Formation dry‐out from CO2 injection into saline aquifers: 2. Analytical model for salt precipitation

From a mass balance for water dissolved into the flowing CO2 stream and a consideration of saturation profiles from the Buckley‐Leverett fractional flow theory, we derive an equation that directly relates gas saturation Sg,d at the dry‐out front to temperature, pressure, and salinity dependence of fluid properties. The equation is easily solved by iteration or interpolation. From gas saturation at the front we derive the average gas saturation in the dry‐out region, from which we obtain the “solid saturation” SS, i.e., the fraction of pore space filled with solid precipitate. Values of SS derived from this theory show excellent agreement with numerical simulations presented in the preceding companion paper. Thus, from relative permeabilities and fluid properties at in situ conditions prior to CO2 injection, it is possible to directly make an accurate estimate of solids precipitation, without having to perform a numerical simulation of the injection process.