Geothermal measurements

Properties measured in the laboratory include thermal conductivity, which indicates a material’s ability to conduct heat; specific heat capacity, which determines a material’s ability to store heat; and thermal diffusivity, which determines how quickly a sample can change its temperature.

Using the divided bar method, thermal conductivity is measured from a 7 mm thick disc cut from a core sample. Before measurements, the samples are saturated with water for two days at normal room temperature. Specific heat capacity can be determined using a calorimeter. If the density of the sample is known, thermal diffusivity can also be calculated from these values.

Another option is the Hot Disk, which can be used to measure thermal conductivity, thermal diffusivity, and heat capacity directly from a core sample. Measurements can be taken from a sample with at least one sawn surface. This method requires less sample preparation than the divided bar method but is significantly more sensitive to sample heterogeneity.