Petroleum Engineering 626 Offshore Drilling Lesson 6C Motion Compensation

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Petroleum Engineering 626Offshore
DrillingLesson 6C Motion Compensation
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Lesson 6C - Motion Compensation

• Bumper Subs
• T H - wd
• Buoyant Riser
• Jackup Rig

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Bumper Subs

• Fit into the drill collar string, but do not
  have the ruggedness of drill collars. To obtain
  a reasonable operating life from bumper subs,
  action has to be taken on the following
  points of concern
• 1. Always run the bumper subs at the neutral
  point in the string.

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Bumper Subs, contd

• 2. Bumper subs are designed to stroke, and if
  operated at a single position, they will wear
  at that position.
• 3. Running the subs in tension minimizes the
  area through which the torque will be
  transmitted, and will cause excessive wear and
  fatigue.

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Bumper Subs

• 4. Running the joint in compression increases
  torque reversals and fatigue in the tool. It
  also increases bit chatter and instantaneous
  peak torque, causing unnecessary wear to the
  tool and the string. This is the fault of the
  operation, not the sub.

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Bumper Subs

• 5. From items 3 and 4 above, it is evident that
  once the string has been run, the weight on the
  bit is fixed. This weight should not be changed
  until the string has been pulled and the
  number of drill collars below the bumper sub
  changed.

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Bumper Subs

• 6.Do not separate the bumper subs in a
  drillstring for heavy drilling operations.
• 7.Special care and maintenance are required to
  obtain a reasonable operating life.
• Remember bumper subs fit into the same part of
  the drillstring where drill collars and
  stabilizers have been destroyed. This is a severe
  test of workmanship maintenance.

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Unbalanced Bumper Subs
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Buoyant Riser Module
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Cantilever Jackup Rig
Float out to location Then lower legs to
seafloor Then jack up
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Jackup Rig Side View
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Jackup Rig Deck Plan