Molecular effects in heat conduction through porous rocks

Abstract

Thermal conductivity measurements were made on a natural Berea sandstone sample of porosity 22 per cent, with the pore space filled with various fluids at atmospheric pressure. The results indicate that the effective conductivity of the sample, when filled with a gaseous saturant, is lower than when filled with a liquid saturant of the same conductivity as the gas. This effect is qualitatively accounted for by the reduction in thermal conductivity of the gas which occurs when the gas occupies spaces which are small relative to its mean free path. The presence of such spaces is confirmed by pore size distribution data and by the increase in effective conductivity with increase in gas pressure. The effect on the thermal conductivity of a simulated net overburden pressure of 275 bars was also investigated.