Abstract
Rock salt formations represent key options for storage of natural gas, hydrogen,
and compressed air energy, and for storage or disposal of radioactive waste. At depths beyond
a few tens or hundreds of meters, undisturbed halite-dominated (>90%) rock salt deposits are
usually impermeable and have very low porosity. However, as a result of excavation, nearfield microcracking and associated dilatancy occur in rock salt, increasing porosity and
permeability. The connectivity of a brine- or water-vapour-filled microcrack network in
deformation-damaged salt, is expected to decrease over time, partly due to dissolutionprecipitation healing. Here, we employ 4D (i.e., time-resolved 3D) microtomography to study
the long-term evolution of dilated grain boundary and microcrack networks developed in
deformation-damaged natural salt by such brine-assisted processes. We found substantial
microstructural modification or “healing” over periods of days to a few months. Cracks and
dilated grain boundaries became crystallographically faceted, necked, discontinuous, and
disconnected, and often migrated to “recrystallize” the material, producing an increase in
tortuosity and a decrease in connectivity of the crack network. The magnitude and rate of
associated permeability reduction and its evolution with time remain to be determined in future
studies.
and compressed air energy, and for storage or disposal of radioactive waste. At depths beyond
a few tens or hundreds of meters, undisturbed halite-dominated (>90%) rock salt deposits are
usually impermeable and have very low porosity. However, as a result of excavation, nearfield microcracking and associated dilatancy occur in rock salt, increasing porosity and
permeability. The connectivity of a brine- or water-vapour-filled microcrack network in
deformation-damaged salt, is expected to decrease over time, partly due to dissolutionprecipitation healing. Here, we employ 4D (i.e., time-resolved 3D) microtomography to study
the long-term evolution of dilated grain boundary and microcrack networks developed in
deformation-damaged natural salt by such brine-assisted processes. We found substantial
microstructural modification or “healing” over periods of days to a few months. Cracks and
dilated grain boundaries became crystallographically faceted, necked, discontinuous, and
disconnected, and often migrated to “recrystallize” the material, producing an increase in
tortuosity and a decrease in connectivity of the crack network. The magnitude and rate of
associated permeability reduction and its evolution with time remain to be determined in future
studies.
| Original language | English |
|---|---|
| Title of host publication | The Mechanical Behavior of Salt X |
| Subtitle of host publication | Proceedings of the 10th Conference on the Mechanical Behavior of Salt (SaltMech X), Utrecht, The Netherlands, 06-08 July 2022 |
| Editors | J.H.P. de Bresser, M.R. Drury, P. A. Fokker, M. Gazzani, S.J.T. Hangx, A.R. Niemeijer, C.J. Spiers |
| Place of Publication | London |
| Publisher | CRC Press |
| Pages | 88-97 |
| Number of pages | 10 |
| Edition | 1 |
| ISBN (Electronic) | 9781003295808 |
| ISBN (Print) | 9781032282206 |
| DOIs | |
| Publication status | Published - 5 Jul 2022 |
| Event | 10th Conference on the Mechanical Behavior of Salt - Utrecht University, Utrecht, Netherlands Duration: 6 Jul 2022 → 8 Jul 2022 |
Conference
| Conference | 10th Conference on the Mechanical Behavior of Salt |
|---|---|
| Abbreviated title | SaltMech X |
| Country/Territory | Netherlands |
| City | Utrecht |
| Period | 6/07/22 → 8/07/22 |