TAMU Pemex Offshore Drilling Lesson 12 Special Problems Rigs

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TAMU - PemexOffshore DrillingLesson 12-
Special Problems- Rigs
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Lesson 12 - Special Problems

• Special Problems
• Navigation
• Workboats
• Tides
• Miscellaneous
• API RP 2P- Spread Mooring
• Rigs, Arctic Drilling, etc.

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Navigation
M
Measured distance
Measured distance
Known distance
A
B
Figure 9.1. Navigation using circular grid
Need two or more fixed radio stations -
electromagnetic signals. Circular Navigation
System. Short range. Quite accurate. Stations A
B can be on shore or on platforms. A third
station may be needed...
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• Fig. 9-2. A hyperbolic grid formed by taking the
  difference in distance to the fixed stations A
  and B.

Stations A B are contacted simultaneously.
Difference in arrival times locates you on a
hyperbola. A third station is needed to specify
where on the hyperbola. Not very accurate. A B
are slave stations.
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Time T2
Satellite Orbit
Time T3
Time T1
Computer Receiver
Figure 9.4 - Relative geometry of shipboard
user and satellite
On the first pass, position to 1/10 mile. After
several passes 100 ft. 9 EA 2-minute messages
are available on each pass. Utilizes Doppler
frequency shift.
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Drillship R.F. Bauer Global Marine WD 2000'
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Comparison of Vessel Characteristics
Property Workboat Drilling Vessel
Primary In Transit Moored location
Location Maneuver or Moored during
or go to Storm harbor
Vessel Generally bad, Must motion
but of minor be low concern
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Comparison of Vessel Characteristics
Property Workboat Drilling Vessel
Load Load and unload For
drilling arrangement part of cargo, then
operation ballast to safe trim
efficiency
Loading and Easy to load and
Relatively little unloading discharge
full cargo cargo change
Maneuver- Very important
Relatively ability unimportant
Propulsion/ 2 to 4 hp/ton Less
than displacement 1 hp/ton
load line limit
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Note Volumes in bbl, gal, cu.ft - all in one
table
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The workboat is the workhorse of the offshore
industry. One per ship? Less? Up to 3!
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Fresh Water
Engine Room
Drill Water
Fuel Tanks
Pneumatic Tanks
The workboat brings supplies for drilling a well.
Places anchors. Most tanks are below deck.
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Jack-up Rig
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Dimensions and Capacities

• Jacking System
• Number 3 X 12 pinions
• Size 1,000 kips (446 T) per pinion continuous
  jacking
• Size 1,600 kips (726) per pinion maximum holding
• Jacking speed 1.55 ft/min.
• Rack Chock System
• 6 racks per leg for 3 legs
• Design Friede Goldman
• 39,000 kips capacity--- hydraulic

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Figure 9.8 - Idealized oscillations of tides
14-19 Days
Spring tide
Neap Tide
Mean Water Level
Once or twice per day
Tide sea level oscillations of approximately
daily or twice per day. Affect KB height above
ML. Measurements should be normalized to Mean
Water Level. Tides vary from lt1 ft to 50 ft.
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Figure 9.9 - Typical tide curves for United
States ports.
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Figure 9.9 - Typical tide curves for United
States ports
Boston
New York
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Figure 9.9 - Typical tide curves for United
States ports.
Hampton Roads
Savannah River Entr.
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Figure 9.9 - Typical tide curves for United
States ports.
Ft
Key West
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Pensacola
Galveston
NOTE Pensacola - almost disappears! Galveston
- from 1 to 2 cycles per day!
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API RP 2P January 1 1984
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Figure 9 - Basic Catenary Relationships
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Figure 10. Force Geometry and Vecto r Diagram
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NOTE API RP 2P has different force equations
Fig. 11 - Example Analysis Wind Areas
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Vessel
Hydrophone signal
Hydrophones
Beacon- signal transmission
Wellhead position
Ship position
Wellhead assembly
Position Indicating Display
Short base Line phase comparison system
Sea bottom
Acoustic Position Reference System. Source
Honeywell
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Tilt Indicator for Guide Structures
May be mounted on temporary guide base. View with
camera. Start hole within 1/2 deg. of vertical.
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Offshore Drilling Structures

• Offshore Drilling Structures
• Fixed
• Floating
• Tension Log

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Can be up to 10 miles 20 miles 200 ft
52,800 105,600 200 62.4 0.9 6.26 E13
lbs ? 31 billion tons!
Ice Floes in the Beaufort Sea
It is a good idea to get out of the way when one
of these babies comes along! Glory Hole may be
needed
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WL
ML
Spud Cans
Platform Piles
Typical Jack-up Platform layout
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Fixed Jacking System with Leg Locking Device
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Noble Drillings Cecil ForbesA Jack-Up Rig
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Shells CognacConventional20-well
PlatformWells are directionally drilled
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Shells BullwinkleWorlds tallest offshore
structure1,353 water depthProduction began
in 198945,000 b/d80MM scf/d
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Small concrete monotower concept
Concrete Monotower Concept Gravity Structure
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Several guy wires and clump weights support a
compliant platform.
Guy wires
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Main Deck
Column
A semisubmersible with floats that are located
below the waterline when drilling
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Sonats George Washington
A Semi-Submersible Rig
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Zapatas TraderA Drillship
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Joides Resolution Ocean Drilling Program
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Production Platform
Several tensioned tubes hold a tension-leg
platform on station.
Steel Tubes
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