In many geothermal systems in the Himalayas, carbon dioxide concentration is high and calcite scale is common, preventing the resources being properly utilized for power generation. It has been difficult to solve this technical problem which has been an issue in development investment for a long time.An economic and effective solution is needed.
Hi Zhonghe,
For the carbonate scaling in geothermal wells and pipeline, the main reason behind is the CO2 degassing process. This typically happens at a certain depth inside of a geothermal well, where the pressure is dropping due to well production. The transfer of CO2 from fluid to gas phase reduces the pH value of the geothermal water and causing a lower dissolvable calcite content.
To treat this problem, there are existing technologies. The standard way is to add a capillary injection system inside of the well, the function of which is to inject anti-scaling chemicals at a very slow rate while the well is producing. The main objective is to trap precipitating calcite in a colloid form and prevent it from attaching to the wall of well or pipelines. You can also try to manipulate the pressure but that will typically cost more.
I had a presentation prepared for this issue. If you are interested, we can discuss the details next week when I am in Beijing for the UCAS lecture.
Dear Zhonghe, as Haibing indicated, let's discuss this issue in more detail next week during our OpenGeoSys Geothermal Training Course in Miyun/Huairou and we should raise this important question for the 2. German-Chinese Geothermal Symposium in Potsdam 2017. Best regards Olaf
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