Key Seat Causes Stuck Pipe

While drilling, with high tension and torsion in a drilling string, the drill string creates wear, called “key seat “ at wellbore where there are changes in the direction. The soft to medium hard formation has a great tendency to get key seat. While pulling out of the hole, BHA gets stuck into the key seat.

Key Seat

Key Seat

Warning signs when you get stuck due to Key Seat

  • High dog leg severity
  • Long drilling hours without reaming back through the high dog leg area

 Stuck identification for Key Seat

  • This situation occurs when pulling out of the hole only.
  • Circulation is not restricted.
  • High over pull is suddenly seen when the BHA is pulled into the key seat.
  • Tripping back is possible.

 What should you do for this situation?

  1. Because the drill sting gets stuck while moving up, jar down with maximum trip load, which must be applied. Torque while jarring down can be applied as well.
  2. Bring the rotation at a slow speed and attempt to ream back with a small over pull into the key seat areas.

 Preventive actions:

  1. Do not try to drill with a lot of dog leg severity
  2. Back ream some areas where high dog leg severity is presented.
  3. Run a short trip or wiper trip to minimize the key seat.
  4. Utilize a reamer in high dog leg zones.

References

John Mitchell Drilbert Engineering, 2002. Trouble-Free Drilling Volume 1: Stuck Pipe Prevention. Edition. Drilbert Engineering Inc.

Fanarco.net. 1999. Stuck Pipe Prevention Self-Learning Course. [ONLINE] Available at: http://www.fanarco.net/books/drilling/stuck-pipe.pdf. [Accessed 21 June 2016

Steve Devereux, 2012. Drilling Technology in Nontechnical Language, 2d Ed.. 2 Edition. PennWell Corp.

 

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