Publications

Deepwater drilling is a high-cost operation. A client operating in the deep water of the Arafura Sea faced a problem with drilling interbedded formations in a 17½-in. section. Previously, the section was drilled with a two-bit trip strategy because of various formation types and hardness, a tungsten carbide insert (TCI) bit for Tertiary limestone and interbedded sands, and a polycrystalline diamond compact (PDC) for the Wangarlu shale and Puffin sand. The solution was a hybrid drill bit that combines roller cones and fixed-cutters. The bit was designed to combine the best attributes of both bit types, the fast aggressive drilling action of the PDC and the smooth, low-torque action of the TCI. Such hybrid bits are now being employed in difficult and challenging applications worldwide and are delivering a step change in performance and significantly lowering overall costs. In this application, the new hybrid bit was able to drill the section with one bit run which saved approximately 28 hours of tripping time, saving USD 1,000,000. In addition, the rate of penetration (ROP) increased by 45% from the best offset well, especially in the “hard limestone” above the Wangarlu. This saved an additional 23 hours, which is equivalent to USD 900,000. This paper presents the results of the field test, and compares the performance of the hybrid bit with conventional PDC and roller-cone bits used on offset wells.