3C Seismic and VSP: Converted Waves and Vector Wavefield Applications

James E. Gaiser

This short course discusses the growing importance of three-component (3C) seismic technology that combines shear waves with compressional waves in the acquisition, processing, and interpretation of surface-seismic and borehole data.

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Duration

Two days

Intended Audience

Intermediate

Prerequisites (Knowledge/Experience/Education Required)

The course is for those with a basic background and experience in conventional P-wave acquisition, processing and interpretation techniques.

Who should attend?

  • The course is intended for geophysicists, geologists, and engineers to:
    • develop a practical understanding of vector wavefield applications (VSP) and
    • understand how recorded S-waves are a benefit to P-waves for elastic-property and petrophysical inversion.
  • It is also intended for seismic:
    • processors and imagers who want to learn about joint prestack migration and tomography, and
    • interpreters who want to use S-waves to improve impedance and density inversion for reservoir petrophysics.
  • The course would be most relevant to those currently involved with, or considering:
    • AVO/A inversion
    • fracture/stress analyses and “brittleness” characterization of unconventional reservoirs, or
    • interpretation in gas-obscured reservoirs.

Course Outline

  1. Introduction – Overview
    • Definitions and wavefield properties
    • Three components
    • Anisotropy, coordinate systems, and 3C full wavefields
    • Applications and PS-wave emphasis
  2. S-waves and VSP in the 20th century
    • Development and sources
    • Shear-wave properties from P-wave AVO and anisotropy
    • Converted wave and VSP applications
  3. Fundamentals: wavefield dynamics and kinematics
    • Elastodynamic, reflection, and transmission responses
    • Seismic response, reflection point coverage
    • Modeling and resolution
  4. Acquisition
    • Sources, receivers, and surface responses
    • Geometries and PS-wave illumination
    • Common-offset vector gathers
    • VSP geometries
  5. Processing and analysis
    • Preprocessing: rotation, statics, and S-wave splitting
    • Signal processing: vector fidelity, rotation, and wavefield separation
    • Transformation to zero offset: CCP gathering, velocity, NMO, registration, and VP/VS analysis
    • VSP wavefield separation, processing, and velocity analyses
  6. Imaging applications
    • Anisotropy and VMB: post and prestack Kirchhoff migration
    • Tomography
    • VSP imaging
    • Imaging through gas zones
  7. Inversion applications
    • Layer stripping and inversion for S-wave splitting
    • Joint AVO/A inversion
    • Unconventional reservoirs
    • Time lapse
  8. Interpretation and business drivers
    • Inversion for petrophysical properties
    • Vector wavefield strategy: P- and S-wave anisotropy coupling
    • Unconventional reservoir opportunities

Learner Outcomes

Students will obtain an understanding of theoretical and practical aspects of 3C seismic and VSP, including how to use PS-wave and vector wavefield data to improve rock property applications, as well as:

  • Explain the basics of PS-wave registration, velocities, and birefringence (S-wave splitting) 
  • Describe elastodynamic processes that generate converted waves and how they relate to elastic rock properties
  • Understand the issues of PS-wave asymmetry and illumination
  • Associate VSP multicomponent wavefields with 3C land and marine surface-seismic events
  • Recognize the unique characteristics of PS-wave processing: time registration with P-waves, S-wave splitting, VP/VS analyses, velocities, and conversion-point gathering
  • Explain and characterize the importance of 3C vector fidelity
  • Describe applications of 3C seismic and VSP data for prestack migration, elastic impedance joint inversion, imaging through gas, fracture/stress characterization, and timelapse
  • Understand interpretation techniques of converted-wave and VSP wavefields for petrophysical properties

Instructor Biography

James E. Gaiser