In the oil and gas industry, an underreamer is a tool used to extend and enlarge the diameter of a previously-drilled bore. The problem proposed to the Study Group is to obtain appropriate mathematical models of underreamer dynamics, in forms that will lead to feasible computation. The modes of dynamics of interest are torsional, lateral and axial. This report describes some initial models, two of which are developed in more detail: one for the propagation of torsional waves along the drill string and their reflection from contact points with the well bore; and one for the dynamic coupling between the underreamer and the drill bit during drilling.

Problem presented by
Wajid Rasheed, SmartReamer Ltd

Study Group contributors
Erhan Coskun (University of Trabzon, Turkey)
Andrew Lacey (Heriot-Watt University)
Maike Lorenz (Kaiserslautern)
Johannes Maringer (Kaiserslautern)
Colin Please (University of Southampton)
Giles Richardson (University of Nottingham)