| Title | Laboratory Corrosion Testing of Casing Steels in Acidic Brine and Field Testing at Kakkonda Geothermal Field, Japan |
|---|---|
| Authors | Masatake SATO, Kaichiro KASAI, Kazumi OSATO, Norio YANAGISAWA, Yu YAMAMOTO, Toshihiko FUKUI, Koji SAKURA, Bruce MOUNTAIN, Soroor GHAZIOF, Keith LICHTI |
| Year | 2020 |
| Conference | World Geothermal Congress |
| Keywords | Corrosion, Casing Steel, TN95Cr13S, TN125Cr13U, 17Cr, Acidic brine, electrical resistance (ER) probe, polarization resistance (LPR) probe, Cylinder coupon, Kakkonda, NEDO |
| Abstract | Casing steels of geothermal wells are exposed to high temperature brine and brine of especially low pH, which are capable of causing serious corrosion. The object of this work was to identify cost-effective casing materials under several acidic geothermal brine conditions. Prior to the laboratory test program, separated brine fluids from a production well of the Kakkonda geothermal field were used for corrosion testing of candidate casing materials for acid well applications. The casing materials were exposed in as-produced mildly acidic fluids, and selected alloys were also tested in further acidified brine fluid. The corrosion test was conducted by a newly developed corrosion test loop which is able to set an Electrical Resistance probe (ER Probe), Linear Polarization Resistance probes (LPR Probe), and Coupon exposure test rods to monitor the corrosion and scaling data. These works identified pH limits for utilization of the readily corroded casing materials. ER and LPR Probe will measure more realistic corrosion rate reflected the effect of protective film in short time. It will be one of methods for monitoring actual condition of material and to make maintenance plan for a plant. The obtained results provide cost effective casing materials options for utilization of mildly acidic geothermal well fluids. We have conducted laboratory corrosion tests using a hydrothermal apparatus that can conduct corrosion tests under continuously flowing condition at Wairakei Research Centre, GNS Science. The objective of the experiment was to determine the extent and characteristics of corrosion of several casing materials after being exposed to fluid at elevated temperatures between 250-350 deg. C and low pH. We have conducted initial experiments using this apparatus and take corrosion rate data for about 6 hours exposure time. We will have a plan to conduct the experiments for more long exposure time. The corrosion data will be important to se1ect a suitable material using material selection chart. This paper is based on results obtained from a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO). |