METHODS, SYSTEMS, AND TOOL ASSEMBLIES FOR DISTRIBUTING WEIGHT-ON-BIT BETWEEN A PILOT EARTH-BORING ROTARY DRILL BIT AND A REAMER DEVICE

摘要

Methods, systems, and tool assemblies for distributing weight between a bit and a reamer device are disclosed. For example, at least one of the drill bit and the reamer may be configured to selectively distribute a weight-on-bit between the drill bit and the reamer, such as within a predetermined range. Additionally, methods of drilling wellbores may include selectively distributing a weight-on-bit applied to a bottom hole assembly between a drill bit and a reamer of the bottom hole assembly. Also, a reamer may be configured to exhibit a first maximum rate-of-penetration into a relatively hard formation, and a drill bit may be configured to exhibit a second maximum rate-of-penetration into a relatively soft formation that is less than the first maximum rate-of-penetration.