Modern Seismic Reservoir Characterization

Instructor: Dr Leon Thomsen (Delta Geophysics, United States)
Language: English
Level: Advanced
Duration and formats:
Online: 4 live sessions of 4 hours CPD Points: 8
Classroom: 2 days CPD Points: 10

Course Description

Classical reservoir characterization typically assumes that the reservoir is elastically and hydraulically isotropic, and may be adequately analyzed using core and/or log data. However, most real reservoirs are elastically and hydraulically anisotropic, and spatially heterogeneous (on many scales), so that core and/or log data are not representative of the larger reservoir volume. This applies to both conventional and unconventional reservoirs. Hence, the best means to physically characterize most real reservoirs, throughout their volume, uses seismic data, acquired and interpreted anisotropically. This course summarizes the state-of-the-art of seismic reservoir characterization, using anisotropic seismic rock physics.

The course normally requires 16 hours of instruction, and includes numerous classroom exercises. Topics include:

  • Context: A world with excess supply of oil, and low demand. The shale revolution. Hubbert’s extended Peak.
  • Physical principles: Aliased data. Inhomogeneous formations. Friendly multiples. Spatial resolution.
  • Introduction to Anisotropy: Weak. Polar. Azimuthal. Shear wave splitting.
  • Lithology: Shale content from anisotropy itself.
  • Geomechanics: Without Poisson’s ratio or Young’s modulus, since these are isotropic concepts.
  • Fluids: Logical error in Gassmann poroelasticity.
  • Pore pressure: Subsurface fluid compartments. Anisotropic velocities for calibration.
  • Anisotropic AVO: Including the anisotropic term in the AVO gradient, a first-order effect!
  • Fractures: No penny-shaped cracks. Multiple fracture-sets.
  • Permeability: 4D gives the best seismic measure. Impermeable barriers.

Course Objectives

Upon completion of this course, participants will:

  • realize that many of the assumptions of conventional reservoir characterization do not apply to the Real World
  • understand the basic elements of anisotropic seismics
  • be able to implement that understanding to estimate lithology, pore pressure fractures, and permeability from seismic data, with appropriate caveats
  • be able to apply post-Gassmann fluids estimation
  • be able to forward-model anisotropic AVO, and to find the missing parameter from the data.

Course Outline

  • Context
  • The Shale Revolution
  • Hubbert’s Extended Peak
  • The geophysical response: subsurface physical characterization
  • Physical principles
  • Requirement for, and limitations of seismic data
  • Equation of motion vs wave equation
  • Friendly multiples
  • Exercise: Thin layers
  • Anisotropy
  • Weak polar anisotropy parameters
  • Exercise: Plane-wave velocities
  • P-waves: normal moveout; abnormal moveout
  • Azimuthal anisotropy
  • Lithology
  • Shale content from anisotropy
  • Geomechanics
  • Compliance vs stiffness
  • Young’s modulus, Poisson’s ratio, bulk modulus
  • Exercise: geomechanics moduli
  • Fluids
  • Biot, Gassmann
  • Biot vs Gassmann
  • Brown and Korringa
  • Determining the parameters
  • Exercise: Post-Gassmann fluid dependence
  • Effective media
  • Fluid effects on anisotropic formations
  • Exercise: Thin-layer fluid dependence
  • Pore pressure
  • Subsurface fluid compartments
  • Effect of anisotropy on pore pressure estimation
  • Anisotropic AVO
  • Effect of polar anisotropy on AVO gradient
  • Exercise: Anisotropic AVO
  • Determining the parameter
  • Effect of azimuthal anisotropy on AVO gradient
  • Cracks and fractures
  • Crack formation by unequal stresses
  • Microfractures and macro joints
  • Effects of cracks on velocities
  • Shear wave splitting
  • Exercise: 2Cx2C rotation
  • Permeability
  • Permeability tensor
  • Cleating in CoalBed Methane
  • Fractures in the Austin Chalk
  • 4D permeability in the North Sea

Participants’ Profile

This course is designed for geophysicists with five or more years of professional experience, whose management expects them to go beyond subsurface imaging to physically characterize subsurface reservoirs. Their conventional tools for doing that are based on demonstrably false assumptions. This course will help them to use their experience in modern ways to address the same challenges.

Prerequisites

This course is designed for geophysicists with five or more years of professional experience, whose management expects them to go beyond subsurface imaging to physically characterize subsurface reservoirs. Their conventional tools for doing that are based on demonstrably false assumptions. This course will help them to use their experience in modern ways to address the same challenges.

About the Instructor

Leon Thomsen holds titles of Chief Scientist at Delta Geophysics, Research Professor at the University of Houston, and Visiting Scientist at Lawrence Berkeley National Laboratory. He holds a B.S. in geophysics from California Institute of Technology (Pasadena), and a Ph.D. in geophysics from Columbia University (New York). He held postdoctoral positions at Centre Nationale de la Recherche Scientifique (Paris), International Business Machines (Palo Alto), and Caltech. He was Assistant, then Associate Professor at the State University of New York (Binghamton), with sabbatical positions at Goddard Institute for Space Studies (New York) and the Australian National University (Canberra).

Leon’s industrial career began in 1980, at Amoco’s famous research center in Tulsa, where he was the Amoco inventor of what we now call seismic AVO. He led significant revisions to the exploration seismic paradigm, helping to establish the basic ideas of polar anisotropy and azimuthal anisotropy. His 1986 paper, establishing the modern field of seismic anisotropy, is the single-most-cited paper in the history of Geophysics; a Google search of the term “Thomsen parameter” returns over 300,000 hits. In 1995, he moved to Amoco’s Worldwide Exploration Group in Houston, where his 1997 paper established the modern field of converted-wave exploration, defining such concepts as “C-waves”, “registration”, “gamma effective”, “diodic velocity”, etc. In 2008, Leon retired from BP, and established the consultancy Delta Geophysics (cf. deltageophysics.net).

Leon has served the Society of Exploration Geophysics as Distinguished Lecturer, Vice-President, President (2006-07), and Chairman of the Board of SEAM. He served as SEG/EAGE DISC Instructor in 2002. He holds the SEG's Fessenden Award, and the Russian Academy of Natural Sciences' Kapitsa Medal. He is an Honorary Member of the Geophysical Society of Houston, and of the EAGE, and is a Foreign Member of the Russian Academy of Natural Sciences.