2015 SETS Presentation_WK
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Transcript of 2015 SETS Presentation_WK
Suction Pile Installation Application Utilizing Predicted and Real-time Monitored Suction Pressures
Yuan-Hung KuoMcDermott International, Inc.
1
Purposes
Offshore and Subsea Foundations
Suction Pile History and Needs
Challenges of Designing a Suction Pile
Conclusions
Contents
Browse the big picture of the offshore foundations
Introduce the history and the needs for Suction Piles/Anchors
Discuss the challenges and risks of designing a suction pilePurposes
Offshore and Subsea Foundations
Source: http://en.wikipedia.org/wiki/Oil_platform
Offshore and Subsea Foundations
Source: http://www.internationalsubseaconsultantsllc.com/services
Offshore and Subsea Foundations
Concrete Gravity TypeMudmat
Driven PilesSource: http://matdl.org/failurecases/File%253ASleipner_A_Tower.png.html; http://www.offshore-technology.com/projects/hutton-field/hutton-field2.html; http://www.oceanworks.com/our-business/oil-gas/subsea-chemical-storage-and-injection/
Suction Piles
Mooring/Holdback TypeFoundation Type
1950s and 1960s: Military equipment to fasten on the seabed and release when necessary1970s: Shell develops the concept of suction anchor.1981: Shell installed suction anchor in 40 m water for buoy device.1990s: Mainly mooring suction piles have being installed in water up to 1450 m.2000s: Subsea foundation suction piles have being installed2010s: Heavy subsea modules emerged
Suction Pile HistorySource: http://www.marinewellcontainment.com/may-2012-news/
Suction Pile Installation
Self Penetration DepthDesign Penetration DepthSuction Penetration Range
Thin wall structure buckling failure controlledComplex of offshore soil property sand/silt/claySoil and structure interaction Geotechnical & Structural Engineering Boundary conditionsPile handlingsSoil failure or structural failure
Challenges of Suction Pile design
Soil Plug Failure
Thin Shell Buckling Failure
Source: Google Images
Criticality of Suction Pile Design
Small D/t, Small L/DSmall D/t, Large L/DLarge D/t, Small L/DLarge D/t, Large L/D
LDt = wall thickness
Suction Pile Design
Myth 2:Structural Buckling CurveStiff Soil Self Penetration Depth Soft Soil Self Penetration Depth
Myth 1:Installation PressureSafety Factor
Myth Buster round 1 what the Real Suction Record tell us?
Pile Information:
Gulf of Mexico
Pile diameter 5.5 m
Pile length 22.9 m
Pile thickness 25.4 mm
Clay strength: 2.4 KPa to 38.8 KPa
Myth Buster round 1 Why the difference?
Flow Rate/Installation RealitySoil Uncertainty
Soil Static Friction
Soil Set-up
Installation practice
Real project to be installed this yearGulf of Mexico 1 Wall Thickness20 Diameter X 100 LengthMyth Buster Round 2 What the code check tell us?Where is the Safety Factor ??
API RP 2A
API Bulletin 2U
DnV RP C202
ABS Buckling Codes
Others
Eigen Analysis Approach
Material Nonlinearity
Imperfection Assumption
Boundary Conditions
Residual Stress
Soil Effect, Load Interaction, etc.FEA ApproachesSemi-Experimental CodesMyth Buster round 2 Why the difference?
Assuming 1.5 Wall ThicknessWhat shall be designed?
Myth 3 FEA Factor of Safety
Lb =20Lb =40Lb =60Lb =80Lb =100
Myth 4 Deformation limitation1.5 Wall Pile
The subsea development is limited by the foundation options
Suction pile foundation has both cost and capacity advantages but has limitations
There are a few myths of design a suction pile in the industry
Ignoring or being unaware of the myths could have huge financial impact to a project
Conclusions