EVALUATION OF CORROSION INHIBITORS FOR ACIDIC GEOTHERMAL WELLS

Abstract

As enhanced geothermal systems (EGS) grows so too is the
need for dealing with acid brines. Already in Indonesia,
Philippines, Turkey, Japan and Europe some plants cannot
utilize their geothermal resources due to the acidity and
aggressiveness of the brine. Geothermal wells can be
sometimes acidic due to high levels of carbon dioxide (CO2)
and hydrogen sulfide (H2S). Often the pH can drop to 5, and
in some cases to 3, under these conditions. This acidic, often
saline, water is very corrosive. This led to the investigation of
corrosion inhibitors under these highly aggressive conditions
in order to assist the wider use of existing and future acidic
geothermal resources.
Corrosion inhibitors were evaluated in a series of screening
tests. Initial screening was conducting using 5 minute visual
tests at room temperature. This process quickly eliminated a
number of obviously poor inhibitors. Next, jar test screening
was conducted for 18 hours at pH 7 and 95 oC. This further
reduced the number of acceptable inhibitors. Finally the
leading candidates were evaluated at acidic pH. The
promising inhibitors were also evaluated using several
electrochemical techniques.