Intermittent gas lift in Aghajari oil field, a mathematical study

The gas lift is a widely used method of artificial lift, for which there are different options. Previous work in this regard to optimize the continuous gas lift (CGL) of Aghajari oil field located in the south of Iran was promising. A new intermittent gas lift (IGL) simulator is developed considering all aspects of this artificial lift method including the temperature differences between the injected and produced fluids. In order to check the validity of the mathematical model, the intermittent gas lift experimental data, i.e. pressure gradient as a function of time, of Brown [Gas Lift Theory and Practice, Prentice-Hall, Englewood Cliffs, NJ (1967)] were compared with the results obtained by this simulator. The calculated pressure gradient matched well with the experimental data. For the same system, the pressure under the liquid slug as a function of opening pressure of gas lift valve was also calculated and compared with the experimental data. It was found that ignoring the heat transfer between the injected gas and the liquid slug shifts away the calculated results from the experimental points and therefore, decreasing the accuracy of the model. The model then was used to study the Aghajari oil field. The results showed that the production of this oil field will increase significantly using intermittent gas lift method.