The speed at which drilling fluid or cement moves in the annulus. It is important to monitor annular velocity to ensure that the hole is being properly cleaned of cuttings, cavings and other debris while avoiding erosion of the borehole wall.

The annular velocity is commonly expressed in units of feet per minute or, less commonly, meters per minute. The term is distinct from volumetric flow.

Related Terms

• Slip Velocity

1. the rate at which drilled solids tend to settle in the borehole as a well is being drilled. 2. difference between the annular velocity of the fluid and the rate at which a cutting is removed from the hole....

• Rate Of Penetration (ROP)

a measure of the speed at which the bit drills into formations, usually expressed in feet (meters) per hour or minutes per foot (meter)....

• Slow Formation

A formation in which the velocity of the compressional wave traveling through the borehole fluid is greater than the velocity of the shear wave through the surrounding formation. In such conditions, there is no critical refraction of the shear wave and no shear head wave generated, so that standard techniques based on monopole transducers cannot...

• Blast Joint

a tubing sub made of abrasion-resistant material. It is used in a tubing string where high-velocity flow through perforations may cause external erosion....

• Circulating Rate

volume flow rate of circulating drilling fluid expressed in gallons or barrels per minute...