Experimental studies on perturbed acoustic resonant spectroscopy by a small rock sample in a cylindrical cavity |
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Authors: | CHEN Dehua WANG Xiuming CONG Jiansheng XU Delong SONG Yanjie MA Shuilong |
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Institution: | 1. Department of Geophysics,Daqing Petroleum Institute,Daqing,163318,China;Institute of Acoustics,Chinese Academy of Sciences,Beijing,100080,China 2. Institute of Acoustics,Chinese Academy of Sciences,Beijing,100080,China;Division of Petroleum,Australian Commonwealth Scientific and Industrial Research Organization,Bent ley WA 6102,Australia 3. Department of Geophysics,Daqing Petroleum Institute,Daqing,163318,China 4. Daqing Testing and Technology Services Corporation,Daqing,163153,China |
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Abstract: | A measurement system for acoustic resonant spectroscopy (ARS) is established, and the effects of resonant cavity geometry,
inner perturbation samples and environmental temperature on the ARS are investigated. The ARSs of the small samples with various
sizes and acoustic properties are measured. The results show that at the normal pressure, the resonant frequency decreases
gradually with the increase of liquid temperature in the cylindrical cavity, while the resonant amplitude increases. At certain
pressure and temperature, both the resonant frequency and the amplitude decrease greatly when there exist air bubbles inside
the cavity fluid. The ARS is apparently affected by the sample porosity and the sample location in the resonant cavity. At
the middle of the cavity, the resonant frequencies reach their maximum values for all of the measurement samples. The resonant
frequencies of the porous rock samples are smaller than those of the compacted samples if other acoustic parameters are the
same. As the sample is moved from the top to the middle of the cavity along its axis, the resonant amplitude increases gradually
for the compacted rocks while decreases for the unconsolidated rocks. Furthermore, the resonant amplitude increases firstly
and then decreases if the porosity of the rock sample is relatively small. In addition, through the comparisons between the
experimental and theoretical results, it is found that the effects of the acoustic parameters and sizes of the samples and
the size of the cylindrical cavity on the laboratory results agree well with the theoretical ones qualitatively. These results
may provide basic reference for the experiment study of rock acoustic properties in a low frequency using ARS. |
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Keywords: | acoustic resonant spectroscopy acoustic velocity and attenuation experiment measurement rock acoustic property |
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