Using High Pressure Thermal Vessel For Mineral Solubility Experiments in Geothermal System

Abstract:

Due to the serious scaling problems of the production in pipeline, Qingshui geothermal power plants closed after 12 years in the past. Because the pressure reduced in the process of upwelling, the hot spring from the reservoir will scaling CaCO₃ immediately by large CO₂ escape. This result will cause the space of pipeline reduced. On the other hand, as the temperature decreases, the SiO₂ scaled in the part of heat exchanger. This study chose the Hongchailin and Qingshui IC-21 well as objects to simulate, and the Szeleng sandstone and the Lushan slate are the target layer of drilling well, respectively. We use pure water and saturated water pressure in our experiments. Besides, the previous studies showed that temperature of reservoir in Qingshui site was not over 300℃, so we set 300℃ as the upper limit temperature. The pressure was less than 800 bar by calculated the rock density of target layer. The original rock sample were placed in first autoclave, and added pure water in the second autoclave. Then we heat the first autoclave to reach the target temperature, and make the pressure saturated over water vapor pressure. After 72 hours the saturated water were leaked into the second autoclave. As the temperature cooling down, we removed the water from second autoclave and diluted the water. Finally, the Na⁺, K⁺, Mg⁺², Ca⁺² ions were analyzed by ICP. We want to get the maximum solubility of calcite and amorphous silica in equilibrium with sandstone and slate, and then check whether the method of geothermometer calculated is reasonable or not by calculated the concentration of Na⁺, K⁺, Si⁺⁴ in hot spring.