The definition of commercially and technically feasible development strategy is one of the major tasks of the reservoir engineering analysis. Despite the fact that this task appears very obvious, the result is not always considered as straight forward. Actually, a massive work has to be performed to find out the optimum plan that needs to be followed. For this purpose, the common practice is to build a dynamic reservoir model, which may handle large amount of reliable data used as a tool to predict the production forecast for different scenarios and, consequently, choose the best one that will honor the contractual, technical and commercial constraints. This thesis covers, in the first place, the development plan of a field in south Tunisia by simulating a dynamic reservoir model using ECLIPSE 300 to provide different possible scenarios prior to production. However, the sensitivity study of this work has shown that the most productive case is the one of higher permeability. In the second place, it analyzes the behaviour of the reservoir during the production phase by conducting well testing analyses on Saphir (KAPPA) in order to identify the causes of production drop and hence find solutions to reinstate the relatively high production estimated during the exploration phase. In this case, the results showed that the increase of skin factor is the major reason behind the reduced permeability and thus lower productivity.