At present, the Rohöl Aufsuchungs AG (RAG) is operating two underground gas storage facilities (UGS) in Upper Austria. Due to the high demand on these facilities RAG is planning to build additional UGS installations. Three potential sandstone reservoirs in the RAG concession area in the Molasse Basin are being investigated. The goal of this thesis is to calculate the working gas volume for these three prospected UGS installations and to conduct sensitivity analysis on different well and reservoir parameters which have an impact on the underground gas storage performance. The results of this thesis research are compared with those of previous integrated reservoir and simulation studies. Additionally, different completion size and well paths are investigated and compared with each other. To achieve these objectives a method combining material balance with empirical deliverability equations and wellbore flow calculations is devised and used to calculate the working gas volume and the best-performing production profile for the three prospected gas storage installations, respectively. A newly implemented routine in Excel Visual Basic simplifies the input of different parameters, controlling the gas storage capacity. This program automates the calculation of well and reservoir capacity, facilitating a quick sensitivity analyses for any well and reservoir parameters. For material balance calculations the commercial material balance simulation program MBAL and for well and inflow performance relationship calculations the commercial well modelling software PROSPER are used. The implemented method is applied to assess the turnover volume for each of the potential development scenarios preempting a full reservoir simulation study. As compared with the findings of a previous reservoir simulation study, my results do not deviate more than seven percent, but consistently indicate a reduced performance. To guarantee a minimum manifold pressure of 30 Bara during production, some cushion gas has to always remain within the reservoir. The amount needed depends on the number and performance of the underground gas storage wells. The parameter "skin" is used to quantify the predicted reservoir quality after drilling. A sensitivity analysis conducted with my model indicates a linear relationship between skin and the proportion of cushion gas present. My recommendation for the development of the underground gas storage reservoir Zagling, is to use steeper well trajectories than those initially planned. Due to confidality reasons other findings of this work are restricted.