The duration of operation will be used to determine the required setting time for the cement formulation. The duration of operation will be calculated on the basis of the mixing rate for the cement, the pumping rate for the cement slurry and
the pumping rate for the displacing mud. An additional period of time, known as a contingency time, is added to the calculated duration to account for any operational problems during the operation. This contingency is generally 1 hour in duration.
The duration of the operation can be calculated from: