A method to measure thermal conductivity and thermal diffusivity under pore and confining pressure

Abstract

A measuring equipment was developed for the determination of thermal conductivity and thermal diffusivity of rocks under pore and confining pressure up to 90 MPa and 300 MPa, respectively. A quadratic heater placed between two cubic samples generates a rectangular heat pulse of 5 s length. In one of the cubes the pulse response at a known distance from the heater is measured by a thermocouple. The sample holder is mounted on the upper plug of the used high pressure vessel. The whole sample arrangement is sealed against the pressure medium by an elastic polyurethene jacket. Pore fluid is introduced into the pore space of the rock sample by a perforated back plate. A numerical modelling of the pulse propagation is used to determine thermal conductivity and thermal diffusivity from the measured pulse amplitude and half value time. First results are given for a 16 % porosity sandstone from Obernkirchen, Germany.