Speaker
Description
Permeability and diffusion evolution in well cement during CO₂ exposure using time-resolved micro-CT
The long-term sealing performance of wellbore cement is critical for underground hydrogen storage (UHS) and carbon capture and storage (CCS), where exposure to reactive CO₂ environments can substantially modify cement microstructure and transport behavior. However, the pore-scale mechanisms linking CO₂-induced structural evolution to changes in permeability and diffusion remain insufficiently quantified.
In this study, high-resolution micro-computed tomography (micro-CT) datasets of Class G cement samples exposed to a CO₂-rich environment for 0, 7, 14, 28, and 56 days are used to construct three-dimensional digital cement models. Image segmentation and pore structure characterization are first performed to quantify the evolution of porosity, pore size distribution, connectivity, and tortuosity at different reaction stages. Pore-scale simulations are then conducted to evaluate transport properties, where permeability is obtained from numerical flow simulations based on the resolved pore geometry, and diffusion is modeled by accounting for both molecular diffusion and Knudsen diffusion mechanisms to capture gas transport behavior in nano-scale pore throats dominated by wall scattering.
The results reveal a strongly heterogeneous, multi-zone evolution of cement pore structure during CO₂ exposure. Dissolution in the outer reaction layers locally increases porosity and connectivity, whereas precipitation processes, including CaCO₃ formation and gypsum-induced nanopore filling, reduce pore space and connectivity within the carbonation layer and cement interior. This competing dissolution–precipitation mechanism leads to partial self-sealing at early reaction stages, followed by a pronounced increase in alteration depth after 28 days as the carbonate layer becomes defective and allows deeper fluid penetration. Consequently, permeability and diffusion are expected to exhibit non-monotonic temporal evolution governed by the balance between pore opening and pore blockage.
By directly linking time-resolved microstructural evolution to pore-scale transport simulations, this study provides quantitative insight into the permeability and diffusion behavior of wellbore cement under CO₂-rich conditions, with important implications for assessing long-term wellbore integrity in UHS and CCS applications.
| Country | UK |
|---|---|
| Student Awards | I would like to submit this presentation into both awards |
| Acceptance of the Terms & Conditions | Click here to agree |
