Fig. 1

Fluid properties relevant to deep geological storage of CO₂ in the Swiss Molasse Basin (SMB), plotted as a function of depth. Dashed line at 800 m marks the minimum depth recommended for CO₂ injection. Two examples of brines are shown: low salinity 1 molal NaCl (5.5 mass% NaCl) and high salinity 5.5 molal NaCl (24.3 mass% NaCl), from data in Mao and Duan (2009) and Akinfiev and Diamond (2010). Data for pure CO₂ from Span and Wagner (1996). a Pressure of in situ formation brine assuming hydrostatic conditions. b Range of geothermal gradients in the SMB (Rybach 1992). c Comparison of fluid densities for CO₂ and CO₂-saturated brines over the range of geothermal gradients in the SMB. d Comparison of fluid viscosities for the range of geothermal gradients in the SMB. e Solubility of CO₂ in model NaCl brines