunder Hawk Riser System Design: An Integrated Experience

The Thunder Hawk field was developed through a Steel Catenary Riser (SCR) system connected to a DeepDraft Semi^® Floating Production Unit (FPU) installed in approximately 6,060-ft. water depth in the central Gulf of Mexico (GoM). This paper presents an integrated riser design experience, focusing on the significant design challenges and solutions. The Thunder Hawk FPU was one of the first deepwater projects to address the enhanced GoM environment criteria. These criteria required the integrated design team to configure a feasible and robust hull, mooring and riser system. Model tests were performed to validate the design and calibrate the analysis model. Other challenges included the SCR fatigue and fracture design, titanium stress joint and receptacle design for the high pressure production risers, flex joint over-rotation design, and porch fatigue design. A significant amount of sensitivity analyses were performed to cover the uncertainty of the various hull, mooring, and riser design parameters that affected the SCR performance. The SBM Atlantia (SBMA) riser team worked closely with the Murphy Integrated Project Team (IPT) to achieve a robust and comprehensive riser design 16 months before the first SCR was installed. The highly integrated engineering approach enabled prompt and full considerations of the system interactions, and provided instant design evaluation throughout the project. The sensitivity analyses established the system design envelopes, and resulted in significant flexibility in offshore installation and operation.