Abstract There has been a significant increase in the produced water volumes at the Norwegian continental shelf the last decade, and the operators have worked systematically to fulfil the ambition from the Norwegian Pollution Control (SFT) of "Zero harmful discharge" to sea. Statoil has in cooperation with other operators developed an environmental risk management tool (Environment Impact Factor, EIF) which has been used to select cost-efficient measures to meet "Zero harmful discharge" ambition goal.
Environmental risk assessment at the Statfjord field has shown that the discharge of corrosion inhibitor contributes significantly to the potential environmental impact (EIF-value). Statfjord field is an old field with flowlines of carbon steel which demand injection of inhibitor for corrosion control.
Statoil and M-I Production Chemicals started a joint R&D-project in 2002 aiming to develop and implement environmentally friendly corrosion control at the Statfjord field. In the present project the following tasks have been investigated:-Modification of chemical formulation
-Reduction of the chemicals consumption
-Documentation of the environmental impact
-Purification of produced water
-Development and field testing of new low-toxic inhibitors
The output of this project enables Statoil to start implementation of an environmentally friendly solution within 2006 at the Statfjord field. The first step will be to perform a full scale pilot test at one of the three Statfjord installations with 6 months duration.
Introduction The main focus in reducing the environmental risk of the discharge of produced water has traditionally been to reduce the discharge of dispersed oil. Even though some countries have addressed their attention on other components, international regulations like the new OSPAR regulations [1] still focus on dispersed oil content in produced water.
In the Norwegian sector of the North Sea, all operators must, in addition to fulfilling and reporting according to the dispersed oil regulations, report the total environmental impact of the produced water release to the sea to the Norwegian Pollution Control Authorities (SFT) [2]. This reporting is done on an annual basis and is based on thorough (GC-MS) analysis of the produced water to quantify the content of all compounds of interest. The method for quantifying the environmental impact is the Environmental Impact Factor, EIF [3], which relies on DREAM (Dose Related Risk and Effect Assessment Model) [4]. The model is based on an environmental risk assessment approach where a comparison is made between the concentrations of potential environmentally harmful compounds and the predicted no effect concentration. The EIF is not only a valuable tool for quantifying the potential environmental impact from one platform or a group of them, but also for evaluating the contribution from the different constituents in the produced water. However, the EIF does not provide an accurate description of the ecosystem status, but must be regarded as a discharge management tool. Linking the risk assessment based EIF to environmental monitoring is crucial for a complete understanding and documentation of environmental impact of discharges to sea.
Traditionally, the naturally occurring oil components give the main contribution to the EIF-value. However, at some installation the production chemicals have shown to be the dominating contributors to the environmental risk. This was the case at the Statfjord field, and at Statfjord C in 2002 the corrosion inhibitor was represented with 82 % contribution to the EIF as shown in figure 1.