OCEN 201 Introduction to Ocean

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OCEN 201Introduction to Ocean Coastal
Engineering

• Offshore Structures
• Jun Zhang
• Jun-zhang_at_tamu.edu

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• Offshore Structures
•      
• Drilling rigs Exploration of oil and gas
• Stay in a place for a few months (Mobil or
  movable) 
• - Jack-up drilling rig
• - MODU (Mobil Offshore Drilling Unit)
•    
• Production platforms Production of oil and gas
• Stay in a place for at least a few years
  (usually 20 -30 years)
• - Ground-base structure ( lt500800 m)
• - Floating Structures (gt 800 m)
•  

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Fig. 3-2 Example of jack-up drilling rig Legs
are retractable

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• Fig. 3-3
• A semi-submersible
• Drilling Rig
• Mooring system
• or Dynamic positioning

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DP - Dynamic Positioning
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Fig. 3-5 Steel Jacket Platform in 20 200 m
waters lt 500 m Cannot be moved
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OFFSHORE PLATFORM
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Fig. 3-6 Concrete Gravity Structure
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OFFSHORE STRUCTURES
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OFFSHORE PRODUCTION DRILLING

• AUGER TLP

• OCEAN CLIPPER

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OFFSHORE PLATFORM

• SPAR

• FIXED JACKETED

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DRILLING RIG SPAR
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Articulated Tower
Fig. 3-10 pp56 New version Fig. 12 pp61
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Single Anchor Leg Mooring System
Fig. 3-11 pp56 New Version Fig.13 pp62
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• Wave Forces on Offshore Structures
• Morrison Equations
• Diffraction/Radiation Theory
• (Potential theory, neglect water viscosity)
• CFD (Computational Fluid Dynamics)
• (Navier-Stokes Equations, considering water
  viscosity)

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Morrison Equations Modified ME
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Wave Forces on A Vertical Cylinder Velocity
acceleration are a function of z t Force
(function of t)
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Wave Forces on A Vertical Cylinder
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Wave Forces on a Horizontal Cylinder Velocity
acceleration are a function of t only
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Wave Forces on a Horizontal Cylinder
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Example of Problem 3-1 pp73 (old v.
pp64) Computing the horizontal load on a
vertical cylinder Drag coefficient of a
cylinder pp 72 75 (old v. pp63
64) Added-Mass coefficient of a cylinder pp 72
(old v. pp64)
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Wind Current Forces Steady oscillatory
portions Steady current forces
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Wind Forces
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Forces on Pipeline Due to Wave Currents
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Free Body diagram of A Pipe under the impact of
Wave Currents