Experimental and numerical simulation of fatigue corrosion behavior of V150 high-strength drill pipe in air and H2S-dilling mud environment

Experimental and numerical methods have been used to investigate the fatigue corrosion behavior of V150 drill pipes in different environments. In this study, a fatigue test machine was designed and utilized to analyze the behaviors of V150 high-strength drill pipe steels under different stress amplitudes in air, mud, and H2S mud. Subsequently, the fracture morphology and mechanism were analyzed, and the coupling behavior of stress and electrochemical corrosion was studied via numerical simulations. Finally, some suggestions were proposed for safe drilling using V150 drill pipes. The results revealed that the fatigue life of the V150 drill pipe in H2S-mud is approximately 10% of that in air and 33% of that in mud. The equations governing the fatigue life of V150 in air, mud, and H2S mud are N-air = 8.59 x 10(10)(S -330)(-2), N-mud = 3.45 x 10(10)(S -270)(-2), and N(H2S-mu)d = 2.13 x 10(10)(S -167)(-2), respectively. The fracture surface exhibited ductile fracture in air, mixed ductile and brittle fracture in mud, and brittle fracture in mud containing H2S. The numerical simulation results demonstrated that the greater the longitudinal displacement, the greater the stress at the center of the corrosion pit; additionally, the more negative the electric potential, the faster the electrochemical corrosion. This study therefore explains the mechanism behind the fracture of V150 drill pipes and provides guidance for the safe use of V150 drill pipes in the drilling process.