drilling · hydraulics
Pipe/Casing Displacement
click formula to derive ↑
Inputs
in
in
ft
Description
Computes the volume of drilling fluid displaced by the steel cross-section of a pipe or casing string — distinct from Buoyed Weight, which is the force effect of the same submerged steel, not its displaced volume. This is the steel-displacement figure that feeds directly into Trip Volume for open-ended-pipe tripping calculations.
Variables
| Symbol | Unit | Description |
|---|---|---|
| Ds | bbl/ft | Steel Displacement (per unit length) |
| V | bbl | Displaced Volume (Total) |
| OD | in | Outside diameter of the drillpipe, drill collar, or casing string being tripped or run. |
| ID | in | Inside diameter of the pipe or casing — must be smaller than OD. For a common 5in, 19.5 lb/ft drillpipe this is about 4.276in (108.6 mm). |
| L | ft | Length of the pipe or casing string (or the segment of it) being evaluated. |
Assumptions
- Pipe or casing is a simple, uniform-OD/ID tubular over the length evaluated — tool joints, upsets, and BHA components of a different diameter require evaluating each section separately
- Steel volume only — does not include fluid trapped inside the pipe ID, which is a separate quantity relevant only for closed-ended (plugged or float-equipped) strings
- OD and ID are nominal (new-pipe or tally-sheet) values — significant wear or wall-thickness variation is not accounted for
Limitations
- Computes displacement, not weight — for the force/hook-load effect of the same submerged steel, use Buoyed Weight instead; the two are related but answer different questions
- A single uniform section only — a full BHA or a tapered string requires summing this calculation per section of distinct OD/ID
- Does not account for pipe protectors, stabilizers, or tool joints, which locally increase effective OD beyond the tubular body value used here
Use Cases
- → Trip volume input: Provide the steel displacement per unit length that Trip Volume uses to compute expected fill/bleed volume while tripping open-ended pipe.
- → Casing running displacement planning: Estimate the total volume of fluid a casing string will displace as it is run in the hole, for tank/pit capacity planning.
- → Tally-sheet cross-check: Verify a pipe tally sheet's published steel-displacement figure against a first-principles geometry calculation for a given OD/ID.
Related Calculations
Region Notes
Global
A common 5in, 19.5 lb/ft drillpipe (OD 127 mm, ID 108.6 mm) displaces about 0.0034 m³/m (0.0065 bbl/ft) of steel — a typical figure carried on rig floor pipe tally sheets.
References
Need geoscience support? BauerCalc is just one of the tools we build. If you're looking for independent expertise in well planning, geosteering, reservoir characterization, or opportunity evaluation, visit BauerSubsurface.com.