Vibrating characteristics of drill string in gas drilling and its control measures

To solve an engineering problem of severe vibration and frequent failure of drill string in gas drilling,we analyzed vibrating behaviors of drill string during gas drilling based on a dynamic model for the whole-interval drill string in gas drilling,and presented two control measures against vibration in terms of anti-vibration and anti-drag,namely a well-drilling technique of air hammer and the adoption of anti-vibration and anti-drag tools.Taking a gas drilling section of a field well in west Sichuan as an example,we quantitatively evaluated vibrating characteristics of drill string both in conventional gas drilling and in drilling with vibration control measures,on condition that the feasibility and reliability of the triaxial coupling vibration mechanics model for the whole-interval drill string system were validated with the field data provided by the ESSO Production Co.A comparison indicates that these two technologic measures are of clear effectiveness in anti-vibration and anti-drag,they can not only effectively weaken the vibration intensity of the lower drill string in gas drilling but also remarkably reduce the dynamic stress of the upper drill string.