Track 4 @ Troldtog Real time risk management and integrity management
14:00 - 14:30 Ormen Lange Flow Assurance System (FAS) - online flow assurance monitoring and advice
A Flow Assurance System (FAS) is installed on Ormen Lange in order to give information about the multiphase flow through the entire subsea production and pipeline system and onshore slug catchers to support the operation of the field. The FAS includes the following modules:
- Virtual Flow Metering System (VFMS):
Model generated values of flow rates (gas, condensate and water) as backup to physical multiphase meters.
- Pipeline Monitoring System (PMS):
Model generated values of pipeline flowing conditions and onshore receiving facilities.
- Leakage and Blockage Detection (LDS):
Combining information from measurements and model generated values of pressures and flow rates along with statistical process control methods.
In 2011 the Ormen Lange FAS was upgraded with new PMS and LDS modules based on the new transient multiphase flow simulator FlowManager Dynamic, replacing the previous transient simulator. The new simulator has proven to give accurate predictions of pressure, temperature and flow rates of gas, condensate and water/MEG in the wells, templates, flowlines and slug catchers.
The flow assurance challenges of the Ormen Lange field are significant. Due to sub-zero temperatures at the sea bed, there is a risk of hydrate and ice formation. However, the FAS reduces the risk of hydrate and ice formation. The PMS module calculates pressure, temperature, water content and MEG concentration through the entire subsea system, giving the margin to the hydrate formation curve for actual operation conditions.
Another flow assurance challenge is liquid surges. The long transport (120 km) of unprocessed fluids in a hilly seabed terrain induces liquid surges in the pipelines due to liquid accumulation at low rates. In the worst case, the result can be flooding of slug catchers. In this paper it is shown that the upgraded PMS module is able to accurately predict the liquid surges in the pipelines, liquid surge arrival in the slug catcher and the liquid level in the slug catchers. Thus, the operators and flow assurance engineers have a tool to optimize the ramp-up speed avoiding flooding of the slug catchers.
The PMS module gives full overview of current operation conditions and predicted changes in the subsea system and slug catchers the next hours. All operations (e.g. shut-in, restart or ramp-up) can be simulated in advance. This ensures safe and optimized operation of the complex Ormen Lange production systems.