Applied Seismic Anisotropy

The vertical seismic profile, acquired with an array of 3C receivers and either a single source or several arranged in a multi-component configuration, provides an ideal high fidelity calibration tool for seismic projects involved in the application of seismic anisotropy. This book catalogues the majority of specialized tools necessary to work with P-P, P-S and S-S data from such VSP surveys at the acquisition design, processing and interpretation stages. In particular, it discusses 3C, 4C, 6C and 9C VSP, marine and land surveys with near and multiple offsets (walkways), azimuths (walkarounds) or a combination of both. These are considered for TIH or TIV flavours of seismic anisotropy arising from cracks, fractures, sedimentary layering, and shales. The anisotropic adaptation of familiar seismic methods for velocity analysis and inversion, reflected amplitude interpretation, are given together with more multi-component specific algorithms based upon the principles dictated by the vector convolutional model. Thus, multi-component methods are described that provide tests and compensation for source or receiver vector fidelity, tool rotation correction, layer stripping, near-surface correction, wavefield separation, and the Alford rotation with its variants. The work will be of interest to geophysicists involved in research or the application of seismic anisotropy using multi-component seismic.

Understanding Seismic Anisotropy in Exploration and Exploitation (second edition) by Leon Thomsen is designed to show you how to recognize the effects of anisotropy in your data and to provide you with the intuitive concepts that you will need to analyze it. Since its original publication in 2002, seismic anisotropy has become a mainstream topic in exploration geophysics. With the emergence of the shale resource play, the issues of seismic anisotropy have become central, because all shales are seismically anisotropic, whether fractured or not. With the advent of wide-azimuth surveying, it has become apparent that most rocks are azimuthally anisotropic, with P-wave velocities and P-AVO gradients varying with source-receiver azimuth. What this means is that analysis of such data with narrow-azimuth algorithms and concepts will necessarily fail to get the most out of this expensively acquired data. The issues include not only seismic wave propagation, but also seismic rock physics. Isotropic concepts including velocity, Young’s modulus, and Poisson’s ratio have no place in the discussion of anisotropic rocks, unless qualified in some directional way (e.g., vertical Young’s modulus). Likewise, fluid substitution in anisotropic rocks, using the isotropic Biot/Gassmann formula, leads to formal errors, because the bulk modulus does not appear, in a natural way, within the anisotropic P-wave velocity. This updated edition is now current as of 2014.

All rock masses are seismically anisotropic, but we generally ignore this in our seismic acquisition, processing, and interpretation. The anisotropy nonetheless does affect our data, in ways that limit the effectiveness with which we can use it, as long as we ignore it. This book, produced for use with the fifth SEG/EAGE Distinguished Instructor Short Course, helps us understand why this inconsistency between reality and practice has been so successful in the past and why it will be less successful in the future as we acquire better seismic data (especially including vector seismic data) and correspondingly higher expectations of it. This book helps us understand how we can modify our practice to more fully realize the potential inherent in our data through algorithms which recognize the fact of seismic anisotropy.

Takes readers on a path of discovery of rarely examined wave phenomena and their possible usage. Chapters begin by formulating a question, followed by explanations of what is exciting about it, where the mystery might lie, and what could be the potential value of answering the question.