Gas lift Optimization based on injection rate, gas gravity, and water cut effects A Field Case Study Using PROSPER Simulator

Abstract

Gas lift optimization has become increasingly important in mature oil fields where natural reservoir energy is insufficient to sustain economic production rates. In this study, a continuous gas lift oil well (X001) located in the Sirte Basin, Libya, was modelled and optimized using the PROSPER production modelling software based on actual field data. The well model was developed, using reservoir properties, PVT data, inflow performance relationship (IPR), and completion details, and was calibrated against measured production data to ensure model reliability. Sensitivity analyses were conducted to evaluate the effects of gas injection rate, injection gas gravity, and water cut on oil production performance. The results show that oil production increases with gas injection rate up to an optimum value, beyond which further gas injection becomes inefficient. The optimum gas injection rate, identified at approximately 0.4 MMscf/day, yielding a maximum oil production rate of about 1201 STB/day. In addition, lighter injection gas resulted in improved lifting efficiency and higher oil production, while increasing water cut significantly reduced production performance. The applied methodology demonstrates the effectiveness of production modelling and sensitivity analysis as decision-support tools for optimizing gas lift systems in mature oil fields.