Modeling and Simulation Study of Gas Injection in Three-Phase Flow Riser-Pipe System to Mitigate Severe Slugging

Severe slugging in risers hinders the steady production of oil, and it may also damage the equipment. Thus, finding a proper way to prevent such a phenomenon is of great importance. The aim of this study was to provide a mathematical model to investigate the three-phase flow of oil, water and gas in a riser-pipeline system. To do so, a bulk model was chosen to simulate the pipeline under two scenarios. In the first scenario, gas can penetrate the riser and flow upward whereas, in the second scenario, liquid holdup limits the gas flow in the riser. Moreover, the riser system was modeled with the assumption of a distribution parameter system that used dynamic nodes to evaluate the local conditions. Mass transfer between the oil and gas phase was also estimated by the black-oil approximation. After modeling the riser-pipeline system, gas injection at the riser base was simulated to stabilize the flow and prevent the upcoming issues. In addition, a criterion to determine the amount of the injected gas was proposed. Finally, results obtained from modeling were compared with the results of the OLGA simulation software which showed good agreement.