Development of a New Deep-Water Riser System Daniel Karunakaran Subsea 7
Introduction Grouped SLOR TM is an open bundle riser solution developed by Subsea 7 and 2H Offshore Array of close standing SLOR s/cor s connected together by a buoyant guide frame
Single Line Offset Riser - SLOR TM
ExxonMobil Kizomba A & B SLOR TM
SLOR TM and COR TM Design SLOR TM and COR TM Excellant fatigue performance Decoupled from vessel motion Pre-installable Low vessel payload Gas lift capability Field proven
Multiple single SLOR TM Spacing Clash avoidance - flexibles Wake interference of air cans
Grouped SLOR TM Design
Grouped SLOR TM Design Riser and air can - Single line or pipe-in-pipe - Slender air can Guide Frame - Light weight truss with buoyancy tanks - Tethered to suction pile - Integral receptacles with bearing pads SLOR STEM RECEPTACLE GUIDE FRAME CENTRAL FLANGED CONECTION BUOYANCY TANK TETHER
Grouped SLOR TM - Configuration Typical 4 SLOR s/cor s - 5 to 6m air can diameter - 10 to 25m air can length with compartments - 100 to 150Te base tension - 50Te tether base tension - Suction pile foundations
Grouped SLOR TM Design Development Pipe sizing Air can sizing Optimization - F/L routing Vessel interface Clearance Stability / splay optimization Storm / fatigue analysis Special joint / forging design Installation planning
Grouped SLOR TM - Qualification Finite Element Analysis (FEA) - Assumed C D of 2.0 - Frame Offset < 2% water depth for deep water (800m), <6% for ultra-deep water (2000m) - Guide frame typically 150m away from vessel - Frame bearing loads <10Te, well within capacity of bearing pads - Riser stroke < 4m Elevation from Mudline (m) 750 740 C D =10 100yr Current 730 C D =2.0 100yr Current 720 710 700 No Current SLOR Frame 690-30 -20-10 0 10 20 30 Distance from Frame Centreline (m)
Grouped SLOR TM - Qualification Computational Fluid Dynamics (CFD) - Confirm hydrodynamic coefficients employed in FEA - Drag coefficient (C D ) < 2.0 - Air can spacing of 1.0 diameter gives best response in terms of VIV, wake effects and galloping - CFD further verified using model tow test
Grouped SLOR TM - Qualification Tow Model Test - Conducted in MARIN s test centre in Holland - Model towed at speeds up to 0.7m/s - Incidence of model to flow is varied - Air can separation increased from 0.5D 2.0D -C D ~ 1.0 to 1.5 for air can spacing of 1.0 time diameter - No possibility of clashing between air cans
Full Grouped SLOR TM Model Test MARIN (in Netherlands) was engaged to conduct the model test of Grouped SLOR involving for a water depth of 800m Model scaling of 1:73 is adopted Model test results gathered should be applicable for deeper water depth Results indicate VIV response of risers in Grouped SLOR is smaller than single SLOR
Grouped SLOR TM Installation Assessment Installation of Guide Frame Installation of Riser - Towing : Tug boats - Reel-lay vessel : Seven Oceans - J-Lay vessel : Seven Seas Mating of SLOR/COR with Guide Frame Installation of Flexible Jumper Seven Oceans Seven Seas
Grouped SLOR TM Installation Assessment Riser Installation by J-Lay - Subsea 7 Vessel Seven Seas - Assembling of double joints - Lower riser components via the moon pool using the A&R wire - Cross-haul operation to transfer riser to main crane and auxiliary crane for connecting riser bottom assembly
Conclusions Well developed riser solution for deep and ultradeep water environments. Concepts are qualified Eliminate clearance issue with good fatigue performance. Installation flexibility. High usage of local content.
Contact Information: Daniel Karunakaran, Subsea 7 Daniel.Karunakaran@subsea7.com subsea partner of choice