Advanced Velocity Modelling
Jaap Mondt
40 hours
Business context
Where do we need velocity for?
Velocities have many uses. They are used in processing as well
as interpretation. In processing they allow, for example, Normal
Moveout (NMO) corrections to offset arrivals which facilitates
stacking of events. This increases the signal-to-noise ratio
significantly and makes interpretation easier. In processing the
correct velocity-depth model allows "true-to-nature" imaging of the
subsurface. But especially in interpretation there are huge
benefits in obtaining accurate velocities for the different
"geo-bodies", as they can be used for lithology and pore fill
determination. In some processing methods, take Full Waveform
Inversion (FWI), they can be the main aim of its application. It is
fair to say that for an accurate image of the subsurface, an
accurate velocity-depth model is paramount in obtaining a "true"
image of the subsurface, in terms of structure/geometry as well as
amplitudes of reflections needed for quantitative
interpretation.
Who should attend
An understanding of the role of geophysics in the context of
exploration and production of oil and gas and a basic knowledge of
geophysics, but above all an inquisitive mind is required.
Course content
Kinds of velocities.
Wave Velocity, Particle Velocity, Interval Velocity, Average
Velocity, Stacking Velocity, NMO Velocity, DMO Velocity, Migration
Velocity, Phase Velocity, Group Velocity, Instantaneous Velocity,
Love wave Velocities, Rayleigh wave Velocities and maybe many more.
Each of these velocities are derived either by a special method or
serve a specific purpose. Also, the accuracy varies. It is
important to aim for the appropriate velocity, that means a
velocity of sufficient accuracy for the purpose. In the
course various velocity determination methods will be discussed and
it will become clear that for increasing accuracy not only more
advanced processing methods are needed, but also more sophisticated
acquisition. Think of multi-azimuth acquisition to derive azimuth
depend velocities providing information on fractures and in situ
stresses.
The Course.
All items of importance to velocity model building will be dealt
with in the course; by studying course material based on recent
publications, videos and by applying the theory in many practical
exercises, thereby enhancing the learning.
References.
An Introduction to: Velocity Model Building by Ian F. Jones, EAGE
Publications, ISBN978-90-73781-84-9.
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. In addition, an excellent book by
the Velocity Model Building guru is used for background
reading.
Day by day programme
