[MIS02-P05] Thermal property measurements of core samples retrieved from Futagawa fault drilling
Keywords:Drilling, thermal properties, Temperature
We measured density, porosity and three thermal transport properties (thermal conductivities, thermal diffusivities, specific heat capacities) of 20 cores drilled from the borehole in the depth range from 300 m to 700 m. I selected typical rock cores to cover not only the depth intervals and also all the main rock types. The rock types of cores are basal sedimentary rocks in 300 m - 353 m , andesite in 353 m - 514 m, sandstone and/or conglomerate in 514 m - 562 m, and tuff in 562 m - 700 m. Measured wet densities and porosities are 1.57 g/cm3 - 2.02 g/cm3, 40.0% - 47.8% for basal sedimentary rocks, 2.31 g/cm3 - 2.95 g/cm3, 3.1% - 25.5% for andesite, 2.29 g/cm3 - 2.41 g/cm3, 21.6% - 29.4% for sandstone and/or conglomerate, 1.99 g/cm3 - 2.29 g/cm3, 9.4 % - 35.8% for tuff. Measured thermal conductivities are 0.88 W/(mK) - 1.10 W/(mK) for basal sedimentary rocks, 1.00 W/(mK) - 1.81 W/(mK) for andesite, 1.26 W/(mK) - 1.31 W/(mK) for sandstone and/or conglomerate, 0.96 W/(mK) - 1.27 W/(mK) for tuff. And measured thermal diffusivities and specific heat capacities are 0.85 J/(g･K) - 3.46 J/(g･K) for alluvium, 0.48 m2/s - 0.91 m2/s, 1.36 J/(g･K) - 2.60 J/(g･K) for andesite, 0.49 m2/s - 0.66 m2/s, 1.95 J/(g･K) - 2.70 J/(g･K) for sandstone and/or conglomerate, 0.40 m2/s - 0.99 m2/s, 1.40 J/(g･K) - 2.93 J/(g･K) for tuff. From data of measured temperature of borehole and thermal conductivities of the cores, we calculated heat flow of in the borehole. Using this heat flow and thermal conductivities, we reconstructed the temperature profile in the borehole.
In this estimation, we couldn't reproduce the anomaly of measured temperature. So we conclude that the anomaly of measured temperature is not caused by the significant change of the thermal conductivity in 310 m - 430 m depth.