Annular Velocity for a Given Pump Output Formula |
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\( AV \;=\; \dfrac{ P_o \cdot 1029.4 }{ C_{id}^2 - C_{od}^2 }\) (Annular Velocity) \( Po \;=\; \dfrac{ AV \cdot \left( C_{id}^2 - C_{od}^2 \right) }{ 1029.4 }\) \( C_{id} \;=\; \sqrt{ \dfrac{ Po \cdot 1029.4 }{ AV } + C_{od}^2 }\) \( C_{od} \;=\; \sqrt{ C_{id}^2 - \dfrac{ Po \cdot 1029.4 }{ AV } }\) |
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| Symbol | English | Metric |
| \( AV \) = Annular Velocity | \(bbl\;/\;min\) | - |
| \( P_o \) = Pump Output | \(bbl\;/\;min\) | - |
| \( C_{id} \) = Casing ID | \(in\) | - |
| \( C_{od} \) = Casing OD | \(in\) | - |
Annular velocity for a given pump output is the speed at which a fluid moves upward through the annular space between two cylindrical surfaces, typically the drill pipe and the wellbore or casing when a specific pump rate is applied. In drilling and well-servicing operations, the pump output determines how much drilling fluid is circulated through the system, and this flow rate directly influences how fast the fluid travels in the annulus. Annular velocity is important because it indicates the fluid’s ability to lift cuttings, maintain wellbore cleanliness, and ensure efficient drilling performance. Higher pump outputs generally increase annular velocity, improving cuttings transport, while lower outputs reduce the upward fluid speed and may lead to settling of solids. Therefor, annular velocity for a given pump output helps engineers assess whether the circulating system is operating effectively and safely under the current pumping conditions.
