Prediction of Corrosion Front Propagation and Safety Margins in Deep Sandstone Reservoirs: A Coupled Reactive Transport Model

To quantify the long-term integrity of deep sandstone reservoirs for CO 2 sequestration, this study integrates 120-day high-pressure immersion experiments with a coupled reactive transport model. X-ray diffraction (XRD), SEM–EDS, and ion concentration analyses were employed to identify the dissolution–precipitation behaviors of minerals like calcite. Results indicate that at a reservoir pressure of 15 MPa, the corrosion depth exhibits a unique three-stage “decrease–increase–stabilization” trajectory, reaching a maximum theoretical depth of ∼36.2 m over 40 years. Thermodynamic analysis shows that increasing pressure from 15 to 45 MPa expands the corrosion zone thickness from 7.7 to 22.4 m, driven by the enhanced CO 2 solubility and interfacial acidity. Spatially, the corrosion concentration exhibits exponential attenuation with depth, confirming that a reservoir thickness exceeding 80 m provides a sufficient safety margin against chemical leakage. Based on these findings, a four-stage evolution mechanism─initial structure, enhanced dissolution, secondary precipitation, and quasi-steady state─is proposed. Furthermore, a semiempirical power-law model ( L c = α· t β · e γ P ) is established as a rapid engineering tool for defining the safety boundaries of large-scale sequestration projects.