Horizontal Stratified Air-Foam-Water Flows: Preliminary Modelling Attempts with OLGA

Water accumulation is a major problem in the flow assurance of gas pipelines. To limit liquid loading issues, deliquification by means of surfactant injection is a promising alternative to the consolidated mechanical methods. However, the macroscopic behavior of foam pipe flow in the presence of other phases has barely been explored. The goal of this work was to propose an approach to simulate air-water-foam flows in horizontal pipes using OLGA by Schlumberger, an industry standard tool for the transient simulation of multiphase flow. The simulation results were compared with experimental data for 60 mm and 30 mm ID (Inner Diameter) horizontal pipelines. Preliminary validation for two-phase air-water flow was carried out, which showed that correct flow pattern recognition is essential to accurately reproduce the experimental data. Then, stratified air-foam-water flows were investigated, assuming different models for the foam local velocity distribution. Foam rheology was considered through the Herschel-Bulkley model with the yield stress varying in time due to foam decay. The results showed good agreement for a uniform velocity profile and fresh foam properties in the case of the 60 mm ID pipeline, whereas for the 30 mm ID, which was characterized by significantly higher velocities, a linear velocity profile and 2000 s foam aging provided the best agreement. In both cases, the pressure gradient was overestimated, and the mean absolute prediction error ranged from about 5% to 30%.

Automated summary

Water accumulation in gas pipelines is a major issue in flow assurance, and using surfactant injection for deliquification is a promising alternative. However, the behavior of foam pipe flow in the presence of other phases is not well understood. This study proposes a simulation approach using the OLGA tool to model air-water-foam flows in horizontal pipes. The simulation results show good agreement with experimental data, but there is an overestimation of pressure gradient and the mean absolute prediction error ranges from 5% to 30%.