| Abstract |
Interest in superhot geothermal (SHG) wells, including superhot rock geothermal wells, has grown due to their potential for higher productivity and access to untapped geothermal resources. These wells typically require drilling deeper than 3 km to access fluids with enthalpy above the critical level (>2.086 MJ/kg). However, SHG wells face major challenges due to extreme temperatures (>300°C), pressure (>100 bar) and the corrosive nature of geothermal fluids, which contain gases like CO₂, H₂S, and HCl. These conditions can lead to increased corrosion and erosion-corrosion of well casing materials. To ensure the durability of casing materials, corrosion testing under harsh conditions—high temperature, high pressure, and corrosive gases—is essential. This study reports results on the corrosion resistance of selected casing materials tested in simulated SHG environments in a unique high-temperature, high-pressure (HTHP) autoclave corrosion laboratory at University of Iceland. The corrosion tests were conducted on carbon steel and corrosion-resistant alloys (CRAs) in the HTHP autoclave at 350°C, 400°C, and 450°C, using H₂O vapor with CO₂ and H₂S. Microstructural and chemical composition analyses using Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS), along with corrosion rate measurements, were performed. The study provides insight into the corrosion effects of these materials under SHG conditions and compares laboratory findings with limited field data, such as corrosion testing from the Iceland Deep Drilling Project’s IDDP-1 well. The results of the study can aid in material selection for future SHG wells to improve long-term well integrity. |