There is an increasing demand for high strength (more than 110 ksi grade) tubing that is applicable at high temperatures between 175 and 200 oC for XHPHT (Extreme High Pressure and High Temperature) wells in mildly sour environments. Super 13Cr stainless steels categorized as "13-5-2" in ISO13680 are typically used in HPHT wells containing CO2 with and without small amount of H2S. However, the temperature limit of super 13Cr stainless steels is equal to or less than 175 oC. In this study, the effect of alloying elements of stainless steels on general corrosion resistance at high temperature and environmentally assisted cracking resistance at the high temperatures and room temperature was investigated. The new steel shows good cracking resistance in both the typical gas and severe oil well conditions in 0.001 MPa H2S + 3 MPa CO2 environments at 200 oC. Furthermore, the no Sulfide Stress Cracking (SSC) region of super 17Cr stainless steel - 125 widens in lower pH direction compared with that of super 13Cr stainless steel with 110 ksi grade.
There is an increasing demand for high strength (more than 110 ksi grade) tubing that is applicable at high temperatures between 175 and 200 oC for XHPHT wells for mildly sour environments. Super 13Cr stainless steels categorized as "13-5-2" in ISO13680 are typically used in HPHT wells containing CO2 with and without small amount of H2S. However, super 13Cr stainless steels are considered to be not applicable for the XHPHT wells because the temperature limit of super 13Cr stainless steels is equal to or less than 175 oC. In addition, for consideration of the applicability of super 13Cr stainless steels, it is important to evaluate environmental cracking resistance at both room temperature and maximum expected service temperature.
