H2S Resistant Seamless X65 Girth Welds for Dense CO2 Transport

Abstract An increase of the acceptable level of impurities in dense CO2 streams is a contributor to cost-efficient capture and transport processes. Among those impurities, H2S focuses attention as responsible of quick and severe hydrogen related cracking phenomena in Oil and Gas industry. Four-Point Bend tests according to NACE TM0316 were performed on two girth welds of X65 seamless grades, 244 mm outer diameter (OD) for 14.5 mm wall thickness (WT) and 323.9 mm OD for 25 mm WT. Autoclave environment reproduced condensed water saturated by 250 bar CO2 containing 550 ppm of H2S. Special cares on the test protocol were applied to adjust the target partial pressure of H2S and to maintain it throughout the test duration. Detailed micrographic investigations were conducted to confirm the absence of Sulfide Stress Cracking (SSC) after test.