Environmental Report 1998 Index

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Glossary Acid Rain Rain which is slightly acidic due to the mixing in the atmosphere of various industrial atmospheric pollutants (e.g., sulphur dioxide) with naturally occurring oxygen and water vapour. Acid rain is thought to be partly responsible for the decline in freshwater fish populations and woodlands in parts of central and northern Europe. Climate Change Concerns about enhanced warming of the planet because heat radiating from the ground is absorbed by greenhouse gases such as C02 to an increasing degree as more of these gases are produced from the burning of fossil fuels. CFCs/HFCs Chlorine based chemicals (chlorofluorocarbons and hydrochlorofluorocarbons) that contribute to the depletion of the stratospheric ozone layer (see ozone layer). C02 The chemical formula for carbon dioxide. C02 is the basis for plant respiration and is liberated when vegetable matter rots or burns, and when fossil fuels are burned. C02 is one of the major 'Greenhouse Gases' (see climate change). Decommissioning Planning for the eventual shut down of an oil or gas field - in particular from the standpoint of what to do with the platform structure. Drill Cuttings Rock chippings produced by the action of the drill bit on rock as it works its way down to the subterranean oil or gas bearing formations. Drill cuttings are removed from the well-bore by drilling mud (see drilling mud). Drilling Mud A specially formulated fluid used to lubricate the drill bit and remove drill cuttings. Different fluid bases exist for different types of mud. They may be water based (WBM), mineral oil based (OBM), or synthetic oil based (SMS). Muds have to be carefully formulated to match the varying geological, temperature, and pressure conditions that are met as an oil well is being drilled. DTI The UK Department of Trade and Industry, the primary environmental regulator for the UK offshore oil and gas industry. EEMS The Environmental Emissions Monitoring System, also known as the SCOPEC database. This database records environmental emissions and discharges from offshore installations in the UK sector of the North Sea. Flaring The controlled burning off of combustible gases mainly for safety reasons. Greenhouse Gases (see climate change). OBM (see drilling mud). OSPAR The Oslo and Paris Commission which regulates pollution from offshore and onshore sources in the North East Atlantic. Ozone Layer A stratospheric layer that absorbs much of the harmful ultraviolet rays that would otherwise reach the earth. Chemicals such as CFCs (see CFCs) can react in the stratosphere to reduce the effectiveness of the ozone layer. Photo-chemical Smog An atmospheric haze sometimes emanating from large industrial and urban areas. The primary ingredients of photo-chemical smog are pollutants such as oxides of nitrogen and VOCs (volatile organic compounds). The reaction of these chemicals to form the haze is catalysed by the presence of sunlight. Produced Water Water naturally present in the reservoir or injected into the reservoir to ensure sufficient pressure. The amount of produced water increases as the well ages. Residual amounts of oil are present in produced water which in most cases is treated and eventually discharged to the marine environment. SMS (see drilling mud) Seismic Survey Technique in which sound waves are used to characterise the shape of underground rock formations and so identify, amongst other things, possible hydrocarbon bearing formations. In the UKCS, seismic surveys are carried out from specially equipped boats. UNFCCC The United Nations Framework Convention on Climate Change. One of three conventions signed at the Rio Earth summit in 1992. The convention commits signatory countries to controlling the emissions of Greenhouse Gases (see climate change). UKOOA The United Kingdom Offshore Operators Association - the trade association for the UK offshore oil and gas industry. Venting The release of unburned gases to the atmosphere. WBM (see drilling mud)