In the second part of the pressure build-up analysis, we focus on multi-phase effects. We see how the injection of CO2 over time leads to the formation of a "cushion" zone that absorbs part of the pressure build-up. This leads to important update in the prediction of pressure evolution at various locations through time. Pressure build-up monitoring is very important as it may trigger breach of containment, leaks to other formations or fault/fractures activation. We show how TKRISK can be used to model the propagation of pressure pulses around injection sites. The non-linear coupling of pressure and saturation can be modeled using a mixture of analytical models and simple regressions. The evolution through time can be formulated very simply and efficiently by sampling the network at different time steps. This leads to a transparent model that captures the major uncertainties and propagates them through to produce robust probabilistic evaluations of quantities of interest.