research activities in the norwegian deepwater programme - cesos
TRANSCRIPT
Research activities in the Norwegian Deepwater ProgrammeConference on CeSOS Highlights and AMOS Visions
Rolf Baarholm, Statoil6/5/2013
− Norwegian Deepwater Programme
− VIV characterization and prediction
− VIV mitigation
− Marine growth
− Concluding remarks
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Outline of presentation
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www.L2S.no www.ndwp.org
• NDP is an organisation of the deep water licences awarded in 15th round (1996) in the Norwegian Sea. Later extended to include 16th 17th 18th 19th 20th and 21st round deepwater licences. About MNOK 400 in projects investment since start. 2012 budget MNOK 24.0.
• The objective is to join forces and carry out cost effective preparations for safe and efficient drilling and field development.
• The program phases are: Phase 1 (1996-2000), Phase 2 (2001-2005), Phase 3 (2006-2008), Phase 4 (2009-2012) and agreed Phase 5 (2013-2016).
• 2012 members: Statoil , Norske Shell, Chevron, Suncor , ENI, Total, and BP.
PL215PL217 PL218
PL210
PL207 PL208
PL209
15th Round
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NDP Riser & MooringObjectives
• Development and verification of design tools
• Development of Guidelines or Recommended Practices
• Bring extended knowledge into engineering companies
• Make the results available to the end users in a transparent format
Focus areas
• Norwegian Sea
• Water depths: 1200-1500 m
• Harsh environment
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VIV in the Norwegian Deepwater Programme
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NDP Riser & Mooring expenditure year 2000From NDP Riser & Mooring
Brochure for 1997-1999.
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NDP funded experimental VIV projects at MARINTEK
Year Project Client
19981999199919992003200320042005200620072011
Clashing criteria and VIVAnalysis full-scale drilling riser VIV experimentVIV in current and floater motions Clashing energy and VIVDual riser clashing testsHigh mode VIV model testsFaired 3D riser VIV test, effectiveness and instability Parametric 2D tests of strakes2-D strake riser VIV test, extended study (with marine growth)NDP Fairing study, pendulum tests, fixed 2D tests, 3D elastic testsVIV riser tests (bare, straked, fairings)*
NDPNDPNDPNDPNDPNDPNDPNDPNDPNDPSHELL/NDP*
* Test funded by Shell and analysis funded by NDP
Understanding VIV phenomenon
• Analysis of full-scale field measurements
• Analysis of Hanøytangen experiments
• NDP high mode VIV experiments at MARINTEK
• Analysis Shell high mode VIV
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NDP High Mode VIV Test in Ocean Basin3D tests with 38m long riser model, dia=27mm
riser
gondol
riser
gondol
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Max. fatigue damage vs. tow speed
1.00E-11
1.00E-10
1.00E-09
1.00E-08
1.00E-07
1.00E-06
1.00E-05
1.00E-04
1.00E-03
1.00E-02
1.00E-01
1.00E+00
0.00 0.50 1.00 1.50 2.00 2.50
Velocity [m/s]
D [1
/yrs
] Bare17.5D0.25D5D0.14D
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Analysis of Shell VIV tests• Similar set-up as for the NDP high mode tests
• Three different pipes tested: L/D = 3800, 1085, 333
• Various suppression devices/coverage
• Marine growth and pipe roughness
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Ref: Halvor Lie et al, “COMPREHENSIVE RISER VIV MODEL TESTS IN UNIFORM AND SHEARED FLOW”, OMAE2012-84055
Compliant: fn < fviv
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NDP Analyses 2012-2014• Modal analysis
• Wavelet analysis
• Estimation of hydrodynamic forces and hydrodynamic coefficients
• Spatial variation in VIV response
• Stability of fairings response
• Response overlap – Reynolds number effects
• Damping regions and power-in regions
• Explore responses with various mitigation devices
• Analysis of higher order responses
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VIV Suppression
Success factors for VIV suppression devices:• Suppress vortex induced vibrations effectively (VIV)
• Avoid global instability (galloping)
• Low drag forces
• Ease of handling (short cord length, low weight, potential pre-installation)
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Helical strakes
• Several R&D test campaigns
• Parametric model tests 2D
• Flexible riser tests 3D
• Full scale testing at high Re
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0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0 2 4 6 8 10 12 14
Reduced velocity (-)
rms
z/D
[-]
P8.8_H10 P8.8_H14 P8.8_H20
Example: effect of strake height
xRMS / D
Increasing strake height
Reduced velocity, Vr =U / fn D
20% of D
10% of D
14% of D
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• Do we need to clean?
• If so, WHEN?
But, what about marine growth?
Pictures from BP: Marine growth on risers fitted with helical strakes
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Effect of hard marine growth
Cross-flow vibrations
Hard marine growthStraked cylinder 17.5D/0.25D
0.000
0.100
0.200
0.300
0.400
0.500
0.600
0.700
5.00 7.00 9.00 11.00 13.00 15.00 17.00 19.00
Reduced velocity (-)
rms(
z)/D
0% growth10% growth20% gorwth35% growth60% growth100% growth
xRMS / D
Reduced velocity, Vr =U / fn D
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Hard35Hard35
Hard20Hard20
Hard60Hard60
Hard100Hard100
100%60%
100%,
50% Cov
35%10% 20%
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Effect of soft marine growth
Cross-flow vibrations
Soft marine growthStraked cylinder 17.5D/0.25D
0.000
0.100
0.200
0.300
0.400
0.500
0.600
5.00 7.00 9.00 11.00 13.00 15.00 17.00 19.00
Reduced velocity (-)
rms(
z)/D
0% growth10% growth20% growth35% growth60% growth100% growth
xRMS / D
Reduced velocity, Vr =U / fn D
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NDP Fairing studyObjectives:
• Study the dynamic behavior of several fairing geometries with respect to transverse and rotational motion
• Develop and qualify catalogue ready fairing for production and drilling risers.
Focus on drag reduction, suppression of vortex induced vibrations and instability motion onset
Fairing
Riser
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Low Re-number fairings tests• Elastically mounted rigid cylinder: pendulum tests
• Fixed cylinder: cavitation tunnel tests
• Flexible cylinder: towing tank tests
10 different profiles tested
Results: New VERY good fairings
Max CF RMS strain
Max IL RMS strain
Great success:
• New fairings with very good performance
But:
• Needed to be tested at higher Re-number in order to verify the performance at full scale conditions
Fairing 3 Fairing 4
Fairing 4 Fairing 3
Comparative Fairing Study - Stability Analysis
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Increased damping
Stable
Unstable
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Flutter theory
Finding:We can construct unconditionally stable fairings by moving CoGforward of mid-point of riser (EC)
Fairing 1 Fairing 2
Fairing 3 Fairing 4
Fairing 6Fairing 5
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High Re-number fairings tests on 15” pipe Oceanic Consulting Corporation, St. John’s
Single pipe tests
Tandem pipe tests:• Fairing downstream of straked riser• Fairing downstream of fairing
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Single pipe tests Tandem pipe tests
Drag coefficient of downstream pipeDrag coefficient
Cross-flow amplitudeCross-flow amplitude of downstream pipe
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A successful program
- Has benefited from the active and open
participation of all members.
- Has enabled strengths of the various
companies to be effectively combined.
- Strengthened cooperation between Academia,
R&D institutes and operators
- Provides a sound foundation to build on.
Selected references
Huse E., Kleiven G. and Nielsen F.G. “Large Scale Model Testing of Deep Sea Risers”, OTC 8701, 1998
Baarholm R. and Lie H. (2005) “ Systematic parametric investigation of the efficienyof helical strakes”, Deep Offshore Technology Conference
Skagset K. and Baarholm R (2008) “Effect of marine growth on an elastically mounted circular cylinder”, OMAE2008-57586
Baarholm R. and Skagset K. (2008) “Modelling and characterization of articifialmarine growth”, OMAE2008-57587
Trim A.D., Braaten H., Lie H. and Tognarelli M. (2005) ”Experimental Investigation of vortex-induced vibration of long marine risers”, J. Fluid and Structures.
Lie H et al (2012) “Comprehensive riser VIV model tests in uniform and sheared flow”, OMAE2012-84055
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Research activities in the Norwegian Deepwater Programme
Rolf BaarholmPrincipal ResearcherE-mail [email protected]: +4748045296
www.statoil.com
6/5/2013