Dynamic Characteristics of Metal Seals in Roller Cone Bits

Abstract

During the drilling process, the sealing performance of the roller cone bits is severely challenged by the complex downhole environment and frequent vibrations. In this paper, a comprehensive thermal–fluid–solid–dynamic multi-field coupling numerical model of new-generation single energizer metal seals (SEMS2) is developed. The instantaneous sealing performance of SEMS2 is studied under periodic vibration, instantaneous shock, and random vibration. Time-domain and frequency-domain changes in the sealing parameters with environmental pressures and rotational speeds under different vibrations are analyzed and compared. The results show that the liquid film distribution and lubrication state on the sealing end faces change constantly as the drill bit vibrates, which in turn affects the sealing performance of the SEMS2. The instantaneous leak rate fluctuates alternately between positive and negative under the three kinds of vibrations, aggravating the tendency of lubricant oil leakage and drilling mud invasion. With increasing environmental pressure and rotational speed, the fluctuation amplitudes of the maximum temperature increase, leakage rate, and friction torque under random vibration and instantaneous shock are significantly larger than those under periodic vibration. Our model and results have important theoretical significance for improving the design system of metal seals for drill bits.