V

V Door
An opening in a side of a derrick at the floor level having the form of an inverted v. This opening is opposite the drawworks. It is used as an entry to bring in drill pipe and casing from the pipe rack.

Vacuum
Theoretically, a space absolutely devoid of all matter and exerting zero pressure. However, it commonly refers to a condition that exists in a system when pressure is reduced below atmospheric pressure.

Vacuum Stripping
To remove gases from a liquid by applying a vacuum.

Valence
(1) A number representing the combining power of an atom; i.e., the number of electrons lost; gained; shared by an atom in a compound.(2) A measure of the number of hydrogen atoms with which an atom will combine or replace; i.e., an oxygen atom combines with two hydrogens; hence has a valence of 2. Thus, there are mono-, tri-, etc., valent ions. Also referred to as: Valency.

Valence Effect
The higher the valence of an ion the greater the loss of stability to emulsions, colloidal suspensions, etc., these polyvalent ions will impart.

Value Less Tax Amount
The value of minerals after the deduction of all applicable taxes.

Valve
Device by which the flow of a liquid or a gas may be regulated or controlled. A movable part within the valve body that opens or obstructs passage.

Valve Bore Sealing Mechanism
Those internal valve parts which close off the flow through the valve bore, such as gates, balls, plugs, poppets, flappers, and their respective seats.

Valve Drilling Operation
Drilling of a hole through the blocking element of a valve that is stuck in the closed position with pressure on the wellbore side of the valve. The drilling is accomplished through a lubricator that confines the pressure after the valve is penetrated.

Valve Lifter
A device for manually unseating a compressor valve to reduce the compressor capacity.

Valve Top Works Pilot
A mechanical regulating device mounted on or above a valve to assist in opening or closing the valve.

Van Slyke
A laboratory test for determining the concentration of primary amines and ammonia in amine solutions.

Vanish Point
That location where the thread tool mark runs out or terminates on the pipe surface.

Vapor Bath
A vat used in a process lab with a set temperature of 100 degrees Fahrenheit used to raise a sample bomb to a constant temperature.

Vapor Lock
The occurrence of a pocket of evaporated fuel which inhibits the fuel pump (which can only pump liquids) and causes the engine to stop.

Vapor Pressure Bomb
A sampling container for determination of vapor pressure.

Vapor Recovery Unit
A packaged vessel used to capture low pressure vapors from stock or storage tanks and pump them into a pipeline or flare, preventing their loss to the atmosphere.

Vapor Tight Lighting Fixture
SEE: Enclosed and Gasketed Lighting Fixture.

Variable Density Log
An acoustic log in which the acoustic wave train is recorded in the variable photographic density or intensity modulated time mode.

Variance
Sanction granted by a government body for delay or exception in the application of a given law, ordinance, or regulation.

Vector Averaging Method
A borehole survey calculation method which uses inclination and direction measurements at both ends of the measured course to establish vector space directions. It is then assumed that each of these two vectors is projected for one-half the course length in creating the borehole path. Each half course length segment can be treated tangentially. Results obtained are essentially the same as the Acceleration, Balanced Tangential, and Trapezoidal Methods.

Vee Path
The angle beam path in materials starting at the search unit examination surface, through the material to the reflecting surface continuing to the examination surface in front of the search unit, and reflection back along the same path to the search unit. The path is usually shaped like the letter V.

Velocimeter
(1) A device which measures fluid flow.(2) A flowmeter.

Velocity
(1) Time rate of motion in a given direction and sense.(2) The measure of a fluid flow and may be expressed in terms of linear velocity, mass velocity, volumetric velocity, etc.(3) A material property.

Velocity Survey Run Flag
An indicator of whether a velocity survey was run.

Velocity Type
The type of velocity; e.g., interval; average.

Venn Diagram
The use of circles and lines to visually depict organizational, technical, and social relationships, power and communication.

Vent
A pipe or hatch on a vessel that opens to the atmosphere. A vent line might contain a pressure and/or vacuum relief device.

Vented From Gas Wells Volume
The disposition of gas into the atmosphere from gas wells.

Vented From Oil Wells Volume
The disposition of gas into the atmosphere from oil wells.

Vented Greater Than 1 Hour Volume
The disposition of gas into the atmosphere for a period greater than 60 minutes.

Vented Less Than 1 Hour Volume
The disposition of gas into the atmosphere for a period less than 60 minutes.

Vented Or Flared Code
An indicator of whether the gas stream is flared (burned) or vented.

Venturi Valve
A valve with a reduced opening, in which the transformation from the full opening ends to the reduced closure area is well streamlined to reduce pressure loss.

Verified Nomination
A nomination that has been validated against the conditions specified in the service contract and with any upstream/downstream or third parties involved in the transaction.

Vertical Axis Orientation
The orientation of a vertical coordinate axis with respect to a coordinate system. This is defined as either "upwards" or "downwards".

Vertical Datum
A reference surface used as the basis of elevation and depth measurements.

Vertical Depth
The vertical component of the borehole measured depth.

Vertical Drilling
Drilling with the intent of maintaining the wellbore path directly vertically below the wellbore origin.

Vertical Hole
SEE: Vertical Wellbore.

Vertical Limit
The maximum readable level of vertical indications determined either by an electrical or a physical limit of an A scan presentation.

Vertical Permeability
Absolute permeability measured on a vertically oriented sample.

Vertical Profile
A projection of the wellbore path into a vertical plane parallel to the course bearing.

Vertical Section
SEE: Vertical Profile.

Vertical Seismic Profile
A collection of seismic traces taken at sequential depths in a wellbore and processed to display direct, reflected, refracted and diffracted waves. It is a correlation tool for relating the well logs and lithologic logs to the field seismograms. Commonly abbreviated as VSP.

Vertical Seismic Profile Receiver Level Count
The quantity of seismic receiver levels used in the wellbore or the number of receivers on the surface if the vertical seismic profile (VSP) is transposed.

Vertical Seismic Profile Receiver Type
The type of receiver used in the tool during the vertical seismic profile (VSP); e.g., single component geophone; three component geophone; hydrophone.

Vertical Seismic Profile Source
The source of seismic energy used to acquire the vertical seismic profile (VSP); e.g., Vibroseis; airgun; watergun; dynamite.

Vertical Seismic Profile Source Offset
The offset distance of the vertical seismic profile (VSP) source from the wellhead.

Vertical Sum
Combining (adding) source gathers from several sources at nearly the same earth location without correcting for static or receiver offset differences.

Vertical Sweep Efficiency
The percentage of vertical section of pay that is swept by the injected fluid.

Vertical Thickness
The thickness of the stratigraphic unit measured vertically through the unit.

Vertical Wellbore
A wellbore path that is nearly vertical from wellbore origin to wellbore terminus.

Vessel Filter
A vessel containing a porous or mass element through which gas or liquid is passed to screen out foreign matter.

Vessel Heading
The heading of the seismic vessel, relative to true north, at the time the record is generated.

Vessel Heel Angle
The mean heel angle of the seismic vessel at the time the record is generated; starboard side down is positive, port side down is negative.

Vessel Mean Draft
The mean draft of the seismic vessel at the time the record is generated.

Vessel Trim Angle
The mean trim angle of the seismic vessel at the time the record is generated; bow down is positive, stern down is negative.

Vibrating Screen
A screen with motion in a vertical plane which operates generally above 600 RPM at less than 1 inch stroke.

Vibration Analyzer
Diagnostic and monitoring equipment measuring distortional movement on high speed equipment such as turbines.

Vibroseis Sweep
SEE: Sweep.

Video Presentation
In ultrasonic testing, the rectified radio frequency (rf) signal.

Vintage
The term used to indicate the period during which a gas sales contract was made and/or the well spud date.

Viscometer
A device for measuring viscosity. Also referred to as: Viscosimeter.

Viscosimeter
SEE: Viscometer.

Viscosity
(1) The property of a substance offering internal resistance to flow.(2) A measure of the degree of fluidity.

Viscosity Funnel
SEE: Marsh Funnel.

Viscosity Gel Viscometer
The name commonly used for the direct indicating viscometer. Also referred to as: VG Meter.

Viscous Flow
SEE: Laminar Flow.

Visual Examination
Examination of parts and equipment for visible defects in material and workmanship.

Vitrinite
A microscopically recognizable coal maceral (organic analog to mineral) composed of humic material that is characteristically found in the coal lithotype vitrane. Vitrinite is the major maceral of most humic coals, and occurs in amorphous, mixed and structured forms. Vitrinitic kerogens and coals have the potential to generate gas. The maceral is used to measure vitrinite reflectance.

Vitrinite Reflectance
The percentage of vertically incident light reflected from a polished surface of the maceral vitrinite in thin section. An arithmetic mean of reflectance readings on a sample is widely used as a measure of geothermal maturity of the sample, which in turn is used to infer stages of petroleum generation and destruction within the sample rock.

Vitrinite Type
The form of vitrinite recognized in the thin section sample; e.g., amorphous; mixed; structured.

Void Framework
The amount of the rock framework that is porous (void), as a percent of the total framework volume.

Volatile
Evaporating readily at a relatively low temperature.

Volatile Flammable Liquid
A flammable liquid having a flash point below 100 F (37.8 C), or a flammable liquid whose temperature is above its flash point, or a Class II combustible liquid having a vapor pressure not exceeding 40 psia (276 kPa) at 38 C (100 F) whose temperature is above its flash point.

Volatile Matter
Normally gaseous products, except moisture, given off by a substance, such as gas breaking out of live crude oil that has been added to a drilling fluid. In distillation of drilling fluids, the volatile matter is the water, oil, gas, etc., that are vaporized, leaving behind the total solids which can consist of both dissolved and suspended solids.

Voltage
The unit of potential causing the flow of current.

Volume Tax Amount
The tax calculated on volume.

Volumetric Efficiency
In a single pump stroke, the ratio of the actual volume delivered to the volume displaced.

Volumetric Nondestructive Examination
Examination for internal material defects by methods such as radiography and/or ultrasonic testing.

Vortex Breaker
A device located on outlet nozzles to prevent vortex formation.

Vortex Finder
A hollow cylinder extending axially into the barrel of a hydrocyclone forming an annulus into which the feed enters tangentially. The overflow exits from the separating chamber through the vortex finder, and the vortex is centered in the hydrocyclone by the hole in the vortex finder, hence the name.

Vsp
SEE: Vertical Seismic Profile.

Vug
Natural cavity formed in certain rocks or veins, caused by leaching out of soluble minerals.