The increasing dependency of the European Union (EU) on natural gas imports from non-EU countries, such as Russia, Norway and Algeria expresses the need to analyze and detect potential risks and threats affecting security of gas supply from a multinational perspective. This requires the use of mathematical models that includes all relevant facilities and that can capture the dynamic behavior of the gas infrastructure in an accurate and adequate manner. In this paper, we present a simulation tool for analyzing the consequences of gas supply disruptions and the effectivity of strategies to mitigate these disruptions. Firstly, we develop a modelling framework for analyzing gas supply disruptions, where we elaborate the following three questions: a) What are potential gas disruption scenarios? b) What are the degrees of freedom and strategies available to Transmission System Operators (TSOs) to react and to mitigate supply disruptions? c) How can we quantify the consequences of gas supply disruptions in order to compare the effectivity of mitigation strategies? Secondly, we develop a transient hydraulic model, which reflects the dynamic behavior of large-scale gas transport systems and includes sub models of all relevant facilities, such as compressor stations, underground gas storage facilities and LNG terminals. Finally, we translate the framework and the hydraulic model into a software tool named SAInt – Scenario Analysis Interface for Energy Transport Systems, which we apply to a real world instance.