Glossary of Terms


Acid A generic term used to describe a treatment fluid typically comprising hydrochloric acid and a blend of acid additives
Annulus The space between a casing string and the borehole or between two casing strings
Aquifer A water-bearing stratum of permeable rock, sand or gravel
Biocide An additive that eliminates bacteria in the water that produce corrosive by-products
Blender The equipment used to prepare the slurries and gels commonly used in fracture stimulation treatments
Borehole The hole drilled into the earth
Breaker An additive that reduces the viscosity of fluids by breaking long-chain molecules into shorter segments
CAS Chemical Abstract Service
Casing A steel tubular placed in a borehole
Cement A mixture of sand, water and a binding agent with no aggregates
Cement Bond Log A geophysical log that graphically displays the bond between cement and casing
Clay stabilizer An additive that prevents clays from swelling or shifting
Conductor casing The first casing string placed in a borehole.  The purpose of conductor is to prevent the collapse of the hole in unconsolidated material such as soil
Corrosion inhibitor An additivie used in acid treatments to prevent corrosion of tubulars by the corrosive treating fluid
Crosslinker An additive that reacts with multiple-strand polymers to couple the molecules, creating a fluid of high but closely controlled viscosity
Darcy's law The mathematical equation which quantifies the ability of fluid to flow through porous material such as rock
Data van The truck used to monitor all aspects of the hydraulic fracturing job
DOE U.S. Department of Energy
Drilling rig The equipment used to drill the borehole
EPA U.S. Environmental Protection Agency
EPCRA Emergency Planning and Community Right to Know Act
Frac tank The container used to store water or proppant that will be used for hydraulic fracturing
Friction reducer An additive used to reduce the friction forces on tools and tubulars in the wellbore
Gelling agent An additive that increases the viscosity of a fluid without substantially modifying its other properties
Groundwater Water in the saturated zone in the subsurface
GWPC Ground Water Protection Council
Hydrology The study of the flow of water
Intermediate casing A casing string sometimes used where needed for pressure control or additional isolation of formations such as coal.
IOGCC Interstate Oil and Gas Compact Commission
MSDS Material Safety Data Sheet
Natural gas Methane CH4 (With or without impurities such as Nitrogen).  Natural gas is often classified as either biogenic (of biological origin), or thermogenic (of thermal or heat origin)
NGWA National Ground Water Association
Oxygen scavenger An additive that prevents corrosion of tubulars by oxygen
Packer A downhole device used in completions to isolate the casing-tubing annulus from the production conduit, enabling controlled production, injection or treatment.
Permeability A number expressed in darcies or millidarcies that describes the directional ability of a porous material to allow the flow of fluid.  Rocks have vertical, horizontal and tangential permeability.
pH adjusting agent An additive that adjusts the acidity/ alkilinity balance of a fluid
Production casing The casing string set near the bottom of a completed borehole through which oil or natural gas is produced
Proppant Solid material such as Silica sand which is used to hold or "prop" open fractures
Reservoir A bed of rock containing oil or natural gas
Saturated zone The subsurface zone where the interstitial spaces of rock are filled with water
Shale A fine grained sedimentary rock that may contain oil or natural gas but which may not be producible naturally
Site The location of a well including the area used for fluid storage and well treatment
Spring The intersection of groundwater and surface water 
Surface casing The casing string set below fresh water aquifers to prevent their contamination
Surfactant A chemical that acts as a surface active agent. This term encompasses a multitude of materials that function as emulsifiers, dispersants, oil-wetters, water-wetters, foamers and defoamers.
Toxicology The study of symptoms, mechanisms, treatment and detection of poisoning
TRI Toxic Release Inventory
Tubing A string of casing not typically cemented into a hole but which may be used to carry produced oil or natural gas from the subsurface
Unsaturated zone The subsurface zone where the interstitial spaces of rock contain but are not completely filled with water
Vadose zone The subsurface zone between the surface and the unsaturated zone through which water travels
Variable Density Log The geophysical log the is a graphic representation of the bond between the cement and the borehole
Wellbore See borehole

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