Offshore Natural
Resource Extraction
Overview
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History
Exploration
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Platform models
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Seismic surveys
Drill ships
Fixed Platforms
Compliant Towers
Semi-submersible Platforms
Jack-up Platforms
Tension-leg Platforms
Spar Platforms
Subsea Systems
Recent Affairs
History
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1986 - Companies drilled from piers extending off the beach at
Summerland California
1911 - Gulf Oil drilled the worlds first truly “offshore” well
detached from the shore at Caddo Lake, Louisiana/Texas border
1947 - Although drilling in the Gulf of Mexico has been taking
place for some time, Kerr McGee completed first offshore well
out of sight of land
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1965 – The 5600 ton drilling barge “Sea Gem” was first to
discover hydrocarbons in the British North Sea sector
Exploration
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Seismic Surveys
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Maps rock layers without
drilling a well
Send shockwaves using air guns
and record echoes
The time for each echo to
return as it bounces depends
on depths and properties of
rock layers
Problem: presence of
hydrocarbons can only be
confirmed by drilling
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Drill Ships
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Ship with oil derrick on deck
Used to quickly drill and check for hydrocarbons
Not as stable as other rigs
Very mobile
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Early ships used anchors to maintain position
Modern vessels use Dynamic Positioning
Platform Models
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Fixed Platform
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Used in shallow waters up to 520m
Legs constructed of concrete or
steel
Rest on their own masses, very
stable in strong winds or rough
waters
Designed for long term use
Concrete legs serve as storage tanks
Gravity base platform being built in Norway
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Jack-up Platforms
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Moving legs attached to platform
Legs can be lowered like jacks and rested on seabed
Designed to easily move from place to place
Used in relatively low depths (up to 150m)
Problem: cannot be used in extremely deep
waters
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Compliant Towers
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Similar to fixed platforms
Used in deeper waters ( 450 – 900m)
Slender tower attached to foundation
slab on seabed
Very flexible compared to fixed
platforms
Can sustain significant lateral
deflection cause by water movement
Strong enough to withstand
hurricanes despite it’s flexibility
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Semi-submersible Platforms
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Supported by hulls or pontoons
Can be ballasted up and down by regulating flooding in buoyancy tanks
Can be moved from place to place
Anchored by cable or dynamic positioning
Very stable in rough, deep seas
Used in depths from 180 – 1,800m
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Tension-leg Platforms
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Similar to semi-submersible, consisting of
a floating rig
Attached to seabed by tethers
Tethers have high axial stiffness which
eliminates most vertical movement
Used in depths of up to 2000 m
Miniature version called Seastar platforms
are used in depths between 200 - 1100m
Examples of Seastar platforms
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Spar Platforms
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The largest of all platforms
Consist of a large cylinder used to
stabilize the platform
Does not extend to the floor
Tethered by lines and cables
Unlike the TLP platforms it has
conventional cables but is more stable
due to the large ballast
-The Genesis hull, travelling past condominium complex in Port
Arkansas, Texas
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Subsea Systems
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Do no have ability to drill
Extract and transport only
Used in depths of up to 2000m
Tied in to underwater pipeline or production platform
Avoids the need of production platform for each well
Summary
Recent Affairs
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Hurricane Rita and Katrina Facts
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394 platforms in the path of the storms
18 rigs suffered major damage or were totally lost
16 rigs damage to varying degrees, up to 2 weeks to repair
Furthest rig drifted 80 miles during the storms
No loss of life
- Billiton Oil Platform Beached by Rita, just off of Dauphin Island, Alabama
Chevron’s TLP platform before the storms
- What remains of Chevron’s TLP platform after being hit by hurricane Rita
References
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http://www.offshore-technology.com/projects/shtokman/images/image2.jpg
http://www.sv.vt.edu/classes/MSE2034_NoteBook/MSE2034_kriz_NoteBook/design_pro
j/ten_leg/tlp.gif
http://www.solentwaters.co.uk/Vessel%20Types/Vessel%20Types%204/_wp_generated/w
p94c9b6c4.jpg
http://www.offshore-technology.com/projects/siri/
http://www.mossww.com/mossmaritime/
http://www.km.kongsberg.com/ks/web/NOKBG0239.nsf/obj/kristin_rig_200.jpg/$File/k
ristin_rig_200.jpg?OpenElement
http://www.jraymcdermott.com/images/jrme/compliant.jpg
http://en.wikipedia.org/wiki/Condeep
http://www.mms.gov/tarprojectcategories/deepwate.htm
http://dsc.discovery.com/fansites/oilsweatrigs/photo/photo_05.html
http://thomko.squarespace.com/display/ShowJournal?moduleId=209208&categoryId=353
73
http://www.solarnavigator.net/oil_rigs.htm
http://en.wikipedia.org/wiki/Oil_platform
http://www.naturalgas.org/naturalgas/extraction_offshore.asp
http://www.eia.doe.gov/kids/energyfacts/sources/non-renewable/offshore.html
http://science.howstuffworks.com/oil-drilling.htm
http://www.mms.gov/tarprojectcategories/Assets/Photos/abb.jpg
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http://www.rigzone.com/data/rig_report.asp?rpt=reg
http://www.solentwaters.co.uk/Vessel%20Types/Vessel%20Types%204/page7.html
http://www.gomr.mms.gov/homepg/regulate/environ/louisiana_coast.html
http://www.schoolscience.co.uk/content/4/chemistry/petroleum/knowl/4/2index.htm?pla
tforms.html
http://www.offshore-technology.com/projects/mensa/index.html#mensa6
http://www.mustangeng.com/content.aspx?upstream_compliantpiledtowers
http://www.offshore-technology.com/projects/genesis/genesis3.html