Hydraulic model for the continuous gas lift at the bottom of L-type marine riser system

In order to study the hydraulic model for the continuous gas lift at the bottom of L-type marine riser system, the two-phase flow process that may occur in an L-type riser system was analyzed based on the condition of continuous gas injection at the bottom of the riser. Then, a one-dimensional quasi-steady numerical model was established to simulate the continuous gas lift at the bottom of the riser in the working condition of severe slugging in the downdip pipe-riser system. This new model can be used to perform numerical simulation on the related parameters of different flow behaviors, namely cyclic flow with fallback, cyclic flow without fallback, unsteady oscillation and steady two-phase flow. By virtue of this model, the variation laws of flow parameters over the time in different flow behaviors can be obtained. Furthermore, the simulation results are in agreement with the experimental data provided by the third party. This model is superior to the Jansen model in terms of applicability and stability. Finally, the influence of gas injection rate on the continuous gas lift at the bottom of the riser was analyzed based on simulation results and experimental data so as to provide a reference for the safe and stable flow in marine riser systems.