On the use of photothermal methods for thermal characterization of sedimentary rocks from the Paranل Basin in Brazil

The thermal conductivity, thermal diffusivity, specific heat and thermal effusivity of rocks taken from Paraná Basin, in Brazil, have been measured using photothermal methods. We have used the open photoacoustic cell (OPC) for determining the thermal diffusivity and the temperature detection under continuous illumination technique for the volumetric heat capacity measurements. Using these properties and knowing the density, the determination of the heat capacity and the thermal effusivity is straightforward. We investigated three distinct types of rocks of the basin, namely, sandstone, from the Botucatu Formation, black shale and marl, from the Irati Formation. The thermal properties were determined with uncertainties around 3–13%, comparable to other methods. These values consider not only the experimental errors but also take into account the heterogeneity of the materials. The results presented in this work permit us to point the photoacoustic and a related photothermal technique as useful tools for thermal characterization of sedimentary rocks.