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Evolution Glossary of Oilfield Terms



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API - American Petroluem Intitute (http://www.api.org/) is a national trade association that represents all aspects of America’s oil and natural gas industry. The American Petroleum Institute traces its beginning to World War I, when Congress and the domestic oil and natural gas industry worked together to help the war effort.  API specifications are critical to a number of oil tools.

Artificial Lift - Artificial lift refers to the process by which internal pressure of an oil reservoir is raised in order to drive oil to the surface.  This system increases the productivity of the well.


Beam Pump - The most common form of artificial lift used is beam pumping.  Beam pumping employs equipment on the surface and below to increase pressure and pump oil to the surface.  The system is made up of a sucker rod string and a sucker rod pump.  Beam pumps are familiar jack pumps seen in oil fields.

Bed Line - A short section of slickline installed on the inner core of the wireline drum, prior to spooling on a new working line.  The two lines are tied together.

BHP - Bottom Hole Pressure - Pressure at the bottom or at the drilled depth of a well.

Box - Female thread located at the lower end of the wireline toolstring components.

Bridge Plug - A downhole tool that is located and set to isolate the lower part of the wellbore. Bridge plugs may be permanent or retrievable, enabling the lower wellbore to be permanently sealed from production or temporarily isolated from a treatment conducted on an upper zone.


C.F. to K.B. - A surface measurement that is added to wireline depths reached or subtracted from well file depths to correlate expected wireline run depth desired.

Casing - Steel pipe cemented in place during the construction process to stabilize the wellbore. The casing forms a major structural component of the wellbore and serves several important functions: preventing the formation wall from caving into the wellbore, isolating the different formations to prevent the flow or crossflow of formation fluid, and providing a means of maintaining control of formation fluids and pressure as the well is drilled. The casing string provides a means of securing surface pressure control equipment and downhole production equipment, such as the drilling blowout preventer (BOP) or production packer. Casing is available in a range of sizes and material grades.

Casing Flange (CF) / Casing Head- A flange located near the lower portion of the wellhead. It is almost always connected to the surface casing string, and provides a means of suspending and packing off the next casing string.

Completion -  A generic term used to describe the events and equipment necessary to bring a wellbore into production once drilling operations have been concluded, including but not limited to the assembly of downhole tubulars and equipment required to enable safe and efficient production from an oil or gas well. Completion quality can significantly affect production from shale reservoirs.

Crooked Tubing - Tubing that is usually crooked downhole because of squat weight to secure packers set in the casing.

C.S.G. - The abbreviation for Well Casing.


Deviated - Wells drilled on a slant or sections of the well bore not being truly vertical

Drift - Minimum inside diameter tolerance for tubular configurations in a well completion.


Drilling Rig - The machine used to drill a wellbore. It includes virtually everything except living quarters. Major components of the rig include the mud tanks, the mud pumps, the derrick or mast, the drawworks, the rotary table or topdrive, the drillstring, the power generation equipment and auxiliary equipment.


Element -

EUE - External Upset End  - An eight round thread used in tubular configurations for lower pressure and low hydrogen sulfide well completions.


Fish - An object or equipment that was accidentally lost in the well, or a subsurface tool being recovered from the well bore.

Fish Neck (F/N) - (Two Types)

1) External - A flange located immediately below the threaded pin connection on the toolstring components. Located near the top of the rope sockets and subsurface   wireline conveyed accessories.

2) Internal - A machined recess inside subsurface wireline conveyed accessories, near the top.



H2S - Hydrogen Sulphide, a mixture of hydrocarbons and sulfur. Also known as Sour Gas.

Helical Bourdon Tube - A spiral shaped tube vacuum filled with a special type of fluid. Used as a pressure sensor to rotate a stylus assembly in mechanical recorders.

Holding or Feeling the line by hand - Is a term referred to when it becomes necessary to guide the line by hand.  Feeling the line by hand is done by grasping the wire in your hands.  This is done at a midway point between the wireline unit and the wellhead.


Hydrates -The freezing of gasified water contained well production as cooler formation temperatures are encountered during the production path to surface.


I.D. - Inside Diameter

Inhibitors - Inhibitors are liquid chemicals developed to aid in the protection of equipment such as wireline ran in well bores, that are corrosive.



Kelly Bushing (K.B.) - The Kelly Bushing is part of the turn table on a drilling rig floor that allows the addition and removal drill stem. The well depths are measured from the Kelly Bushing elevation when the well is being drilled.


Landing Nipple - A landing nipple, also called a profile nipple, is as a short section of heavy wall tubular with a machined internal surface that features a seal area and a locking profile. Landing nipples are included in most completions at predetermined intervals to enable the installation of Flow Control devices, like blanking plugs, instrument hangers and chokes. There are three basic types of landing nipples: no-go nipples, selective-landing nipples and ported or safety-valve nipples.

Lock Pin - A pin that is inserted through two components threaded together to prevent the threads from backing apart.


MP - 35N - An Alloy Nickel used to manufacture wireline used in wells with critical H2S and CO2 environments.

Managed Pressure Drilling (MPD) - defined by the International Association of Drilling Contractors (IADC) as “an adaptive drilling process used to more precisely control the annular pressure profile throughout the wellbore." The objectives of MPD are “to ascertain the downhole pressure environment limits and to manage the annular hydraulic pressure profile accordingly."


N.P.T. - The abbreviation for National Pipe Thread.

NACE - The abbreviation for National Association of Corrosion Engineers.

No-Go Shoulder - A restricted bore with in the lower I.D. of a nipple profile or a larger O.D. section of a seating nipple accessory.


O.D. - Outside Diameter

On-Off Connectors - A latching / disconnecting component placed between the tubing string and the packer system in a well completion.


P.S.N. - Pump Seating Nipples.

Packer - A tool that can be run into a wellbore with a smaller initial outside diameter that then expands mechanically to seal the wellbore. Packers employ flexible, elastomeric elements that expand. The most common forms are the production or test packer. The expansion of the packer elements is typically done by compressing them between two plates, forcing the sides to expand outward. Production or test packers are run on wireline, pipe or coiled tubing. Some packers are designed to be retrievable, while others are permanent. Permanent packers are constructed of materials, like cast iron or composites that are easy to drill out if required.

Pickup - The depth when the mechanical jars are fully opened and the complete toolstring is lifted from the depth the work is being performed.

Pin - Male thread located at the upper end of the wireline toolstring components.

Plough Steel or Hardline - High tensile hardened steel used in the manufacture of standard well service slickline.

Positive - Referred to fishing overshots and spears as no means by which such tools can not be released when ran on wireline.

Pressure Measurements:

KPa - Kilopascal - The metric measurement of pressure in units.

MPa - Megapascals - The metric measurement of pressure in 1000's of units.

PSI - Pounds per Square Inch - The imperial measurement of pressure in units.

Progressing Cavity Pump (PC Pump) - Progressing cavity pump dates back to the 3rd century B.C. and the Greek scientist Archimedes. Through the centuries the principle has remained simple. Today, synthetic elastomers are bonded within a steel tube, the stator, with a double internal helix design. The only moving part of the pump, the rotor, is a single external helix design and is rotated within the stator, forming cavities. They progress from the inlet (suction end) to the outlet (discharge end). The tight seals between the rotor and stator helices keep fluids moving at a steady rate proportional to the rate generated by the prime mover mechanism. The number of stages is predetermined by the force required to move fluid a given depth or distance plus any line forces (head pressure) acting upon the fluid.

Pull Load - Line weight registered on the wireline unit weight indicator, when applying a pulling motion.



Retrievable Bridge Plug - A type of downhole tool for isolation that may be released and retrieved from the wellbore after use. A retrievable bridge plug is frequently used in combination with a packer to enable accurate placement and injection of stimulation or treatment fluids.

Rod Wrenches - A wrench with a pivotal jaw sized to fit wrench flats machined on downhole wireline tools.  The wrenches have a slapping action to tighten and loosen downhole tool joints.


S.C.S.S.V. - Surface Controlled Sub Surface Safety Valve.

S.I.C.P. - Shut in Casing Pressure.

S.I.T.P. - Shut in Tubing Pressure.

S.R. - Sucker Rod most common thread connection on slickline tools.

S.S.S.V. - Sub Surface Safety Valve.

Shear Pin - Round pin used to pin running tools to subsurface controls and to pin pulling tools to remove subsurface controls.

Slurry - A thickened but not solid liquid. This term is commonly used when a bailing operation is in progress.

Snubbing Tubing - Conveying tubing in and out of the well bore under pressure.

Selective Nipples - Landing nipples that are used to be run in a series throughout the wellbore are typically selective nipples. Any number of Evolution's SLX or SLR landing nipples could be put into the tubing string, and tools can pass through each and every one if necessary without hindrance. To set into a nipple its required to pull back in from below after passing through, hence the nipples are selective locating.

Sour Gas - Hydrogen Sulfide, a mixture of hydrocarbons and sulfur. Also known as H2S.

Sour Well - Referred to environments with hydrogen sulfide.

Stainless Steel - Used to manufacture oil tools for use in the most corrosive well conditions, such as hydrogen sulfide and carbon dioxide.

Stroke - A term referred to the travel of jars or sandpump bailers.

Sweet Well - Referred to as well environments that do not contain deadly toxins.


Tbg - Abbreviation for Tubing.

TSTM - The abbreviation for Too Small Too Measure. Used when pressures are not enough to move the pressure measuring component from the zero position.

Tubing - The production pipe ran in the well bore.

Tubing Hanger - A mechanism used to hang the tubing from within the tubing head by means of a thread.

Tubing Head - Equipment attached to the casing spool used to hang the tubing (smallest casing string) and seal the annulus between the tubing and casing.




Waterflooding - Where water is injected into the reservoir formation to displace residual oil. The water from injection wells physically sweeps the displaced oil to adjacent production wells. Waterflood techniques may involve inefficient recovery due to variable permeability, or similar conditions affecting fluid transport within the reservoir, and early water breakthrough that may cause production and surface processing problems.

Well Killing - The process of circulating weighted fluids into the well bore creating a hydrostatic overbalance of wellbore pressures.

Wellbore - The drilled hole or borehole, including the open hole or uncased portion of the well. Borehole may refer to the inside diameter of the wellbore wall, the rock face that bounds the drilled hole.


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    Evolution Oil Tools offers our E-Plus Tubing Rotator, which complies with API 6A bolting requirements, with 3 different Drive options: Manual, Mechanical & Electric (12V, 110V or 460V). Our Electric Drive Assembly includes our proprietary Gear Reducing System.

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  • Model G Retrievable Casing Packer

    The Evolution Model G Retrievable Casing Packer is a compact economical setdown, weight activated, production packer. The Model G can be used by itself for production applications.

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  • EL Sliding Sleeve

    The Models "EL" Sliding Sleeves are sub-surface flow control devices.
    They are primarily intended to control flow between the tubing and the casing.

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