drilling · hydraulics
Trip Volume
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Inputs
bbl/ft
bbl/ft
ft
Description
Computes the volume of mud that must be added (tripping out) or displaced (tripping in) to account for open-ended pipe steel displacement over a trip interval, and the corresponding expected change in mud level. This is the standard trip-sheet calculation used to confirm the well is taking or giving back exactly the volume expected — any material mismatch against the actual trip tank reading is a well-control warning sign (a kick while tripping out, or losses while tripping in).
Variables
| Symbol | Unit | Description |
|---|---|---|
| Vfill | bbl | Expected Fill/Bleed Volume |
| ΔLevel | ft | Expected Mud Level Change |
| Cap | bbl/ft | Capacity of the open hole or casing around the pipe being tripped, from Annular Capacity. |
| Ds | bbl/ft | Steel displacement per unit length of the pipe being tripped, from Pipe Displacement. |
| L | ft | Length of pipe pulled out of (or run into) the hole over the interval being monitored — a single stand (default is a common ~93 ft/28.3 m triple), a full trip, or any interval between trip-tank readings. |
Assumptions
- Pipe is open-ended (mud moves freely through the pipe ID) — a closed-ended string (plugged, or running casing with a float shoe holding) displaces its full OD-based volume instead, not just the steel cross-section, and needs a different calculation
- Annular capacity is uniform over the interval being tripped — washouts or a casing-to-open-hole transition partway through the interval require evaluating each uniform section separately
- No fluid gain or loss to the formation during the interval — this calculation assumes the only volume change is the mechanical one from pipe movement
Limitations
- Assumes open-ended pipe throughout — does not itself distinguish open- from closed-ended tripping; the correct steel-displacement figure (from Pipe Displacement) must be supplied for the actual string configuration
- A single average annular capacity — does not account for a multi-diameter interval (e.g., pipe crossing from open hole into casing) within one trip-interval evaluation
- Reports the expected volume/level change only — it does not itself compare against an actual trip tank reading or flag a well-control event; that comparison is a manual field procedure this calculator supports but does not automate
Use Cases
- → Trip-sheet monitoring: Calculate the expected fill (tripping out) or bleed (tripping in) volume for each stand or interval, to compare against the actual trip tank reading in real time.
- → Kick/loss early-warning screening: Flag a well-control concern when the actual trip tank volume materially disagrees with this calculated expected volume for the same pipe interval.
- → Trip tank sizing: Estimate the volume range a trip tank needs to accommodate over a full trip, from the steel displacement and hole geometry.
Related Calculations
Region Notes
Global
An 8.75in hole around 5in drillpipe (0.026 m³/m annular capacity) pulling a single ~93 ft (28.3 m) stand of open-ended 5in, 19.5 lb/ft drillpipe expects roughly 0.6 bbl of fill volume and about a 12 ft mud-level change in the annulus over that stand — always cross-check against the actual trip tank reading, not just this calculated figure.
References
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