Course

This short course discusses the growing importance of the seismic anisotropy of rock masses in seismic acquisition, processing, and interpretation.

All rock masses are seismically anisotropic, but we often ignore this in our seismic acquisition, processing, and interpretation. The anisotropy nonetheless does affect our data, in ways that limit our effectiveness in using it, if we ignore that anisotropy. In this short course, we will understand why this inconsistency between reality and practice has been so successful in the past, and why it is less successful now and in the future, as we acquire better seismic data, and correspondingly higher expectations of it. We will further understand how we can modify our practice so as to more fully realize the potential inherent in our data, through algorithms which recognize the fact of seismic anisotropy. To use the seismic data for subsurface physical characterization, we will require the application of anisotropic rock physics. This more realistic basis for seismic exploration and exploitation is particularly important (naturally!) for the shale resource. We will see that the anisotropy, although usually weak (when defined as a rock property), has weak effects on some seismic data, strong effects on other seismic data, and sometimes completely novel effects. The course is accompanied by numerous class exercises, presented in .xls format.

Duration

Two days

Intended Audience

Intermediate and Advanced levels

Prerequisites (Knowledge/Experience/Education required)

The course is designed for those with a few years of experience in conventional reflection seismic analysis.

Outline

1. Physical principles (Day 1, morning)
   1. Definition of anisotropy
   2. Anisotropy vs.heterogeneity
   3. Anisotropy as a function of scale
   4. Elasticity and Symmetry
   5. The Power of Notation
2. P-waves: imaging (Day 1, afternoon)
   1. Polar anisotropy
   2. Azimuthal anisotropy
   3. Slowness ellipses
3. P-waves: characterization (Day 2, morning)
   1. Polar anisotropy
   2. Azimuthal anisotropy
   3. Stress and Fractures
4. S-waves: (Day 2, afternoon)
   1. Polar anisotropy
   2. Azimuthal anisotropy: S-wave splitting
   3. Crossed-dipole sonic data
5. C-waves: (Day 2, afternoon)
   1. C-wave basics
   2. Polar anisotropy
   3. Azimuthal anisotropy: C-wave splitting
6. Epilogue: (Day 2, afternoon)

Who Should Attend

This is an excellent opportunity for all geophysicists to learn how a fundamental property of rocks affects our data, and how to deal with it. It is particularly important for those working with shale resource plays, since shales are particularly anisotropic, whether fractured or not.

Learner Outcomes

Class participants will be able to discuss with colleagues:

• the physical principles of seismic anisotropy, with examples
• the application of these principles to P-wave imaging, specifically including the effects on moveout
• the application of these principles to physical characterization of the subsurface (specifically including the effects on P-wave reflection amplitudes), using anisotropic rock physics
• the application of these principles to S-wave data, specifically including shear wave splitting
• the application of these principles to Converted-wave data, specifically including registration, diodic moveout, effective Gamma, and C-wave splitting

Instructor Biography

Leon Thomsen