Quantitative determination of the hydrostatic pressure of oil-well cement slurry using its hydration kinetics

This study investigated the hydration kinetics and microstructure of oil-well cement slurry in the early hydration stage using calorimetry, X-ray powder diffraction, thermogravimetry, scanning electron microscopy, and X-ray computed tomography to reveal the hydrostatic pressure reduction mechanism and the quantitative relationship between the hydration kinetics and hydrostatic pressure of the cement slurry. The results showed that the time-varying characterisation of the hydrostatic pressure of the cement slurry was in accordance with the Arrhenius equation. During the hydrostatic pressure reduction of the cement slurry, its microstructure developed from “suspension particles” to a “particles framework,” and the “framework” bonded to external interfaces. The hydration products strengthened the “framework” and decreased the porosity, pore size, and connectivity of the cement slurry, leading to the gravity of the entire cement slurry being supported by external interfaces and the slurry lost hydrostatic pressure. Hydration kinetics indicated that the cement slurry hydrostatic pressure changed linearly with hydration heat increments. Using hydration heat increments, a prediction method which successfully predicted the hydrostatic pressure of oil-well cement slurry was developed.