Effective thermal conductivity of fluid-saturated rocks: Experiment and modeling

Effective thermal conductivity (ETC) of dry, gas-, oil-, and water-saturated rocks with various porosities has been measured over a temperature range from 273 K to 523 K at atmospheric pressure with a steady-state guarded parallel-plate apparatus. The expanded uncertainty of thermal conductivity and temperature measurements at the 95% confidence level with a coverage factor of k = 2 were estimated to be 4% and 30 mK, respectively. This uncertainty in ETC measurement does not include the uncertainty due to contact thermal resistance and radiative conductivity. The temperature coefficients, (∂ ln λ/∂ T)P, for fluid-saturated rocks were calculated by using the measured ETC. We interpreted measured ETC data for fluid-saturated rocks using various theoretical models in order to check their accuracy, predictive capability, and applicability. The effect of saturating fluids, structure (size, shape, and distribution of the pores), porosity, and mineralogical composition on temperature and porosity dependences of the ETC of fluid-saturated rocks was discussed. A new simple equation for ETC of fluid-saturated rocks which takes into account structure of porous media has been proposed. Using the Hofmiester model and measured thermal conductivities of dry rock materials, the values of thermodynamic properties (density, thermal expansion coefficient, enthalpy, and heat capacity) were predicted.