Petroleum Engineering 406 Floating Drilling Lesson 11a Motion Compensation

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Petroleum Engineering 406Floating
DrillingLesson 11a Motion Compensation
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Lesson 6 - Motion Compensation

• Reentry
• Tensioners
• Heave Compensators
• Passive Motion Compensation
• Active and Semiactive Systems

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Re-entry

• It is possible to re-enter a borehole without
  using guidelines!
• 1. Use land-based navigation equipment to get
  the vessel in the vicinity of the well
• or better still Use GPS (Global
  Positioning System)

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Re-entry, contd

• 2. Lower reentry string to a safe distance
  above the wellhead
• 3. Use position location equipment to complete
  the job
• (i) Television camera
• (ii) Acoustic device - pinger or transponder
  (iii) ROV - Remote Operated Vehicle

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Heave Compensation

• How do you maintain a constant tension
• on the marine riser - when the vessel heaves?

• How do you maintain a constant weight
• on the bit - when the vessel heaves?

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Deadweight Riser Tensioning System
Dead Weight (constant tension)
Dead Weight
Slip Joint
Marine Riser
Early design - OK up to 100,000 lbf. Attached
to lower half of telescoping joint. Adds weight
is bulky...
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Pneumatic Riser Tensioning System
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Pneumatic/Hydraulic Heave Compensation System

• Pneumatic/Hydraulic Tensioners
• Take up much less room
• Facilitate changing the tension by changing
  the air pressure
• Can be used for the marine riser,
• the guidelines and the drill string

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Pneumatic/Hydraulic Heave Compensation System

• Passive Systems are the most popular
• Require essentially no energy input
• Use an air spring with a variable
  spring constant
• Can keep the tension within 15 or even
  less.

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Pneumatic/Hydraulic Heave Compensation System

• Active Systems
• Require external energy through each load
  cycle
• Provides a highly consistent force
• But -- Has a high initial cost
• Has a high operating cost

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1,500 psig WP
5 ft
Typical Tensioner
20 ft
Lower sheaves are attached to the cylinder (and
vessel), upper sheaves are attached to the
piston rod