es7b00594_si_001.pdf (1.57 MB)
Incorporating Nanoscale Effects into a Continuum-Scale Reactive Transport Model for CO2‑Deteriorated Cement
journal contribution
posted on 2017-08-07, 00:00 authored by Qingyun Li, Carl I. Steefel, Young-Shin JunWellbore cement deterioration is
critical for wellbore integrity
and the safety of CO2 storage in geologic formations. Our
previous experimental work highlighted the importance of the portlandite
(CH)-depleted zone and the surface dissolution zone in the CO2-attacked cement. In this study, we simulated numerically
the evolution of the CH-depleted zone and the dissolution of the cement
surfaces utilizing a reduced-dimension (1D) reactive transport model.
The approach shows that three nanoscale effects are important and
had to be incorporated in a continuum-scale model to capture experimental
observations: First, it was necessary to account for the fact that
secondary CaCO3 precipitation does not fill the pore space
completely, with the result that acidic brine continues to diffuse
through the carbonated zone to form a CH-depleted zone. Second, secondary
precipitation in brine begins via nucleation kinetics, and this could
not be described with previous models using growth kinetics alone.
Third, our results suggest that the CaCO3 precipitates
in the confined pore space are more soluble than those formed in brine.
This study provides a new platform for a reduced dimension model for
CO2 attack on cement that captures the important nanoscale
mechanisms influencing macroscale phenomena in subsurface environments.