Squirt driven by local pressure imbalance between contact of grains (or throat) and the main pore space is a mechanism of P-wave attenuation in consolidated rocks. In this paper, we investigate squirt in unconsolidated and consolidated porous media (represented by Toyoura sands and compressed glass beads, respectively). The former sample has very small bulk modulus and shear modulus, manifested by relatively free/mobile grains. As such, solid stress on the surface tends to be uniform and squirt should be minor. Biot’s theory improved with dynamic permeability successfully predicts the ultrasonic velocity and quality factor of P wave measured in the unconsolidated sands, confirming the aforementioned judgment. Dynamic permeability inverted at a high frequency is far lower than Darcy permeability. However, the improved model remains to be incapable of predicting velocity and attenuation measured in the latter sample; the reason is that the compressed beads allows a high pressure at compliant throat which drives strong squirt between throat and the main pore space.

中文翻译：

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松散沙子中的少量喷射与压缩玻璃珠中的强烈喷射

由颗粒（或喉道）与主要孔隙空间接触之间的局部压力不平衡驱动的喷射是固结岩石中纵波衰减的机制。在本文中，我们研究了松散和固结多孔介质（分别以 Toyoura 砂和压缩玻璃珠为代表）中的喷射。前一个样品具有非常小的体积模量和剪切模量，表现为相对自由/流动的晶粒。因此，表面上的固体应力趋于均匀，喷射应该很小。Biot 的动态渗透率改进理论成功地预测了在松散砂岩中测量的 P 波的超声速度和品质因子，证实了上述判断。高频反演的动态磁导率远低于达西磁导率。然而，改进后的模型仍然无法预测在后一个样本中测得的速度和衰减；原因是压缩的珠子允许在柔顺的喉咙处产生高压，从而在喉咙和主孔隙空间之间产生强烈的喷射。