2015 ARKH-P4.0 Offshore Structures General
.pdf
Types of platforms / various uses and environments
Drilling Units
Fixed units on fixed platforms
Mobile Units
Jack ups
Drill ships
Semi submersible
Tender assisted rigs
Production platforms
Fixed platforms
Artificial islands
Steel jackets
Gravity based structures (G.B.S.)
Concrete
Steel
Mobile platforms
Semi submersible platforms
Floating semi submersible
Tension leg platform
SPAR
Vessels ( ships or barges)
Subsea developments
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« Conventional » offshore field architecture
In shallow to medium water depth (< 400 m) offshore fields are developped using :
Fixed platforms with surface wells : > 95%
Floating platforms with subsea wells : < 5%
Subsea wells can also be tiedback to fixed platforms
Different field architecture options for :
Wells & Drilling mode
Platforms
Storage and export facilities
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Decision tree for Conventional Offshore
Mobile platforms 
Fixed platforms
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Semi-Sub |
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Dynamic |
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Steel |
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Positionning |
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Concrete |
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Gravity |
Function |
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Base |
Number of legs |
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Structure |
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Environmental conditions |
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Fabrication Method |
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Installation Method |
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Jacket |
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Foundations |
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Platform options
For large fields
in shallow to medium water depths ( < 400 m ), fixed platforms are generally preferable to floating production systems for following reasons :
Simplicity and better reliability
Lower operating costs
For small fields and for Early Production Systems,
the use of floating production systems are often preferable :
Shorter time to start of production
Possibility to convert existing floating drilling rig into production platform
Lower investment cost
Reusable
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Platform options
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Fixed steel |
Fixed |
platform |
Steel
Concrete
Self erected (Jack up type)
Floating
Semi-submersible (associated with subsea wells only)
Selection depends on :
Water depth
Type of wells (surface, subsea)
Environmental conditions (waves, wind, current)
Construction strategy & constraints
(yard availability, …)
Costs, economy |
Semi submersible production |
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platform |
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Fixed concrete platform
Self erected platform
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Platform options
The purpose of an offshore platform is to provide a stable and safe area above sea level to install equipment and to work.
Offshore platforms are used for different functions :
Drilling
Fluids processing
Water, gaz injection
Utilities
Oil storage & offloading
Living quarters
Functions can be :
Split (one platform = one function )
Integrated (one platform = several functions)
Living quarters platform
Integrated platform
Field architecture
Mainly depends on :
-location, water depth, reservoir characteristics…
-field life duration
-available techniques
-available contractors and means
-economical data at Project decision
-…
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Field architecture : ex. Abu Dhabi 30m WD
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Field architecture : Ekofisk 100 m WD
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YADANA Myanmar
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