Composite frac plug milling on coiled tubing
- Max. deviation 92°
- Max. dog leg severity 12° @ 100 ft
- Plugback total depth 12,970 ft
- Bottom hole temperature 120°F
- Hydrostatic pressure 1,776 psi
- Casing size 5.5” (4.89” ID)
A US operator required two composite frac plugs to be removed from a shale gas well. The particular well in question extended to 12,970 ft and had a maximum deviation of 92° while the lateral length was approximately 8,300 ft.
Predicted lock up depth for the 2.375“ coil was at 11,700 ft. The plugs were located at 12,030 ft and 12,500 ft, respectively. It was decided to mill out the 5.5” plugs using a 4.79” bit mounted on a mud motor deployed by a CT Well Tractor® on coiled tubing.
The crew arrived late in the afternoon and rig-up commenced shortly thereafter. Within three hours, the CT Well Tractor assembly was run in hole and before midnight the first plug was tagged. Five minutes later the milling was commenced and after just twenty minutes, the first plug had been milled out. The second plug required approximately 30 minutes to be removed. The CT Well Tractor applied the correct weight on bit and prevented reactive torque build-up on the coiled tubing.
By using a tractor to pull the coiled tubing, the risk of helical buckling was also eliminated, enabling the longer reach required for this successful intervention. The entire operation was carried out without any events and demonstrated the efficiency of the chosen approach.
Within a 17 hour period, from rig up to rig down, the two frac plugs were milled out opening up the wellbore for production. The CT Well Tractor was instrumental in this very efficient intervention.
CT Well Tractors are designed to give a constant and known traction force at a predetermined pumped down fluid flow rate to establish a controlled situation and ensure that the target depth of milling is reached. In this particular case, the average speed of the tractor was about 35 ft/min while the average pull force was 2,500 lbs