Evaluation on Chloride Cracking of S135 High-strength Drill pipe

摘要

During the process of deep drilling with high temperature and high pressure,downhole drilling tools might be exposed to various corrosive mediums,such as water/oil-based drilling fluid systems,dissolved oxygen,H2S/CO2,halogen elements (Cl-and Br),etc.Halogen elements existing in the drilling fluid are ions promoting corrosion of metals.This effect is mainly manifested in the forms of uniform corrosion,pitting corrosion,stress corrosion cracking,etc.of carbon steel.Quality of the drill pipe is determined by the DP body,joint and welding area of the drill pipe.Reasonable friction welding process and proper post weld heat treatment can make the mechanical property of weld joint satisfy related standards.If process of friction welding or post weld heat treatment is improper,the weld joint will be easily damaged and accidents of pricking,breaking,etc will be likely aroused.This paper carries out an evaluation experiment of chloride cracking on the DP body,joints and weld joints of the high-strength drill pipe (S 135) and discusses corrosion of the high-strength drill pipe caused by chloride ions.