Indirect Inversion Schemes: Tomographic and Full Waveform Inversion

Over the past thirty years, characterization of the subsurface has been achieved using various forms of tomographic indirect inversion. This has evolved from isotropic ray-based tomography, into structurally constrained orthorhombic ray-based tomography, and more recently into using the full elastic wave equation (FWI and eFWI).  FWI has emerged and developed to the point that is now the main technique of choice for detailed model building and reflectivity estimation for complex geological environments.

Use of FWI for model estimation, reflectivity generation, and pre-sack attribute analysis (AVA) will be covered.

Real data examples will be used to demonstrate the application and limitation of each technique.

Duration

16 hours; 4 hours per day

Intended Audience

Entry level

Prerequisites (Knowledge/Experience/Education required)

The course is designed to be followed by anyone with a broad geoscience background: no specific detailed foreknowledge is required, although a familiarity with geophysical terminology will be useful.

Course Outline

Why do we need a detailed velocity model?

• Short scale-length lateral parameter (velocity) variation and the limitations of ray-theory
• Anisotropy versus heterogeneity (and other higher order moveout effects)

Resolving short-scale-length lateral velocity variation using indirect inversion:

• The mechanics of tomographic inversion with ray theory
• Structural constraints and Q tomography
• The mechanics of tomographic inversion with wavefield extrapolation theory (FWI)
• High-Frequency-FWI, FWI-derivative imaging, and explicit reflectivity inversion (imaging with multiples)
• FWI_AVA: pre-stack attribute estimation
• Examples of current industrial practice for various geological settings

Learner Outcomes

Upon completion of this course, the participants should be able to:

1. Describe how wavefield extrapolation migration works, in terms of the underlying physics and the associated approximations involved.
2. Characterize the limitations of differing FWI schemes, in terms of:
   1. the components of the wavefield being used,
   2. the (minimization) norms being used,
   3. use of multiple and ghost energy,
   4. reflectivity estimation.
   5. AVA applications.

Instructor Biography

Ian F. Jones

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Ian F. Jones

Ian F. Jones received a joint honours BSc in Physics with Geology from the University of Manchester, UK, in 1977, an MSc in Seismology from the University of Western Ontario, Canada, and a PhD in Geophysical Signal Processing from the University of British Columbia, Canada. Read more.