Vibration of drillstring was found responsible for the severedamage and premature failure of drillstrings during drilling thegas-bearing igneous formations in the Songliao Basin, China.The vibration significantly shortened the life of drillstrings andhad a great impact on drilling performance in the area. Theobjective of this study was to identify the key factors affectingdrillstring vibration and develop a control-mechanism toreduce the failure rate of drillstring.This study investigated the combined effect of axial andtorsional vibrations on the damage of drillstring. Acomputerized model was built to simulate loads from axial andtorsional vibrations. An analytical method for predicting thefatigue life of drillstring was developed. The method uses theoutput from the computerized model. Engineering charts werealso generated for typical drilling conditions. These chartshave been adapted in a Drillstring Damage Control Programimplemented in the Songliao Basin, China.
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