Low-load repeated impact testing of G-105 and S-135 drill pipes in H2S environment

In view of drill pipe washout and fracture failures, etc. caused by multiple impact loads of small energy during drilling operations, this paper presents a kind of low-load repeated impact experiment method to assess the drill pipe materials. The G-105 and S-135 drill pipe materials were tested using this method. In an environment where there is no corrosion medium, test was conducted to the change of single-impact energy and test result indicates that, with the increase of single-impact energy, the low-load repeated impact resistance of G-105 and S-135 drill pipe materials reduced to 22.2% and 28.7% of the original values respectively, so the low-load repeated impact resistance of drill pipe decreases significally. In H2S environment, the test blocks of G-105 and S-135 were soaked in the A solution of NACE TM 0177-96 standard for different durations, and lowload repeated impact test was conducted under single-impact energy of 2.21 J. The test result shows that the low-load repeated impact resistances of the materials of two drill pipes reduced to 49.8% and 46.9% of their original values respectively with the extension of H2S corrosion time, and the higher grade S-135 is more sensitive to corrosion environment. Besides, typical fracture was selected to observe and analyze the microstructure and the embrittlement phase causing fracture was found. The above experiment results indicate that this low-load repeated impact experiment method can remarkably shows the actual failure of drill pipe in its working process, esp. the failure pattern in corrosion media containing H2S.