Surge, Swab & Tripping
Tripping maths — hole-fill per stand, a simplified surge/swab pressure estimate, trip margin, and usable accumulator volume. Field and metric units, fully offline. Surge/swab is an estimate only.
Open Surge, Swab & Tripping →What is the surge, swab & tripping calculator?
A tripping calculator that runs entirely in your browser. It works out four things a driller needs when running pipe in or out of the hole: the mud volume needed to keep the hole full as each stand is pulled (trip fill), a simplified steady-state estimate of the surge or swab pressure a moving string generates, the trip margin — the extra mud weight whose hydrostatic offsets swabbing — and the usable fluid volume of a BOP accumulator bottle. Field units (in, ft, psi, gal) and metric units (mm, m, bar, L) are both supported, and every result updates as you type. Nothing is uploaded — the maths uses the standard Lapeyrouse constants and stays on your device.
How to use Surge, Swab & Tripping
- Choose your units — Use the Field / Metric switch at the top. Field is inches, feet, psi and gallons; metric is millimetres, metres, bar and litres.
- Pick a calculation — Select a tab — Trip fill, Surge & swab, Trip margin or Accumulator — for the value you need.
- Enter the known values — For trip fill, choose dry/closed-end or open-end and type the pipe sizes and stand length. The other tabs take rheology, hole and pipe sizes, running speed or accumulator pressures.
- Read the result — The main figure is your answer; the smaller line shows a helpful equivalent, such as the fill per foot or the clinging velocity used.
Frequently asked questions
What is the difference between dry and open-end trip fill?
A dry or closed-end pull (floats holding, mud unable to enter the pipe) displaces the full OD footprint, OD² ÷ divisor. An open, free-draining string displaces steel only, (OD² − ID²) ÷ divisor. Dry is the usual trip-fill case and the default here.
How accurate is the surge and swab figure?
It is an estimate only. The model is steady-state and neglects fluid inertia and pipe acceleration, so a real peak surge is higher. Use it for a quick check and verify critical trips against a transient hydraulics model.
Which pressures does the accumulator tab use?
Absolute pressures. It adds 14.7 psi (or 1.013 bar) to the precharge, minimum and maximum settings and applies Boyle's law, so the usable volume is isothermal and ignores gas non-ideality and temperature.
Does it work offline?
Yes. There are no dependencies and no network calls, so it runs on a rig laptop with no signal, and your last inputs are saved on your device.
Tips
- Trip fill assumes dry, closed-end pipe by default — switch to open-end only when the string is genuinely free-draining, or you will under-fill the hole.
- Surge and swab are equal in magnitude: surge adds to bottom-hole pressure as you run in, swab subtracts the same amount as you pull out.
- Trip margin is a rough guide to the mud-weight bump that offsets gel-strength swabbing, not a replacement for a full swab calculation on a tight hole.