Every foot drilled makes a fixed volume of rock that has to go somewhere — across the shakers, into the centrifuge and out to the waste skip. Size that volume up front and your dilution budget, your waste haulage and your equipment duty stop being guesses.
The number behind the whole train
Cuttings volume is the master input for solids control and waste management alike. It sets how hard the shakers and centrifuge have to work, how fast low-gravity solids build, how much dilution you'll burn, and how many cubic metres of waste you'll pay to move. It comes straight from geometry — bit size, footage and how much of the rock is solid.
Rock volume, then solids
The open hole volume for an interval is its capacity per foot times the footage. But rock is not all solid — a fraction is pore space. Multiply by one minus the porosity to get the true volume of solid cuttings the surface system must remove. That solid volume, not the raw hole volume, is your drilled-solids load.
The equation
Hole capacity and cuttings volume:
Hole capacity (bbl/ft) = D² ÷ 1029.4
Cuttings volume (bbl) = Hole capacity × Interval (ft) × (1 − φ)
D = bit / hole diameter in inches; φ = formation porosity as a fraction. Convert to cubic metres with 1 bbl = 0.159 m³.
This is dry rock only. In practice cuttings leave the well wet with mud, so the volume you actually haul and pay to treat is larger — see the disposal-cost calculation for how retained fluid bulks the waste figure up.
Common questions
Should I use bit size or hole size?
Use bit size for the volume of rock actually cut. If the hole is enlarged or washed out, the true excavated volume is larger — a caliper-corrected diameter gives the more honest number for waste planning.
Why include porosity?
Because pore space isn't solid rock. Only the solid grains become cuttings the shakers and centrifuge must remove, so multiplying by one minus porosity converts gross hole volume into the real drilled-solids load.
