Effect of pressure and temperature on the thermal conductivity of rocks

Effective thermal conductivity (ETC) of five dry rocks (sandstone, limestone, amphibolite, granulite, and pyroxene-granulite) have been measured over a temperature range from (273 to 423) K and at pressures up to 350 MPa with a steady-state parallel-plate apparatus. It is an absolute, steady-state measurement device with an operational temperature range of (273 to 1273) K and hydrostatic pressures up to 1500 MPa. The estimated uncertainty of the method is 2 The porosity of the samples (sandstone, limestone, amphibolite, granulite, and pyroxene-granulite) was 5 %, 5 %, 1.0 %, 1.0 %, and 1.2 %, respectively. A sharp increase of ETC was found for rocks at low pressures between (0.1 and 100) MPa along various isotherms between (273 and 423) K. At high pressures (P > 100 MPa), a weak linear dependence of the ETC with pressure was observed. The measured values of ETC of rocks were used to test and confirm of applicability of the various theoretical and semiempirical models. The effect of structure (size, shape, and distribution of the pores), porosity, and mineralogical composition on temperature and pressure dependences of the ETC of various rocks types is discussed.