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Formulas
- Capacity (bbl/ft) = ID² ÷ 1029.4, with ID in inches
- Annular capacity (bbl/ft) = (hole or casing ID² − pipe OD²) ÷ 1029.4
- Annular volume (bbl) = annular capacity × length
- Strokes = volume ÷ pump output per stroke
Frequently asked questions
Where does 1029.4 come from?
It converts inches squared into barrels per foot: one barrel per foot corresponds to a diameter of about 32.08 inches, and 32.08² ≈ 1029.4.
Should I add washout to open hole volume?
Often yes. Open hole is usually larger than bit size, so many engineers add an allowance based on caliper logs or offset wells.
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