Simulation of pigging dynamics in gas-liquid two-phase flow pipelines

• In steady state cases, due to taking into account the exact and detailed geometry by OLGA, the simulated outlet liquid flow rate is more than its numerical result.
• By inserting the transient condition due to changing the inlet flow rate, pipeline touch again a steady state condition after a while by passing the time.
• There is a high compatibility between predicted and simulated parameters of gas phase (maximum error = 4.83%).
• There is a maximum 16% difference between predicted and simulated parameters of liquid phase.

Pigging is mainly done for cleaning the deposits and liquid removal in order to reduce the overall pressure drop and increase the pipeline flow efficiency. In this study, a simplified pigging model in two-phase flow pipelines with 657 mm diameter and 108 km length sea line of South Pars located in south of Iran has been developed to predict the pigging operation. At the beginning, the steady state condition was modelled to find the initial values, then the transient state cause to variable of feed flow rate was modelled, and finally the transient model was coupled with pigging model to describe the pig behaviour based on three flowing zones. The one dimensional differential equations and explicit finite difference were used as solution method. The results obtained with the code were compared with OLGA simulation and three real field pigging displacement and there was good agreement between them, thereby validating the method.