Temperature-baric dependence of the effective thermal conductivity of amorphous and polycrystalline rocks

Abstract

The paper presents the results of experimental studies of the temperature-baric effective thermal conductivity of a number of sandstones and granites. For the presentation we have chosen four sandstone samples from Dagestan and Tyumen deposits, two of which have a prevailing crystalline ordering, and two – a structure close to amorphous, and two samples of granite from Dagestan and Kola deposits. The experiment was provided by the absolute stationary compensation method of flat plates in the temperature range of 273–523 K in the range of hydrostatic pressures from atmospheric to 400 MPa. The results confirmed the proposed low-parameter model. The measured values of the thermal conductivity of the samples at 300 K were in the range from 0.7 to 3.5 W/m K. The temperature dependence in the considered range in all cases is well described by the power-law dependence. In addition, we have found a fairly significant correlation between the baric dependence of the effective thermal conductivity itself in the normalized dimensionless representation and the baric dependence of the exponent in the temperature dependence. This correlation can be traced for all studied samples of granites and sandstones and it makes possible to reduce the number of independent parameters. We have also shown that for sandstones with an amorphous structure, a simultaneous increase in temperature and pressure can lead to a rather significant total contribution. If taking into account the temperature-baric dependence of the effective thermal conductivity for rocks with a more common predominantly crystalline order, as noted by a number of authors, is not necessary due to the compensation of the pressure and temperature contributions, then for significantly amorphous rocks these contributions are summed up, and the total contribution may turn out to be significant.