Produced water purification 

Volumes of produced water on the ageing Statfjord field are so high that they can no longer be discharged after standard treatment.

Injection into the reservoirs for pressure support is technically out of the question, while injection into a shallower saline aquifer would be too expensive.

The only solution is to install a highly effective purification system capable of handling the vast quantities involved. 

Initiated by the former Rogaland Research institute in Stavanger, development of the CTour concept was primarily supported by StatoilHydro.

This solution involves injecting condensate, a light hydrocarbon liquid, into the oil-contaminated water after primary separation.

The condensate extracts dissolved hydrocarbons from the water and increases the size of any oil droplets. This means such oil can be easily removed from the water prior to de-gassing and discharge to the sea.

Several CTour tests successfully carried out on the Statfjord B platform during 2002 and 2003 showed that the system is qualified for high-pressure flow conditions.

This outcome also led to the construction of a full-scale pilot plant on Statfjord C for low-pressure use, which worked so well that it is now a permanent installation.

In both cases, the results were more than sufficient to meet the target of zero harmful discharges.

Following an encouraging response from the Norwegian Pollution Control Authority (SFT), the Statfjord partners agreed to establish full-scale plants on all three platforms.