Modeling the hydration, viscosity and ultrasonic property evolution of class G cement up to 90 ℃ and 200 MPa by a scale factor method

A comprehensive experimental program has been performed to characterize the hydration and engineering property evolution of a class G oil well cement under various curing temperatures from 30 to 90 ℃. The progress of hydration was monitored by isothermal calorimetry (atmospheric pressure); the viscosity evolution was measured using a high temperature and high pressure consistometer (up to 200 MPa); the ultrasonic property development was evaluated by an ultrasonic cement analyzer (up to 100 MPa). Test results indicate that the influences of curing temperature and pressure on the hydration, viscosity and ultrasonic property development can be modeled by a scale factor method that is similar to the maturity method used in the concrete industry. However, the key parameters of the scale factor model, namely the apparent activation energy and the apparent activation volume of cement showed obvious variations with test method and curing condition. The test results indicate that the curing temperature has a stronger effect on cement hydration rate than viscosity and ultrasonic property development rate, while the curing pressure has a much stronger influence on cement slurry properties before setting (viscosity) than after setting (ultrasonic property).