STP869: Measurement of Thermal Conductivity and Thermal Expansion at Elevated Temperatures and Pressures

    Van Buskirk, R
    Project engineer, and lab director, Terra Tek, Inc., University Research Park, Salt Lake City, UT

    Enniss, D
    Project engineer, and lab director, Terra Tek, Inc., University Research Park, Salt Lake City, UT

    Schatz, J
    Assistant vice-president, Science Applications Incorporated, La Jolla, CA

    Pages: 20    Published: Jan 1985


    Abstract

    Laboratory procedures and equipment have been developed to measure thermal response of rock under a simulated in situ environment of overburden stress, pore fluid pressure, and temperature. Routine tests are conducted up to 250°C, with stress levels to 100 MPa, on basalt, shale, tuff, and sandstone. High-pressure high-temperature use of the transient “needle-probe” heat source technique for the measurement of thermal conductivity is discussed. Considerations in the design of the thermal expansion apparatus, which maximize stability and minimize error, are included.

    Laboratory procedures used, calibration techniques, and overall accuracy of the testing are reviewed. Thermal conductivity and thermal expansion are measured on equipment calibrated by using fused quartz as a standard. Uncertainty of calibrations caused by some inconsistency in published values for fused quartz is discussed. Methodical specimen preparation, frequent calibrations and computer test control, and data reduction allow accuracy to be maximized and relatively long-term tests to be conducted with a high degree of repeatability.

    Where possible, results of the tests are compared with previously published values. A suite of data obtained in support of studies on a potential nuclear waste repository in tuff is examined. Comparisons of theoretical thermal conductivities and expansions, derived from the behavior of the mineral constituents of the rock, and the measured responses are made.

    The advantages of these systems lie in the relative ease by which specimens may be tested at elevated temperatures and pressures, and the repeatability of the results. The accuracies (which are dependent upon calibration accuracies) are well within the range of engineering investigations.

    Keywords:

    thermal properties, pressures, temperature, thermal expansion, transient technique, laboratory procedures, comparison to theoretical values, fused quartz calibration


    Paper ID: STP32833S

    Committee/Subcommittee: D18.12

    DOI: 10.1520/STP32833S


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