| Title | Development of a Corrosion Prediction Model for Casing Materials in Acidic Geothermal Environments |
|---|---|
| Authors | Masatake Sato |
| Year | 2026 |
| Conference | World Geothermal Congress |
| Keywords | Corrosion, acidic geothermal fluid, 17Cr |
| Abstract | Casing materials used in geothermal wells are exposed to high-temperature geothermal fluids, which may, in some cases, be encountered to low pH fluid and caused a serious corrosion. This study aims to identify cost-effective casing materials suitable for use in such acidic geothermal environments. Corrosion tests were conducted using a flow-through test apparatus owned by the Wairakei Research Center of GNS Science, which allows evaluation under flowing geothermal fluid conditions. The focus of these tests was to assess general corrosion. Specimens were exposed to high-temperature (250 – 350 deg.C), low-pH fluids, and their corrosion behavior was evaluated through weight loss measurements, Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray Spectroscopy (EDS). Additional corrosion tests were carried out using geothermal water in Japan. In these tests, casing materials were exposed to naturally acidic geothermal fluids as well as fluids whose pH was adjusted using acids, and corrosion data were obtained. Based on the corrosion data obtained under these various test conditions, along with data from the Sunshine Project in Japan, we developed corrosion prediction models for carbon steel, 1Cr, 13Cr, S13Cr, 17Cr, and duplex stainless steels. The results have been compiled into a database and integrated into a software-based risk assessment system using the developed prediction models. This tool is expected to be useful for identifying suitable casing materials based on the chemical characteristics of acidic geothermal fluids encountered during geothermal development. This work utilizes the results of a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO). |