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Lessons learned from long-term corrosion investigations and –monitoring in saline thermal waters
(2018)
Investigations of corrosion processes in geothermal well in Groß Schönebeck showed
Most tested materials (apart of carbon steel) proved to be corrosion resistant within the installations.
- Stability of coatings cannot be guaranteed.
- Main risk: Electrochemical corrosion of carbon steel casing with dissolved Cu resulting in clogging the reservoir
The corrosion prevention strategy requires use of higher alloyed casing materials depending on resistance parameters, availability and economic feasibility.
Since geothermal wells are a feasible energy source to replace fossil fuel supply, many technologies have been developed to take advantage of geothermal energy. Nevertheless, service conditions in geothermal facilities are in many cases extreme in terms of corrosion due to the chemical composition of hydrothermal fluids and temperatures. Therefore, materials selection based on preliminary material qualification is essential to guarantee a secure and reliable operation of the facilities. During operation of a geothermal research facility in Groß Schönebeck copper and lead effects have been found downhole. Occurring mechanisms and measures to prevent precipitation or scaling needed to be investigated as well as potential influences of such precipitates on corrosion resistance of metallic materials used for equipment.
This contribution deals with the evaluation of the corrosion behavior of carbon steel and corrosion resistant alloys in copper and/or lead containing artificial geothermal water, simulating the conditions in the Northern German Basin.
The behavior of these materials in an artificial geothermal water obtained by electrochemical measurements and exposure tests are presented. While carbon steel exhibits precipitation and deposition, higher alloyed material shows different response to such species and a higher resistance in saline geothermal water.
Basing on these results the suitability of the investigated corrosion resistant alloy is given for use in such conditions, whereas carbon steel creates difficulties due to its susceptibility to Cu- and Pb-precipitation.