🌀 Annular Velocity Calculator
Enter the pump flow rate, hole diameter, and pipe diameter to find the annular velocity in ft/min — the up-hole speed that carries cuttings out and keeps the wellbore clean.
🧮 Find the Up-Hole Velocity
What is an Annular Velocity Calculator?
It works out how fast drilling fluid travels up the annulus — the gap between the drill pipe and the wall of the hole. Feed in the flow rate and the two diameters, and it applies V = (Q × 24.5) / (hole² − pipe²) to return the velocity in feet per minute.
Use it to check that your pump rate cleans the hole, to compare velocities across bottom-hole assembly sections, or to plan a flow-rate change. It assumes a nominal gauge hole, so verify against your own hydraulics program before acting.
❓ Frequently Asked Questions
How is annular velocity calculated?
Annular velocity in feet per minute equals the flow rate (gpm) times 24.5, divided by the difference of the squares of the hole and pipe diameters in inches: V = (Q × 24.5) / (D_hole² − D_pipe²). The 24.5 constant converts gallons per minute and inch diameters into feet per minute of up-hole flow in the annulus.
What annular velocity is enough to clean the hole?
It depends on hole angle, cuttings size, and mud rheology, but many operators target roughly 100–120 ft/min in vertical sections as a rule of thumb, with higher rates for larger cuttings or poor mud properties. Hole cleaning in deviated wells is more complex, so treat any single number as a starting point and consult your hydraulics program.
Which diameters do I enter?
Use the open-hole (or casing inside) diameter for the hole, and the outside diameter of the drill pipe or collars for the pipe. The annulus is the gap between them, so the velocity is highest around the larger-OD components like drill collars, where the flow area is smallest.
Why does annular velocity matter?
It governs hole cleaning. Fluid moving up the annulus fast enough overcomes the settling velocity of cuttings and carries them to surface; too slow and cuttings accumulate, risking pack-off, stuck pipe, and high torque. Balancing flow rate against equivalent circulating density is central to hydraulics design.