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Use of indicators for showing environmental performance is widespread used both on a corporate level and for analysing whole sectors and societies. When carrying out environmental management, demonstration of continuous improvement with respect to environmental performance is a requirement. But the contents of this concept are often not clearly defined. Air emissions from the offshore oil and gas production in the Danish part of the North Sea has been used to exemplify the use of environmental indicators. The emissions have been compared with the total emissions from the Danish society, in order of indicating the relative significance of the various emittants. It has been shown that it is necessary to distinguish between emissions with a global environmental impact from emissions with a regional or local impact. In the first case the relative environmental effect is simply proportional to the relative contribution to the total emission of the pollutant. In the second case, the location of the emission source, and also the variation in emission with time, is necessary to take into account when evaluating the environmental impact. The analysis of emissions to air from the offshore oil and gas production has highlighted the need for a common calculation basis. Even for calculation of an essential parameter as the emission of CO2 various calculation methods used in various countries showed large differences. Comparison of environmental performance in between the various countries is therefore difficult, until common calculation methods possibly are agreed on. Introduction Environmental indicators are widespread used for a lot of purposes, both at a local/corporate level and on a national and international level. The purpose of using environmental indicators in the E & P industry is often to be able to document continuous improvement, which is a key philosophy in environmental management. When identifying which indicators should be used in order to monitor the impact on nature caused by E & P activities, it is important to have the purpose in mind. Prior to any definition of indicators, an identification of the most significant environmental impacts of the activity has to be done. Indicators enabling us to quantify both the actual state and future trends in environmental performance should thereafter be identified. These targets are usually set with a view to both what is the environmental gain of the fulfilment of the target and a view to what is the cost of making this environmental effort. Expected future constraints with respect to authority requirements are often also incorporated in the target setting. It could be argued that indicators related to emission rates should be normalised with the production rates. When society demands oil and gas at as low environmental impact as possible, it could make sense to normalise the emissions relative to the produced oil and gas amount, in order to get a measure of "environmental efficiency" of the production. Seen from the industrial point of view, indicators taking into account the maturity of the field seem reasonable, both with respect to possible increased environmental challenges and with respect to technological improvements with time. The most important aspect of environmental indicators is maybe to be used for communication. Adapting indicators that are already used on a national and international scale for monitoring the overall environmental strain on nature caused by societal activities makes communication of the environmental performance of the E & P industry to the authorities and to the public more efficient. In addition, direct comparison with other activities in society is easier to carry out. This paper gives examples on environmental indicators used in the E&P industry in the Danish sector and in society in general. The usefulness of the various types of indicators, taking into account the above considerations is discussed.

Summary When produced water from offshore production is discharged to sea, itcontains some oil (aliphatic and aromatic components), production chemicals,and naturally occurring radioactive materials (NORM). These groups of materialsare traditionally treated in different ways in the regulations andstandards. Regulations of oil in produced water are mainly related to maximumconcentrations and the total discharge of the aliphatic (dispersed) fraction.Regulation of chemicals is based on the environmental risk profile of eachproduction chemical, although efforts are made toward regulations based on riskassessment of the discharge of the mixture of substances. For discharge of NORMdissolved in the produced water, no limit values are imposed. For NORM solids(scale, sludge, sand) from process equipment, discharge to sea is in generalnot allowed--it is reinjected or taken to a deposit onshore. Management of safety risks takes place on the basis of the principle thatrisks shall be reduced to a level as low as reasonably practicable (ALARP). Theconcept of environmental risk is not as unambiguously defined as safety risks.With respect to accidental environmental impacts, the parallel is relativelystraightforward, but with respect to planned environmental impacts (e.g.,emissions/discharges during operation), the parallel to the safety ALARP levelis not so clear; the consequence (the environmental impact) is not linked to acertain frequency (i.e., we cannot talk about risk as likelihood timesconsequence). Costs are normally defined as money, effort, and time. But what if the costof a reduced health, safety, and environmental (HSE) risk or impact is anincrease in another HSE risk or impact? Produced-water reinjection might causeincreased carbon dioxide (CO2) emissions. Handling solid NORM duringshipping to shore causes health risks to the people handling the NORM. Can thatrisk be justified on the basis of the possible reduction in environmentalimpact by not discharging the solid NORM to sea instead? This paper highlights the aforementioned issues and proposes a method called’integrated HSE ALARP assessment’ for supporting such analysis. Theenvironmental risks and impacts of discharge of oil, chemicals, and NORM,respectively, with produced water to sea are used to illustrate theseprinciples.