Formation Mechanism and Control Techniques of Calcium Carbonate Scale in the Langjiu Geothermal Field Tibet

Calcium carbonate scale is one of the challenges which must to be solved during the process of mass production in middle to high temperature geothermal fields. The formation trend of the calcium carbonate scale in the Langjiu Geothermal Field of Tibet is apparent. The speed of the scaling is 2 mm/d. In this paper, based on the research of geothermal geologic conditions in the area and formation characteristics of the geothermal fluids, the authors concluded that the inherent mechanism for calcium carbonate scale formation is the catalyst precursor formation of supersaturated solutions—the transformation of solubility between aragonitecalcite. The external condition is the mixture of the deep geothermal fluids and the cold surface water, which occur after the pressure decreases. According to the scaling control and scaling removal in the discharge-spray tests, the authors proposed that the first choice of scale control is the combination of compression and the addition of a resistance scale agent, which is from the series of phosphate molybdenum. Moreover, the preferred methods for scale removal are mechanical scale removal and chemical scale removal.