Statoil’s goal is to operate without harming the environment, and we have different cleaning processes for the various waste streams. Even after cleaning, water, sand and rock still contain oil and chemical residues. In high concentrations, these substances can be harmful to the marine environment.
For example, both cooling water and washing water are generated on the platforms, as is produced water which is the water that is entrained with the oil and gas from the reservoirs. Additional waste sources include the rock that is drilled out of the wells, drilling fluid used during drilling and sand from the reservoirs.
The greatest challenges on the Norwegian continental shelf relate to produced water.
The amount of produced water increases as the fields mature, and increased recovery rates from the fields, i.e. better use of resources, also increases the volume of produced water.
In addition, the petroleum activities on the Norwegian continental shelf are shifting north to important spawning and fishing grounds.
Statoil are continuously working to reduce water production as much as possible through different measures in the wells. We are working in a focused and systematic manner to find the best solution for dealing with produced water.
The company has led the development of the EIF (Environmental Impact Factor) risk assessment tool which is now used by the authorities and by the industry.
The EIF shows which components in the discharge water are most harmful, and it enables measurement, monitoring and comparison of discharges to sea from the various fields.
The EIF thereby provides a good basis for finding optimum environmental solutions for each project or field.
The amount and composition of produced water from the different platforms vary greatly. Such variations require different solutions.
On some fields, reinjection of water to the reservoir or another formation is the best solution, even though reinjection often leads to increased energy consumption and increased emissions to the atmosphere.
For other fields, cleaning adapted to the individual platform may be the best solution.
In addition, Statoil is working to reduce the use of chemicals, and we are continuously seeking more environment-friendly versions.
Reinjection is the preferred choice for new fields
Statoil carries out complete assessments of discharges to sea and our assessments therefore include energy consumption, emissions to the atmosphere, chemical requirements and amounts of special waste.
The company is continuously and extensively engaged in the development and testing of relevant cleaning technologies and new chemicals, and we have been a pioneer in using hydrocyclones for cleaning the water. The company has also been at the forefront in testing and using new cleaning technology such as C-Tour, Epcon, CFU, among others.
Today, the average concentration of oil in discharged water is approx. 25 mg/l. This is below the authorities’ requirement of 30 mg/l.
The environmental impact of our platforms, measured in terms of EIF (Environmental impact factor), fell by more than 80 per cent from 2000 to 2006 as a result of measures implemented on each individual platform. Discharges of oil have been halved.
That this has been achieved, even though the amount of water has increased, can be attributed to the focused measures implemented on each individual field in order to reduce discharges of the most harmful components.