Environmental Report 1999 Index

Glossary of Terms Acid Rain Rain that 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 The world's climate may be changing due to the planet getting warmer. This may be because heat radiating from the ground is increasingly absorbed by greenhouse gases such as C02. CFCs/HFCs Chlorofluorocarbons and hydrochlorofluorocarbons: chlorine-based chemicals 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 the eventual shut down of an oil or gas field - in particular, what to do with the platform structure. Drill Cuttings Rock chippings produced by the drill bit as it works its way down through the rock 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 are used for different types of mud. They may be water-based (WBM), mineral oil-based (OBM), or synthetic oil-based (SMS). Muds are carefully formulated to match the varying geological, temperature, and pressure conditions that are met as an oil well is being drilled. DTI The 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 records environmental emissions and discharges from offshore installations in the UK sector of the North Sea. Flaring The controlled burning 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 that may affect the north east Atlantic Ocean. 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 occurs over 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 that forms the haze is catalysed by sunlight. Produced Water Water that is either naturally present in the reservoir or injected into the reservoir to ensure sufficient pressure, and which is subsequently produced along with the oil. The amount of produced water increases as the well ages. In most cases, produced water is treated to remove all but residual amounts before it is discharged to the sea. SMS (see drilling mud) Seismic Survey A process that uses sound waves to characterise the shape of underground rock formations and to identify, among other things, possible hydrocarbon-bearing formations. On the UK Continental Shelf, seismic surveys are carried out from specially equipped vessels. 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 muds)