Annular velocity is the speed of the

drilling fluid In geotechnical engineering, drilling fluid, also called drilling mud, is used to aid the drilling of boreholes into the earth. Often used while drilling oil and natural gas wells and on exploration drilling rigs, drilling fluids are also us ...

's movement in a column called an

annulus Annulus (or anulus) or annular indicates a ring- or donut-shaped area or structure. It may refer to: Human anatomy * ''Anulus fibrosus disci intervertebralis'', spinal structure * Annulus of Zinn, a.k.a. annular tendon or ''anulus tendineus com ...

in oil wells.

Annulus (mathematics) In mathematics, an annulus (plural annuli or annuluses) is the region between two concentric circles. Informally, it is shaped like a ring or a hardware washer. The word "annulus" is borrowed from the Latin word ''anulus'' or ''annulus'' mean ...

It is commonly measured in feet per minute (ft/min) or meters per minute (m/min). Annular velocity is often abbreviated as AV, though this is not exclusively so, as AV also refers to

apparent viscosity In fluid mechanics, apparent viscosity (sometimes denoted ) is the shear stress applied to a fluid divided by the shear rate: :\eta = \frac For a Newtonian fluid, the apparent viscosity is constant, and equal to the Newtonian viscosity of ...

which is calculated from

rheometer A rheometer is a laboratory device used to measure the way in which a dense fluid (a liquid, suspension or slurry) flows in response to applied forces. It is used for those fluids which cannot be defined by a single value of viscosity and t ...

readings from tests that the

mud engineer A mud engineer (correctly called a drilling fluids engineer, but most often referred to as the "mud man") works on an oil well or gas well drilling rig, and is responsible for ensuring the properties of the drilling fluid, also known as drilling mu ...

performs.

Scope

For this article, annular velocity is described, as used in drilling fluid applications in the oil exploration industry. There may be other applications in other fields of study such as

fluid mechanics Fluid mechanics is the branch of physics concerned with the mechanics of fluids ( liquids, gases, and plasmas) and the forces on them. It has applications in a wide range of disciplines, including mechanical, aerospace, civil, chemical and bio ...

(the study of the movement of fluid) or

fluid dynamics In physics and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids— liquids and gases. It has several subdisciplines, including ''aerodynamics'' (the study of air and other gases in motion) an ...

(the study of the flow of fluid).

Determination

The annular velocity can be calculated using one of the following ''formulas''. :

AV = \frac\,

Or :

AV = \frac\,

Where: *AV = annular velocity in Ft/min (feet per minute) *PO_bpm = pump output in bpm (barrels per minute) 1 barrel = 42 gallons *PO_gpm = pump output in gpm (gallons per minute) 1 gallon = 0.0238095238 barrels *ID² = inside diameter of the

wellbore A borehole is a narrow shaft bored in the ground, either vertically or horizontally. A borehole may be constructed for many different purposes, including the extraction of water ( drilled water well and tube well), other liquids (such as petrole ...

or casing, squared *OD² = outside diameter of the drill pipe or tubing, squared *1029.4 = A conversion factor constant used to calculate the volume between the outside of a tube within the inside of another tube, using barrels. *24.5 = A conversion factor constant used to calculate the volume between the outside of a tube within the inside of another tube, using gallons. *Pump Output = Refers to the measurement of the quantity of a fluid (to put that fluid in motion).

Application

The annular velocity is one of two major variables in the process of cleaning solids (

drill cuttings Drill cuttings are broken bits of solid material removed from a borehole drilled by rotary, percussion, or auger methods and brought to the surface in the drilling mud. Boreholes drilled in this way include oil or gas wells, water wells, a ...

) from the

. By maintaining the annular velocity at certain rates (speeds) in conjunction with the rheological properties of the

, the wellbore is kept clean of the

to prevent them from settling back down to the bottom and causing drilling problems. The other major variable is the

rheology Rheology (; ) is the study of the flow of matter, primarily in a fluid ( liquid or gas) state, but also as "soft solids" or solids under conditions in which they respond with plastic flow rather than deforming elastically in response to an appl ...

of the drilling fluid. Rheology is sometimes thought of as

viscosity The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the inte ...

to the uninitiated, though improperly. Viscosity (sometimes thought of as its thickness) is a very basic measurement of the fluids resistance to change in movement or flow. The viscosity of a fluid can be measured with a

Marsh Funnel The Marsh funnel is a simple device for measuring viscosity by observing the time it takes a known volume of liquid to flow from a cone through a short tube. It is standardized for use by mud engineers to check the quality of drilling mud. Other ...

. Rheology is the study of viscosity and requires more precise and complicated procedures and

equipment Equipment most commonly refers to a set of tools or other objects commonly used to achieve a particular objective. Different job Work or labor (or labour in British English) is intentional activity people perform to support the needs and ...

for its determination. For drilling fluid applications a rheometer is used.

References

{{DEFAULTSORT:Annular Velocity Fluid dynamics Drilling fluid

Scope

Determination

Application

See also

References