How Grooves Can Improve Casing Tripping-Out from the Cemented Borehole

Field observation shows a challenge to pull out a cemented casing without cutting it into pieces due to the limitation of pulling force. Required force can often be beyond the capacity of pulling equipment and it can also be beyond the material strength of the casing causing failure if one should be able to use excessive force for removal. For cases where removal of the cemented casing is necessary different approaches have been considered. Introducing grooves to the casing lowers the pulling force to remove it from the cemented wellbore and has been conceptually considered. This method has been demonstrated successfully in lab-scale experiments. The simulations, based on lab-scale geometry, verify the experimental observation and frictional cohesion, the key parameter to control pulling force, is quantified. The field-scale simulation indicates a significant reduction of the pulling force even with small grooves (5 mm width). The peak of the pulling force also illustrates the possibility of pulling a 10-meter grooved casing without cutting it into pieces. This study demonstrates a potential to shorten the non-productive time and save cost on plug and abandonment tasks.