Transient simulation of severe slugging and riser topside choking

A transient model was developed using OLGA to study the dynamic behavior of sever slugging in a pipeline-riser system. The simulated test loop, with 50.8 mm ID, has a 114 m long horizontal loop connected to a 19 m long pipe which is inclined to-2 degree from horizontal, followed by a 15.3 m high vertical riser. The flow pattern map obtained numerically was tested against previous experimental results, as well as the detailed characteristics of severe slugging such as, pressure at the riser base, liquid holdup at the riser topside, slug frequency, etc. Topside choking, as a common slug control method, was also simulated using present model and compared with the experimental results. The results showed that the four flow patterns observed in experiments could be reproduced well in the simulation. However, the detailed characteristics of severe slugging cannot be predicted accurately by the code, and there are still large discrepancies between the experimental results and simulation in the process of topside choking. It is recommended that further research should be done on the mechanism of topside choking.