Multicomponent Data Interpretation
The principles of seismic stratigraphy form the basis of modern seismic data interpretation. Seismic stratigraphy was formalized as a science by researchers at Exxon and was made available to the public through AAPG Memoir 26, published in 1977 by the American Association of Petroleum Geologists (Payton, 1977). After the publication of Memoir 26, an intense period of industry education focused on the concepts and applications of seismic stratigraphy in the late 1970s and into the 1980s. Several books were published to promote the science (Sheriff, 1980; Berg and Woolverton, 1985; Hardage, 1987), articles too numerous to cite were published to provide case histories, and short courses were held in many oil companies and among professional societies to implement seismic-stratigraphy practice. As a result, the interpretational principles of seismic stratigraphy became the accepted methodology for interpreting seismic images of subsurface geology in the early 1980s, and the science of seismic stratigraphy now is practiced widely and consistently.
Literature searches show that the number of published papers on seismic stratigraphy is into the many hundreds, far too many citations to accumulate into a reference list. Until the mid-1990s, however, there appear to have been only five published papers that considered S-wave data in a classic seismic-stratigraphy context (Meissner and Hegazy, 1981; Ensley, 1984, 1985; McCormack et al., 1984; McCormack et al., 1985). More examples of S-wave seismic sequences and seismic facies are being inserted into
Figures & Tables
A principle that is emphasized throughout this book is that the physics of any multicomponent seismic technology cannot be understood unless that technology is viewed in terms of the particle-displacement vectors associated with the various modes of a seismic wavefield. This material therefore begins with a discussion of seismic vector-wavefield behavior to set the stage for subsequent chapters.
Several approaches can be used to explain why each wave mode of nine-component (9C) and three-component (3C) seismic data that propagates through subsurface geology provides a different amount and type of rock/fluid information about the geology that the wave modes illuminate. Some approaches appeal to people who have limited interest in mathematics. Other options need to be structured for people who have an appreciation of the mathematics of wavefield reflectivity. Another argument that can be used focuses on the fundamental differences in P-wave and S-wave radiation patterns and the distinctions in target illuminations associated with 9C and 3C seismic sources. We will consider all of those paths of logic.
A principle that will be stressed is that each mode of a multicomponent seismic wavefield senses a different earth fabric along its propagation path because its particle-displacement vector is oriented in a different direction than are the particle-displacement vectors of its companion modes. Although estimations of earth fabric obtained from various modes of a multicomponent seismic wavefield can differ, each estimate still can be correct because each wave mode deforms a unit volume of rock in a different direction, depending on the orientation of its particle-displacement vector. Those deformations sense a different earth resistance in directions parallel to and normal to various symmetry planes in real-earth media. The logic of that nonmathematical approach appeals to people who are interested in the geologic and petrophysical information that multicomponent seismic data can provide and are less concerned about theory and mathematics.
A second approach that is helpful for distinguishing one-component (1C), 3C, and 9C wavefield behavior focuses on the mathematics of the reflectivity equation associated with each mode of the full-elastic seismic wavefield. The mathematical structure of the reflectivity equation associated with each seismic wave mode describes why and how petrophysical properties of the propagation medium affect different wave modes in different ways. The logic of that analytical approach is appreciated by scientists who are comfortable with mathematics.
All of these concepts lead to the development of a new seismic-interpretation science based on multicomponent seismic data called elastic wavefield seismic stratigraphy.