| Title | The effect of CO2 coinjection on silica scaling in acid dosed subduction zone geothermal brines |
|---|---|
| Authors | A. Kamiya, P. Rendel, B. Mountain, A. Nichols, M. Jermy |
| Year | 2024 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Carbon emissions, non-condensable gas, CO2 reinjection, silica scale |
| Abstract | Geothermal energy is not inherently carbon neutral; it releases non-condensable gases (NCG) during energy production. Although geothermal energy is a strong contender in the low-carbon energy space, it must reduce these emissions to compete effectively with other renewable energy sources. For this reason, capturing and reinjecting NCG is an emerging method being implemented and considered by the geothermal industry. However, carbon emissions are not the only concern in geothermal energy production. Another common issue faced by the geothermal industry is silica scaling. At the interface between the reinjection brine and reservoir rock, shifts in pH can cause amorphous silica scale to form. Previous research has suggested that the co-injection of CO2 with acid-dosed brines may help inhibit this scaling. To investigate this potential solution, we conducted two reinjection simulation experiments using a high-pressure and high-temperature (HPHT) flow-through system to replicate conditions typical of island-arc geothermal systems, such as those in Japan, Indonesia, and The Philippines. The significant geothermal energy potential in these regions makes studying these systems essential. In the experiments, we used a synthetic geothermal brine and exposed it to andesite + calcite. Our results indicate that adding CO2 to acid-dosed brines can significantly reduce the rate of silica scaling in the reservoir. In our experiments, introducing 2000 ppm CO2 into the fluid maintained a low pH solution, resulting in almost no scaling—a stark contrast to the outcomes observed without adding CO2. These results suggest that the co-injection of CO2 in geothermal power plants will be beneficial in reducing plant emissions while at the same time mitigating silica scaling within the reservoir. |