Abstract

AbstractWe have performed ultrasonic measurements on tight siltstone samples to obtain thePwave coda and intrinsic attenuations using a single isotropic scattering model and the spectral ratio method. The results indicate that attenuation is predominantly caused by scattering. Intrinsic attenuation increases with gas saturation and permeability and decreases with grain size, whereas coda attenuation is stronger under partial saturation conditions and increases with grain size. Porosity and mineral composition do not have significant effects on attenuation. The triple‐porosity and scattering models are used to simulate the intrinsic and scattering attenuations, respectively. The results show that the intrinsic attenuation is predominately caused by wave‐induced fluid flow between microcracks/micropores and intergranular pores. The model incorporating the scattering effects of microcracks underestimates the scattering loss in the coda, which may thus be better explained by heterogeneities in the clustering structure of grains.

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