Reverse Circulating Bit mills frac plug to re-establish communication with lower zone
- Target depth 11,766 ft
- Casing 5-½ 20#
- BHT 230°F
- WBF Water, 8.35 PPG
- WHP 3,800 psi
- Total BHP 6,900 psi
- Hydrostatic 3,100 PSI
An operator in the Eagle Ford shale play near Laredo, Texas, was in the middle of a zipper frac operation with two adjacent wells when a plug was accidentally set off depth at 11,766 ft, over untreated, open perforations. The client needed to re-establish communication with the well section below the frac plug. The zone above the plug had been perforated and a frac ball had been pumped down on top of the plug.
Wireline was already rigged up on the well, and the client did not want to disrupt the current wellsite configuration. So Welltec® was contacted for a quick solution and proposed running the Well Cleaner® Reverse Circulating Bit (RCB) and Well Tractor® in combination to mill the ball on top of the plug to regain access to the lower zone.
The RCB/Well Tractor combo was an ideal solution for this job for a number of reasons: the tractor provides weight on bit (WOB) and torque control, the RCB works with the well fluids, the attached modular bailers recover debris while milling and field engineers monitor real-time tool feedback from the surface. Welltec performed detailed simulations to model the forces in the well based on provided information. Once the simulations determined the job was feasible, the tools were mobilized to the wellsite from nearby Houston.
During the operation, the Well Tractor conveyed the toolstring to the target depth. After confirming the location via the surface readout, the Well Cleaner RCB engaged the ball while the Well Tractor provided approximately 1,200 lbs of WOB, milling for 3.7 hours. The RCB dislodged the ball and milled the top section of the plug mandrel, thereby re-establishing communication within the well across the frac plug. The client was then able to treat the perforations in the lower zone.
The job was completed in under 12 hours with no incidents. Afterwards, the mill bit was found to be in good condition, and it is estimated that the entire plug could have been released within two hours of additional milling time if the client chose to continue milling.
Heavier alternatives would have required additional time for mobilization and setup and would have resulted in a greater cost to the client. Moreover, Welltec’s lightweight wireline solution reduced HSE risks onsite.