Wang D, Qu S L, Zhao Q, Yin X Y, Zhou F
SINOPEC Key Laboratory of Geophysics, Nanjing 211103, China; SINOPEC Geophysical Research Institute, Nanjing 211103, China.
SINOPEC Geophysical Research Institute, Nanjing 211103, China.
Ultrasonics. 2017 Sep;80:101-112. doi: 10.1016/j.ultras.2017.05.007. Epub 2017 May 13.
Ultrasonic wave propagation in a synthetic medium with different scale fractures is investigated through the physics modeling research. The experiment model consisting of two layers, the first layer is divided into four fractured blocks with a constant fracture density but different dimension and a block without fractures as the reference region. The velocity and reflected amplitude of wave derived from the wide azimuth data processing are anisotropic due to the fractured layer. Coda wave characteristics versus offset and azimuth are obviously different for varying fracture scales. The ratio of wavelength and fracture dimension is an important parameter in the wave-fracture interaction based on the multiple scattering theory. When the wavelength of the incident wave is close to the fracture length, the scattering is dominant in the shot records and the waves are slowed and attenuated largely for the reflections from the bottoms of fractured layer and base model. The physical modeling results demonstrate that it is possible to extract fracture dimension and orientation information by analyzing code and primary waves from the reflection data.
通过物理模拟研究，对超声波在具有不同尺度裂缝的合成介质中的传播进行了研究。实验模型由两层组成，第一层被划分为四个具有恒定裂缝密度但尺寸不同的裂缝块以及一个无裂缝块作为参考区域。由于裂缝层的存在，从宽方位数据处理得到的波的速度和反射振幅是各向异性的。对于不同的裂缝尺度，尾波特征随偏移距和方位角的变化明显不同。基于多重散射理论，波长与裂缝尺寸之比是波与裂缝相互作用中的一个重要参数。当入射波的波长接近裂缝长度时，散射在炮记录中占主导地位，并且对于来自裂缝层底部和基础模型的反射，波会大幅减速和衰减。物理模拟结果表明，通过分析反射数据中的尾波和初波，可以提取裂缝尺寸和方位信息。
