Design Evolution of Drilling Tools To Mitigate Vibrations

Abstract

Summary The development of modeling methods to characterize the relative vibration tendency of alternative bottomhole assemblies (BHAs) 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 in which important configuration parameters are most easily adjusted. This paper outlines several design issues to resolve so that 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 (RWD) 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 is composed of 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 one case study, the spacing below a reamer is evaluated, and drilling data are compared with 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 the reamer to seek the centerline with less interference. Another 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 modeling study illustrates how changing BHA components and dimensions affects the vibration indices. The operator has field experience with BHA redesign that has directly led to significant improvement in drilling performance. The benefits include a higher rate of penetration (ROP), a longer time on the bottom, less wear of drilling-tool components, and a reduced frequency of trips.