Introduction
With more than 7,000 wells successfully drilled using WWT Non-Rotating Protectors (NRPs), the recorded lost-in-hole rate is less than 0.2%. While the loss of a NRP in the wellbore is an extremely rare occurrence, WWT conducted full-scale drillability testing to verify that NRPs can be safely drilled through should such an
event occur. The tests were performed on a dedicated test rig using S4-400-Slim-RS and SS3- 400-Slim NRPs installed inside 10-3/4 in. casing.
Test Setup and Drilling Performance
A 6-1/8" open-hole was simulated by cementing and then drilling the cement with a 6-1/8" bit. Each NRP and 4" slim collar were then dropped into the hole and drilled using water only. Cement was drilled at an average ROP of 60ft/hr, while a controlled ROP of 50 ft/hr was maintained when drilling the NRPs. Torque remained consistent in all drilling runs, averaging 3,000–3,500 ft-lb. Some bit cutter wear was observed, which would likely be further reduced when using conventional drilling mud.
Results and Conclusion
The results were successful for both NRP models. The NRPs were drilled without issue and torque stabilized after drilling. The testing, together with 37+ years of field experience, confirms that WWT NRPs are fully drillable. No well has ever been abandoned due to NRP failure.