Earth’s Cryosphere, 2009, Vol. XIII, No. 2, p. 35-43
TEMPERATURE DEPENDENCE OF UNFROZEN WATER CONTENT IN SEDIMENTS ON THE WATER POTENTIAL MEASUREMENTS
V.A. Istomin, E.M. Chuvilin*, N.A. Makhonina**, B.A. Bukhanov*
JSC NOVATEK, 117420, Moscow, Nametkina str., 12а, Russia, vlistomin@yandex.ru
* Lomonosov Moscow State University, Department of Geology, 119992, Moscow, Vorobyovy Gory, Russia
** Research Institute of Natural Gas and Gas Technologies – VNIIGAZ, 142717, Moscow region, Leninsky district, pos. Razvilka, Russia, istomin@novatek.ru
The procedure of thermodynamic calculation of pore water phase state in sediments at subzero temperatures Celsius is based on experimental data on pore water potential, obtained at positive temperatures. Proposed exact thermodynamic relationships permitt calculation of the unfrozen water content in sediments taking into account the external (gas) pressure influence, and estimation of the equilibrium “pore water–gas–gas hydrate” for definition of non-clathrated water content in sediments depending on temperature and pressure.
An express-method of definition of unfrozen water content in sediments by water potential is developed. Analysis of experimental data on pore water potential of various sediments has demonstrated that it is expedient to consider the pore water enthalpy distinction from volumetric water enthalpy in “dry” sediments. Unfrozen water content in the range of subzero temperatures is calculated for kudinovskaya clay, using data on pore water potential. Calculation data are in good agreement with experimental data obtained by the contact method.
Key words: Thermodynamics of pore water, ice, frozen sediment, phase equilibrium, unfrozen water, pore water potential.