Sediment porosity and permeability reduce along a complex mechano-chemical compaction pathway with burial due to the increase of the overburden pressure. The compaction can involve pressure solution, cementation, slow-crack growth, and mineral stabilization. However, we still do not understand the role of the solution in governing the compaction dynamics, despite the expectation that fluid confined between grains mediates the molecular interactions, allows easier particle rearrangement and sliding, and simultaneously provides the resistance to overburden pressure.<br/>Here, we present molecular modeling of the evolution of water structural arrangement and dielectric properties during the calcium carbonate compaction. These properties are significantly different in the nanoconfined environment provided by the ensemble of carbonate particles than in the unconfined conditions. We also compared the characteristics of the interfacial water in the confined environment with those of the interfacial water properties for an isolated carbonate/electrolyte interface and water confined in the porous materials. In general, the spatial distribution of the dielectric constant is consistent with the density variation. However, in the case of a mineral grain ensemble, the proximity of the surfaces, overlapping double layers, and long-range molecular interactions affect the interfacial water properties.<br/>When an irregular suspension of calcite grains in the electrolyte is squeezed under applied compressive stress, the interfacial hydration layers are pushed to the side as the calcite grains approach each other, allowing the calcite grains to come into direct contact. The development of the particle-particle contacts and increased rigidity of the hydrogen-bond network of pore water are responsible for increasing the stiffness of sediment upon burial and water dielectric properties.

Water dielectric signatures in the carbonate confinement and along the compaction pathway

Where thousands of chemistry professionals meet to share ideas and advance scientific and technical knowledge. Spring 2023 abstracts, posters, and presentations will launch at the end of March.

ACS Spring 2023

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.