Produced Water Glossary of Terms and Acronyms

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Aquifer storage and recovery (ASR): ASR is a process in which clean water is injected into a shallow aquifer, stored for some period of time, and then withdrawn for later use.

Barrel (bbl): In U.S. oil and gas operations, volumes of oil and water are traditionally expressed using the unit of barrels. 1 bbl = 42 U.S. gallons.
bcf: billion cubic feet, a unit of measure for natural gas production
Beneficial use: This term is used here to describe a secondary use or reuse of produced water for a purpose that has a positive value to some entity or to the environment. This website describes a variety of potential beneficial uses for produced water.
Bin: Bin is used to describe a unit of subdivision within a ranking scale. For example, bins established for different concentration ranges of total dissolved solids are used as part of the decision process in this website.
Biocide: Biocides are chemicals added to a process to control microbial growth. Biocides are often injected into oil and gas wells to prevent growth of organisms that could cause corrosion within the well. Biocides may end up in produced water.
Brine: Brine is another term sometimes used for produced water. Most produced water samples are at least partially salty, giving rise to the term "brine".

Casing: Casing is the pipe used to line oil and gas wells. Most wells are constructed using several concentric sets of casing. Once a section of well is drilled, casing is inserted into the well, and it is cemented into place.
Cement: Following placement of casing in a well, cement is pumped into the annular space between the casing and the rock wall of the well. Cement is used to create and impermeable seal in the annular space that blocks vertical migration of fluids.
Chemical additives: During well drilling and production, various types of chemicals may be injected into a well to control undesirable chemical or biological processes. Examples of chemical additives are biocides, corrosion inhibitors, scale inhibitors.
Coal bed methane (CBM): Methane is generated during coal formation and is contained in the coal microstructure. Typical recovery entails pumping water out of the coal to allow the gas to escape. Methane is the principal component of natural gas.
Concentrate: Concentrate refers to one of two byproducts resulting from treatment of salty water or produced water. One of the byproducts is clean water, while the other byproduct contains all the salt and other contaminants removed by the treatment process. The levels of these parameters are higher in the concentrate than they were in the untreated water.
Condensate: Condensate is a natural gas liquid recovered from gas wells from lease separators or field facilities. It is light in density and is similar to gasoline.

Electrical conductivity: Conductivity is easily measured with a meter. It can be correlated to the total dissolved solids or salinity of a water sample.

Frac flowback water: Frac flowback water is water that has been injected into a formation under high pressure for hydraulic fracturing, and then returns to the surface. Much of the flowback returns to the surface within the first few days or weeks following the hydraulic fracturing job. Smaller volumes of flowback may return to the surface over many months.

Hydraulic fracturing (frac job): Hydraulic fracturing is a process used to prepare or stimulate a formation to produce more hydrocarbons. A combination of fluid and proppant (usually sand) is injected through a well into a producing formation. The pressure is raised to a level high enough that the formation near the well develops cracks or fractures. The frac fluid and proppant enter the fractures. When the pressure is dropped later, most of the liquid (frac flowback water) returns to the surface. However, the proppant remains in the fractures and holds them open, thereby allowing the oil or gas to flow more freely to the production well.
Hydrostatic pressure: Hydrostatic pressure is the fluid pressure in a formation caused by the weight of overlying fluids.

Impoundment: An impoundment is a pond in which CBM produced water is stored or allowed to infiltrate to the subsurface. There are several terms for these impoundments: "holding ponds", "zero discharge ponds" or "infiltration ponds". Although they do not directly discharge water on the land surface, most impoundments are not lined and do discharge to the subsurface. Some percentage of seepage flow from impoundments is likely to reach stream channels via subsurface flow.
Injection well: The U.S. EPA defines injection well as any bored, drilled or a driven shaft or a dug hole, where the depth is greater than the largest surface dimension that is used to inject fluids underground. Class II injection wells are used to inject produced water into the ground, inject other fluids underground to increase the recovery of hydrocarbons, or to store hydrocarbons underground.

Mcf: thousand cubic feet, a unit of measure for natural gas production
Mmcf: million cubic feet, a unit of measure for natural gas production

Natural gas: gaseous mixture of hydrocarbon compounds, the primary one being methane.
NORM (naturally occurring radioactive material): Some hydrocarbon bearing formations contain naturally occurring radionuclides. Crude oil, natural gas, or produced water may contain small quantities of NORM as a result of being in contact with the formation rock for many years. Typically, the concentrations of NORM in oil, gas, or water are not high enough to cause concern. However, NORM can accumulate in pipe scale or tank sludges.
NPDES: This term refers to the National Pollutant Discharge Elimination System regulatory program. NPDES permits are issued by states or EPA to regulate discharges of wastewater to surface water bodies.

Oil: Oil refers to mixture of hydrocarbons usually existing in the liquid state in natural underground pools or reservoirs. Gas is often found in association with oil.
Oil and grease: Oil and grease refers to a mixture of organic compounds that are measured using a common analytical test. There is no individual chemical called "oil and grease". Oil and grease is frequently limited in NPDES permits for discharges of produced water.

Permeability: Permeability refers to the ease at which fluids can move through the pores of a rock formation.
Primacy: Under some federal regulatory programs, like NPDES and UIC, states can petition EPA to gain the authority to administer the program at the state level. When a state receive authority to administer the program, the state has primacy for the program.
Produced water: Produced water is water trapped in underground formations that is brought to the surface during oil and gas exploration and production.

Residual: Residual refers to a solid or semi-solid byproduct resulting from wastewater or produced water treatment.
Reuse: Reuse in the context of this website refers to collecting water from natural gas production, treating it if necessary, and putting the water to another use.

Salinity: Salinity is a measure of salt content in a water sample. Salinity can also be expressed as total dissolved solids or electrical conductivity. High salinity waters cannot be put to beneficial reuse with first treating the water to remove some of the salt.
Saltwater: Saltwater is another term used interchangeably for produced water or brine.
Sodium adsorption ratio (SAR): SAR measures the relationship between sodium concentration vs. calcium and magnesium concentration. In equation form, SAR = Na⁺¹ / [(Ca⁺² + Mg⁺²)/2]^0.5.
Sodicity: Sodicity is a measure of the sodium concentration in a water sample.

Tcf: trillion cubic feet, a unit of measure for natural gas production
Total dissolved solids (TDS): TDS is an analytical test that can be easily correlated to salinity. Because the measurement can be made easily, it is often used as a regulatory limit.
Tubing: Tubing is the innermost layer of piping in an oil or gas well (see casing). Typically, production of oil and gas occurs through the tubing

UIC: This term refers to the Underground Injection Control regulatory program. UIC permits are issued by states or EPA to regulate injection of fluids to underground formations.

Water rights: Water rights represent legal authorizations to withdraw and/or use natural water resources from both surface water and ground water. Water rights are administered throug state laws. Several different systems for assigning water rights can be found throughout the United States. Each state has its own unique way of allocating and sharing water.