A numerical model for a unique form of gas-lift, termed "Liquid-Assisted Gas-Lift (LAGL)," is presented in this study. The LAGL technique uses a liquid-gas mixture to unload wells and initiate gas-lift, rather than the industry standard practice of installing multiple unloading mandrels and valves. The intent of the modelling presented in this work is to validate experimentally and to analyse some of the key parameters behind LAGL approach. The modelling results are validated with data from a field-scale test well, with a total vertical depth of 880 m (2,880 ft.).
From the simulation results and experimental data, it is possible to demonstrate how the use of a gas-liquid flow injection can significantly decrease the injection pressure for unloading operations. Different combinations of gas-liquid injection rates are numerically tested to evaluate the effect of these parameters on the injection pressure.
The modelling results show that the use of the LAGL technique enabled the reduction of the injection pressure of 83 bar, when using single-phase gas in a single point injection system, to approximately 21 bar, when injecting gas-liquid mixtures in a single point injection system. Analysis of the effect of valve opening size also presented in the paper shows that the use of large orifice sizes may reduce the effect of multiphase flow friction through the gas-lift valve.
The LAGL concept is a novel and alternative technique to perform gas-lift unloading operations. Modelling studies and details about this concept have not been presented in the open literature. In addition to that, the findings of this paper can also provide insights on the modification of existing gas-lift valves to allow them to handle multiphase flow more efficiently.