Design Evolution of Drilling Tools to Mitigate Vibrations

Abstract

Abstract The development of methods to characterize the relative vibration tendency of alternative bottomhole assemblies (BHA) has enabled deliberate tool redesign to reduce vibrations. To achieve the greatest benefit, tool redesign is most effective if applied early in the tool design cycle where important configuration parameters are most easily adjusted. This paper outlines several design issues that need to be resolved so the future generations of tools have inherently lower vibration levels. The use of multiple special-purpose tools (such as logging tools, rotary steerable assemblies, and ream-while-drilling tools) generates significant constraints on BHA configuration options. A redesign methodology to achieve lower vibration indices can be used to investigate modified components, dimensions, and configurations to select the best BHA configuration for specific drilling operating conditions. Case studies are used to investigate BHA designs with flex stabilizers above rotary steerable tools. The flex stabilizer comprises a stabilizer with a smaller diameter connecting flex sub to facilitate rotary steerable directional objectives. It is typically wired for tool signals and is frequently run by vendors. In another case study, the spacing below a reamer is evaluated and drilling data is compared to other assemblies in the same formation. In this example, the spacer provides an increase in the distance between contact points to allow both the stabilizer and reamer to seek the centerline with less interference. The fourth case study evaluates changing contact locations in the BHA by swapping the order of logging tools resulting in different borehole contact positions. Finally, a theoretical study illustrates how changing BHA components and dimensions affect the model vibration indices. The operator has field experience with BHA redesign that has directly led to significant improvement in drilling performance. The benefits include higher rate of penetration (ROP), longer time on bottom, less wear of drilling tool components, and reduced frequency of trips.