压力对含裂缝岩石各向异性速度的影响

深入了解压力作用下裂缝性岩石的声学各向异性,在地球物理应用中具有重要意义.本文基于各向异性微分等效介质模型,结合不同压力下含硬币状定向排列裂缝岩石以及不含裂缝岩石在不同方向上的超声速度测量数据,计算得到不同压力下的裂缝参数,并进一步分析了压力引起的裂缝参数的改变,及其对岩石各向异性速度的影响.结果表明,岩石的裂缝密度与...

Pressure effects on the anisotropic velocities of rocks with aligned fractures

Understanding the pressure-dependent anisotropic acoustic properties of fractured rocks is of great importance in a range of geophysical applications. Using the anisotropic differential effective medium model, and based on published experimental data of the pressure dependent anisotropic ultrasonic velocities of dry rocks with and without aligned penny-shaped fractures, we calculated the crack density and crack aspect ratio with varying pressure. We also studied theoretically the effects of the pressure-dependent fracture parameters on the anisotropic acoustic properties of fractured rocks. The results showed that crack density decreases exponentially while crack aspect ratio reduces linearly with increasing pressure. We also showed that all the five anisotropic velocities increase to different degrees with decreasing crack density resulting from the increasing pressure, where the most significant increase is found for the P-wave velocity propagating in the direction vertical to the fractures. The reducing crack aspect ratio as a result of increasing pressure showed negligible impact on the velocities, and the anisotropy parameters were found to gradually decrease with the decrease of the crack density caused by the increasing pressure, the anisotropy of the rock decreases.