The efficient operation of offshore gas turbine driven compressor trains is becoming more and more important. With the introduction of the CO2 tax on fuelgas in Norway, the operating costs have dramatically changed. It is now necessary to focus on energy-saving operation and maintenance in order to include the influence of CO2 taxation. In the Statfjord and Gullfaks fields, the LM2500 high efficiency aeroderivative gasturbines have been in operation for several years, and the operational experience is presented and discussed here with regard to efficiency and reliability. An optimised gas turbine maintenance program has been introduced in order to obtain energy-saving and cost reduction. The problems relating to the gas compression trains are discussed with regard to energy conservation and reliability. Off design operating conditions on compressors have caused problems, both with regard to power losses and machinery safeguard control systems. Energy-saving improvements have been implemented on the compressors and the system they are working in. The reliable operation of the compressors can be put at risk by the shaft-sealing system. It is of vital importance to ensure correct operation of seal system in order to obtain safe and economical operation. Improvements to shaft-sealing systems are discussed.

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