Preface 1. Basic tools 2. Elasticity and Hooke's law 3. Seismic wave propagation 4. Effective media 5. Granular media 6. Fluid effects on wave propagation 7. Empirical relations 8. Flow and diffusion 9. Electrical properties Appendices.

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The Rock Physics Handbook: Tools for Seismic Analysis of Porous Media

Responding to the latest developments in rock physics research, this popular reference book has been thoroughly updated while retaining its comprehensive coverage of the fundamental theory, concepts, and laboratory results. It brings together the vast literature from the field to address the relationships between geophysical observations and the underlying physical properties of Earth materials - including water, hydrocarbons, gases, minerals, rocks, ice, magma and methane hydrates. This third edition includes expanded coverage of topics such as effective medium models, viscoelasticity, attenuation, anisotropy, electrical-elastic cross relations, and highlights applications in unconventional reservoirs. Appendices have been enhanced with new materials and properties, while worked examples (supplemented by online datasets and MATLAB® codes) enable readers to implement the workflows and models in practice. This significantly revised edition will continue to be the go-to reference for students and researchers interested in rock physics, near-surface geophysics, seismology, and professionals in the oil and gas industries.

The Rock Physics Handbook

Preface 1. Introduction to rock physics 2. Rock physics interpretation of texture, lithology and compaction 3. Statistical rock physics: combining rock physics, information theory, and statistics to reduce uncertainty 4. Common techniques for quantitative seismic interpretation 5. Case studies: lithology and pore-fluid prediction from seismic data 6. Workflows and guide lines 7. Hands-on References Index.

Quantitative Seismic Interpretation: Applying Rock Physics Tools to Reduce Interpretation Risk

Seismic reflections from gas sands exhibit a wide range of amplitude‐versus‐offset (AVO) characteristics. The two factors that most strongly determine the AVO behavior of a gas‐sand reflection are the normal incidence reflection coefficient R0 and the contrast in Poisson’s ratio at the reflector. Of these two factors, R0 is the least constrained. Based on their AVO characteristics, gas‐sand reflectors can be grouped into three classes defined in terms of R0 at the top of the gas sand. Class 1 gas sands have higher impedance than the encasing shale with relatively large positive values for R0. Class 2 gas sands have nearly the same impedance as the encasing shale and are characterized by values of R0 near zero. Class 3 sands have lower impedance than the encasing shale with negative, large magnitude values for R0. Each of these sand classes has a distinct AVO characteristic. An example of a gas sand from each of the three classes is presented in the paper. The Class 1 example involves a Hartshorn channel s...

Amplitude‐versus‐offset variations in gas sands

Amplitude versus offset concepts can be used to generate weighted stacking schemes (here called geo-stack) which can be used in an otherwise standard seismic data processing sequence to display information about rock properties. The Zoeppritz equations can be simplified and several different approximations appear in the literature. They describe the variation of P-wave reflection coefficients with the angle of incidence of a P-wave as a function of the P-wave velocities, the S-wave velocities and the densities above and below an interface. Using a smooth, representative interval velocity model (from boreholes or velocity analyses) and assuming no dip, the angle of incidence can be found as a function of time and offset by iterative ray tracing. In particular, the angle of incidence can be computed for each sample in a normal moveout corrected CMP gather. The approximated Zoeppritz equation can then be fitted to the amplitudes of all the traces at each time sample of the gather, and certain rock properties can be estimated. The estimation of the rock properties is achieved by the application of time- and offset-variant weights to the data samples before stacking. The properties which can be displayed by geo-stack are: P-wave reflectivity (or true zero-offset reflectivity), S-wave reflectivity, and the reflectivity of P-wave velocity divided by S-wave velocity (or ‘pseudo-Poisson's ratio reflectivity’). If assumptions are made about the relation between P-wave velocity and S-wave velocity for water-bearing clastic silicate rocks, then it is possible to create a display which highlights the presence of gas.

Weighted stacking for rock property estimation and detection of gas

The compressional wave reflection coefficient R(θ) given by the Zoeppritz equations is simplified to the following: R(θ)=R0+[A0R0+Δσ(1-σ)2]sin2θ+1/2ΔVpVp(tan2θ-sin2θ). The first term gives the amplitude at normal incidence (θ = 0), the second term characterizes R(θ) at intermediate angles, and the third term describes the approach to critical angle. The coefficient of the second term is that combination of elastic properties which can be determined by analyzing the offset dependence of event amplitude in conventional multichannel reflection data. If the event amplitude is normalized to its value for normal incidence, then the quantity determined is A=A0+1(1-σ)2ΔσR0. A0 specifies the normal, gradual decrease of amplitude with offset; its value is constrained well enough that the main information conveyed is Δσ/R0, where Δσ is the contrast in Poisson’s ratio at the reflecting interface and R0 is the amplitude at normal incidence. This simplified formula for R(θ) accounts for all of the relations between R(θ...

R. T. Shuey

Papers

A simplification of the Zoeppritz equations