Environmental Report 1998 Index

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Chemical Discharges to the Marine Environment Chemical Additives are an essential part of the business of producing oil and gas. They lubricate drill bits and protect pipelines and machinery against corrosion. They stop the unwanted growth of marine organisms and help separate oil from water. By far the greatest use of chemicals in the offshore oil business use is in association with drilling operations (see Fig. 6) Some of these chemicals end up in the sea. This is sometimes due to accidental spillage, and more often because they are present in waste streams at such low concentrations that they would be impossible to recover. As environmental awareness grows, oil companies are reducing their use of these additives and choosing less harmful alternatives. The problem is that sometimes the choices are not always clear-cut. Switching from oil-based to synthetic drilling fluids, although reducing the amount of oil released to the environment, means the use of more chemical additives. Similarly, reducing the amount of chemical de-oilers increases the amount of residual oil discharged with produced water. In order to try and achieve an objective balance, the oil industry, regulators, and research centres are working together on two important initiatives: The first is the development of a framework for hazard assessment called CHARM (Chemicals Hazard Assessment and Risk Management). The CHARM hazard assessment process makes use of computer based models in order to take into account how specific chemicals are being used, and the special circumstances that exist on a specific platform with regard to their fate and effects in the marine environment. The second joint initiative relates to the measurement and reporting of the amounts of different types of chemicals released to the environment - the Offshore Chemical Notification Scheme (OCNS). OCNS is a voluntary scheme where oil companies report quarterly on their use and discharge of chemicals. The first version of OCNS was introduced in 1979. Since 1993, the rules for reporting have been progressively amended in order to integrate with other European schemes. Full implementation of a Europe-wide mandatory reporting system (which may include some features of the CHARM system) is expected to be in place by the year 2000 at the latest. The OCNS is administered by the DTI, with scientific assistance from other Government Departments. The scheme identifies chemicals used offshore in one of 5 classifications depending upon their impact on the environment. Annual tonnage limits are set for use and the discharge each class which trigger the need for consultation between oil companies and Government well in advance of any proposed discharge and again where the tonnage limits have been reached. Fig. 6 shows the total discharges of chemicals in each of the 5 categories for both 1996 and 1997. Group 'E' chemicals are the most environmentally benign and group 'A' the least so. Fig. 6 shows that for the chemicals of greatest concern (categories A, B, and C) some reduction in the amounts discharged have been achieved over the last 2 years. On the other hand, usage of group D and E chemicals has increased. This is largely a result of the move away from Oil Based Mud, which although reducing oil pollution, requires the use of more chemicals. Increasing chemical usage is also due to efforts to reduce the level of oil in produced water.