This change of scale allows us to conclude that the behavior of P wave velocity is due to different geological features (matrix porosity, cracks, and fractures) related to the different wavelengths used. Indeed, with upscaling, the wavelength varies from millimetric to pluri-metric. To explain the variations due to upscaling, we relate the concept of representative elementary volume with the wavelength of each scale of study. Nevertheless, the median of the sonic measurements acquired on outcrop surfaces seems to fit with the seismic data, meaning that sonic acquisition may be representative of seismic scale. By comparing the median of each data set, we show that the P wave velocity decreases from laboratory to seismic scale. At one study site, we perform a seismic refraction survey (100 Hz), as well as “sonic” (54 kHz) and ultrasonic (250 kHz) measurements directly on outcrop and ultrasonic measurements on samples (500 kHz). To deal with this problem, we investigate the elastic properties of dry lacustrine carbonates. ![]() Linking ultrasonic measurements made on samples, with sonic logs and seismic subsurface data, is a key challenge for the understanding of carbonate reservoirs.
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