A B C D E F G H I J K L M N O P Q R S T U V W X Y Z   Energy Units



API gravity – The gravity or density of liquid petroleum products devised jointly by the American Petroleum Institute and the NIST – National Institute of Standards and Technology. The measuring scale is calibrated in terms of degrees API.

API Number – American Petroleum Institute Number; an identification number assigned to every oil and gas well in the United States.

Degree API Specific Gravity Weight
    (lb/US gal) (kg/m3)
8 1.014 8.448 1012
9 1.007 8.388 1005
10 1.000 8.328 998
15 0.966 8.044 964
20 0.934 7.778 932
25 0.904 7.529 902
30 0.876 7.296 874
35 0.850 7.076 848
40 0.825 6.870 823
45 0.802 6.675 800
50 0.780 6.490 778
55 0.759 6.316 757
58 0.747 6.216 745



Amine Treating – The removal of impurities, such as water, sulfur compounds, carbon dioxide and nitrogen. The amine treating process involves a continuous circulation of a liquid chemical called amine that physically contacts with the natural gas. The gas and amine are separated and the impurities are removed from the amine by heating. Amine treating plants are sized according to the amine circulation rate in terms of gallons per minute (GPM).

Associated Natural Gas –
Natural gas that occurs in crude oil reserves as free gas.

Back To Top



Bottom Hole Pressure – The pressure, in pounds per square inch (PSI), in an oil or gas reservoir. If the bottom hole pressure is more than the hydrostatic head, the well should flow.


Butane – (C4H10) – A normally gaseous hydrocarbon extracted from natural gas or refinery gas streams. It includes isobutene and normal butane. Butane is used primarily for blending in high-octane gasoline, for residential and commercial heating, and in the manufacturing of chemicals and synthetic rubber.

Back To Top



Casing Bond Log (CBL) – test run to determine if there is a good bond with the cement and the production casing.


Compressed Natural Gas (CNG) – Natural gas that has been compressed to less than 1% of the volume it occupies at standard atmospheric pressure. CNG is the primary fuel used in natural gas-powered vehicles.

Compression –
Compression is used to maximize natural gas and crude oil production by increasing the pressure of the gas or liquid by reducing its volume, thereby allowing it to be transported along a pipe.

Condensate –
The liquid resulting when a vapor is subjected to cooling or pressure reduction.

Back To Top



Dehydration – The process during which water is removed from the gas; also called Glycol Absorption.


Dipmeter – A well log used to determine the angle or slope of the reservoir rock within the different beds, or layers in the well. This is accomplished by using a borehole scanner with sound waves to make a detailed, 360 degree, 3-D image of the rock of the well bore.


Drawdown – When a well is flow tested, the choke is gradually opened to increase the flow rate until a “drawdown” is seen, which means the pressure begins to decline. The drawdown is part of the criteria the petroleum engineers use to calculate optimum production rates and the size of the reservoir.


Drill Collars – When drilling, the drill pipe is in tension, not compression. The drilling rig supports most of the weight of the drill pipe with only a fraction of the total weight on the bit. To accomplish this, heavy-weight drill collars are placed right behind the drill bit to keep the drill pipe in tension. Placing the full weight of the drill pipe on the bit would very simply destroy it.


Drive Pipe/ Conductor Pipe – Pipe that is literally driven into the ground, to very shallow depths, to create a starter hole for the drilling rig to follow as a guide for initial drilling.

Dry Gas –
Natural gas that contains few or no liquefiable liquid hydrocarbons. Dry gas is also called “lean gas.”


Dry Hole Tree – A one-valve well head installed after the cement job, when no perforations are present, to prevent accidental flow and keep unwanted debris out of the well bore.

Back To Top



EIA – Energy Information Administration – An agency of the federal government which, among other things, is the chief federal statistical service for energy information.


Elevators – The tools on the travelling block used to lift each joint of pipe to be raised or lowered into the well.

Environmental Protection Agency – A federal agency charged with protecting the environment.

Ethane –
Ethane is primarily used in the petrochemical industry as feedstock for ethylene, one of the basic building blocks for a wide range of plastics and other chemical products.

Ethylene –
Ethylene is primarily used as a petrochemical feedstock in production of chemicals and plastics, and as a solvent in enhanced oil recovery processes.

Back To Top



Fault Block – An oil or gas reservoir that is bounded on all sides by faults trapping the oil or gas in a "fault block."


Fee-based Contract – A contractual arrangement under which a company receives a set fee for gathering, processing, treating or transporting natural gas. Therefore, revenues generated under fee-based contracts are less dependent on commodity prices.

Federal Energy Regulatory Commission – The regulatory arm of the Department of Energy that is responsible for overseeing the regulation of natural gas and electrical jurisdictional activities. For the natural gas industry, this includes regulation of the operation of interstate pipelines, including the rates charged, determining the prudency of pipeline expansion projects.

Firm Service (FT) –
Transportation service offered to customers under schedules or contracts on a guaranteed basis.


Fish – A dropped or stuck section of pipe or tool to be removed from the well bore.


Fishing – Attempting to retrieve a dropped or stuck section of pipe or tool to be removed from the well bore.


Formation Density Compensated (FDC) – Also known as density logs, these well logs determine porosity by measuring the density of the reservoir rock.


Formation Water – Salt water produced from an oil or gas well.

Frac Spread –
The difference between the sales price of natural gas liquids and the cost of natural gas.

Fracking –
The process of pumping crude oil, diesel, water or chemicals into a reservoir with such force that the reservoir rock is cracked and results in greater flow of oil or gas from the reservoir.

Fractionation –
The separation of the mixed natural gas liquids (NGL) stream into saleable NGL products: ethane, propane, normal butane, isobutane and natural gasoline.

Freeze-off –
Occurs at the wellhead when the water exiting the well with the natural gas freezes during cold weather. When this occurs, production from the well is halted and it is shut in until the water thaws.


Flowing Tubing Pressure (FTP) – The pressure (PSI) measured at the well head, indicating the pressure of the oil and/or gas flowing to the production equipment.

Back To Top



Gamma Ray (GR) – Well logs that measure radioactivity to determine what types of reservoir rocks are present in the well. Because shale contains radioactive elements, it emits a lot of gamma rays. Conversely, clean productive sandstones emit very few gamma rays.

Back To Top



Hydrochloric Acid (HCL) – acid used to dissolve limestone rock to liberate trapped oil and/or gas.


Heater Treater/Separator – Surface well equipment used to separate oil, gas and water to the proper facilities.


Hydraulic Fracturing (Fracking) – A stimulation technique intended to improve the permeability of oil and/or gas wells.


Hydrill – Part of the Blow Out Preventer system.


Hydrocarbon – An organic compound that consists entirely of hydrogen and carbon, the majority of which are found in crude oil.


Hydrostatic Head – The weight of a fluid in a column. 0.52 is a constant for determining the hydrostatic head of a particular fluid. For example, water weighs 8.33 pounds per gallon (PPG). 8.33 PPG times 0.52 = .433 pounds per foot. A well drilled to 10,000 feet times .433 pounds per foot = 4,333 pounds per square inch of hydrostatic head.

Back To Top



Interruptible Service (IT) – Low-priority or non-guaranteed transportation service offered to customers under schedules or contracts in which interruptions are anticipated or allowed on short notice, by reason of the claim of firm service customers and higher priority users (IT generally occurs during peak seasons).

Interstate –
A natural gas pipeline engaged in the transportation of natural gas across state boundaries and is therefore subject to the jurisdiction of the Federal Energy Regulatory Commission (FERC).

Intrastate –
A natural gas pipeline engaged in the transportation of natural gas within a single state. Intrastate pipelines are not subject to the jurisdiction of the Federal Energy Regulatory Commission (FERC).


Initial Production (IP) – The initial production rate of an oil or gas well. Generally speaking, the daily production rate would be 1/3 to 1/4 the initial production rate.

Isobutane –
Isobutane is typically fractionated from mixed butane (a stream of normal butane and isobutane in solution), principally for use in enhancing the octane content of motor gasoline.

Back To Top



Joint – Any single piece of drill pipe, casing or tubing.

Back To Top



Keep Whole Contract – A contractual arrangement in which the plant owner/operator processes a party’s gas and pays the producer the full thermal equivalent volume of raw natural gas received from the producer in processed gas, or its cash equivalent.


KCL – Typically described as 2% or 3% KCL fluid, KCL is water with potassium chloride (salt) added which prevents clays encountered while drilling from swelling.


Kelly – A square section of drill pipe that fits into the square hole on the drilling rig rotary table which rotates and turns the drill pipe and drill bit.


Kill Well – Pump drilling mud or water into a well to keep it from flowing.

Back To Top



Laminated Sands – A potentially productive oil or gas sand is laminated when the sand is not homogenous, that is laminated by shale sections within the sand that are non-productive.


Lay Down (L/D) – The laying down of pipe or tools pulled from the well bore on racks at ground level.


LCM Pill – A slug of high-viscosity gel that contains material to stop or slow down lost circulation of drilling mud. Cotton seed hulls, pecan shells, and plastic insulation stripped off of electric wiring are often used as lost circulation material. These materials tend to flow to wherever the drilling mud is flowing out into the formation.


Lean Gas – Natural gas that contains few or no liquefiable liquid hydrocarbons. Lean gas is also called “dry gas.”

Liquefied Natural Gas (LNG) –
Natural gas that has be liquefied by reducing its temperature to -260 degrees Fahrenheit at atmospheric pressure. LNG is also used in natural gas-powered vehicles, though less commonly than compressed natural gas (CNG).


Load Water – Water pumped into the well during drilling and completion operations.


LWD (Logging While Drilling) and MWD (Measurement While Drilling) – The placement of the logging tool right behind the drill bit to record data during the drilling of the well in real time.

Long –
A position of a party who has bought and is holding futures or options contracts or owns a commodity that has not been settled by sale or delivery.

Looping –
A looped pipeline runs parallel to another pipeline and both provide the same gas or liquid to the final destination.


Lost Circulation – When drilling, drilling mud is pumped down the center of the drill pipe and "U-Tubes" up the outside of the drill pipe to lubricate the bit and circulate cuttings to the surface. Good circulation means the drilling mud is seen returning to the surface. Lost circulation means the mud is not returning to the surface and is being lost into the formation.

Back To Top



MCF – 1000 Cubic Feet; natural gas is priced per 1000 cubic feet of gas.


MCFGPD – 1000 Cubic Feet of Gas Per Day.


Methane – The major portion of natural gas.


MIRU (Move in and rig up) – Move equipment to well location and prepare to begin work.


Mouse Hole – A hole drilled next to the drilling rig to have the next joint of drill pipe staged in a vertical position and ready to go.


Mud Logger – Takes physical samples of the cuttings from drilling the well as they are circulated to the surface. These cutting samples are analyzed so the geologist can determine the strata being drilled through and compare the results to other wells in the area.


Mud Motor – When drilling horizontally, because of the curve of the drill pipe to “get horizontal,” it is not possible to rotate the pipe. Drilling mud is pumped through the center of drill pipe which operates a hydraulic motor (mud motor) on the end of the drill pipe which turns just the drill bit, not the pipe.

Back To Top



Natural Gas – Natural gas is a naturally occurring mixture of hydrocarbons and non-hydrocarbon gasses found in porous underground rock. Natural gas deposits are formed when gas becomes trapped underground by other solid rocks that the gas cannot pass through. The primary component of natural gas is methane.

Natural Gasoline –
A mixture of pentanes and heavier hydrocarbons used primarily as motor gasoline blend stock or petrochemical feedstock.

Natural Gas Condensate –
Also known simply as condensate or liquids, is a low density, high gravity mixture of hydrocarbon liquids present in natural gas. Typically, condensate requires a less rigorous refining process than crude oil, which makes it more valuable.

Natural Gas Liquids (NGLs) –
Liquid products separated from natural gas during natural gas processing, including propane, butane, ethane and natural gasoline.

Natural Gas Processing –
The separation of natural gas into pipeline-quality natural gas and a mixed natural gas liquid (NGL) stream through some type of absorption or cryogenic process. The heavier components are typically ethane, propane, isobutene, normal butane and natural gasoline.


ND BOP – Nipple Down Blow Out Preventer; Uninstall the Blow Out Preventer.


Net Pay – The "net" productive section of an oil or gas formation. The formation drilled through may be 20' thick, with 12' considered productive.

Non-hydrocarbon Gases –
Typically, non-hydrocarbon gases are those which may be present in reservoir natural gas, such as carbon dioxide, helium, hydrogen sulfide and nitrogen.

Normal Butane –
Normal butane is used as a petrochemical feedstock in the production of butadiene (a key ingredient in synthetic rubber) and as a blend stock for motor gasoline.


NU BOP – Nipple Up Blow Out Preventer; Install the Blow Out Preventer.


Nuclear Magnetic Resonance (NMR) – Well logs that measure the magnetic response of the fluids present in the pore spaces of the reservoir rock. These logs measure porosity, permeability and the types of fluid of the reservoir rock.


NU Tree – Nipple Up Tree; install the wellhead.

Back To Top



Packer – A tool set at the end of the production tubing which forces oil and gas production up the tubing instead of the casing.


Paraffin – Heavy organics, known as paraffin, exist in all crude oil in various quantities. The paraffin precipitates into a solid wax when the temperature or pressure drops in the well bore. The wax sticks to the walls of the production tubing causing a barrier to the flow of oil. Eventually, the buildup spreads from the well tubing to flow lines and to production separators, pumps, strainers and other fluid-handling equipment creating further operational problems. In extreme cases, oil wells can be completely shut down after being plugged by the paraffin. The paraffin can be removed by physically scrapping it off the affected surfaces or by circulating hot oil to melt the paraffin and circulate it out of the well.


PBTD – When an oil or gas reservoir has been tested and/or produced and the decision is made to move up hole to another potentially productive zone, that section of the well is plugged. This section of the well now has a new plugged back total depth.


Percussion Sidewall Cores – After drilling and logging the well, a physical core sample of potentially productive oil or gas zones will be gathered by using a tool firing into the sidewall of the well bore and bring the cores to the surface for analysis.


Perforating Gun – Perforating guns are lowered into the well by wire line and used to penetrate the production casing and cement in oil and gas wells to allow oil and gas to flow from the reservoir into the well bore. Each perforating gun assembly can measure up to 70 feet in length and weigh in excess of 150 pounds when loaded with explosives. Perforating gun assemblies are commonly housed within hollow thick-walled steel tubes and contain shaped explosive charges. Each individual shaped charge typically contains between 25 and 45 grams of high explosives and is initiated by detonating cord and a detonator. The spent gun is then recovered from the wellbore. Penetration distance through the casing, cement & into the reservoir ranges from 12 inches to 4 feet.


Perforations – Holes punched through the production casing and cement out into the oil & gas reservoir to initiate production. Typically the perforations are 0.5 inches in diameter.


Permeability – The ability of the oil or gas to move through the reservoir from one pore space to another and then to the well bore.


POOH – Pull Out Of Hole; pulling pipe or tools out of the well bore.


POP Contract – A contractual arrangement in which the plant owner/operator gathers raw natural gas from producers at the wellhead, transports it through a gathering system, processes and sells the processed gas and NGLs at prices based on published index prices. In this type of arrangement, the owner/operator retains the sales proceeds, less the amount remitted to producers.


Porosity – The pore space in the rock that contains the oil or gas. 25% porosity in a reservoir indicates that 25% of the rock is pore space.


Power Swivel – Hydraulic power unit mounted on top of pipe which rotates the pipe.


Pounds Per Gallon (PPG) – All fluids are quantified in pounds per gallon to determine the hydrostatic head of the fluid in the well bore. Water weighs 8.33 pounds per gallon.

Processing Plant –
A plant that uses a multi-stage process to purify the gas stream by separating out undesirable components such as water vapor, free liquids, hydrocarbon products such as ethane, propane and butane, and contaminants such as hydrogen sulfide and carbon dioxide.

Propane –
Propane is used both as a petrochemical feedstock in the production of propylene and as a fuel for heating, engines and industrial uses.

Propylene –
Propylene is primarily used in residential and commercial heating and cooling, as well as a transportation fuel and petrochemical feedstock.


Pump Slug – Pumping a slug is a very high viscosity or high mud weight volume of fluid to quickly remove debris from the well bore or to stop fluid loss during lost circulation.

Back To Top



Rabbiting – As each joint of pipe is picked up to be lowered into the well, a metal rabbit about a foot long, approximately the same diameter of the pipe, is dropped through the pipe to check for obstructions.


Rat hole – Typically, a well is drilled 30 to 100 feet deeper than the last potentially productive oil formation, creating a "cellar" for unwanted debris to collect below any future perforations so as not to interfere with production.


RDMO – Rig down and move out; work finished and move equipment off well location.


Resistivity – One method used to determine if a reservoir is oil or gas productive. Oil or gas does not conduct electricity and water does. Small electrical current measures the resistivity of the reservoir. Generally speaking, high resistivity indicates oil or gas, while low resistivity indicates formation (salt) water.


Resistivity Logs – Well logs used to determine what types of fluids are present in reservoir rock by measuring how effective the rock is at conducting electricity. Because freshwater and hydrocarbons (oil and gas) are poor conductors of electricity, they have high resistivity. By contrast, most formation water has a high enough salt content to easily conduct electricity. Therefore, formation water usually has low resistivity.


Reservoir – A rock formation that forms a trap in which oil and natural gas may accumulate.

Rich Gas –
Natural gas that contains heavier hydrocarbons and liquids than a lean gas.


ROP – Rate of Penetration; speed of drilling measured in feet per minute or hour.

Back To Top



Shaker – A vibrating conveyor belt from which samples of the cuttings from drilling are separated from the drilling mud for analysis by the mud logger and geologist.


Shale – Gas reserves found in nonporous rock that require special drilling and completion techniques for extraction of the gas.


Shoe – When casing is cemented after all or part of a well, cement is pumped down the center of the pipe, it hits the bottom of the hole and "U-Tubes" up the outside of the pipe. When complete, the end result is a piece of pipe, full of water with a cement bottom. The cement bottom is known as the shoe.

Short –
Usually the physical sale of a product that will profit from a decrease in prices.

Shut In –
Producers shut down (shut in) the production of a well in response to a number of factors, including weather, commodity prices and infrastructure issues, such as freeze-offs.


Shut In Casing Pressure (SICP) – Oil or gas is produced via the production tubing, typically 2 3/8" diameter, run inside the casing, typically 5 1/3" diameter. The tubing is designed to handle the production pressure and at some point, wear out and be replaced. The casing is the structural foundation of the well and cannot be replaced, so it is important to isolate the casing from wear and tear. Monitoring the Shut in Casing Pressure is critical to the maintenance of the well bore.


SONRIS – The proprietary software program for the State of Louisiana Office of Conservation website.

Sour Gas –
Any natural gas containing more than 1½ grains of hydrogen sulfide per 100 cubic feet, or more than 30 grains of total sulfur per 100 cubic feet. Or, gas which in its natural state is found to be unfit for use in generating light or fuel for domestic purposes.


Spontaneous Potential (SP) – Well logs that indicate the permeability of reservoir rock in a well by measuring the amount of electrical current generated between the drilling mud and the formation water held in the pore spaces of the reservoir rock. Porous sandstones with high permeability tend to generate more electricity than impermeable shale. Therefore, SP logs are often used to differentiate sandstone from shale.


Spud Date – The day a drilling rig starts "digging" the well.


Squeeze Job – Used to repair a cement job when the cement bond log (CBL) determines a poor bond between the pipe, cement, and well bore. A lack of cement (void) indicated by the CBL is perforated and cement pumped (squeezed) into the perforation.


Strapping Pipe – All pipe lowered into an oil and gas well is measured to the nearest 1/10th of an inch.


Stratigraphy – A common goal of stratigraphic studies is the subdivision of a sequence of rock strata into mappable units, determining the time relationships that are involved, and correlating units of the sequence—or the entire sequence—with rock strata elsewhere.


Strip Gun – A disposable perforating gun with the explosive shape charges spaced out on a wire strip, like a pearl necklace. When fired, the strip gun disintegrates and the debris falls into the rat hole.


Swab or swabbing – A method to manually "pump" or test the production rate of an oil well without installing permanent pumping equipment.

Sweet Gas –
Natural gas not contaminated by corrosion-inducing impurities, such as hydrogen sulfide, or with a low level of impurities.

Back To Top



Tailgate – The natural gas line exiting a plant that reintroduces gas back into the pipeline system.

Take In Kind –
The clause in a gas supply contract that allows for a specific period a specified minimum quantity of gas must be paid for whether or not delivery is accepted by the purchaser. Some contracts contain a time period in which the buyer may take later delivery of the gas without penalty.


Total Depth (TD) – The depth of the well.

Throughput –
The maximum amount of natural gas that a pipeline can flow through its system on a firm basis.


Trip In Hole (TIH) – Running pipe and/or tools into the well bore.


TIW Valve – A manually operated valve mounted on the tubing as a temporary shut-off valve.


True Measured Depth (TMD) – The actual depth (length) of the well bore, including all deviations from true vertical depth. A horizontal well may be 6000' true vertical depth with a 3000' horizontal lateral resulting in a true measured depth of 9000'.


Top of Cement (TOC) – After cementing a well bore, there is some cement left inside the pipe. The operator would then go in the well bore to find out exactly where the "top of cement" is to continue operations on the well.


TOF – Top Of Fish; depth of the top of the fish to be removed from the well bore.


TOOH – Trip Out of Hole; pulling pipe or tools out of the well bore.


Triple Combo Log – The Triple Combo Log is designed to measure formation density, porosity, deep/intermediate/shallow resistivity, natural gamma radiation, hole size, and fluid temperature, all in a single logging pass.


True Vertical Depth (TVD) – The depth of the well from the surface, straight down regardless of directional or horizontal deviation.

Back To Top



Wellhead – The topmost point of a well and the structure built over it.

Wet Gas –
Gas produced in association with condensate.


Wing Valves – Side valves used to bleed off pressure or direct flow once the main valves have been closed.


Wireline – Refers to a cabling technology used to lower equipment or measurement devices into the well. Tools inserted into the well for both workover and logging efforts, wirelines and slicklines are very similar devices. While a slickline is a thin cable introduced into a well to deliver and retrieve tools downhole, a wireline is an electrical cable used to lower tools into and transmit data about the conditions of the wellbore called logs.

Back To Top


Bbl – barrel

Bbl/d – barrels per day

Bcf – one billion cubic feet

Bcf/d – one billion cubic feet per day

BTU – British thermal units – A unit of energy needed to raise the temperature of one pound of water by one degree Fahrenheit

GPM – Gallons Per Minute – Measure of the amount of liquefiables in the gas. Low GPM gas is referred to as lean gas. High GPM gas is referred to as rich gas.

HP – horsepower

MMbtu – one million British thermal units

MMbtu/d – one million British thermal units per day

MMcf – one million cubic feet

MMcf/d – one million cubic feet per day

Tcf – one trillion cubic feet

Tcf/d – one trillion cubic feet per day

Back To Top