Inventors:
David W. McCulloch - Arlington TX, US
Timothy S. Steffenhagen - Fort Worth TX, US
William B. White - Bedford TX, US
William G. Stewart - Fort Worth TX, US
Assignee:
National Oilwell Varco, L.P. - Houston TX
International Classification:
E21B 19/22
US Classification:
166 773, 166384, 166 772, 226172
Abstract:
A coiled tubing injector comprises a drive system for independently driving a plurality of chains independently but otherwise retarding relative motion between the driven chains when a chain begins to slip uncontrollably.