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Easily calculate annular velocity with our free Annular Velocity Calculator. Learn the formula, rule of thumb, and best range for safe hole cleaning.
If you work in drilling, you’ve heard the term annular velocity. It’s the speed of fluid as it moves in the space between the drill pipe and the wellbore. Getting this speed right is key. Too low, and cuttings settle. Too high, and you risk washouts or pressure issues.
That’s why we built our Annular Velocity Calculator. It helps you find the exact velocity in seconds. You’ll only need the hole size, pipe size, and flow rate. The tool does the rest.
The formula is simple. In feet per minute (ft/min), it looks like this:
AV = (24.5 × Qgpm) / (Dh² − Dp²)
Where:
If you use barrels per minute (bbl/min), the formula changes slightly:
AV = (1029.4 × Qbbl/min) / (Dh² − Dp²)
This gives you a clear answer in ft/min. You can then convert it to m/s or ft/s if you like.
A good number depends on your well angle and fluid type. For vertical wells, 100–150 ft/min often works. For deviated or horizontal wells, higher speeds help lift cuttings. Around 150–250 ft/min is the sweet spot in most cases.
Think of it like water in a pipe. A slow stream leaves dirt behind. A faster flow keeps it moving. That’s what you want inside your wellbore.
The simple rule of thumb says:
There’s no one-size-fits-all. The optimum range depends on your setup. Most drilling engineers agree that 150–200 ft/min works best for efficient hole cleaning without high risks.
It’s like driving a car. Too slow, you never reach your destination. Too fast, you lose control. Somewhere in the middle is safe and smooth.
You’ll see the step-by-step math, including unit conversions and the applied formula. We’ll also show a recommendation, like “good velocity” or “too low.”
The Annular Velocity Calculator makes drilling math easy. No more manual formulas or mistakes. You’ll know if your velocity is safe for hole cleaning in seconds.
Use it as a quick check before or during operations. It saves time, avoids errors, and helps you keep the wellbore clean.
It keeps drill cuttings moving to the surface. Without it, cuttings settle and may cause stuck pipe.
Yes. Too much velocity may erode the wellbore or increase pressure losses.
It’s usually measured in feet per minute (ft/min). You can also use meters per second (m/s).
The math is accurate. But fluid type, density, and wellbore angle can change the optimum velocity needed.