Under certain conditions of deep drilling with PDC bits, violent stick-slip torsional vibrations take place in the drilling strueture. In the classical approach used to analyze this problem, it is assumed that stick-slip events arc triggered by a bit-rock interaction law, characterized by a decrease of the torque with angular velocity (which is formally equivalent to a decreasing apparent friction coefficient with angular velocity). Based on laboratory data, we argue that this relationship is not an intrinsic characteristic of the bit-rock interaction. We then elaborate on the coupling between vertical and torsional vibrations at the bit as a possible primary cause of stick-slip. Preliminary results obtained with this model indicate that such coupling is sufficient to generate stick-slip without the need to assume a decreasing friction coefficient.
|Original language||English (US)|
|Title of host publication||4th North American Rock Mechanics Symposium, NARMS 2000|
|Publisher||American Rock Mechanics Association (ARMA)|
|Number of pages||8|
|ISBN (Print)||9058091554, 9789058091550|
|State||Published - 2000|
|Event||4th North American Rock Mechanics Symposium, NARMS 2000 - Seattle, United States|
Duration: Jul 31 2000 → Aug 3 2000
|Name||4th North American Rock Mechanics Symposium, NARMS 2000|
|Other||4th North American Rock Mechanics Symposium, NARMS 2000|
|Period||7/31/00 → 8/3/00|
Bibliographical noteFunding Information:
ACKNOWLEDGMENTS The research presented in this paper is funded by a grant from BP Amoco and Security DBS. This support is gratefully acknowledged.
© 2000 Balkema, Rotterdam.