Earth Resources Laboratory, Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
J Acoust Soc Am. 2012 Aug;132(2):630-40. doi: 10.1121/1.4733545.
The seismic response of saturated porous rocks is studied numerically using microtomographic images of three-dimensional digitized Berea sandstones. A stress-strain calculation is employed to compute the velocities and attenuations of rock samples whose sizes are much smaller than the seismic wavelength of interest. To compensate for the contributions of small cracks lost in the imaging process to the total velocity and attenuation, a hybrid method is developed to recover the crack distribution, in which the differential effective medium theory, the Kuster-Toksöz model, and a modified squirt-flow model are utilized in a two-step Monte Carlo inversion. In the inversion, the velocities of P- and S-waves measured for the dry and water-saturated cases, and the measured attenuation of P-waves for different fluids are used. By using such a hybrid method, both the velocities of saturated porous rocks and the attenuations are predicted accurately when compared to laboratory data. The hybrid method is a practical way to model numerically the seismic properties of saturated porous rocks until very high resolution digital data are available. Cracks lost in the imaging process are critical for accurately predicting velocities and attenuations of saturated porous rocks.
利用三维数字化 Berea 砂岩的微断层图像，对饱和多孔岩石的地震响应进行了数值研究。采用应力-应变计算方法计算了尺寸远小于感兴趣地震波长的岩样的速度和衰减。为了补偿成像过程中丢失的小裂缝对总速度和衰减的贡献，开发了一种混合方法来恢复裂缝分布，其中差分有效介质理论、Kuster-Toksöz 模型和改进的喷射流模型在两步蒙特卡罗反演中得到了应用。在反演中，使用了干燥和饱和情况下测量的 P-和 S-波速度，以及不同流体测量的 P-波衰减。通过使用这种混合方法，与实验室数据相比，准确地预测了饱和多孔岩石的速度和衰减。在获得非常高分辨率的数字数据之前，混合方法是对饱和多孔岩石的地震特性进行数值建模的一种实用方法。在成像过程中丢失的裂缝对于准确预测饱和多孔岩石的速度和衰减至关重要。
