A METHOD FOR THE DETERMINATION OF THE THERMAL CONDUCTIVITY OF SANDSTONES USING A VARIABLE STATE APPROACH*

Autor: G. V. Keller, K. M. Strack, C. H. Stoyer, A. W. Ibrahim
Rok vydání: 1982
Předmět:
Zdroj: Geophysical Prospecting. 30:454-469
ISSN: 1365-2478
0016-8025
DOI: 10.1111/j.1365-2478.1982.tb01317.x
Popis: Common problems encountered during the determination of the thermal conductivities of tight sandstones are rock specimen-to-heat source contact and complicated sample preparation. An experimental technique using an electromagnetic heat source solves the direct contact problem between the heat source and the sample. Also, it simplifies the sample preparation and reduces the measurement time. A CO/sub 2/ laser operating in a pulsed mode is used as a heat source with about 500 W output power. Thus, heat losses due to radiation and air convection are negligible. Unpolished penny-sized samples of tight sandstones are irradiated on one side and the temperature is measured on the opposite side. The temperature is recorded with 12-bit accuracy by a digital data acquisition system. Carbon black is used to give the samples a uniform absorption. The transient temperature data are acquired, processed, and interpreted with interactive computer programs. Transients for each sample can be stacked, to improve the signal-to-noise ratio, and normalized. The thermal conductivity is calculated from the rise portion of the transient using a ridge-regression type generalized linear inversion scheme. As many as 20 samples per hour can be measured with this simple but expensive set-up. In the long run, this means a reductionmore » of laboratory expenses. In addition, the resolution of this method is superior to other variable-state measurement methods due to the real time controlled data acquisition and the numerical interpretation.« less
Databáze: OpenAIRE
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