Seismic Wave Velocity and Attenuation in Rocks with Mesoscopic-scale Heterogeneity

Download or read book Seismic Wave Velocity and Attenuation in Rocks with Mesoscopic-scale Heterogeneity written by Yuki Kobayashi and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation describes theoretical developments, numerical simulations, and a field case study on the effect of mesoscopic-scale medium heterogeneity on seismic velocity and attenuation. We focus on the relationship between the wave properties and water saturation. There are three approaches for the study of the effect mesoscale heterogeneity: regular geometry models, branching approaches, and statistical approaches. We develop a hybrid model providing velocity dispersion and attenuation in partially saturated rocks based on the last approach. It will be called Bounds-Averaged Dynamic-Equivalent-Medium Approach (BA-DEMA) and the variable characteristic length model. The developed model has advantages of both the branching and the statistical approaches; it has the appropriate low and high frequency limits; it has an analytical interpolation function which gives appropriate frequency dependence both in low and high frequency regimes, the interpolation function is defined with measurable parameters; and most of all, the mathematical expression is quite simple. These features are the advantages of the new model that would be enough to be recommended for the future use to predict seismic velocity and attenuation in multiphase-fluid saturated media. Forward seismic modeling is an inevitable step to connect rock's properties and their spatial distribution with observable seismic signatures. We describe a practical workflow to evaluate the effects of wave-induced fluid flow. It will serve as a practical guide in forward seismic attenuation modeling. Compared to classical forward seismic modeling procedures, two additional steps are required in attenuation modeling: permeability modeling and estimating dry rock heterogeneity scale. Many authors are trying to develop sophisticated algorithms to extract reliable attenuation information, and broad band seismic data is increasingly available even in exploration projects. The quantitative use of attenuation information derived from surface reflection seismic data is still quite challenging; however, it will become reality in the near future, where forward attenuation modeling discussed in this dissertation will become important. Not only surface reflection seismic but also other techniques such as vertical seismic profile or cross-well seismic profile are utilized to infer subsurface elastic properties and provide the useful information across a target reservoir or the overburden. The latter techniques use high frequency seismic pulse and transmitted waves, which are preferable in attenuation studies and open the possibility of extracting attenuation information more accurately. Recently, attenuation of full-waveform sonic data is also attracting attention. Procedures for the forward attenuation modeling shown in this dissertation can also help the analyses and the interpretations of the different seismic surveys.