Geophysical Electromagnetics: Fundamentals and Applications

2017 Distinguished Instructor Short Course

Doug Oldenburg

Geophysical Inversion Facility
Vancouver, British Columbia CA

 

Summary

Electromagnetics has applications in oil and gas exploration and production, mineral exploration, groundwater exploration and monitoring, geotechnical and environmental industries. Although it has widespread applications as a geophysical technique, it is not generally understood by the geoscience community. As a result it is underutilized, and in some cases, misused, as a technology.

The aim of this course is to provide a fundamental understanding about EM geophysics so that practitioners can decide if an EM technique can help solve their problem, select which type of survey to employ, and set realistic expectations for what information can be gleaned. Case histories, spanning applications from many areas in the geosciences, are used as an underlying framework to bind the material together.  For more information, please see our online resources at  http://disc2017.geosci.xyz

Fundamentals and Applications

Case histories pertain to problems in resource exploration, including oil and gas, minerals, water, environmental, and geotechnical areas and are contributed by experts worldwide. (http://disc2017.geosci.xyz/).

 

These include:

  1. resource detection (eg. methane hydrates) or de-risking (eg. offshore-hydrocarbons),
  2. imaging SAGD steam chambers or monitoring hydraulic fracturing,
  3. mineral exploration (on land, on the ocean floor sea floor massive sulfides),
  4. water issues (eg. monitoring salt water intrusion, imaging aquifers)
  5. imaging geothermal systems,
  6. detecting and discriminating unexploded ordnance,
  7. geotechnical characterization, including slope stability,
  8. and more (see http://em.geosci.xyz/content/case_histories/index.html for a growing list).

We use these applications as motivation for investigating fundamentals of electromagnetics. We successively look at  applications that make use of

  1. Steady state fields (e.g. DC resistivity, induced polarization)
  2. Frequency domain EM (eg. marine CSEM, airborne surveys)
  3. Time domain EM (eg. airborne, ground, borehole surveys )
  4. Natural source EM (eg. Magnetotellurics, Z-Axis Tipper / ZTEM)

The energy sources for these surveys can be man-made or natural. Man-made sources include inductive transmitters (loops of wire carrying a current) or galvanic sources where current is injected into the ground. The natural energy sources promote MT (magnetotellurics), which is important for characterizing deep conductivity structures for geothermal energy, and ZTEM which has proven to be valuable in geologic mapping and mineral exploration. The various surveys can be carried out in the air using helicopters or airplanes, on the earth’s surface, or underground; the geoscientific question to be addressed determines which survey is selected. Case histories and survey types presented will be tailored to each location at which the DISC is presented, and chosen based on the local problems of general interest.

Each case history is presented in a seven-step process that begins with the description of the geologic or geophysical problem to be solved and ends with the impact of the EM geophysical survey to help solve the problem. At points in the middle, we investigate the details of the particular EM survey, some fundamentals of electromagnetic induction, and techniques for processing/inverting  the data. The ability to move seamlessly between these different levels of information, so that relevant questions or concepts can be addressed, is facilitated by new open-source numerical software, interactive simulations, and the “textbook” resource http://em.geosci.xyz. Although we work continually with Maxwell’s electromagnetic equations, the presentations are mathematically “light” and the learning aspect is facilitated by the use of open-source, interactive numerical software  and visual aides.

The site http://disc2017.geosci.xyz contains further details on the course, its goals, links to the open-source resources that will be used, and ways to get connected!

Who should attend?

Geophysicists and any geoscientists who have the potential to use, or be associated with, electromagnetic data. The 2017 DISC is designed to be of interest to a broad audience, including researchers, practitioners, and industry geoscientists, and accessible to those with little background in EM.

Biography

Oldenburg

Doug Oldenburg’s forty-year research career has focused upon the development of inversion methodologies and their application to solving applied problems. He, with students and colleagues at the University of British Columbia Geophysical Inversion Facility (UBC-GIF), have developed forward modelling and inversion algorithms for seismic, gravity, magnetic and electromagnetic data. The inversion techniques and software are widely used in resource exploration problems. In recognition for his  work  building collaborative interactions between industry and academia, he was awarded the NSERC Leo Derikx and the AMEBC Special Tribute awards as well as the J.Tuzo Wilson medal.  In 2011, Doug was the SEG Distinguished Lecturer; his presentation was entitled Imaging the Earth's near surface: The why and how of applied geophysics for the 21st century.

Doug’s current research activities include: inversion of EM data and their application to a wide range of problems, development of practical methodologies for combined inversion of geophysical and geological data, development of software for unexploded ordnance discrimination, and the use of self-potentials for dam safety investigations. He is passionate about the development of open-source educational resources for applied geophysics and increasing the visibility and benefits of using quantitative geophysics to help solve geoscience problems (http://geosci.xyz). These efforts will form the cornerstone of the SEG 2017 DISC.

Doug received his BSc Honors degree in Physics in 1967, and his MSc in geophysics in 1969, from University of Alberta in Edmonton. He completed his PhD in 1974 at UCSD in earth sciences. After a three-year postdoc in Alberta, he joined the Geophysics and Astronomy department at University of British Columbia. He remains at UBC where he is currently a Professor, Director of UBC-GIF and holder of the TeckCominco Senior Keevil Chair in Mineral Exploration. He is an honorary member of the CSEG, SEG and a Fellow of Royal Society of Canada

Instructor Welcome

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Course Materials

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