AirWaterGas SRN



Temporarily or permanently cease production from a well or to cease further drilling operations.


A well stimulation technique used to increase the flow of oil and gas from a well.


The space around a pipe in a well bore, sometimes termed the annular space.


American Petroleum Institute. API is a national trade association that represents all aspects of the oil and natural gas industry. API develops industry standards, conducts and sponsors research, and organizes seminars, workshops, conferences and symposia on public policy issues.

API Well Number

A unique number assigned to each well in the United States. An API Number is comprised of four parts: state code, county code, well code and wellbore code. An optional extension code may be attached.


The lowest or deepest part of a well.


A unit of measure for oil and petroleum products that is equivalent to 42 U.S. gallons.

British thermal unit (BTU)

A measure of the heating value of a fuel.


Chemical Abstracts Service is a division of the American Chemical Society, whose objective is to find, collect and organize publicly disclosed substance information.

CAS number

A unique number assigned by the CAS that identifies a chemical substance or molecular structure.


Pipe placed in an oil or gas well to (1) prevent the wall of the hole from caving in, (2) to prevent movement of fluids from one geologic formation to another and (3) provide a means of maintaining control of formation fluids and pressure as the well is drilled. A surface casing is set first to protect groundwater. The production casing is the last one set. The production tubing (through which hydrocarbons flow to the surface) will be suspended inside the production casing..

Casing pressure

The pressure in a well that exists between the casing and the tubing or the casing and the drill pipe.

Casing string

Pipe that lines a well after it has been drilled. It is formed from sections of tube that have been screwed together.


A powder consisting of alumina, silica, lime, and other substances that hardens when mixed with water. Extensively used in the oil industry to bond casing to the walls of the wellbore.

Cement bond

The adherence of casing to cement and cement to formation. When casing is run in a well, it is set, or bonded, to the formation by means of cement.

Cement casing

To fill the annulus between the casing and wall of the hole with cement to support the casing and prevent fluid migration between permeable zones.


The application of a liquid slurry of cement and water to various points inside or outside the casing.


To finish work on a well and bring it to productive status.


An engine used to increase the pressure of natural gas so that it will flow more easily through a pipeline.

Conductor casing

Generally, the first string of casing in a well. It may be lowered into a hole drilled into the formations near the surface and cemented in place; it may be driven into the ground by a special pile driver. Its purpose is to prevent the soft formations near the surface from caving in and to conduct drilling mud from the bottom of the hole to the surface when drilling starts. (Also known as “conductor pipe" and “drive pipe.")

Directional drilling

Intentional deviation of a wellbore from the vertical. Although wellbores are normally drilled vertically, it is sometimes necessary or advantageous to drill at an angle from the vertical.

Directional hole

A wellbore intentionally drilled at an angle from the vertical.


A term used to describe tools, equipment, and instruments used in the wellbore, or conditions or techniques applying to the wellbore.


When referring to the oil and gas industry, this term indicates the refining and marketing sectors of the industry. More generically, the term can be used to refer to any step further along in the process.


To bore a hole in the earth, usually to find and remove subsurface formation fluids such as oil and gas.

Drilling mud

A specially compounded liquid circulated through the wellbore during rotary drilling operations.

Dry gas

The volume of gas remaining after all water and natural gas liquids have been removed.

Dry hole

Any exploratory or development well that does not find commercial quantities of hydrocarbons.


An area consisting of a single reservoir or multiple reservoirs all grouped on, or related to, the same individual geological structural feature or stratigraphic condition. The field name refers to the surface area, although it may refer to both the surface and the underground productive formations.

Fluid flowback volume

The amount of fluid that returns to the surface of a well after hydraulic fracture stimulation. The flowback can occur for days and weeks after hydraulic fracture stimulation.

Formation fluid

Fluid (such as gas, oil, or water) that exists in a subsurface formation.

Formation pressure

The force exerted by fluids or gas in a formation, recorded in the hole at the level of the formation with the well shut in.

Formation water

Any water that resides in the pore spaces of a formation.


A crack or crevice in a formation, either natural or induced.


The application of hydraulic pressure to the reservoir formation to create fractures through which oil or gas may move to the wellbore.

Fracturing fluid

A fluid, such as water, oil, or acid, used in hydraulic fracturing. The fluid carries propping agents that hold open the formation cracks after hydraulic pressure dissipates.

Gas well

A well that primarily produces gas. Legal definitions vary among the states.


A standard adopted by the American Petroleum Institute for measuring the density of a liquid. Gravity is expressed in degrees with lower numbers indicating heavier liquids and higher numbers indicating lighter liquids.

Horizontal drilling

Deviation of the borehole from vertical so that the borehole penetrates a productive formation in a manner parallel to the formation.

Hydraulic fracturing

An operation in which a specially blended liquid is pumped down a well and into a formation under pressure high enough to cause the formation to crack open, forming passages through which oil can flow into the wellbore.

Intermediate casing

Provides protection against caving in of weak or abnormally pressured formations and enables the use of drilling fluids used to drill into lower formations.

Intermediate casing string

The string of casing set in a well after the surface casing but before production casing is set to keep the hole from caving in and to seal off formations. In deep wells, one or more intermediate strings may be required.


A legal document conveying the right to drill for oil and gas, or the tract of land on which a lease has been obtained where the producing wells and production equipment are located.


To conduct a survey inside a borehole to gather information about the subsurface formations; the results of such a survey. Logs typically consist of several curves on a long grid that describe properties within the wellbore or surrounding formations that can be interpreted to provide information about the location of oil, gas, and water. Also called well logs, borehole logs, wireline logs.

Mechanical integrity

The measure of a well's casing, tubing, packer and cement to contain fluids traveling up and down the well without the fluids leaking into surrounding geologic formations.


The liquid circulated through the wellbore during rotary drilling and workover operations.

Multiple completion

An arrangement for producing a well in which one wellbore penetrates two or more petroleum-bearing formations.

Natural gas

A highly compressible, highly expansible mixture of hydrocarbons with a low specific gravity and occurring naturally in a gaseous form.


A simple or complex liquid mixture of hydrocarbons that can be refined to yield gasoline, kerosene, diesel fuel, and various other products.


The person or company, either proprietor or lessee, actually operating a well or lease, generally the oil or gas company that engages the drilling, service, and workover contractors.


Any object or device that blocks a hole or passageway (such as a cement plug in a borehole).

Plugged and abandoned

A depleted well or dry hole that has been (typically) filled with cement and marked, with all surface equipment removed.


To pierce holes in the casing and cement in a well to allow formation fluids, such as oil and gas, to enter into a well and to allow fluids to be injected into a geologic formation. Perforating is accomplished using a perforating gun, or perforator.

Perforated interval

A section of casing that has been perforated during hydraulic fracturing operations.


The quantification of how easily fluids, such as oil, gas, and water, flow through the pore spaces in a geologic formation and into the wellbore.


A ratio between the volume of the pore space in reservoir rock and the total bulk volume of the rock. The pore space determines the amount of space available for storage of fluids.

Produced water

The water extracted from the subsurface with oil and gas. It may include water from the reservoir, water that has been injected into the formation, and any chemicals added during the production/treatment process.


The amount of oil or gas produced in a given period.

Production casing

The last casing set in a well though which oil and gas are extracted.


A granular substance (sand grains, crushed walnut shells, aluminum pellets, or other material) that is carried in suspension by the fracturing fluid. Proppant keeps fractures open in a formation when fracturing fluid is withdrawn after a fracture treatment.


The unproduced but recoverable oil or gas in a formation that has been proved by production.


A subsurface, porous, permeable or naturally fractured rock body in which oil or gas are stored. Most reservoir rocks are limestones, dolomites, sandstones, or a combination of these.


To restore production from an existing formation when it has fallen off substantially or ceased altogether.


A percentage interest in the value of production from a lease that is retained and paid to the mineral rights owner.


An abrasive material composed of small quartz grains formed from the disintegration of pre-existing rocks.


A sedimentary rock composed of individual mineral grains of rock fragments between 0.06 and 2 millimeters (0.002 and 0.079 inches) in diameter and cemented together by silica, calcite, iron oxide, and so forth.


The process of separating liquid and gas hydrocarbons and water. This is typically accomplished in a pressure vessel at the surface, but newer technologies allow separation to occur in the wellbore under certain conditions.


A fine-grained sedimentary rock composed mostly of consolidated clay or mud. Shale is the most frequently occurring sedimentary rock.

Shut in

To close the valves on a well so that it ceases production of oil and gas or the injection of fluids into the surrounding geologic formation.


The distance between wells producing from the same reservoir. Spacing is often expressed in terms of acres, e.g., 40-acre spacing, and is often established by regulatory agencies.


To begin drilling a well; such as, to spud in.


A cementing operation in which cement is pumped behind the casing under high pressure to recement channeled areas or to block off an uncemented zone.

Squeeze cementing

The forcing of cement slurry by pressure to specified points in a well to cause seals at the points of squeeze.

Squeeze job

A remedial activity whereby a cement slurry is pumped into open perforations, split casing, or a fractured formation, to effect a blockage.


The action of attempting to improve and enhance a well's performance by the application of horsepower using pumping equipment, placing sand in artificially created fractures in rock, or using chemicals such as acid to dissolve the soluble portion of the rock.

Surface casing

Isolates freshwater zones during the drilling and oil production phases of a well.

Tight formation

A petroleum- or water-bearing formation of relatively low porosity and permeability.

Tight sand

Sand or sandstone formation with low permeability.

Total dissolved solids (TDS)

The total amount of solids, such as minerals, salts, or metals that are dissolved in a given volume of water.

True vertical depth

The vertical distance from a point in the well (usually the current or final depth) to the surface.


A small-diameter pipe that is run inside well casing to serve as a conduit for the passage of oil and gas to the surface. Tubing can be a permanent or temporary part of the well bore.

Tubing strings

The entire length of tubing in a well.

Underground injection

The placement of gases or fluids into an underground reservoir through a wellbore. May be used as part of enhanced oil recovery or waterflooding processes or for disposal of produced water.


The exploration and production portions of the oil and gas industry.

Water well

A well drilled to obtain a fresh water supply to support drilling and production operations.


The hole made by the drilling bit, which can be open, cased, or both. Also called borehole, hole, or well bore.

Well bore

A borehole; the hole drilled by a drill bit; also called a borehole or hole.

Well stimulation

Any of several operations used to increase production by increasing the permeability of an oil or gas bearing formation, such as acidizing or hydraulic fracturing.


The equipment at the surface of a well used to control the pressure; the point at which the hydrocarbons and water exit the ground.

Wet gas

Natural gas containing significant amounts of liquifiable hydrocarbons.


Operations on a producing well to restore or increase production. A workover may be performed to stimulate the well, remove sand or wax from the wellbore, to mechanically repair the well, or for other reasons.