Abstract:
This paper is the result of geothermal survey engineering.
Objective Xining area is rich in medium and low temperature geothermal resources, but the high salinity and strong corrosion of geothermal water limit the efficient development of geothermal energy. The proposed safe, economic and effective comprehensive well bucket anticorrosion measures are the basis and key to the effective utilization of high salinity geothermal resources.
Methods In this study, the typical geothermal water in Xining area was collected, and the ionic composition and content of corrosive bacteria were tested. The high-temperature and high-pressure reactor was used to carry out metal plate corrosion tests to evaluate the corrosion performance of geothermal water on different steels under typical wellbore conditions. The corrosion type and the relationship between the corrosion rate and the influencing factors was analyzed. Finally, the anti-corrosion measures for geothermal water reinjection were proposed.
Results The main corrosion components in geothermal water are Cl-, SO42-, H+ and dissolved oxygen, which cause uniform corrosion, platform corrosion and a small amount of pitting corrosion. The main corrosion products are FeO(OH) and Fe3O4; the corrosion rate along the wellbore gradually increases, and the corrosion risk at bottom hole is the greatest. In addition, the corrosion rate has a greater correlation with the geothermal water properties, P-T condition, flow speed and dissolved oxygen mixed into wellbore.
Conclusions By fitting carbon steel corrosion experiment data, an empirical equation is established. The predicted value obtained by using the empirical equation is in good agreement with the experimental value. Safe, cost-effective and comprehensive wellbore anti-corrosion measures can be taken from the perspective of anti-corrosion pipes, reinjection geothermal water pretreatment, reinjection process parameters.
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