Rational use of associated petroleum gas (APG) is the most important task of the oil industry. One of the options for its solution can be the use of pump-ejector systems for injecting APG together with water into the reservoir when implementing simultaneous water and gas injection (SWAG) in order to increase oil sweeping. However, the problem of increasing the pressure developed by the pump-ejector system is currently insufficiently studied issue. This paper presents an improved layout of the pump-ejector system, recommendations for the optimal composition of the working fluid, as well as the calculation of the system for the conditions of one of the fields in the Ural-Volga region. © Published under licence by IOP Publishing Ltd.