Using AST for directional drilling with rig heave
Bad weather on floating drilling facilities can make the heave compensator struggle and the WOB becomes unstable. An AST can be used to improve on this.
During the winter season, rig movements will quickly pick up in response to a passing weather system and not subside until long after the system has gone. It was in such a situation that Statoil was drilling a subsea producer towards a tight ERD target in the Njord field.
The 12 ½” PDC bit and the optimized RSS system had been performing well until it was found that the system was subjected to increasing stick-slip and orientation problems in a historically “easy” formation. A 9″ HD-AST tool was called out and made up to go in hole on the fly without any other changes to the BHA.
The stick-slip immediately fell to a low level and directional performance was regained along with a steadier torque and a boost in ROP. The AST service was maintained throughout the program as the weather remained unstable.