Hydrogen damage of carbon steel fragments from the IDDP-1 geothermal well

The IDDP-1 well was the hottest flowing geothermal well in the world producing 450°C and 140 bar superheated steam. The IDDP-1 steam contained dissolved gases, H₂S, CO₂, H₂, HCl and HF, which upon condensation became highly corrosive. Unfortunately, the well had to be closed after several months of discharging to due to failure in the master valves after leakage occurred in sampling valves due to corrosion. After shut-down small fragmented steel samples were retrieved from the well during down-hole camera inspection. Microstructural and chemical composition analyses were done on the samples with SEM and XEDS. The result showed that the samples have extensive corrosion damage, in the form of corrosion pits and internal micro-cracks and fissures. These are filled with corrosion products and are parallel to the surface. The chemical composition and microstructural analysis of the steel fragments indicate that they are from the API K55 carbon steel production casing of the IDDP-1 well. The corrosion damage was present deep into the material. The samples were etched for metallurgical analysis which revealed disappearance of pearlite close to the micro-cracks and fissure. High Temperature Hydrogen Attack (HTHA) is believed to be the cause of the decarburization of the steel and the corrosion damage of the samples.