Corrosion in geothermal environment: Part 1: Fluids and their impact

Abstract

Energy production from geothermal resources can be challenging if geothermal fluid chemistry promotes metal corrosion of the production equipment's construction material. This fluid chemistry is normally unknown until deep production wells are drilled and tested. This paper reviews available literature on corrosion in geothermal environment due to different geothermal fluid chemistries. The existing geothermal fluid corrosiveness classification systems are also reviewed, compared and harmonized into a single classification system. In the harmonized system, the types of geothermal fluids identified from two existing classification systems were merged into one. New geothermal fluid chemistry types that were not considered in the two existing indices were also created. This new fluid types includes the very low pH and high salinity brines encountered in deep volcanic and sedimentary systems, A sub-class was similarly created for steam-dominated geothermal reservoirs, producing steam with HCl gas.The geothermal power industry has reported a wide variety of corrosion problems. At least nine modes of corrosion were reported in this review from uniform corrosion to microbiologically induced corrosion (MIC). Varying degrees of uniform corrosion is most prevalent phenomena under any geothermal fluid condition and is mostly observed in carbon steel pipelines and equipment. Medium and high-strength carbon and alloy steels are susceptible to sulphide stress cracking under various conditions in geothermal fluid Erosion-corrosion occurs in the pipes for two phase flow transport which runs at high velocity. Designers of geothermal facilities and equipment need to properly match materials for any given type of geothermal resource fluid and process condition. Improper use of materials can lead to excessive corrosion damage that can result to catastrophic accidents and losses.