Book contents
- Frontmatter
- Dedication
- Contents
- Preface
- Acknowledgments
- Part I The basics
- Part II Synthetic seismic amplitude
- 4 Modeling at an interface: quick-look approach
- 5 Pseudo-wells: principles and examples
- 6 Pseudo-wells: statistics-based generation
- Part III From well data and geology to earth models and reflections
- Part IV Frontier exploration
- Part V Advanced rock physics: diagenetic trends, self-similarity, permeability, Poisson’s ratio in gas sand, seismic wave attenuation, gas hydrates
- Part VI Rock physics operations directly applied to seismic amplitude and impedance
- Part VII Evolving methods
- Appendix Direct hydrocarbon indicator checklist
- References
- Index
- Plate Section
4 - Modeling at an interface: quick-look approach
from Part II - Synthetic seismic amplitude
Published online by Cambridge University Press: 05 April 2014
- Frontmatter
- Dedication
- Contents
- Preface
- Acknowledgments
- Part I The basics
- Part II Synthetic seismic amplitude
- 4 Modeling at an interface: quick-look approach
- 5 Pseudo-wells: principles and examples
- 6 Pseudo-wells: statistics-based generation
- Part III From well data and geology to earth models and reflections
- Part IV Frontier exploration
- Part V Advanced rock physics: diagenetic trends, self-similarity, permeability, Poisson’s ratio in gas sand, seismic wave attenuation, gas hydrates
- Part VI Rock physics operations directly applied to seismic amplitude and impedance
- Part VII Evolving methods
- Appendix Direct hydrocarbon indicator checklist
- References
- Index
- Plate Section
Summary
Reflection modeling at an interface: the concept
Forward modeling of seismic reflections at an interface between two elastic half-spaces is a traditional way of setting expectations for the character of seismic traces between the overburden shale and sand reservoir; at gas/oil, gas/water, and oil/water contacts; as well as at various unconformities present in the subsurface. To conduct such computations, the elastic properties of both half-spaces are required. If we know the site-specific transforms between the rock properties and conditions and the elastic properties, we can compute seismic reflections at an interface as a function of porosity, lithology, and fluid. In the next section of this chapter we will review the mathematical apparatus used to compute seismic reflections and then proceed with utilizing these equations for assessing the seismic signatures from the properties of the rock half-spaces forming the interface.
Normal reflectivity and reflectivity at an angle
The reflectivity at an interface between two elastic bodies is defined as the ratio of the reflected wave amplitude to the incident wave amplitude. As the wave strikes the interface, it produces the reflected and transmitted waves (Figure 4.1). Here we will analyze only the reflected P-wave. The incident P-wave can approach the interface in the direction normal to the interface or at a non-zero angle (Figure 4.1). The angle of incidence is defined as the angle between the direction of propagation of the wave front and the direction normal to the interface between the two half-spaces. While a normal-incidence P-wave does not produce S-waves, a P-wave at a non-zero incident angle produces reflected and transmitted S-waves. In the following equations for the P-to-P reflectivity, the properties of the upper interface are marked by subscript “1” while those of the lower interface are marked by subscript “2.”
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- Information
- Seismic Reflections of Rock Properties , pp. 53 - 67Publisher: Cambridge University PressPrint publication year: 2014