For deviated wells, cuttings tend to accumulate at the low side of the wellbore and form a cutting bed. When there is a lot of cutting bed, it will fall down and pack the string when circulation is ceased. Moreover, while pulling out of a hole, BHA will move some cutting beds and finally, the cutting bed will pack BHA and drill string (stuck pipe).
Note: A well which has an inclination of more than 35 degrees is classified as a deviated well.
Cutting movement while drilling in a deviated well
Cutting settling while stop drilling in a deviated well causes stuck pipe
Warning signs of cutting setting in deviated wells
- Drilling with high angle well (more than 35 degrees).
- While drilling with a mud motor, cutting cannot be effectively removed due to no pipe rotation.
- Increase in torque and drag over a period of time
- Increase in pump pressure without changing any mud properties.
Indications when you are stuck due to cutting bed in deviated wells
- The stuck pipe can happen while drilling and tripping out of hole. Most of the time, it will happen while POOH.
- Increase in torque and drag while drilling.
- Increase in drag while tripping out.
- Circulation pressure is higher than normal. Sometimes, it is impossible to circulate.
What should you do for this situation?
- Attempt to circulate with low pressure (300-400 psi).Do not use high pump pressure because the annulus will be packed harder and the string cannot be recovered anymore.
- Apply maximum allowable torque and jar down with maximum trip load. Do not try to jar up because you will create a worse situation.
- Be patient, and attempt until the pipe is free, then circulate and work pipe until the wellbore is clean.Do not continue operation until the hole is properly cleaned.Check cutting at shale shakers, torque/drag and pump pressure in order to ensure hole condition.
Preventive actions
- Ensure that annular velocity is more than cutting slip velocity. You can learn more about cutting slip velocity via this links – https://www.drillingformulas.com/cutting-slip-velocity-calculation-method-1/, https://www.drillingformulas.com/cutting-slip-velocity-calculation-method-2/
- Ensure that mud properties are in good shape.
- Consider pump hi-vis pill. Try weighted or unweighted and see which one gives the best cutting removal capability.
- If hi-vis sweep is pumped, ensure that sweep must be returned to surface before making any connection. For a good drilling practice, it is recommended that there should not be more than one sweep in the wellbore.
- Circulate hole clean prior to tripping out of a hole. Ensure that good reciprocation while circulating is achieved.
- Circulate few minutes before making another connection in order to clear cutting around the BHA.
- Record drilling parameters and observe trend changes frequently.
- Maximize hole cleaning.
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
