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

Ranges:

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)

Other References

More details can be obtained from 501 Solved Problems for Drilling Operations.

Glossary of Drilling Operations

Conversion Factors

General Terms

Gel Strength

Mud Weight

Formation Pressures

Well Control Calculations