Modelling stress evolution in cement plugs during hydration
conference paper
In this work, we have developed a methodology to model the stress evolution in cement plugs during hydration. The
model begins with the slurry state of cement and calculates the water consumption and void creation over time as the hydration
reactions progress. The void volume change due to chemical shrinkage is imported into a coupled mechanical model that calculates
the pore pressure drop and the resulting change in stresses. The results of the proposed modelling methodology are verified using lab
experiments from the literature. The results provide new insights in understanding cement behavior under lab and field conditions.
Under most scenarios, cement’s pore pressure drops to saturation pressure of water which leads to partial evaporation of the remaining
pore water. This pore pressure drop controls the radial stress change, according to the theory of poroelasticity. For a plug set under
an initial pressure of 5 MPa, the radial stress drops to 1.6 MPa after 20 hours of curing. This stress drop can cause the cement to
debond from the casing, if the fluid pressure above the plug exceeds the final radial stress. This methodology can be extended to
annular cements and initial cement stress after placement can be readily calculated.
model begins with the slurry state of cement and calculates the water consumption and void creation over time as the hydration
reactions progress. The void volume change due to chemical shrinkage is imported into a coupled mechanical model that calculates
the pore pressure drop and the resulting change in stresses. The results of the proposed modelling methodology are verified using lab
experiments from the literature. The results provide new insights in understanding cement behavior under lab and field conditions.
Under most scenarios, cement’s pore pressure drops to saturation pressure of water which leads to partial evaporation of the remaining
pore water. This pore pressure drop controls the radial stress change, according to the theory of poroelasticity. For a plug set under
an initial pressure of 5 MPa, the radial stress drops to 1.6 MPa after 20 hours of curing. This stress drop can cause the cement to
debond from the casing, if the fluid pressure above the plug exceeds the final radial stress. This methodology can be extended to
annular cements and initial cement stress after placement can be readily calculated.
Topics
TNO Identifier
977886
ISBN
9780979497575
Publisher
American Rock Mechanics Association (ARMA)
Source title
This paper was prepared for presentation at the 56th US Rock Mechanics/Geomechanics Symposium held in Santa Fe, New Mexico, USA, 26-29 June 2022
Pages
1-7
Files
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