Term Description
Abandoned well A well that is not in use because it was drilled as a dry hole or has ceased to produce or for some other reason cannot be operated.
Annulus The space between two concentric cylinders or pipes.
Aquifer A subsurface water bearing geological strata which has high porosity and permeability that allows easy extraction of the water.
Artesian Water bores in which the water surface is above ground level and the water flows.
Base load The minimum amount of electric power delivered or required over a given period of time at a steady rate.
Blowout An uncontrolled flow of gas (oil or other well fluids) occurring when formation pressure exceeds the pressure applied to it by the column of drilling fluid.
Borehole The hole or shaft in the earth made by a well drill; also, the uncased drill-hole from the surface to the bottom of the well.
Casing Pipe cemented in an oil or gas well to seal off formation fluids and to keep the borehole from caving in. Smaller diameter “strings” of casing are cemented inside larger diameter strings as a well is deepened.
Complete a well To finish work on a well and bring it to productive status.
Conventional natural gas reservoir
A geological formation in which the natural gas is in interconnected pore spaces, much like a kitchen sponge, that allows easier flow to a well.
Downstream A term used most commonly in the petroleum industry to describe post production processes (e.g. refining and marketing sectors of the petroleum industry).
Term Description
Drilling rig Usually a large-standing structure employing a drill that creates holes or shafts in the ground for purposes of accessing and producing natural gas or oil from subsurface deposits.
Exploration The act of searching for potential sub-surface reservoirs of gas or oil. Methods include the use of magnetometers, gravity meters, seismic exploration, surface mapping, and the drilling of exploratory test wells.
Flaring The controlled burning of natural gas that can’t be processed for sale or used because of technical or economic reasons.
Flowback Water used as a pressurised fluid during hydraulic fracturing that returns to the surface via the well. This occurs after the fracturing procedure is completed and pressure is released.
Formation A body of earth material with distinctive and characteristic properties and a degree of homogeneity in its physical properties.
Formation water Water that occurs naturally within the pores of a water- bearing rock formation. Oil and gas reservoirs have a natural layer of formation water that lies underneath the hydrocarbons.
Fracking (Hydraulic fracturing) The fracturing of rock with a liquid under high pressure to create artificial openings and cracks in the rock to increase the rock’s permeability.
Fracturing fluid The primarily water-based fluid used to fracture shale. It is basically composed of 99% water, with the remainder consisting of sand and various chemical additives.
Fracturing fluid is pumped into wells at very high pressure to break up and hold open underground rock formations, which in turn releases natural gas.
Fugitive emissions A primary air quality concern from natural gas production (including shale gas) is leaking and venting throughout the supply chain. These fugitive emissions a potentially result in releases of methane, the primary constituent of natural gas and a potent greenhouse gas. In addition, fugitive emissions of natural as can release volatile organic compounds and hazardous air pollutants, according to the study.
Term Description
Gas turbine plant A plant in which the prime mover is a gas turbine. A gas turbine consists typically of an axialflow air compressor and one or more combustion chambers where liquid or gaseous fuel is burned and the hot gases are passed to the turbine and where the hot gases expand drive the generator and are then used to run the compressor.
Gas-in-place The volume of gas in a reservoir at any given time, calculated at standard temperature and pressure conditions, that includes both recoverable and non- recoverable gas.
Grid The layout of an electrical distribution system.
Groundwater All subsurface water as distinct from surface water. More specifically, the part of the subsurface water that is in the zone of saturation.
Horizontal drilling Drilling into the earth in an initially vertical direction, followed by a change in drilling direction to the horizontal at a suitable depth.
Hydraulic
fracturing ('Fracking') The fracturing of rock with a liquid under high pressure to create artificial openings and cracks in the rock to increase the rock’s permeability.
Independent
power producer Corporation, person, agency, authority, or other legal entity or instrumentality that owns or operates facilities for the generation of electricity for use primarily by the public, and that is not an electric utility.
Manufactured gas A gas obtained by destructive distillation of coal or by the thermal decomposition of oil, or by the reaction of steam passing through a bed of heated coal or coke. Examples are coal gases, coke oven gases, producer gas, blast furnace gas, blue (water) gas, carburetted water gas. Btu content varies widely.
Market-based
pricing Prices of electric power or other forms of energy determined in an open market system of supply and demand under which prices are set solely by agreement as to what buyers will pay and sellers will accept.
Such prices could recover less or more than full costs, depending upon what the buyers and sellers see as their relevant opportunities and risks.
Microseismic A faint movement of the earth.
Mud (drilling) Fluid circulated down the drill pipe and up the annulus during drilling operations to remove cuttings, cool and lubricate the bit and maintain a desired pressure in the well.
Term Description
Natural gas A naturally occurring mixture of hydrocarbon and non- hydrocarbon gases beneath the surface, the principal component of which (50-90%) is methane.
Oil shale Shallow shale containing oil. Mined by conventional methods and retorted at high temperature at the surface to distil the contained oil, or by in situ treatment with steam. Should not be confused with “shale oil”, which is oil contained in the natural gas extracted from deep shales.
Operating costs Costs associated with a company’s operations that are deducted against revenue to determine profit.
Permeability The ability, or measurement of a rock’s ability, to transmit fluids, typically measured in darcies or millidarcies.
Porosity The interconnection of pores within a rock; also a measure of the flowability of a fluid within a rock that contains pores.
Produced water Naturally occurring water found in shale formations; it generally flows to the surface during the entire lifespan of a well, often along with natural gas.
Proppant A granular substance, often sand, that is mixed with and carried by fracturing fluid pumped into a shale well. Its purpose is to keep cracks and fractures that occur during the hydraulic fracturing process open so trapped natural gas can escape.
Reserve Those reserves recoverable under current technology and present and anticipated economic conditions. Also a term commonly used in reference to total proved reserves plus half probable reserves.
Reservoir Rock strata that contains liquid or gas within its porosity; not a large void space or cavern under the earth.
Shale A rock structure beneath the earth’s surface formed from mud deposited by riverine, lake or marine systems over geological timescales.
Shale gas Natural gas produced from shale formations.
Shale gas play A set of discovered, undiscovered or possible natural gas accumulations that exhibit similar geological characteristics. Shale plays are located within basins, which are large-scale geologic depressions, often
hundreds of miles across, which also may contain other oil and natural gas resources.
Slickwater Hydraulic fracturing water whose properties (e.g. surface tension) have been modified through the use of additives.
Term Description
Surface water Water that is open to the atmosphere, such as rivers, lakes, ponds, reservoirs, streams, impoundments, seas and estuaries.
Tight gas Natural gas found in low-permeability sandstones and carbonate reservoirs. The rock layers that hold the gas are very dense, preventing easy flow.
Unconventional natural gas reservoir
Coal bed methane, shale or tight gas, where the natural gas does not flow naturally to the well, but instead requires some form of extensive stimulation to generate economic flow rates.
Underground
injection Hazardous waste deposited by force and under pressure into an underground steel and concrete-encased shaft for storage or disposal.
Upstream The sector of the petroleum industry involving exploration and production.
Well completion A well where operations have advanced to a stage where it is ready to produce oil or gas.
Well pad A temporary drilling site to prepare a targeted location for production. The well pad is the area of cleared land, which may be from one to less than five acres. The well pad is covered with lining material to prevent seepage into the ground and the drilling rig is constructed over the pad area. When the well is completed, the drilling rig is replaced by the well-head.
Well stimulation A treatment performed to restore or enhance the productivity of a well.
Well-bore The drilled hole or borehole, including the open-hole or uncased portion of the well.
Well-head The equipment at the surface above the well.