Earth’s Cryosphere, 2025, Vol. XXIX, No. 2, p. 15-24.
GASES AND GAS HYDRATES IN THE EARTH’S CRYOSPHERE
NUCLEAR MAGNETIC RESONANCE INVESTIGATIONS OF PHASE TRANSFORMATIONS IN FROZEN HYDRATE-CONTAINING SOILS DURING INTERACTIONS WITH SALT SOLUTIONS
B.A. Bukhanov*, E.M. Chuvilin, A.Z. Mukhametdinova, E.O. Krivokhat
Center for Petroleum Science and Engineering, Skolkovo Institute of Science and Technology, Bolshoi Boulevard 30/1, Moscow, 121205 Russia
*Corresponding author; e-mail: b.bukhanov@skoltech.ru
Experimental studies of phase transformations in frozen hydrate-containing fine sand samples during their interaction with frozen salt solutions have been conducted using low-field NMR relaxometry. The obtained results confirm that the amount of liquid water in the investigated samples increases with time as a result of salt transfer and pore hydrate dissociation. In addition to the pore hydrate dissociation and the supercooled water increase, a reverse process occurs, which is associated with the freezing of the pore solution as a result of a decrease of a salt concentration. The performed studies enable identifying the boundary of the area with the high liquid water content in soil systems in the direction of salt migration flow. In this case, the velocity of this front in the target samples was determined not only by the concentration of the contacting solution, but also by the initial content of the liquid water and the conditions of pore hydrate existence. Thus, the movement of the liquid water front in frozen sands containing metastable hydrates is about 30–40% faster than in similar soils containing stable hydrates, which is in good agreement with the results of previous studies. As a result, the developed NMR technique opens up great potential for permafrost and gas hydrate studies in general and, in particular, for understanding the contribution of non-equilibrium and equilibrium liquid water to the salt ion migration mechanism in frozen and hydrate-containing soils.
Keywords: permafrost, gas hydrates, NMR relaxometry, salt migration, hydrate dissociation, self-preservation, supercooled water, pore ice.
Recommended citation: Bukhanov B.A., Chuvilin E.M., Mukhametdinova A.Z., Krivokhat E.O., 2025. Nuclear magnetic resonance investigations of phase transformations in frozen hydrate-containing soils during interactions with salt solutions. Earth’s Cryosphere XXIX (2), 15–24.
Received June 16, 2024
Revised October 21, 2024
Accepted January 16, 2025
Translated by E.S. Shelekhova