Effect of Gas Lift Gas Composition on Production Stability / Instability by Dynamic and Steady State Simulation for Continues Gas Lift Injection Mode

Abstract

Abstract Gas lift is one of the artificial lift methods that is used to increase oil recovery by gas injection into production tubing. At the injection point, chocking effect has been identified as one of the factors that affect production instability. Fluctuation of the injected gas pressure, affects the gas/liquid interface behavior. Influence of the gas composition on the production efficiency, to our knowledge, has not been addressed in literature as an additional factor that plays role in efficiency. The flow instability leads to discrepancies between the forecasted and the actual production. The main objective of this study is to address the production instability of gas lift wells in transient (dynamic) and steady state simulations for continuous gas injection regime. Sensitivity investigations for stability analysis are performed for the various gas compositions, gas injection rates, injection pressure, prudctivity index (PI) and gas lift valves (GLV) port size. The results show that higher gas density, higher gas injection rate, higher injection pressure, higher PI and lower gas lift port size can stabilize the gas lifted well. When, relating the gas composition to density for black oil in dynamic and steady state simulation, it is interesting to see opposite effects are obtained from the results that are obtained these simulations, where dynamic simulation shows that the heavier gas gives larger production rates compared to lower gas density, while the opposite is obtained from the used steady state simulator.