| Title | Preliminary Corrosion Testing of Nickel Alloys in Simulated High Temperature Geothermal Environmenty |
|---|---|
| Authors | Andri Í. THORHALLSSON, Tindur JONSSON, Andri STEFANSSON, Sigrún Nanna KARLSDOTTIR |
| Year | 2017 |
| Conference | Stanford Geothermal Workshop |
| Keywords | laboratory testing, simulated geothermal environment, high temperature, corrosion, cracking, UNS N06625, UNS N10276 |
| Abstract | To explore the potential of obtaining more energy output per geothermal well, deep drilling (~5000 m depth) of geothermal wells was started in Iceland few years ago within the Iceland Deep Drilling Project (IDDP). First IDDP well, during its lifetime, provided superheated steam at high temperatues and pressures but the steam also included acidic gas components including H2S, HCl and CO2, which upon condensation becomes extremely corrosive with measured pH level of 2.5-3. To gain more understanding on the corrosion behavior of several alloys at saturation and superheated conditions in deep geothermal wells, preliminary testing of highly corrosion resistant nickel alloys, UNS N06625 and N10276, was done in simulated geothermal environment. The test was done on UNS N06625 at 180°C in flow through reactor and at 350°C on both UNS N06626 and UNS N10276 with a pressure of 10 bar for a 1 and 3 week exposures. The simulated environment was composed of steam with H2S, HCl and CO2 gases, with a pH level of 3 upon condensation. The UNS N06625 performed very well at 180°C where corrosion rate was measured insignificant at 1 week exposure but very low at 3 week exposure. At 350°C the corrosion rate of UNS N06625 was lower than UNS N10275, but corrosion rate for both alloys were though higher than generally accepted. Microstructural and chemical analysis revealed localised corrosion damage and corrosion products cracks in UNS N06625 but no localised damage in UNS N10276. High molybdenum content in UNS N10275 is possible the reason for better localized corrosion resistance. The future work is to develop the tests and the testing facility further i.e. test more alloys at higher temperature and pressure levels and investigate the effect of SiO2 scaling on under deposit and localized corrosion of the alloys. One of the challenges is to simulate precipitation SiO2 on surface of alloys on lab scale that will reflect scaling in geothermal wells at superheated conditions. |