Effect of Immersion Time on the Mechanical Properties of S135 Drill Pipe Immersed in H2S Solution

During drilling process, if oil and gas overflow containing H2S enters drilling fluids, the performance of drill pipes will decline significantly within a short time. In this paper, S135 drill pipe specimen was immersed in the saturated solution of H2S at room temperature for 6, 12, 18, and 24 h, respectively. The tensile properties and impact properties of S135 drill pipe were determined before and after immersion for comparison. In addition, the S135 specimens were immersed for 3 days at 80 °C to determine the changes in fatigue performance. The test results indicated that the yield strength of S135 material fluctuated with immersion time increasing and the tensile strength slightly varied with immersion time. But the plasticity index of S135 decreased significantly with the increase in immersion time. The impact energy of S135 steel also fluctuated with the increase in immersion time. After 3-day immersion at 80 °C, the fatigue properties of S135 steel decreased, and fatigue life showed the one order of magnitude difference under the same stress conditions. Moreover, fatigue strength was also decreased by about 10%. The study can guide security management of S135 drill pipe under the working conditions with oil and gas overflow containing H2S, reduce drilling tool failures, and provide technical support for drilling safety.