The Influence of Chelating Agents on Clays of the Geothermal Cap Rock: Implications for Enhancing Geothermal Reservoir Quality : poster

Geothermal energy (Figure 1) is a green renewable energy source that h as potential to provide long-term energy with lower carbon footprint and maintenance costs than other renewable energy. A large portion of the world’s geothermal reserves is in sandstone reservoirs often characterized by quartz grains cemented with clays. Clays form also often the impervious boundary of the reservoir rock, the so-called caprock. Many geothermal reservoirs tend to lose permeability over time during production, therefore techniques are applied to enhance the reservoir quality in terms of fluid permeability. Partial dissolution of sand grains in the reservoir is a possibility to increase porosity and consequently permeability. However, the fluids used for dissolution should have limited reactions with the cementing clay minerals as this would cause collapse of the sandstone grain skeleton reducing permeability. Biodegradable chelating agents (BCA) compared to conventional chemicals (HF and HCl) have little reaction with clay, but can dissolve the sandstone grains; hence green
chemicals could be effective for enhancing reservoir quality. The emission of
dissolved CO2 from geothermal water becomes more of an issue recently.
Biodegradable chelating agents could reduce CO2 emission since they offer high
chelating capacities on a large variety of minerals including calcium-rich minerals. Calcium has the capacity to bond with CO2, proving to be effective for CO2 sequestration.