Gravity & Magnetic Data Acquisition, Processing, and Interpretation
Jaap Mondt
Course content
What kinds of Geophysical Data could be used?
Various kinds of geophysical data are available. They are
separated into Seismic and Non-Seismic data. Seismic is, without
any doubt, the main method used in the oil and gas industry. But
Non-Seismic data (gravity, magnetics, electrical, electromagnetics,
spectral, etc.) is the main source of information in shallow
subsurface applications (engineering, mapping pollution,
archaeology). It is also used at the early reconnaissance of
hydrocarbon plays and in mapping prospects below salt. However,
seismic has its limitations and therefore also non-seismic methods
are used successfully as complementary tools in subsurface
evaluation. In combination with seismic data, they can
significantly reduce the uncertainty of subsurface models as they
measure different physical properties of the subsurface. Another
important application is in determining the depth to basement.
The Course
The potential of gravity and magnetics will be discussed.
In part 1, various aspects of gravity will be discussed, based
on an EAGE publication, such as the Earth gravity field,
determining anomalies in the global field, establishing the depth
of density anomalies, be it spherical or anticlinal and the
resolution, which is limited because of it being a potential field
described by a 1ste order differential equation. Most promising is
the development of gravity gradiometry, whereby gradients in the
gravity field can be directly measured. These are less sensitive to
airplane and ship movement.
In part 2, the Earth's magnetic field will be studied. Being due
to the internal dipole source, direct interpretation of magnetic
(dipole) data is inherently more difficult than (monopole) gravity
data. As different causative sources can produce the same surface
measurements, non-uniqueness in the interpretation is even more
severe than for gravity data. However, promising developments to
mitigate these issues will be discussed.
The course
There are two types of courses, one F2F (classroom) and the
other virtual using the internet. In both courses Gravity and
Magnetic applications will be discussed using lectures and by
making many practical exercises. In addition, you will benefit from
Moodle facilitating interactions with other participants. In case
of the virtual version you can submit your questions in the
discussion panel or your solutions of the exercises and receive
feedback.
Learning, methods and tools
Learning methods and tools
The course uses a Blended Learning approach based on a
user-friendly Learning Management System, called Moodle. In Moodle
different modules provide study material, videos, and exercises.
The solutions to these exercises can be checked and if the exercise
is not clear or the solution cannot be found you can submit your
"solution" and ask for feedback. Also, each part contains a quiz
which is meant to reinforce the learning. The quiz consists of
multiple-choice questions. For each question, all answers can
be tried. The idea is that if the answer is not correct, one can go
back to the course material to find out what the right answer
should be. So, it is not an exam.
Day by day programme
