Corrosive Influence of Carbon Dioxide on Crack Initiation in Quartz: Comparison With Liquid Water and Vacuum Environments

Abstract

The stimulation of crack growth in quartz and siliceous materials by injecting carbon dioxide (CO2) represents a key technology in long‐term carbon storage and in the development of natural gas wells. While this technology is widely used, the molecular impact of CO2 interactions on the solid matrix is only incompletely understood. In this work, we employ reactive molecular dynamics simulations to study how the CO2 fluid environment affects the mechanical properties of pre‐cracked single‐crystal quartz. The thermodynamic conditions of interest are those relevant to subsurface reservoirs. We report how structural properties of quartz—bond length distribution and crack tip shape—evolve upon introduction of a fluid. These properties are directly related to macroscopic quantities of the global stress–strain curves, thus reaffirming the inherent coupling across multiple scales for fluid–solid interactions in the subsurface. We find that CO2 reduces the fracture toughness of quartz by 12.1% compared to that of quartz in vacuum, thereby promoting crack growth and enhancing fluid transport in the subsurface.

The Local Electronic Structure of Supercritical CO2from X-ray Raman Spectroscopy and Atomistic-Scale Modeling

“…The overall intensity of transitions to 4sσ are higher than those to 3pπ states; hence, the oxygen K-edge spectra are more sensitive to changes in the local electronic structure than the carbon K-edge spectra for supercritical CO 2 . These results support the sensitivity of XRS to extract fundamental electronic structure insights that dictate the response of supercritical CO 2 under nanoconfined environments (such as in tight shales) relevant to CCS, as this ultimately affects the CO 2 chemical reactivity and corrosion propensity …”

“…These results support the sensitivity of XRS to extract fundamental electronic structure insights that dictate the response of supercritical CO 2 under nanoconfined environments (such as in tight shales) relevant to CCS, as this ultimately affects the CO 2 chemical reactivity and corrosion propensity. 11 ■ ASSOCIATED CONTENT * sı Supporting Information…”

“…This phase behavior makes it useful in chemical reactions, separation processes, and energy production. − One of the key applications involving CO 2 is carbon capture and sequestration (CCS), which is an integral part of climate change mitigation efforts. − In CCS, CO 2 is captured from emission sources and stored underground in reservoirs at supercritical conditions . The chemical processes used to extract CO 2 from emission plants, as well as the interactions of CO 2 with rocks and other fluids when stored underground, depend on the microscopic structure, intermolecular forces, and the dynamics of supercritical CO 2 . − The structure of CO 2 has been studied with molecular dynamics (MD) simulations and X-ray and neutron scattering experiments. − Radial distribution functions (RDFs) from MD simulations indicate an evolution in the structural behavior of supercritical CO 2 with pressure and the preferred T-shape alignment of CO 2 molecules in the liquid and supercritical regions. − While previous studies have focused on the extended molecular structure, the local electronic structure of CO 2 at supercritical conditions has not been thoroughly examined. Previous studies have shown that some thermophysical properties have maxima along a line originating from the critical point, which separates the fluid behavior into liquid-like and gas-like regimes. ,− We hypothesize that the electronic structure of CO 2 undergoes similar changes near the critical point as a result of the molecular geometry and orientation at these conditions.…”