Fluid Velocity in Annulus Calculator
Enter circulation rate, outer annular diameter, and pipe outside diameter in the declared field units. The calculator returns average annular fluid velocity in ft/min.
Calculation context and source notes
Fluid velocity in an annulus converts circulating flow rate and concentric annular geometry into an average linear velocity between the hole or casing and the drillpipe or tubing.
Use average annular velocity as a drilling-hydraulics and circulation screening input. Hole-cleaning performance also depends on inclination, rheology, cuttings loading, pipe eccentricity and movement, so velocity alone is not a transport model.
Solves for
v_a (ft/s)
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Formula, variables, and sourceRelated source-backed guides
Formula, variables, and default calculation
Reproducible default result
With the default values shown below, the calculation returns v_a = 5.18726 ft/s. Defaults demonstrate the implementation; they are not recommended field values.
600
8.5
5
Input definitions
Q
gpmFlow Rate
D_o
inOpen Hole Diameter
D_p
inOutside Diameter of Pipe
Output definitions
v_a
Velocity of Fluid in Annulus
Q
Flow Rate
D_o
Open Hole Diameter
D_p
Outside Diameter of Pipe
Engineering use, assumptions, and limits
Use average annular velocity as a drilling-hydraulics and circulation screening input. Hole-cleaning performance also depends on inclination, rheology, cuttings loading, pipe eccentricity and movement, so velocity alone is not a transport model.
Assumptions
- The outer and inner diameters describe the same annular section and the outer diameter is larger.
- Flow is steady and the calculated value represents cross-sectional average velocity.
- The geometry is treated as concentric for the area calculation.
Limitations
- Does not resolve the low-velocity side of an eccentric annulus or a non-Newtonian velocity profile.
- Does not predict cuttings slip, bed formation, erosion, pressure loss, or minimum hole-cleaning velocity.
Common mistakes
- Entering pipe inside diameter instead of pipe outside diameter.
- Using inconsistent flow-rate or diameter units with the field-unit constant.
- Treating average annular velocity as proof of adequate hole cleaning.
Source and record status
Source metadata identifies the relationship implemented by the calculator. Check the cited edition, unit basis, and scope against the engineering case before operational use.
Robello, S.E. 2015. 501 Solved Problems and Calculations for Drilling Operations, Page 321.
Open source reference