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17th FPSO Research Forum April 5th 2006 The utilization of the pendulous motion for deploying subsea hardware in ultra-deep water Francisco E. Roveri Petrobras R&D Rogério D. Machado Petrobras E&P Pedro F. K. Stock Maxwell B. de Cerqueira
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Previous installation of some subsea hardware by Petrobras
Smaller subsea hardware and shallow waters: crane barge, crane of SS, AHTS
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Previous installation of some subsea hardware by Petrobras
Crane barge and slings – 420 Te/620 m (1995)
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Previous installation of some subsea hardware by Petrobras
MODU/drilling riser – 240 Te/940 m (2001)
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Previous installation of some subsea hardware by Petrobras
Sheave Method – 175 Te/1900 m (2002)
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Disadvantage of wire rope: self weight + axial resonance (DAF)
Challenge of deployment in increasing WD (250 Te payload, m WD) Disadvantage of wire rope: self weight + axial resonance (DAF) Alternative: special construction vessels (scarce and high daily rates) installation costs prohibitive Synthetic fiber rope issues to be solved: bending and heating + axial resonance (w/o heave compensation) The Pendulous Method
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frequency ratio β prescribed vertical displacement (Xo) K M, Ma C
L = Ltotal frequency ratio β
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Transportation vessel
The Pendulous Method Transportation vessel Overboarding Hangoff Pendulous Motion
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The Pendulous Method (cont.)
Conceived to overcome the above constraints (DAF1) Utilization of the Pendulous Motion Utilization of two workboats Distance between vessels 80% of cable length Installation cable, from subsea hardware: wire rope with DBM, polyester and chain Due to drag the pendulous motion will be very slow
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damping ratio ξ = 0.20 working region frequency ratio w/wn
Amplitude of dynamic force (KXo multiplier) DAF (displacements) working region frequency ratio w/wn
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General system configuration (side view, just after release)
chain wire rope polyester wire rope and DBM polyester slings manifold
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System components Weight in air: 280 Te
material MBL (Te) Diam. (mm) length (m) mass (kg/m) wet wgt (kgf/m) EA (MN) chain R4 1097 105 30 222.7 193.8 840 polyester 1250 210 1600 29 7.40 300 wire rope 1000 127 60 57.8 44.7 965 Weight in air: 280 Te Dimensions: x 8.50 x 5.15 m (L x B X H) CG 3.15 m above base line (CG≡CB)
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Physics of the problem Equipment of complex topology
Volume of the envelope dimensions: 728 m3 Steel volume: 35.7 m3 (< 5% total volume) Some assumptions are needed in order to simplify the computer model 1st aproach to concentrate drag and added mass at CG inadequate improvement center of pressure and spatial distribution of drag and lift forces
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Physics of the problem (cont.)
G≡B G≡B (1) Suspended at transportation vessel side (2) Just after release (4) Anti-clockwise rotation G≡B CL CN (3) Clockwise rotation G≡B CL CN
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Development of the concept
PROCAP 3000 project Participation in JIPs: VP2002 (Odim), DISH (phases 2&3) Conceived in 2003, based on the procedure for installation of torpedo pile Numerical analyses with Orcaflex to demonstrate the feasibility Model tests at LabOceano (UFRJ) in 2004 1:1 scale prototype test in December 2005
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Some results of numerical analysis
Three distinct phases: equipment at the side of transportation vessel pendulous motion equipment supported by installation vessel
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Configuration 10 minutes after release
installation vessel chain polyester manifold wire rope and DBM
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Cable effective tension, installation vessel side
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Manifold rotation (deg)
1000_sec.avi _sec.avi
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Model tests Model tests at 1:35, 1:70 and 1:130 scales for manifold #2 – excessive rotations detected in some cases
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1:1 Prototype test Decision to build and install a 1:1 prototype for qualification of the method and installation procedure
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Mitigation of excessive rotations
increase of sling forces at start additional buoyancy to the distributed buoyancy modules improvement of hydrodynamic stability dead weight at the equipment bottom – lowers CG a more adequate equipment geometry, e.g., vertical or near vertical (slightly slanted) panels around it
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Pendulous Method to install MSGLs #2 and #3
Construction of Roncador MSGLs #2 and #3 (1850 m WD) awarded to FMC
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Conclusions Utilization of conventional spread
Allow deployment of heavy equipment in ultra deep waters Attenuation of axial force, prevents resonance Cost effective compared to utilization of specialized installation vessels or rigs (about 30% cost reduction) Needs improvement on control of rotations at start
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