drilling · hydraulics
Pressure Loss (Laminar, Drillpipe)
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Inputs
gpm
in
cP
lbf/100ft²
ft
Description
Computes laminar-flow frictional pressure loss for a single drillpipe segment using the Bingham plastic model. Scoped deliberately narrow: laminar flow only (turbulent flow requires a separate empirical friction-factor correlation, out of scope here — check Reynolds Number first to confirm laminar flow applies) and a single drillpipe segment only (not a multi-segment system total spanning drillpipe, annulus, and bit, which is Standpipe Pressure's job, not built in this batch). This calculator's output is exactly the annular/pipe pressure-loss figure ECD's APL input currently requires as an external value.
Variables
| Symbol | Unit | Description |
|---|---|---|
| ΔP | psi | Pressure Loss |
| Q | gpm | Circulating flow rate through this segment. |
| d | in | Internal diameter of the drillpipe segment being evaluated. |
| PV | cP | Plastic viscosity from a Fann viscometer test. |
| YP | lbf/100ft² | Yield point from a Fann viscometer test. |
| L | ft | Length of the drillpipe segment being evaluated — commonly the full string length down to the bit. |
Assumptions
- Flow in this segment is laminar — confirmed independently via Reynolds Number (NRe < 2100), not assumed
- Drilling fluid rheology is reasonably approximated by the Bingham plastic model
- A single uniform-diameter segment — a full drillstring with multiple pipe/collar diameters requires summing this calculation per segment
Limitations
- Laminar flow only — if Reynolds Number indicates turbulent flow, this formula understates the true pressure loss; turbulent-flow pressure loss requires a Fanning-friction-factor correlation, not implemented here
- Single segment only — total system (standpipe) pressure additionally includes surface equipment loss, annulus loss, and bit nozzle pressure drop, none of which are computed by this calculator
- Does not model annular-flow pressure loss (a different geometry term, d2−d1 in place of d) — this batch scopes drillpipe flow only
Use Cases
- → ECD input support: Compute the annular or drillpipe pressure-loss figure that feeds directly into ECD's Annular Pressure Loss input, replacing a value that previously had to come from an external hydraulics model.
- → Hydraulics program design: Evaluate how changing mud rheology (PV/YP) or flow rate affects circulating pressure loss in a given drillpipe segment.
- → Standpipe pressure buildup (component): Provide one component (drillpipe friction loss) toward a manually assembled total standpipe pressure estimate.
Related Calculations
Region Notes
Global
Always check Reynolds Number first — drillpipe interior flow is turbulent at most normal circulating rates, in which case this laminar-flow formula does not apply and will understate actual pressure loss.
References
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