Research activities in the Norwegian Deepwater Programme Conference on CeSOS Highlights and AMOS Visions. Rolf Baarholm, Statoil

Transcription

1 Research activities in the Norwegian Deepwater Programme Conference on CeSOS Highlights and AMOS Visions Rolf Baarholm, Statoil

2 Outline of presentation Norwegian Deepwater Programme VIV characterization and prediction VIV mitigation Marine growth Concluding remarks 2

3 th Round PL217 PL218 PL215 PL210 NDP is an organisation of the deep water licences awarded in 15th round (1996) in the Norwegian Sea. Later extended to include 16 th 17 th 18 th 19 th 20 th and 21 st round deepwater licences. About MNOK 400 in projects investment since start budget MNOK The objective is to join forces and carry out cost effective preparations for safe and efficient drilling and field development. PL207 PL209 PL208 The program phases are: Phase 1 ( ), Phase 2 ( ), Phase 3 ( ), Phase 4 ( ) and agreed Phase 5 ( ) members: Statoil, Norske Shell, Chevron, Suncor, ENI, Total, and BP. 3

4 Norwegian Deepwater Programme Environment Metocean Riser & Mooring Seabed Subsea 4

5 NDP Riser & Mooring Objectives 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: m Harsh environment 5

6 VIV in the Norwegian Deepwater Programme From NDP Riser & Mooring Brochure for NDP Riser & Mooring expenditure year

7 NDP funded experimental VIV projects at MARINTEK Year Project Client Clashing criteria and VIV Analysis full-scale drilling riser VIV experiment VIV in current and floater motions Clashing energy and VIV Dual riser clashing tests High mode VIV model tests Faired 3D riser VIV test, effectiveness and instability Parametric 2D tests of strakes 2-D strake riser VIV test, extended study (with marine growth) NDP Fairing study, pendulum tests, fixed 2D tests, 3D elastic tests VIV riser tests (bare, straked, fairings)* NDP NDP NDP NDP NDP NDP NDP NDP NDP NDP SHELL/NDP* * Test funded by Shell and analysis funded by NDP 7

8 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 8

9 NDP High Mode VIV Test in Ocean Basin 3D tests with 38m long riser model, dia=27mm gondol riser gondol riser 9

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11 CF and IL fatigue vs. tow speed for bare riser in uniform flow 11

12 Max. fatigue damage vs. tow speed 1.00E E E E-03 D [1/yrs] 1.00E E E E E E E E Velocity [m/s] Bare 17.5D0.25D 5D0.14D 12

13 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 Compliant: fn < fviv Ref: Halvor Lie et al, COMPREHENSIVE RISER VIV MODEL TESTS IN UNIFORM AND SHEARED FLOW, OMAE

14 NDP Analyses 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 14

15 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) 1 5

16 Suppression devices Helical strakes Fairings 16

17 Suppression devices Helical strakes Fairings 17

18 Helical strakes Several R&D test campaigns Parametric model tests 2D Flexible riser tests 3D Full scale testing at high Re 1 8

19 Parametric 2D test of helical strakes 19

20 Bare riser Straked riser (P/D=17.5, h/d=0.25) 20

21 Example: effect of strake height x RMS / D P8.8_H10 P8.8_H14 P8.8_H % of D Increasing strake height rms z/d [-] % of D 20% of D Reduced velocity (-) Reduced velocity, V r =U / f n D 21

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26 Coverage = 52% Coverage = 82% Coverage = 75% Coverage = 100% 26

27 But, what about marine growth? Do we need to clean? If so, WHEN? Pictures from BP: Marine growth on risers fitted with helical strakes 2 7

28 Hard Modeled Marine Growth Soft 28

29 Effect of hard marine growth Cross-flow vibrations x RMS / D Hard marine growth Straked cylinder 17.5D/0.25D Hard rms(z)/d Reduced (-) Reduced velocity, V r =U / f n D 0% growth 10% growth 20% gorwth 35% growth 60% growth 100% growth Hard35 Hard60 Hard100 29

30 Effect of soft marine growth Cross-flow vibrations x RMS / D Soft marine growth Straked cylinder 17.5D/0.25D % growth rms(z)/d % growth 20% growth 35% growth 60% growth 100% growth 10% 20% 35% 100% 60% 100%, 50% Cov (-) Reduced velocity, V r =U / f n D 30

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32 NDP Fairing study Objectives: 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 32

33 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 3 3

34 Results: New VERY good fairings Fairing 4 Fairing 3 Great success: New fairings with very good performance But: Needed to be tested at higher Renumber in order to verify the performance at full scale conditions Fairing 4 Fairing 3 Max CF RMS strain Max IL RMS strain

35 Instability of Faired Riser, 3 D Test Fairing Riser 35

36 Comparative Fairing Study - Stability Analysis Fairing 1 Fairing 2 Flutter theory Stable Unstable Fairing 3 Fairing 4 Increased damping Finding: We can construct unconditionally stable fairings by moving CoG forward of mid-point of riser (EC) Fairing 5 Fairing 6 36

37 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 37

38 Single pipe tests Drag coefficient Tandem pipe tests Drag coefficient of downstream pipe Cross-flow amplitude Cross-flow amplitude of downstream pipe 38

39 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. 39

40 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 efficieny of helical strakes, Deep Offshore Technology Conference Skagset K. and Baarholm R (2008) Effect of marine growth on an elastically mounted circular cylinder, OMAE Baarholm R. and Skagset K. (2008) Modelling and characterization of articifial marine growth, OMAE 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, OMAE

41 Research activities in the Norwegian Deepwater Programme Rolf Baarholm Principal Researcher Tel: