Discussion and Conclusions
The study of amplitude variation with offset is an essential aspect of the more general science of quantitative seismic interpretation. As we move beyond simple anomaly hunting, AVO provides the necessary fundamental understanding of seismic amplitudes. For example, acoustic impedance from conventional inversion of stacked seismic data can be expected to be erroneous whenever AVO is significant. Inevitably, the need to better understand seismic amplitudes has become inseparable from the need to understand (and attempt to control) temporal and spatial variations in frequency and phase, as a function of incident angle. Furthermore, as we refine our methods and extend exploration into deeper and more complex structural settings, we will need to pay especially careful attention to factors such as anisotropy, noise-suppression efficacy, imaging, and variations of the propagating seismic wavelet as it travels down to the target and returns to the surface. In this chapter, we will amplify some concepts about the practice of AVO analysis that, in our opinion, are worthy of additional treatment. We will also discuss less-well-studied ideas and will suggest avenues for future research and development.
Figures & Tables
We begin this book with a brief discussion on the basics of seismic-wave propagation as it relates to AVO, and we follow that with the rock-physics foundation for AVO analysis — including the use of Gassmann’s equations and fluid substitution. Then, as food for the inquisitive mind, we present briefly the early seismic observations and how they led to the birth of AVO analysis. Next, we examine the various approximations for the Zoeppritz equations and identify clearly the assumptions and limitations of each approximation. We follow that with a section on the factors that affect seismic amplitudes and a discussion of the processing considerations that are important for AVO analysis. A subsequent section explores the various techniques used in AVO interpretation. Finally, we discuss topics such as the influence of anisotropy in AVO analysis, the use of AVO inversion, estimation of uncertainty in AVO analysis, converted-wave AVO, and the future of the AVO method.