Hydro is evaluating various methods to cut environmentally harmful emissions of produced water from offshore oil and gas operations into the sea. Techniques considered include rinsing produced water before it is released, and reinjecting polluted water back into the oil reservoir.
Hydro, Phillips and Statoil are participating in a project that cleanses water produced with oil extracted from offshore petroleum fields on the Norwegian continental shelf. Studies show water soluble organic compounds pose the greatest environmental risk. These compounds possess phenols, polyaromatic hydrocarbons og naphthalenes.
The oil industry is concerned with developing different rinsing technologies to reduce concentrations of these compounds. One of the most promising rinse technologies is C'Tour, says Hydro project manager Jonny E. Gabrielsen.
According to Gabrielsen, it's still unclear how much of an impact these compounds have on sea life. Several studies have meanwhile concluded that long-term emissions of phenols are damaging to marine life. In addition, the Norwegian Pollution Control Authority now demands significant reductions in marine emissions from offshore installations. On the Snorre platform, which treats oil from both Snorre and Vigdis, the new requirement calls for cutting the so-called environmental factor (EIF) from 5,000 to 1,000.
The C'Tour technology will now be tested on the Hydro-operated Snorre and Oseberg fields, as well as the Ekofisk and Statfjord fields, operated, respectively, by Phillips and Statoil. The tests will determine whether produced water cleansed by C'Tour technology satisfies new environmental demands and can be released into the ocean.
Reservoir reinjection
Parallel to the C'Tour project, Hydro mulls the possibility of reinjecting part of the produced water on Snorre into the field's reservoir after being cleansed of sand. This would have a double advantage.
"Sending the produced water back to the reservoir diminshes environmentally harmful emissions. It would also boost oil recovery," says Gabrielsen, adding reinjection facilities built on platforms can be custom-made for an individual reservoir's needs.
Costs for such a facility on the Snorre platform are estimated at between NOK 500-600 million (USD 56-67 million). Two solutions are under evaluation - a unit integrated into the existing production facility on the platform, and a separate module built on land that would be fastened to one of the tension-leg plaform's four columnar pontoons.
Produced water on the Snorre TLP will gradually increase to 45,000 cubic meters per day. Prognoses indicate environmentally harmful emissions from oil production in Norwegian waters will climb in coming years, Gabrielsen says. This is closely tied to the fact that higher amounts of produced water are generated from maturing offshore fields.