CMSP Seminar (Atomistic Simulation Webinar Series): 23 March at 11:00, Prof. Sylvia M. Mutisya

[CMSP Seminars Secretariat]

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Atomistic Simulation Webinar Series
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WEBINAR_

via Zoom



** * * Wednesday, 23 March 2022 at 11:00*** * **

Speaker:*Prof. Sylvia M. Mutisya *(SUBATECH (UMR 6457 - Institut 
Mines-Télécom Atlantique, Université de Nantes, CNRS-IN2P3) - France )


Title:***Atomistic simulations of the reactivity and transport of 
CO2within cement
*

Register in advance at:
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_Abstract_:

Wellbore cement degradation and the potential migration of fluids to the 
surface through leakage pathways is a major concern in many subsurface 
operations, such as geological CO2 sequestration. While leakage pathways 
can occur in wells due to faulty construction and other mechanical 
defects, geochemical reactions induced by the injected fluids could 
cause cement degradation, resulting in damage of wells and the 
development of leaks. This work focusses on identifying and 
quantitatively characterizing on the fundamental molecular scale, 
possible cement degradation mechanisms and reaction pathways, fluid 
transport rate and the geochemical variables that affect fluid-cement 
interactions.
The interaction of CO2 with cement is investigated using the two main 
hydrated cement phases: calcium silicate hydrate (C-S-H) and 
portlandite. The intercalation potential of CO2/H2O fluid mixtures is 
explored using grand canonical Monte Carlo (GCMC) simulations for 
Calcium Silicate Hydrate (C-S-H) porous systems in equilibrium with 
binary CO2/H2O bulk mixtures. Increasing the Ca/Si ratio of the 
confining cement pores decreases the adsorption of CO2 as water 
competitively adsorbs on the calcium cations, blocking access of CO2. 
Next, we use biased ab-initio molecular dynamics (AIMD) simulations to 
explore the reactivity of CO2 with the basal and edge surfaces of the 
portlandite cement phase in scCO2 and water-rich conditions. The 
metadynamics approach is applied to accelerate the dynamics of the rare 
reaction events and to investigate their mechanisms in detail. Our 
simulations show that supercritical CO2 undergoes a rapid barrierless 
carbonation reaction with the edge surfaces of the portlandite crystals. 
However, the carbonation reaction soon ceases due to the deposition of 
(bi)carbonate surface complexes which form a carbonate layer.  On the 
other hand, the presence of water alters the interaction of CO2 with the 
portlandite surfaces as water forms well-structured aqueous surface 
layers. Thus, the water content within the portlandite pores is the rate 
limiting step in the carbonation reaction of portlandite with H2O/CO2 
fluid. As such, CO2 reactivity for pores with highly structured water 
surface layers (with no bulk-like water) is expected to be limited due 
to the attenuated inward diffusion of the CO2 molecules.



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CMSP, Condensed Matter & Statistical Physics Section
http://www.ictp.it/research/cmsp.aspx

The Abdus Salam International Centre for Theoretical Physics
https://www.ictp.it/

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