Varel International says its 12 1/4-in. BB657XCB polycrystalline diamond compact (PDC) bit, which was run on ChevronTexaco's Alba North A-50 well in the North Sea, had a single run of 15,472 ft, with an average rate of penetration (ROP) of 94.5 ft/hr. The company believes the run was the longest for that bit size in the North Sea.
ChevronTexaco had requested a design incorporating oval cutters and lateral jets for the Alba North project. The bit initiated the sidetrack on March 25 and was downhole for approximately two weeks. It was run on Baker Hughes Inteq's AutoTrak Rotary Closed-Loop Drilling System.
After completing the build to 81-degrees, the well was drilled tangentially for +/- 11,000 ft. The well profile was then built to reach the reservoir sands. More than 30 limestone stringers were encountered and drilled with the BB657XCB.
The bit was retrieved after drilling 15,472 ft in 163.7 drilling hours (270 circulating hours), resulting in an average ROP of 94.5 ft/hr. Since the run, Baker Hughes Inteq has confirmed this to be their longest single bit run ever achieved on AutoTrak.
"This run appears to us to be the longest 12 1/4" PDC bit run in the North Sea and possibly a world record for the longest single bit run on a Rotary Steerable System," said Mark Shepherd of Varel International.
The BB657XCB PDC bit is currently being re-furbished to "as new" condition at the Varel manufacturing facility in Pau, France for use on future Alba North wells. Refurbishment of these bit styles adds value to drilling operations by reducing total bit expenditures.