Abstract

Bearings used in directional drilling operate in conditions which are significantly more severe than those found in traditional industrial applications. One of the most difficult conditions mud motor thrust bearings encounter is misalignment, which is amplified in bent housing motors. The purpose of fixed bend and adjustable bend motors is to build a desired angle in a well. To accomplish this build rate the housing is manufactured with a purposely bent joint which typically deviates between 1 to 3 degrees from the rest of the bottom hole assembly. Radial bearing wear creates uneven thrust bearing loading due to angular misalignment. Uneven loading in ball bearings results in significantly higher Hertzian stresses which reduces bearing life and reliability. Uneven loading in diamond, or PDC, bearings results in premature failures due to increased stresses and chipping. The proposed paper will demonstrate that a thrust bearing design incorporating independent and resiliently mounted thrust pads operating against a continuous rotating bearing surface is effective at handling misalignment in bent housing mud motors.

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