Value Added by Xodus
After working with our client during a previous design phase upon their FPSO, a potential risk of Vibration Induced Fatigue Failure was identified. Our measurement and simulation based capabilities, combined with our advanced monitoring equipment, enabled our vibration specialists to effectively quantify risk and enable the client to remove their self-imposed flow limit. This established a wider safe operating window which resulted in no production limits and increased operator confidence.
Description
Previous design stage analysis carried out by Xodus showed that there was a potential risk of Vibration Induced Fatigue Failure to the turret gas lift system pipework due to Flow Induced Pulsation (FLIP) originating in the corrugated risers. The Client therefore imposed a safe operating flowrate through the gas lift risers of 55 MMSCFD.
In order to overcome this operational restriction, a series of flow trials was performed. These trials involved performing real-time monitoring of pressure pulsation and vibration levels from numerous at-risk locations simultaneously, while incrementally increasing the gas lift flow rates.
Problem
- FLIP excitation evident on the topsides gas lift pipework with the potential to induce high dynamic stresses
- Predefined limits set for gas lift flowrate which limited production
Disciplines Involved
- Real-time monitoring of pressure pulsation and vibration
- Acoustic analysis
- Structural finite element analysis
Solution
- Non-intrusive – Anti-vibration clamps were fitted to small bore attachments identified to be of concern from the acoustic and structural analysis
- Non-intrusive – Xodus personnel installed a multi-channel monitoring system and performed flow trials to enable a safe operating window to be established and increased flowrate limits to be set
Benefit
- Confirmation of minimal threat to the integrity of the pipework despite evidence of FLIP excitation
- Safe operating window established with no requirement to limit production
