SKG11: Civil, Structural, Pipelines
Structural Design Offshore Lecture 1
Overview of Offshore Structures
SKG11: Civil, Structural, Pipelines
Lecture 1 Objective
Overview of the petroleum industry Overview of the petroleum industry
Understanding different types of offshore structuresstructures.
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SKG11: Civil, Structural, Pipelines
Lecture Outline
1 0 Overview of the Petroleum industry1.0 Overview of the Petroleum industry
2.0 Offshore Structures
2.1 Fixed Structures
2.2 Floating Structures
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SKG11: Civil, Structural, Pipelines
Petroleum Industry: Overview
Export pipeline or
Storage (FSO)Storage (FSO)
Off h l tf Offshore platforms are used for exploitation of oil exploitation of oil & gas.
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SKG11: Civil, Structural, Pipelines
Petroleum Industry: Overview
Exploration
Appraisal Is there hydrocarbon?
Production Extent of reservoir, is it connected?
Storage
Platforms, production wells, produceSto age
Transportation In field storage? Storage tanks
Vroommm
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Transportation Vroommm
SKG11: Civil, Structural, Pipelines
Oil and Gas Structures- Purposep
Structures in the Petroleum Industry Structures in the Petroleum Industry are industrial structures which must fulfil their intended purpose.fulfil their intended purpose.
The primary function for all structures is to provide support or shelteris to provide support or shelter.
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SKG11: Civil, Structural, Pipelines
Oil and Gas Structures- Selection
Functiono Drillingo Productiono Productiono LQ (Living quarters) etc
Environmento Water depthpo Storm / hurricanes etc.o Soil / Seismicity (Earthquake)
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o Soil / Seismicity (Earthquake)
SKG11: Civil, Structural, Pipelines
Offshore Structures
Fixed Floating
h fl
Fixed Structures
Floating Structures
Structures that extend to the seabed such as: Jacket
Structures that float near the water surface such as: Jacket
Jack-up GBS (Gravity Base)
TLP (Tension Leg) Semi-submersible G S (G a ty ase)
Compliant tower Spar FPSO
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SKG11: Civil, Structural, Pipelines
Offshore Structures
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SKG11: Civil, Structural, Pipelines
2 1 Offshore Structures2.1 Offshore Structures(Fixed Structures)(Fixed Structures)
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SKG11: Civil, Structural, Pipelines
Offshore Structures- Fixed Platforms
Platform size Platform size depends on its function:
Drilling
Living quarters Living quarters
Processing
Flare or vent
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SKG11: Civil, Structural, Pipelines
Offshore Structures- Fixed Platforms
Load TransferLoad Transfer
1.Topsides
MSL2. Jacket
Seabed / Mudline
3.3.FoundationFoundation-- PilesPiles
12-- SoilSoil
SKG11: Civil, Structural, Pipelines
Lightweight Structures
upto 12 conductors max (limited by drilling envelope) upto 70 m waterdepth range (dynamics govern)
ll 0 d k l f h13
normally 450 Mt topsides or jacket lift weight, max
SKG11: Civil, Structural, Pipelines
Jack-up
Topsides sits on a hull (barge) and hull (barge) and able to move from location to location
ithi th within the same operating envelope
Employ jacking Employ jacking system to move up or lower the hull
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SKG11: Civil, Structural, Pipelines
Jack-up
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SKG11: Civil, Structural, Pipelines
Self Installed Structures
TURKMENISTAN MOPU
HANG TUAH ACE PLATFORM
MOAB
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MOAB
SKG11: Civil, Structural, Pipelines
GBS (Gravity Based Structure)
Shallow foundation Remains in place on
seabed because of self eight o ia s ctionweight or via suction.
Installation via ballasting the base the base
Topsides installation normally via floatover normally via floatover method
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SKG11: Civil, Structural, Pipelines
Compliant Tower
Narrow flexible framed structure supported by piled foundation.
W t d th t 900 Water depths up to 900 m. Undergoes large lateral
deflections under wave deflections under wave loading.
Natural period is kept above Natural period is kept above wave period to reduce dynamic amplification.
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SKG11: Civil, Structural, Pipelines
Freestanding Compliant Tower- Fundamental CharacteristicsFundamental Characteristics
Natural period longer than waves30 f G lf f M i t Fi d ~30 sec for Gulf of Mexico towers vs Fixed
platforms (3 to
SKG11: Civil, Structural, Pipelines
Guyed Tower Platform
E "L " 1 000' 198320
Exxon "Lena", 1,000', 1983
SKG11: Civil, Structural, Pipelines
2 2 Offshore Structures2.2 Offshore Structures(Floating Structures)(Floating Structures)
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SKG11: Civil, Structural, Pipelines
TLP (Tension Leg Platform)
Floater that is tied down tothe seabed by vertical steelthe seabed by vertical steeltubes called tethers.
Very rigid vertically andhelps to tie in productionwells.
Flexible in the horizontal Flexible in the horizontalplane, thereby insensitiveto the primary effect ofwave forces.
Has large columns andpontoons Fairly deep draft
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pontoons. Fairly deep draft.
SKG11: Civil, Structural, Pipelines
Semi-submersible
Held in place by anchors connected to catenary connected to catenary mooring system.
Column-pontoon junctions p jand bracings attract large loads.P i di i ti d Periodic inspection and maintenance is a prerequisite due to possibility of fatigue cracking of braces.
Limited application as dry trees due to high motion
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trees due to high motion responses.
SKG11: Civil, Structural, Pipelines
Spar
Large diameter deep draftcylindrical floating caissoncylindrical floating caissonanchored to seafloor withmultiple taut mooring lines.supporting deck.
Heave natural period isabout 30 sabout 30 s.
Centre of buoyancy isconsiderably above centreof gravity, making it quitestable.
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SKG11: Civil, Structural, Pipelines
Floating, Production, Storage and Offloading (FPSO) g ( )
Ship-shaped structures with several different mooring systems e.g. Single Point Mooring Single Point Mooring (SPM).
Integral oil storage capability
Suitable for deepwater where fixed platform is where fixed platform is not feasible.
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SKG11: Civil, Structural, Pipelines
End ofEnd of
Structural Design Offshore Lecture 1
Overview of Offshore Structures
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