Cement around a casing shoe or open hole cement squeeze becomes unstable and finally, chunks of cement can fall into a wellbore. If there are a lot of cement chunks in the annulus, the drilling string will get stuck.
Cement Blocks
Warning signs when you get stuck due to Cement Blocks
• Rat hole is too long.
• Drilling into areas where open hole cement jobs as cement squeezes or kick off plug was performed.
Stuck identification for Cement Blocks
• Cement chunks are seen at shale shakers.
• There is cement content in mud logger samples.
• Stuck pipe due to cement blocks can occur anytime.
• Circulation is not restricted.
• Torque and drag are drastically increased and erratic.
What should you do for this situation?
1. Stuck while moving up, jar down with the maximum allowable trip load. Gradually apply torque if required.
2. Stuck while moving down, jar up without applying torque.
3. Pump weighted hi-vis sweep with maximum allowable flow rate to clean large pieces of cement from around drilling string/BHA.
Preventive actions:
1. Do not leave a long rat hole.
2. Ream with circulation through casing shoe and areas where there is open hole cement.
3. Attempt to clean cement in the annulus prior to drilling.
4. Wait long enough for the cement to set before drilling ahead.
5. Minimize tripping speed when BHA passes through casing shoe or cement plug/cement squeeze depth.
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.
