The acoustic properties of rocks depend on porosity, pressure, and pore fluid and also on pore geometry. Anelasticity (attenuation and velocity dispersion) is more affected by crack aspect ratio and fraction (soft pores) than by equant (stiff) pores. To study this fact, we have performed ultrasonic measurements on two dolomite samples under variable pressure and fluid content, and used the EIAS (equivalent inclusion-average stress) model to obtain the crack aspect ratio and fraction from the bulk and shear moduli of the rock. The theory has an excellent agreement with the experimental data, and the results show that the crack attributes decrease with increasing differential pressure and are higher for a stiffer fluid. In fact, the interpretation of the experiments with the model shows that crack fraction and aspect ratio increase with the bulk modulus of the fluid (water and oil). Then, by extending the theory to all frequencies, using the Zener mechanical model, we obtain the phase velocities and quality factors as a function of frequency. Our findings reveal the importance of considering differential pressure and fluid type to analyze pore geometry and rock anelasticity. Graphical abstract The EIAS (equivalent inclusion-average stress) model is used to obtain the crack aspect ratio and fraction by fitting the bulk and shear moduli of dolomites with varying differential pressure at full water and oil saturations. The EIAS (equivalent inclusion-average stress) model is used to obtain the crack aspect ratio and fraction by fitting the bulk and shear moduli of dolomites with varying differential pressure at full water and oil saturations.

中文翻译：

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压力和流体对白云岩孔隙几何形状和弹性的影响

岩石的声学特性取决于孔隙度、压力、孔隙流体以及孔隙几何形状。非弹性（衰减和速度弥散）受裂纹纵横比和分数（软孔）的影响比等长（硬）孔的影响更大。为了研究这一事实，我们在可变压力和流体含量下对两个白云岩样品进行了超声波测量，并使用 EIAS（等效包裹体平均应力）模型从岩石的体积和剪切模量中获得裂缝纵横比和分数. 该理论与实验数据具有极好的一致性，结果表明裂纹属性随着压差的增加而降低，并且对于更硬的流体更高。实际上，模型实验的解释表明，裂缝分数和纵横比随着流体（水和油）的体积模量而增加。然后，通过将理论扩展到所有频率，使用齐纳力学模型，我们获得了作为频率函数的相速度和品质因数。我们的研究结果揭示了考虑压差和流体类型以分析孔隙几何形状和岩石非弹性的重要性。图形摘要 EIAS（等效夹杂平均应力）模型用于通过拟合全水饱和度和油饱和度下不同压差的白云岩的体积和剪切模量来获得裂缝纵横比和分数。