The effect of a surfactant on slugs in a flowline-riser system

Based on the success of foam in subsurface applications it is of interest to investigate whether foam can also help overcome liquid management problems in surface flowlineriser systems. Therefore, flow experiments were carried out in the flow loop at the Shell Technology Centre Amsterdam. The facility consists of a 100 m long horizontal flowline (with 50.8 mm diameter) followed by a 16.8-m vertical riser (with 44 mm diameter). Air and water are the working fluids, and operation is at atmospheric outlet pressure. Foam is created by adding "DreftTM" (a dishwashing detergent) in various concentrations to the water/air flow. Experiments were taken both without and with foam. Various measurement techniques were used: differential pressure sensors, flow visualization, and Distributed Acoustic Sensors (DAS) (fibre optics). The focus is on (growing) slugs in the horizontal flowline, and severe slugging in the flowline-riser. It can be concluded from the small-scale lab experiments that adding a surfactant mitigates (growing) slugs in (nearly) horizontal flowlines, whereas the severe slugging cycle in a flowline-riser configuration cannot be broken.