Cause analysis of drill pipe joint thread galling

A number of drill pipe joint thread-galling failures were discovered in the oil field mentioned,and all of them happened on new pipes,which brings a big loss to oil field economy.Field survey was applied to the failure accident.Mechanical properties test,chemical composition analysis,and micro-structure examination to the joint material and the macro-appearance observation to the tool joint threads were taken.The results showed that,as there was a great central axis deviation of the stands in picking-up process,which caused mechanical damage to the joint threads when make-up,and as the guiding process to make-up was in high speed,the thread galling of tool joints happened eventually.In the end,the prevention methods and suggestions were put forward based on the failure cause.