Marine Electromagnetic Methods for Hydrocarbon Exploration

by Steven Constable and Kerry Key

Duration: Two days

Intended Audience: Entry and Intermediate levels

Prerequisites (Knowledge/Experience/Education Required): The course is designed to be followed by anyone with a broad geoscience background and a basic familiarity with geological and geophysical terminology. Although not required, a familiarity with calculus, Fourier analysis, and vector algebra will be useful.

Summary:
Industry has embraced marine electromagnetic methods (controlled-source EM and magnetotellurics) have as a way to reduce risk and improve exploration efficiency. Estimates of seafloor electrical conductivity obtained using EM surveys can be used to generate geological and structural models and even, given appropriate conditions, detect the existence of hydrocarbon reservoirs. While EM methods will never achieve the resolution of seismic methods, they are intrinsically more powerful than potential field methods (gravity and magnetics) and provide a more direct estimation of fluid content than using acoustic properties alone. Marine EM has the potential to play an important role in any integrated exploration strategy.

However, the rapid assimilation of what has in the past been largely an academic enterprise has resulted in a shortage of skilled professionals. While there is a general interest in using marine EM technology, there is an associated general lack of understanding within the exploration community about the techniques, how they work, and their strengths and limitations. This course provides a working understanding of this new technology.

Course Outline:
Participants will learn why electrical methods are useful, the electrical conductivity of Earth materials and the dependence on temperature and porosity, and basic electromagnetic theory. The course begins with an outline of the history of the method, starting with academic work and moving on to the recent efforts by industry and the emergence of several contractor companies, including the inter-relationships between industry and academics. Descriptions of the equipment needed to carry out marine EM surveys and the key technological issues that make the difference between good data and bad are covered. We will discuss operational and logistical issues in mounting a marine EM campaign. Processing both controlled source and magnetotelluric data are explained.

The theory of controlled source EM and magnetotelluric propagation in the marine environment is introduced and illustrated with simple one-dimensional modeling. This leads to an explanation of 2D and 3D computational methods and issues of target size, discrimination, etc. Inversion methodology is presented. Finally, example data sets illustrate the principles and discussed with participants.

This course will be of interest to anyone wishing to use marine EM data in an exploration arena. This course is suitable for exploration managers and geoscientists who wish to commission surveys or exploit existing data, and to new recruits within the contractor industry. Academics wishing to include aspects of marine EM into their curricula will also find this course helpful.

Instructor Biographies:
Steven Constable
Kerry Key