To meet tomorrows demand for Oil new technologies and strategies have to be applied. Artificial Lift technologies such as centrifugal pumps (Electrical Submersible Pumps) will be a key technology to fulfill the needed requirements. The Master Thesis “Screening possible applications of Electrical Submersible Pumps Technology within changing Gas Oil Ratio regimes” deals with the application of ESP pumps in oil wells which have a varying amount of free gas. The operation of ESP pumps under these circumstances has a certain complexity and requires a detailed knowledge of the expected operating parameters. This requires a deep knowledge base, which a design engineer needs, to find the right pump equipment and related to that the ideal completion strategy. This Thesis serves to build up this knowledge base. First, the main components of an ESP pump and their functionality are described in more detail. After a classification of the different design parameters a concept is developed which enables the estimation of future parameters using a calculation spreadsheet and probabilistic methods. If, during the operation of an ESP pump, the free gas content is fluctuating, the possibilities to react on are extremely limited. In this work, a strategy is presented which can be applied. A simulation of this strategy was performed for three different wells and it has been shown that the applicability of the strategy is given. By changing two important operating parameters, an ESP pump which is in unstable operation conditions due to fluctuating free gas can be returned to a stable operating condition. A research of different papers and case studies showed that the operation of ESP pumps in oil wells with high free gas content is an often discussed problem in the industry. Due to new developments of pump manufacturers and the application of new completion strategies and continuous monitoring instruments the operation of ESPs under these conditions is not any more out of scope.