Nowadays, a fundamental requirement for a prosperous society is a reliable energy supply. The complex network theory provides an excellent basis to explore the functionality of such systems in response to severe component failures. In this case study, the European natural gas system is analyzed. The actual natural gas consumption is geospatially allocated to the infrastructure network. The network is abstracted and the flow capacity of the network is computed. A scenario analysis is conducted in order to identify the impact of storage facilities on the actual maximum possible flow. Furthermore, the natural gas supply shortage caused by each pipeline in case of a potential pipeline shutdown or failure is estimated. Finally, potential strategic locations of storage facilities for a more reliable natural gas network are identified. Natural gas is transported and distributed by a well-developed system. The design of such a system requires long-term planning and large infrastructure investments. This kind of investments locks the capital in long-term contracts involving often policy decisions and agreements on national or regional levels (e.g. Carvalho et al., 2014, Mišík and Nosko, 2017). The European natural gas system became over time a large infrastructure network with many components, such as compressor stations, storage facilities, gas processing plants, Liquefied Natural Gas (LNG) terminals, LNG liquefaction and regasification facilities, aiming at assuring high reliability of the supply system. These components should be well planned and coordinated to guarantee a continous and adequate natural gas flow. The natural gas demand cannot be covered by the European countries' available natural gas resources (BP, 2016). Therefore, it is necessary that natural gas is transported by pipelines from the East and South to Europe. Complementary, natural gas is also imported via LNG terminals. The natural gas infrastructure network has to be able to compensate for potential pipeline shutdowns or failures, among others. This can be achieved through the construction of strategic

Growing global energy demands have led us to development of new oil & gas fields. In the meantime interest in eco-friendly solutions has been increasing in the area of stranded & associated gas fields. According to the BP report 2015, global natural gas reserves are approximately 6,607 tcf. Nearly half of that is assumed to be stranded & associated gas that is uneconomical for market delivery due to its remoteness from potential markets and lack of economic transportation, infrastructure and GTL conversion technology. Therefore, Daewoo Shipbuilding & Marine Engineering (DSME) has researched Gas-to-Liquids (GTL) Floating Production Storage and Offloading (FPSO) & Modular GTL as potential solutions for developing offshore oil & gas fields. Because products of the GTL process can be easily combined with crude oil in the Hull tanks and used in the existing energy infrastructure. From a shipbuider's perspective, key design considerations in assessing onshore GTL technology for GTL FPSO & Modular GTL application were studied and analyzed as follows: Robustness to marine motion, Limited space, Weight and height, Self-sufficiency, Safety, Constructability and Certification Requirement. Moreover, commercial & demonstrated GTL technologies involved in Gas Treatment, Pre-Reformer, Reformer, Fischer-Tropsch Reactor, Upgrading and others were compared and reviewed to determine which technology is the best option for GTL FPSO & Modular GTL. Additionally, we have studied which GTL application method would be more competitive depending on the gas production size in offshore fields. Moreover, preliminary market analysis was performed to better define the scope of GTL products to be produced. Economic analysis was also performed to identify the major cost factors and understand their sensitivity on the project. DSME has recently completed the feasibility study to acquire the preliminary design & engineering of GTL FPSO & Modular GTL for stranded gas & associated gas fields in offshore locations. The results of this feasibility study suggest that design concepts of GTL applications are technically practicable. The clean fuel and the chemical feedstock from the GTL process will be profitable in the markets and the design concept will be economically competitive within the range of the current project cost factors. DSME hopes to set up a cooperative network with competitive companies for the next stage of GTL FPSO & Modular GTL. The cooperation network will implement at GTL FPSO & Modular GTL Pre-FEED and the economic study and will result in the commercial realization of this innovative approach for monetizing stranded & associated gas fields offshore.