Shell Curlew D Riser Replacement

Shell Curlew D Riser Replacement

Project:                   Shell Curlew Riser Replacement
Location:           UKCS
Sector: Offshore oil and gas
Duration: 9 weeks
Design stage: Operations support
Contact: Dr. Chris Doo, business leader, Prospect

Client's challenge

Curlew D is a subsea development located in the UKCS block 29/7.  The development comprises 3 wells tied back to the Curlew FPSO vessel through two 1.5km long 8" flexible flowlines and an umbilical.
The Curlew D2 riser production riser suffered a failure and was taken out of service as a result.

To maintain riser integrity during the replacement process, Prospect was contracted by CTC Marine to perform a series of engineering analyses.  The analyses highlighted operational constraints within which the riser replacement could take place.

Workscope and approach

Prospect's engineering team performed the following analyses:

  • Recovery pull-in of existing riser
  • Installation pull-in of replacement riser to Shell Curlew FPSO

The pull-in of the existing riser to the installation vessel, while disengaging the MWA clamp from the MWA, was investigated in two distinct phases.  During phase 1 Prospect used a series of static analyses to capture the pull-in to the vessel chute of the existing riser assembly.  And for second phase, Prospect studied the effect of environmental loading at critical points of the pull-in.

Prospect's solution

Responding quickly to the client's project demands, Prospect successfully optimised the operation to ensure that the operating limits of the risers were not infringed, while also opening up the operating envelope.

Benefits

Replacing existing risers is a costly operation.  Optimising and extending the environmental conditions under which installation is possible reduces the time of recovery and installation, in this case allowing Prospect's client to fully utilise the installation vessel and crew.  Furthermore, the compromised existing riser was recovered without further damage; this may have resulted in a full rupture and subsequent retrieval operations. 

The new riser was installed with confidence, knowing that the riser would interact as desired with its associated equipment (MWA and I-tube) while maintaining structural integrity allowed the client to make informed decisions.