| Title | Corrosion Risk Assessment for Reinjection of Combined Brine Fluid to Intermediate Aquifer |
|---|---|
| Authors | Sigit Prabowo, Keith Lichti, Soroor Ghaziof, Kelly Melia, Farrell Siega, Aimee Calibugan |
| Year | 2026 |
| Conference | World Geothermal Congress |
| Keywords | |
| Abstract | The Rotokawa geothermal field in New Zealand has an intermediate aquifer that is known to be corrosive to carbon steel well casings and cements. The chemistry of the intermediate aquifer contains corrosive CO₂-rich fluids which comes from the arising CO₂ gas from deep reservoir fluids through the permeable features of the intermediate aquifer. A combined brine (mixed brine and condensate from a binary plant) has been reinjected to dilute the corrosive fluid within the intermediate aquifer. However, the reinjection of combined brine can also increase the partial pressure of CO₂ which may increase the corrosivity of the intermediate aquifer fluid. This paper investigates the impact of reinjecting combined brine fluids from several wells on the corrosion of carbon steel casing of the nearby wells using theoretical analysis. We first construct Pourbaix diagrams to predict the stability regions of corrosion products, followed by CO₂ corrosion rate predictions based on the formation of these products. The procedures used for this assessment and the corrosion risk for nearby well casings are described. The results show that the presence of H₂S within the fluid is a critical factor for controlling CO₂ corrosion of carbon steel casing at the nearby wells. |