Cementing Calculations

Slurry Volume

The slurry volume = cement volume, gal+ water volume, gal+ additive volume, gal

Yield of Cement

Y = yield of slurry = (slurry volume gal /7.48) ft3/sack

Cement Slurry Requirements

Number of sacks of cement = slurry volume, cu.ft / yield of cement, cu.ft/sack

Mix Water Requirement

  • Mix water requirement = mix water per sack x number of sacks
  • Number of sacks of additive = number of sacks x percentage of additive
  • Weight of additive = number of sacks of additive x 94 lbs

Slurry Density

Slurry density = (weight of cement, lb+ weight of water, lb+ weight of additive, lb)/ (volume of cement, gal+ volume of water, gal+ volume of additive, gal)

Hydrostatic Pressure Reduction

Hydrostatic pressure reduction due to spacer = 0.292 (density of mud, ppg – density of spacer, ppg)x annular capacity, ft3/ft x spacer volume, bbl

Contact Time

An estimation of the volume of cement needed for removal of mud cake by turbulent flow is :

  • Volume of fluid (in turbulent flow), ft3 /bbl= 5.616 x contact times, minutes x displacement rate, bbl/min

Gas Migration Potential

Gas migration potential = 1.67 x (length of the pipe column exposed to the cement from the reservoir zone, ft /( diameter of the hole, in – outside diameter of the casing pipe, in)/Formation pressure, psi


  • 0 – 3 Low
  • 3 – 8 Moderate
  • > 8 High

Cement Plug

  • Number of sacks of cement = length of plug, ft x capacity of the hole, ft3/ft/ yield of cement
  • Spacer volume ahead of slurry = volume of spacer behind slurry x annular capcity/ pipe volume, ft3
  • Length of Plug = number of sacks x yield/ ( anular volume of pipe + annular volume)