production · tubing performance
Friction Factor (Haaland)
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Inputs
—
in
in
Description
Computes the Darcy-Weisbach friction factor using Haaland's (1983) explicit approximation to the implicit Colebrook-White equation — an accurate, non-iterative, hand-calculable formula for turbulent flow in a pipe of known relative roughness, standard practice for single-phase tubing pressure-drop calculations.
Variables
| Symbol | Unit | Description |
|---|---|---|
| f | — | Darcy Friction Factor |
| NRe | — | Reynolds number for the flow — run the Reynolds Number (Tubing Flow) calculator first and carry its result in here (see relatedCalcs). This calculator is valid for turbulent flow (NRe > ~2,100); the Haaland correlation is not applicable to laminar flow. |
| ε | in | Absolute roughness of the tubing's internal surface. 0.0018 in (0.0457 mm) is the standard commercial steel value; a scaled, corroded, or otherwise degraded tubing surface can be substantially rougher. |
| d | in | Tubing internal diameter, used to compute the relative roughness ε/d. |
Assumptions
- Flow is turbulent (NRe roughly > 2,100) — the Haaland correlation is fit to and only valid for the turbulent regime
- Pipe roughness ε is a representative current value for the tubing's internal surface condition, not a new-pipe specification if scale or corrosion has since roughened it
- The pipe is circular with reasonably uniform internal diameter over the length of interest
Limitations
- Not valid for laminar flow — laminar friction factor follows the simple f=64/NRe relationship instead, not this correlation
- An explicit approximation, not the exact Colebrook-White solution — typically within about 1-2% of the iterative Colebrook-White result across the turbulent range, adequate for engineering design but not exact
- Roughness ε is a single lumped value; it does not account for roughness that varies along the tubing string (e.g., localized scale buildup at one depth)
Use Cases
- → Tubing friction pressure loss: Feeds directly into the Darcy-Weisbach friction pressure loss term used internally by Flowing Bottomhole Pressure (Tubing Traverse).
- → Tubing size/roughness sensitivity: Compare friction factor across different tubing roughness assumptions (new vs. scaled/corroded) to bound the uncertainty in a friction pressure loss estimate.
Related Calculations
Region Notes
Global
Use a higher roughness value for older or scaled wells — commercial-steel new-pipe roughness (0.0018 in) can understate friction loss substantially once scale, paraffin, or corrosion has built up on the tubing wall.
References
Primary source
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