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Subsea Pumping Systems

Subsea Pumping Systems. Intervention Prediction and Condition Monitoring Hallgeir Melbø. Outline. Background Subsea pumps Condition monitoring cost saving potential Key performance indicators. Organisation . Aker Kværner ASA Martinus Brandal , President & CEO Bjørn Erik Næss , EVP & CFO.

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Subsea Pumping Systems

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  1. Subsea Pumping Systems Intervention Prediction and Condition Monitoring Hallgeir Melbø

  2. Outline • Background • Subsea pumps • Condition monitoring cost saving potential • Key performance indicators

  3. Organisation Aker Kværner ASA Martinus Brandal, President & CEOBjørn Erik Næss, EVP & CFO Oil & Gas E&C E&CEurope FieldDevelopmentEurope MMO Subsea Products &Technologies Oil, Gas, Process & Energy Trees / Processing & Boosting

  4. Subsea field development

  5. Outline • Background • Subsea pumps • Condition monitoring cost saving potential • Key performance indicators

  6. Subsea pumps

  7. Subsea pumps • Multi phase pumps • Pumping production fluid containing liquid and gas at pump conditions • Twin-screw pumps • Liquid pumps • Pumping produced oil and water • Water injection pumps • Centrifugal pumps • Gas compressors • Transportation of gas from offshore to onshore

  8. Outline • Background • Subsea pumps • Condition monitoring cost saving potential • Key performance indicators

  9. Subsea condition monitoring • Goal • Avoid unplanned shutdowns due to pump maintenance • Optimal usage of pumps • Tools • Trending • Models • Key performance indicators telling us when to plan for maintenance • Maintenance • Replace pump by a spare one

  10. Cost savings potential, subsea pump intervention • Unplanned intervention • 1-8 weeks • Planned intervention • 24 hours • Example • Pump production increase: 5000 bpd • Oil price: 50 USD • Cost • Unplanned intervention 1.7 – 14 MUSD • Planned intervention 0.25 MUSD • Avoid a single unplanned intervention: • areas where weather is not critical: save appr 1.5 MUSD • areas where weather is critical: save up to 14 MUSD

  11. Outline • Background • Subsea pumps • Condition monitoring cost saving potential • Key performance indicators

  12. Key Performance Indicators • Lube oil accumulator bank status • Vibrations • Lube oil consumption • Valve profiles

  13. KPI: Accumulator Bank Status Models • Flow in umbilical • Response of accumulators • Pump cooling time • Fluid contraction during cooling • ... Pump, topside Gas Gas P Oil Oil Tambient P,T When less than 5 out of 8 accumulators are working there is a risk of losing over-pressure

  14. KPI: Accumulator Bank Status Flow in umbilical, laminar flow in circular pipe: Pump, topside Gas Gas P Oil Oil Tambient P,T

  15. KPI: Accumulator Bank Status Response of accumulators, e.g. ideal gas law: Pump, topside Gas Gas P Oil Oil Tambient P,T

  16. KPI: Accumulator Bank Status Cooling of lube oil inside pump, Newton’s law of cooling: Pump, topside Gas Gas P Oil Oil Tambient P,T

  17. KPI: Accumulator Bank Status Fluid contraction during cooling, e.g.: Volume change proportional to temperature change Pump, topside Gas Gas P Oil Oil Tambient P,T

  18. KPI: Accumulator Bank Status Model: • ODE for time development of pressure for any given number of working accumulators Pump, topside Gas Gas P Oil Oil Tambient P,T When less than 5 out of 8 accumulators are working there is a risk of losing over-pressure

  19. KPI: Vibration Spectra Typical vibration sensor

  20. KPI: Vibration Spectra

  21. KPI: Vibration Spectra

  22. KPI: Lube Oil Consumption • Lube Oil is used inside HV motor and pump gearbox for insulation, cooling and lubrication • Two sources of consumption: • Leak through seals into process • Thermal effects • When leak approaches X L/hour, pump must be replaced Level Pump, topside

  23. KPI: Valve profiles • Pressure in hydraulic function line is measured • Example: Fail-open 4” valve, 1 liter fluid required to move valve CLOSE OPEN

  24. Conclusions • Several observable KPIs • Accumulator Bank Status • Vibrations • Lube Oil Consumption • Valve Profiles • Substantial cost saving potential • Challenging to develop accurate enough models for drawing conclusions about maintenance planning

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