Well Fluids Volume Calculator

Enter well geometry and string makeup once — then just move the bit. Volumes update live for drilling, tripping, running in hole and circulating.

Dashboard — Inputs

CURRENT BIT DEPTH m

CURRENT HOLE DEPTH m

PUMP RATE bbl/min

ACTIVE PIT VOLUME bbl

SAND TRAP VOLUME bbl

SURFACE LINES VOLUME bbl

Dashboard — Outputs

OPEN WELL VOLUME — bbl

ANNULUS VOLUME — bbl

INTERNAL STRING VOLUME — bbl

STEEL DISPLACEMENT — bbl

TOTAL CIRCULATING VOLUME — bbl

BOTTOMS-UP TIME — min

TOTAL SURFACE VOLUME — bbl

FULL SYSTEM VOLUME — bbl

FULL SYSTEM CIRC. TIME — min

RATHOLE (HOLE − BIT) — m

Well Geometry

Enter once. Top MD chains from the section above; the last section's Bottom MD always tracks Current Hole Depth.

Description	Top MD (m)	Bottom MD (m)	Hole ID (in)	Length (m)

String Makeup

Enter once, order from the BIT upward (bottommost component first). Bottom/Top MD are computed automatically from Current Bit Depth.

Component	OD (in)	ID (in)	Length (m)	Bottom MD (m)	Top MD (m)

HOW THE POSITION-BASED VOLUME MODEL WORKS

Most drilling fluid spreadsheets are static — a snapshot of the well with the BHA on bottom at TD. The moment you trip, drill ahead, or circulate off bottom, the manually entered pipe lengths per section are wrong and someone has to re-split them by hand. This calculator removes that step: string position is driven entirely by Current Bit Depth and Current Hole Depth, and every other length is derived automatically.

THE OVERLAP METHOD

Each string component's Bottom MD and Top MD are computed by chaining lengths upward from the bit — the bottommost component's Bottom MD equals Current Bit Depth, and each component's Top MD is its own Bottom MD minus its length, which becomes the Bottom MD of the component above it. Well sections (casing, liner, open hole) chain the same way from surface down, with the last section's Bottom MD tied to Current Hole Depth.

For every component × well-section pair, the length of that component actually inside that section is:

Overlap = MAX(0, MIN(Component Bottom, Section Bottom) − MAX(Component Top, Section Top))

Summed across all pairs, this automatically redistributes pipe between casing, liner and open hole as the bit moves — no manual interval lengths, ever.

DRILLING, TRIPPING AND CIRCULATING

Drilling ahead: update Bit Depth and Hole Depth together as you drill down.
Tripping out: update Bit Depth only — Hole Depth stays fixed at the last drilled TD. Components above surface simply stop contributing volume.
Running in hole: update Bit Depth only, up to the fixed Hole Depth.
Backreaming / circulating off bottom: set Bit Depth to the pipe's actual position; Hole Depth stays fixed.