This paper describes equipment which has been developed for the measurement of axial force, torque, and axial and rotational motions at the top of a drill string. Measurements made in two wells with this equipment represent the first time these quantities have been recorded during drilling. A large number of frequencies of vibration were found in the recordings. Some of these, particularly torsional readings, correlated with predicted natural frequencies, but many did not. Several explanations have been proposed for these “extraneous” frequencies, but no completely satisfactory solution is available. In addition, some interesting interrelations between axial and torsional vibrations were observed.

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