The drill string/BHA is in soft cement and when circulation is established, pumping pressure causes the soft cement to flash set (cement becomes harder quickly). Finally, the drill string gets stuck due to the hard cement around it. The diagrams below demonstrates the process of flash set cement.
BHA in Soft Cement
Turn the pump on while BHA is in the soft cement
Soft cement becomes flash set
Warning signs when you get stuck due to Cement Blocks
• Run in hole after the open hole cement job as cement balanced plug is completed.
• Unable to see firm cement while attempting to find the theoretical top of the cement. It indicates that you may be in the soft cement.
Stuck identification for Soft Cement
• It happens when pump pressure is brought up and pump pressure increases quickly.
• Rotary torque suddenly increases.
• When the soft cement is flash set, you may not be able to get circulation or get low circulation at very high pump pressure.
What should you do for this situation?
1. First of all, before a jarring operation, you must bleed off trapped pressure in the string.
2. Apply jar with the maximum trip load. Jar at the opposite direction of string movement. For example, if you are stuck while moving up, you need to jar down. On the other hand, you need to jar up, if you are stuck while moving down.
Preventive actions:
1. Ensure that cement is properly set prior to tripping to top of cement.
2. Stop at least 100 ft. above the calculated top of cement and establish circulation prior to tagging top of cement.
3. Tag cement slow with pump on.
4. Don’t clean out the cement too fast. Attempt to control drill and check pick up/slack off weight and torque frequently while drilling out cement.
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.
