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.
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?
- 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.
- Bring the rotation at a slow speed and attempt to ream back with a small over pull into the key seat areas.
- Do not try to drill with a lot of dog leg severity
- Back ream some areas where high dog leg severity is presented.
- Run a short trip or wiper trip to minimize the key seat.
- Utilize a reamer in high dog leg zones.
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.