Oil and Gas
Oil and Gas | Geophysics and Seismic Interpretation
Gravity and Magnetics for Petroleum Exploration
This course explains and illustrates, with exercises, the use of gravity and magnetic techniques for petroleum exploration. It provides participants with tools to assess the usefulness of these techniques in their project workflows, and to implement them in a sensible and cost-effective manner.
Schedule
Duration and Training Method
A classroom or virtual classroom course, comprising introductory talks followed by practical exercises. Case histories are presented from a variety of different geological settings world-wide.
Course Overview
Learning Outcomes
Participants will learn to:
- Understand basic gravity and magnetic theory.
- Appraise gravity and magnetic responses of simple block models.
- Assess benefits and limitations of the available survey techniques.
- Use publicly-available gravity and magnetic datasets for regional prospectivity analysis.
- Apply filters and other image processing techniques to emphasise geological features of exploration interest.
- Determine the usefulness of gravity and magnetic techniques on individual petroleum exploration projects.
Course Content
A) Fundamentals (Talk)
- Rock physical properties
- Units of measurement
- Gravity vs magnetic studies
B) Gravity Fields (Talk)
- Introduction
- Physical principles
- The gravity field of the earth
- Data processing
- Data imaging
- Interpretation
- Case studies
C) Block Modelling (Exercise)
We will model some simple bodies to get a feel for how gravity measurements are affected by changes in density and changes in geometry.
D) Magnetic Fields (Talk)
- Introduction
- Physical principles
- The geomagnetic field
- Data processing
- Data imaging
- Interpretation
- Case studies
E) Block Modelling (Exercise)
We will model some simple bodies to get a feel for how magnetic measurements are affected by changes in susceptibility and changes in geometry, and how magnetic measurements compare with gravity measurements.
F) Free and nearly-free datasets (Talk)
Publicly-available gravity and magnetic datasets can be freely downloaded or purchased at nominal rates to help with regional prospectivity analysis. We explore some of these datasets, and use them to model offshore basin development and onshore fault networks.
G) Filtering (Exercise)
A range of geophysical and mathematical filters are available for enhancing the geological information present within gravity and magnetic datasets. We provide a short introduction to Fourier-based filtering techniques, including upward and downward continuation, spatial derivative calculation, edge detection and source localisation. We then apply what we have learned to real-world exploration datasets.
H) Attendees’ Feedback and Conclusions (Open Forum)
Who Should Attend and Prerequisites
Graduate level geoscientists who require a working knowledge of gravity and magnetic techniques applied to petroleum exploration;
Experienced geoscientists who wish to understand the advantages and limitations of these techniques for individual projects.
Instructors
Tim Archer
Background
Tim Archer holds a BSc (Honours) degree in Geophysics from the University of the Witwatersrand (South Africa) and a Management Diploma from the University of Stellenbosch (South Africa). He has worked as a commercial geophysicist for more than twenty years. During that time, he has coordinated airborne surveys for Anglo American’s SPECTREM system in Africa and North America, given technical presentations in South America and Australasia, delivered geophysical training in Europe and West Africa, and provided contracting and consultancy services to projects in numerous countries worldwide.
Having received a Group Vocational Scholarship from Anglo American, Tim worked for that company from 1994 to 2001, mainly with their SPECTREM airborne electromagnetic system, where he was promoted to Head of Processing and Interpretation. From 2004 to 2014, Tim owned and ran a geophysical contracting business, specialising in near-surface hazard detection. In 2014, he joined Dr Alan Reid as a director of Reid Geophysics, where he provides gravity, magnetic and electromagnetic consultancy to petroleum, mineral and UXO explorers. In 2016, Tim and his wife became the owners of Reid Geophysics.
Tim has a particular specialisation in airborne time-domain electromagnetic surveys, as well as extensive experience of potential field (gravity and magnetic) methods, and a good working knowledge of most other non-seismic geophysical methods. He has written and co-developed a range of software applications in Delphi, Visual Basic and C#, both for in-house use and for commercial release. He has substantial GIS experience (both mainstream and customised). He has coordinated a wireline logging database and prospected for groundwater in the Kalahari Desert.
Tim’s specific technical interests include 3D imaging of geophysical data, Improvement of existing workflows, and bespoke software development.
Affiliations and Accreditation
BSc (Honours) University of the Witwatersrand - Geophysics
BSc University of Natal - Geology & Physics
Courses Taught
N405: Gravity, Magnetic and Electromagnetic Techniques for Coal Exploration and Mine Development
N452: Gravity and Magnetics for Petroleum Exploration