Abstract
The severe or terrain slugging is a periodic phenomenon due to liquid accumulation at the low points of a pipe, leading to a temporary blockage. Periodically the upstream pressure increases and generates liquid slugs, for which the instantaneous flow-rate increases to several times the nominal flow-rate. To prevent such phenomena in multiphase production pipelines, a proper design and a control strategy of process equipments are required to avoid operational problems.
The TACITE compositional code is able to simulate the behaviour of transient multiphase flow in pipeline with process equipments such as controllers, valves, separators and lateral injectors which could be used to prevent severe slugging phenomena during production.
The 22 km long, 16" diameter Dunbar pipeline is designed to transport the Dunbar multiphase production to the Alwyn platform. Due to its profile, this pipe is typically subject to riser induced severe slugging for some given operating conditions corresponding to low flow-rates.
The TACITE code has been used to simulate the Dunbar pipeline in the low flow-rate region where riser-induced severe slugging occurs. For the same rates, different slug control schemes have been tested and the simulation results demonstrated that some of them can control or even eliminate the severe slugging phenomenon. This illustrates that these slug control schemes can be easily investigated and tested by use of a transient simulator. Also the simulation results demonstrate that the use of a transient simulator is essential in the engineering design phase of a slug control scheme.
