Sulfide Stress Cracking Assessment of Carbon Steel Welding with High Content of H_2S and CO_2 at High Temperature: A Case Study

摘要

In the oil and gas industry, it has been established that for pipelines fabricated with carbon steels, their limitation is related to H_2S and CO_2 environments, which is 7 to 10 psia of partial pressure of CO_2. Therefore, in carbon steel cracking is shown, after 7 or 10 psia of partial pressure of CO_2. The experimental work was performed under static conditions in autoclaves within a pH of 3 to 3.8; partial pressures of 16 - 96 psi for H_2S and 15-53 psi for CO_2, in the temperature range of 25 °C - 150°C. It was observed that the average yielding stress used in Sulfide Stress Cracking (SSC) tests decreases with temperature increment. Hydrogen Induced Cracking (HIC) evaluations showed that X52 steel, under conditions, was not susceptible to HIC. Results of SSC did not show indications of cracking after exposure to sour solutions, except for the specimen exposed to high H_2S and CO_2 content (96 psi of H_2S and 53 psi of CO_2 of the partial pressure) and high temperature (150°C). Microcracks located between the upper and lower weld beads were also observed. However, the highest average corrosion rate was 0.27 mm/year (10.6 mpy), which occurred in samples exposed to 96 psi of H_2S and 53 psi of CO_2 at 150°C. Likewise, the highest localized corrosion (severe pitting attack) was obtained at the same environment with a corrosion rate of 4.2 mm/year (167 mpy). The oil and gas industry could use carbon steels pipelines in partial pressure higher than 10 psia.