Calculation of CO2 solubility in thermal waters in the context of geothermal utilization

High contents of CO2 in geothermal brines can lead to several ecological and economical challenges in geothermal heat and electricity production. The degassing of CO2 can cause damages at the surface power station leading to higher maintenance costs. Furthermore, if there is no reinjection strategy for the produced CO2, the produced energy cannot be seen as emission free and sustainable. The knowledge of the CO2 contents and their right handling are therefore of utmost importance.
This study focusses on the different approaches of calculating the handling of CO2 in geothermal brines and therefore the calculation of its solubility under different circumstances. Since the publication of the van der Waals equation in 1873 the modeling of the behavior of real gases has led to a development of several equations of state like the approaches of Pitzer, 1955 or Peng & Robinson, 1976. Until today these approaches are further developed and expanded.
The knowledge about the possible solubility of CO2 allows to predict the so-called bubble point, the temperature and pressure conditions where the CO2 starts to shift into the vapor phase. The prediction of the bubble point of the CO2 makes it possible to calculate the required pressure to keep the CO2 in solution respectively to inject it back into the reservoir. ... mehrWith given pressure it is possible to determine the effort and associated financial burdens for the power plant operator to handle the CO2 sustainably.
The scope of this study is to develop and compare possible strategies for the handling of CO2 emissions in geothermal reservoirs to keep the geothermal energy an environment-friendly part of a future mix of energies.