The increased use of hole opening tools remote from the drill bit has led to a critical need to understand the interaction between the drill bit and the hole opening tool itself. Problems that can result from improper matching include vibration, inability to open hole, mechanical damage to string tools or to the bit, and sub-optimal drilling performance.

This paper explores the theoretical relationship between bit and reamer and modeling the relative agressivity and stability of both tools, building on already established indices for predicting and comparing the performance of bits. It also considers stabilization of the hole opening tool using both concentric and eccentric devices. It describes theoretical modeling of the vibration behavior of the assembly. It then describes field validation of the above using a unique downhole data recording device, located at various key points in the BHA and drill string.

Finally, the paper will review a number of case studies and demonstrate a linkage between the theoretical analysis, the measured validation, and actual field results. These relate to a variety of directional applications including vertical rotary, directional motor and rotary steerable, and demonstrate reduced vibration, improved hole quality and hole opening performance, superior penetration rates, and overall significantly reduced drilling costs.

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