题目：Heterogeneity: Challenges in Rock Physics and Geomechanics

报告时间：2017年8月1号（周二）上午10点

报告地点：慧园6栋311会议室

报告人：Qiuliang Yao（Halliburton, Geomechanics & Rock Physics Consultant）

摘要

Heterogeneity, defined as the quality or state of being diverse in character or content, is a natural phenomenon that almost always presents in sedimentary rocks. The porous media is fundamentally a classical heterogeneous material consists of solid mineral and void space filled with fluids. This imposes the main challenges to any studies of the rocks, including rock physics and geomechanics. This presentation will provide an overview of how those challenges have been addressed in the past and discuss couple of recently active topics related to current applications.

In rock physics, researchers have developed various type of effective medium theories (EMT) trying to describe the elastic properties of a complex heterogeneous material equivalently as a continuous homogeneous material. From early volumetric average schemes like Voigt/Reuss bounds and Haashin-Shtrikman bounds, to more advanced inclusion based modeling approach, like Hudson model, Kuster-Toksöz model, and most recently T-matrix model. The fluid in the pore space brings in a second level of heterogeneity to the already complicated situation. While the popular Gassmann’ relationship treats the fluid as non-movable homogeneous medium filling the whole pore space, the reality is that under seismic exploration domain, the fluid can be in multiple phases, with different compressibility, and move around. Such heterogeneities have stimulated the developments of a series of poroelasticity theories, like Biot’s theory, White model, squirt model, etc.

On the other hand, tremendous efforts in experimental studies have also been made to investigate the heterogeneities of rocks, from the early velocity-porosity-shale contents measurements, to partial saturation measurement, to most recently low frequency measurements. The results from those experimental studies generated some of the most widely used robust empirical relations, and significantly improved our understanding to the mechanisms of heterogeneous rocks.

As a contrast, in geomechanics, it is still dominated by concepts and methods of the conventional continuum mechanics, with much less efforts to address the heterogeneities. The current applications in unconventional reservoir characterization and modeling demand the change to this and expose large research opportunities.

Qiuliang Yao is a geomechanics and rock physics consultant working for Halliburton. He earned his Bachelor degree in Physics from Nanjing University, a Master degree in Physics from Sam Houston State University, and a Ph.D. in Geophysics from University of Houston. His research activities ranges from fundamental poroelasticity theory, fluid effects in inhomogeneous porous media, seismic dispersion and attenuation, hydrocarbon fluid properties, to geomechanical applications, like wellbore stability, sand production prevention, and 3D reservoir geomechanical modeling. He has expertise to develop complex lab equipment for experimental rock physics studies. He is an active reviewer for Geophysics, Geophysical Prospecting, Applied Geophysics, Journal of Applied Geophysics, Journal of Earth Science, and Journal of Natural Gas Science and Engineering.