In this section, we review how we can model the average saturation behind the front of CO2. In instances where the relationship between input and output is too complex or simply does not exist, we can use calibration methods to "tune" a model. TKRISK continuous nodes allow such approach. In the example of the average saturation in the plume, the theory of hyperbolic systems of conservation laws governs the displacement mechanism and hence the property of interest. We have a complex non-linear relationship between rock/fluid properties and the fractional flow tangent that will give the average saturation of CO2 that will itself drive the speed of expansion of the plume... We can use an existing model to build a multi-linear model of the average saturation using ordinary least square regression. This leads to a graph where the CO2 front speed propagation can be tied to the reservoir properties.