A comparative study of hybrid bit over roller cone and PDC bits

Abstract

Early hybrid drilling concepts date back to the 1930s, but the development of a viable drilling tool has only become feasible with recent advances in Polycrystalline Diamond Compact (PDC) cutter technology. This paper describes a new generation of hybrid bits based on proven PDC bit designs with roll cutters on the bit periphery. Laboratory and field results will be presented, comparing the performance of hybrid bits with that of conventional PDC and roller bits. A hybrid bit can drill shale and other plastically behaving formations two to four times faster than a roller cone because it is more aggressive and efficient. The penetration rate of a hybrid bit responds linearly to Revolutions Per Minute (RPM), unlike roller taper bits that exhibit an exponential response with an exponent less than one. In other words, a hybrid drill will drill significantly faster than a comparable roller drill in motor applications. Another advantage is the influence of rolling mills on bit dynamics. Compared to conventional PDC bits, torsional oscillations are up to 50% lower, and low-speed slip/slip and high-speed swirl are reduced. This gives the hybrid drill a wider operating window and greatly improves tool face control in directional drilling. The Hybrid Drill is a highly specific drill aimed at traditional cylindrical taper applications limited by the Rate of Penetration (ROP), large-diameter PDC-bit and roller-cone-bit applications limited by torque or Weight on Bit (WOB). Highly interconnected formations with high torque fluctuations can cause premature C3 failure and limit mean operating value torque, and motor and/or P applications where higher ROP and better build speed and tool face control are desired.