Texas Tech University

Hydraulic Fracturing Key Terms

Acronym Definition
AU Assessment Unit
API American Petroleum Institute
BBO Billions of Barrels of Oil
BBOE Billions of Barrels of Oil Equivalent
BCF Billion Cubic Feet
BLM Bureau of Land Management
BOEM Bureau of Ocean Energy Management
BSEE Bureau of Safety and Environmental Enforcement
BTU British Thermal Unit
DOE Department of Energy
DOI Department of Interior
EIA Energy Information Administration
EPA Environmental Protection Agency
EPCA Energy Policy and Conservation Act
MBO Thousand barrels of oil
MMBO Million barrels of oil
NGL Natural Gas Liquids
NOGA National Oil and Gas Assessment
NPRA National Petroleum Reserve Alaska
OCS Outer Continental Shelf
PRB Powder River Basin
TCF Trillion Cubic Feet
TPS Total Petroleum System
USGS United States Geological Survey
Energy Glossary Term Definition
Accumulation A pool of petroleum locally confined by subsurface geologic features.
API gravity (American Petroleum Institute gravity) A measure of how heavy or light a petroleum liquid is compared to water. If its gravity is greater than 10, it is lighter and floats on water; if less than 10, it is heavier and sinks. It is used to compare the relative densities of petroleum liquids.
Aquifer A formation, group of formations, or part of a formation that contains sufficient saturated permeable material to yield significant quantities of water to wells and springs.
Barrels of Oil Equivalent (BoE) A unit of petroleum volume in which the gas part is expressed in terms of its energy equivalent in barrels of oil.
BTU (British Thermal Unit) The amount of heat needed to raise the temperature of one (1) pound of water by one (1) degree Fahrenheit. The BTU is also used to measure the energy content of various fuels.
Continuous Oil Accumulation A “continuous” or “unconventional” oil accumulation means that the oil resources is dispersed throughout a geologic formation rather than existing as discrete, localized occurrences, such as those in conventional accumulations. Unconventional resources often require special technical drilling and recovery methods.
Crude Oil A mixture of liquid hydrocarbons that exists in natural underground reservoirs as distinguished from refined oils manufactured from it.
Drainage The manner in which the water of an area passes or flows off by surface streams or subsurface conduits.
Enhanced Oil Recovery Injection of steam, gas, or other chemical compounds into hydrocarbon reservoirs to stimulate the production of usable oil beyond what is possible through natural pressure, water injection, and pumping at the wellhead.
Field An accumulation, pool, or group of pools of hydrocarbons or other mineral resources in the subsurface. A hydrocarbon field consists of a reservoir with trapped hydrocarbons covered by impermeable sealing rock, or trapped by hydrostatic pressure.
Fossil Any remains, trace, or imprint of a plant or animal that has been preserved in the Earth’s crust since some past geologic or prehistoric time. Fossils are found in sedimentary rocks.
Fossil Fuel Any hydrocarbon that may be used for fuel: chiefly oil, natural gas, and coal.
Gas Also known as natural gas, is a naturally occurring hydrocarbon gas mixture consisting primarily of methane with up to 20 percent of other hydrocarbons as well as impurities in varying amounts.
Gas Hydrates Gas hydrates are naturally occurring “ice-like” combinations of natural gas and water that have the potential to provide an immense resource of natural gas from the world’s oceans and polar regions. It is generally accepted that the volume of natural gas contained in the world's gas hydrate accumulations greatly exceeds that of known gas reserves.
Gas:Oil Ratio (GOR) Ratio of gas to oil (in cubic feet per barrel) in a hydrocarbon accumulation. GOR is calculated by using volumes of gas and oil at surface conditions.
Gas Reservoir A subsurface accumulation of hydrocarbons primarily in the gas phase that is contained in porous or fractured rock formations. A gas accumulation is defined by the USGS as having a gas:oil ratio of 20,000 cubic feet per barrel or greater.
Heavy Oil Any type of crude oil which does not flow easily. It is referred to as “heavy” because its density or specific gravity is higher than that of light crude oil.
Hydraulic Fracturing A well development process that involves injecting water under high pressure into a bedrock formation via the well. This is intended to increase the size and extent of existing bedrock fractures.
Hydrocarbon Any organic compound, gaseous, liquid, or solid, consisting solely of carbon and hydrogen.
Light Crude Liquid petroleum that has a low density and flows freely at room temperature.
Methane A colorless, odorless gas, the simplest paraffin hydrocarbon. It is the principal constituent of natural gas and is also associated with crude oil.
Natural Gas Hydrocarbons that exist as a gas or vapor at ordinary pressure and temperature.
Natural Gas Liquids Those hydrocarbons in natural gas that are separated from the gas as liquids through the process of absorption, condensation, or other methods in gas processing or cycling plants.
Oil A naturally occurring complex liquid hydrocarbon, which after distillation and removal of impurities yields a range of combustible fuels, petrochemicals, and lubricants.
Oil Reservoir A subsurface accumulation of hydrocarbons composed primarily of oil that is contained in porous or fractured rock formations.
Oil Sands A combination of clay, sand, water, and bitumen, a heavy black viscous oil. Oil sands can be mined and processed to extract the oil-rich bitumen, which is then refined into oil.
Oil Shale A kerogen-bearing, finely laminated brown or black sedimentary rock that will yield liquid or gaseous hydrocarbons on distillation.
Permeability A measure of the ability of a rock to permit fluids to be transmitted through it; it is controlled by pore size, pore throat geometry, and pore connectivity. Permeability is typically reported in darcy units.
Petroleum A general term for all naturally-occurring hydrocarbons, whether gaseous, liquid, or solid.
Produced Water A term used to describe water that is produced along with oil and gas.
Reservoir A subsurface, porous, permeable rock body in which oil and/or gas have accumulated.
Shale Gas Natural gas that can be generated and trapped within shale units.
Shale Oil Liquid petroleum that can be generated and trapped within shale units.
Source Rock Rocks containing relatively large amounts of organic matter that is transformed into hydrocarbons.
State Waters State jurisdiction begins at the established baseline for the coast and extends 3 geographic (nautical) miles.
Structural Basin A large-scale structural formation of strata formed by tectonic down warping. Structural basins may be sedimentary basins, which are aggregations of sediment that filled a depression.
Sweet Crude Petroleum is considered “sweet” if it contains less than 0.5% sulfur compared to a higher level of sulfur in sour crude oil.
Tight Gas Natural gas trapped in a highly mixed mineralogy sandstone, shale, or limestone formations which has very low permeability and porosity.
Total Petroleum System (TPS) The essential elements (source, reservoir, seal, and overburden rocks) and processes (generation-migration-accumulation and trap formation) as well as all genetically petroleum that occurs in seeps, shows, and accumulations (discovered and undiscovered) whose provenance is a pod or closely related pods of active source rock.
Trap A geologic feature that permits the accumulation and prevents the escape of accumulated fluids (hydrocarbons) or injected carbon dioxide from the reservoir.