Load-Responsive Hydrodynamic Bearing for Downhole Drilling Tools

Abstract

A load-responsive hydrodynamic thrust bearing has been developed that has capabilities to operate under higher load and speed combinations than the current bearing designs used in roller cone drill bits, downhole drilling motors, and other downhole drilling tools. The bearing dynamic surface, which is initially flat, deflects elastically under load to provide an efficient hydrodynamic geometry that generates a lubricant film, with a minimum film thickness that varies from 0.25 to 2.0μm. The bearing operates with friction coefficients typically in the range of 0.003 to 0.005, which are significantly lower than the conventional roller cone bit thrust bearing designs that operate in a boundary/mixed lubrication regime. Lower friction will allow bit seals to run cooler, and higher load/speed capabilities will increase drilling efficiency and extend component life in hard rock formations. Additionally, the new bearing is suitable for applications where tilting pad thrust bearings are used, offering the advantage of being simple, compact, and more economical.