Development of the Neutralization System for Production Wells at the Miravalles Geothermal Field

The Miravalles geothermal field has been producing electric energy since March 1994. It has provided steam for Unit 1 (55 MWe) since 1994, a Wellhead Unit (5 MWe) installed in 1995, Unit 2 (55 MWe) in 1998, Unit 3 (29 MWe) in 2000 and also Unit 5 (19 MWe, a binary plant) in the year 2004. The thermal water of most of the production wells is slightly alkaline, but 5 wells have produced distinctly acidic water, with pH values between 2.3 to 3.2. Since February of 2000 (in well PGM-19) and October of 2001 (in PGM-07), acid neutralization systems have been used successfully, which has allowed these wells to supply steam to the generating units. Experience has indicated that, with the deep injection of an appropriate dosage and concentration of sodium hydroxide, it is possible to incorporate wells with acidic fluids into production with no corrosion and at a reasonable cost.