ANTHRACITE: A hard, jet black substance with a high luster. It is the highest rank of coal, almost purely carbon. It is primarily mined in northeast Pennsylvania.

ASSOCIATED GAS: Gas combined with oil. Known also as gas cap gas and solution gas, it provides the force (also called the drive mechanism) needed to force oil to the surface of a well. Associated gas is normally present in an oil reservoir in the early stages of production.

BARREL: The standard unit of measure of liquids in the oil industry; it contains 42 U.S. standard gallons.

BASIN: A depression of the earthís surface into which the sediments that can form oil and natural gas are deposited; a broad area of the earth beneath which layers of rock are inclined, usually from the sides toward the center.

BITUMINOUS COAL: Most common type of solid fossil fuel. It is soft, dense, and black with well defined bands of bright and dull material. It is mined chiefly east of the Mississippi River.

BLOWOUT: An uncontrolled flow of gas, oil, or other fluids from a well into the air. A well may blow out when pressure deep in the reservoir exceeds the weight of the column of drilling fluid inside the well hole.

BLOWOUT PREVENTER: A special assembly of heavy-duty valves installed on top of a well which can be closed to prevent high-pressure oil or gas from escaping (a blowout) from the well hole during drilling operations.

BOILER: A tank in which water is heated by burning a fuel like coal, natural gas, or oil to produce steam for spinning a steam turbine to generate electricity or for use in a variety of industrial manufacturing processes.

BOREHOLE: The hole in the earth made by the drill; the uncased drill hole from the surface to the bottom of the well.

Btu (BRITISH THERMAL UNIT): A standard unit for measuring the quantity of heat required to raise the temperature of 1 pound of water by 1 degree F.

CARBON DIOXIDE: A colorless, odorless gas that is produced when animals (including humans) breathe or when carbon-containing materials (including fossil fuels) are burned. Carbon dioxide is essential to the photosynthesis process that sustains plant and animal life, however, it can accummulate in the air and trap heat near the Earthís surface (the "greenhouse effect").

CASING: Steel pipe used in oil wells to seal off fluids in the rocks from the bore hole and to prevent the walls of the hole from caving.

CLEAN COAL TECHNOLOGIES: New ways to burn or use coal that significantly reduce the release of pollutants and offer greater environmental protection and, often, better economic performance than older coal technologies.

COAL: A black or brownish-black solid combustive substance formed by the partial decomposition of vegetable matter without access to air.

COKE: A hard, dry carbon substances produced by heating coal to a very high temperature in the absence of air. Coke is used in the manufacture of iron and steel.

COMBUSTOR: The part of a boiler or a turbine in which fuel is burned.

CRUDE OIL: Unrefined petroleum that reaches the surface of the ground in a liquid state.

DIRECTIONAL DRILLING: The technique of drilling at an angle from the vertical by deflecting the drill bit. Directional wells are often drilled to reach an oil- or gas-bearing reservoir where drilling cannot be done, such as beneath a shipping lane in the ocean. Directional drilling is being used increasingly to intersect reservoirs at angles that exposes more of the rock to the wellbore and increases the amount of oil or gas that flows into the well.

DRAGLINE: A coal mining machine that uses a bucket operated and suspended by lines or cables, one of which lowers the bucket from the boom; the other, from which the name of the machine is derived, allows the bucket to swing out from the machine or to be dragged toward the machine to remove the ground above a coal seam (called overburden).

DRILL CUTTINGS: Chips and small fragments of drilled rock that are brought to the surface by the flow of the drilling mud as it is circulated.

DRILL PIPE: Heavy, thich walled, hollow steel pipe used in rotary drilling to turn the drill bit and to provide a conduit for the drilling mud.

DRILLING MUD: A special mixture of clay, water, or refined oil, and chemical additives pumped downhole through the drill pipe and drill bit. The mud cools the rapidly rotating bit; lubricates the drill pipe as it turns in the well bore; carries rock cuttings to the surface; serves as a plaster to prevent the wall of the borehole from crumbling or collapsing; and provides the weight or hydrostatic head to prevent extraneous fluids from entering the well bore and to control downhole pressures that may be encountered.

DRY HOLE: A well drilled to a certain depth without finding commercially exploitable hydrocarbons.

DRY GAS: Natural gas from the well that is free of liquid hydrocarbons; gas that has been treated to remove all liquids making it suitable for shipping in a pipeline.

ELECTROSTATIC PRECIPITATOR: An electrically charged device for removing fine particles (fly ash) from combustion gases prior to the release from a power plantís stack. The device passes combustion gases through positively and negatively charged plates that attract the tiny particles using static electricity.

EXPLORATION: The process of searching for minerals, like oil and gas, before development and production. Exploration activities include (1) geophysical surveys, (2) drilling to locate an oil or gas reservoir, and (3) the drilling of additional wells after a discovery to determine the boundaries of an underground reservoir. It enables an oil or gas company to determine whether to proceed with development and production.

FLUIDIZED BED COMBUSTION: An advanced way of burning crushed coal (or other fuels) by suspending the coal on a upward stream of hot air. In the fluid-like mixing process, limestone can be injected into the "bed" (floating layer) of coal to absorb sulfur pollutants before they can escape out the smokestack. The mixing process also lowers the temperature of the burning coal below the point where nitrogen oxides, another pollutant, are formed.

FOSSIL FUEL: Any naturally occurring fuel of an organic nature formed by the decomposition of plants or animals; includes coal, natural gas, and petroleum.

FIELD: A geographical area in which one or more oil or gas wells produce. A single field may include several reservoirs separated either horizontally or vertically.

GASIFICATION: A group of processes that turn coal into a combustible gas by breaking apart the coal using heat and pressure and, in many cases, with hot steam.

GREENHOUSE EFFECT: The warming of the Earthís surface and lower atmosphere caused by the trapping of radiated heat, much the same way the coated window panes of a agricultural greenhouse keep heat inside the greenhouse. Several gases, like carbon dioxide and methane, can keep heat from escaping from the Earth into space and are called "greenhouse gases."

HYDROCARBONS: A class of compounds containing hydrogen and carbon formed by the decomposition of plant and animal remains. These compounds include coal, oil, natural gas, and other substances occurring in rocks.

LIQUEFACTION: Processes that convert coal into a liquid fuel, similar in nature to crude oil and/or refined products.

LIGNITE: The lowest rank of coal, which is brownish-black and has a high moisture content. Used mainly to generate electricity, it is mined in Montana, North Dakota, and Texas.

METALLURGICAL COAL: The type of coal which is converted to coke for use in manufacturing steel; often referred to as coking coal.

METHANE: A colorless, odorless gas that is the most simple of the hydrocarbons formed naturally from the decay of organic matter. Each methane molecule contains a carbon atom surrounded by four hydrogen atoms. It is the principal component of natural gas.

NATURAL GAS: A mixture of gaseous hydrocarbons, composed primarily of methane, occurring naturally in the Earth - often among petroleum deposits - that is used as a fuel.

NONASSOCIATED GAS: Dry gas that is not associated with oil in a productive reservoir, as opposed to associated gas or solution gas.

OIL PRODUCTS: Products ready for consumption through the processing of crude oil and natural gas. Refined products include jet fuel, kerosene, waxes, asphalt, motor gasoline, petrochemical feedstocks, lubricants, etc.

OUTER CONTINENTAL SHELF(OCS): All submerged lands seaward and outside the area of lands beneath navigable waters. Lands beneath navigable waters are interpreted as extending from the coastline 3 nautical miles into the Atlantic Ocean, the Pacific Ocean, the Arctic Ocean, and the Gulf of Mexico excluding the coastal waters off Texas and western Florida.

OVERBURDEN: Layers of earth and rock covering a coal seam. In surface mining operations, overburden is removed using large equipment and is either used to backfill areas previously mined or is hauled to dumping areas.

OZONE: A bluish, toxic gas with a pungent odor formed by three oxygen atoms rather than the usual two. Ozone occures in the stratosphere and plays a role in filtering out ultraviolet radiation from the sunís rays. At ground level ozone is a major component of smog.

PEAT: A dark brown or black deposit resulting from the partial decomposition of vegetative matter in marshes and swamps.

PETROLEUM: A term applied to crude oil and oil products in all forms.

PROVED RESERVES: The estimated quantities of crude oil and natural gas in the ground that geological data demonstrate with reasonable certainty to be recoverable under existing economic conditions with current recovery technology.

RESERVES IN PLACE: The amount of oil or gas physically contained in a reservoir (a place - usually totally underground -where oil or natural gas has collected naturally over millions of years). The "proved reserves" may only be 15 to 35 percent of the "reserves in place."

SCRUBBER: A device that removes gaseous pollutants from the combustion gases of burning fuels, typically by spraying into the gases a mixture of water and special chemicals (like lime or limestone) that will absorb the pollutants. Scrubbers are primarily used to remove sulfur pollutants from the combustion gases of coal burning.

SUBBITUMINOUS COAL: A dull, black coal often referred to as black lignite. It is used for generating electricity and space heating. It ranks between bituminous and lignite and is mined in the western U.S.

TURBINE: A machine that has propellar-like blades which can be moved by flowing gas (such as steam or combustion gases) to spin a rotor in a generator to produce electricity.

UNIT TRAIN: A train, typically consisting of approximately 100 cars, which is dedicated to the transport of a single commodity such as coal.

WELL: A hole drilled or bored into the earth, usually cased with metal pipe, for the production of gas or oil. A hole for the injection under pressure of water or gas into a subsurface rock formation.

WORKOVER: Operation on a shut-in or producing well to restore or increase its production.