Operations optimisation of the Waste Heat Recovery Unit (WHRU) system. The Ekofisk 2/7 K platform has three turbines available for power generation and two water injection turbines. A WHRU unit is installed to exploit the exhaust heat for all power turbines and one of the water injection turbines.

The WHRU is mainly used for fresh water generation and heating of the living quarters. Normally, Ekofisk 2/4K is powered through a power cable from the Ekofisk Complex. To operate the fresh water system and in addition have sufficient heat for the living quarters, both a power turbine and a water injection turbine were required.

The improvement measure aimed at optimising the operation of the WHRU by blinding those parts of the WHRU connected to turbines not normally operating, so that the heating medium is not unnecessarily cooled by cold exhaust pipes. In addition, the flow rate of the heating medium through the WHRU on the water injection turbine has been optimised to give increased temperature of the medium.

Together these measures increased the heating medium temperature by 7 degrees C. As a result, the power turbine is no longer required for 9 out of 12 months. This will lead to direct fuel gas savings and reduced emissions due to approx. 3000 hours of operation for the power turbine instead of the original 9000 hours. It will also reduce maintenance costs.

Results:
Emission savings corresponding to approx. 6 300 tons CO₂ per year and 8.7 tons NOx per year

ConocoPhillips has implemented this measure on Eldfisk 2/4 K