| A hot topic for a PhD: multicomponent seismic exploration
What work did you do for your PhD?
It was all about multicomponent seismic
still a hot topic in the industry, generating a lot of interest. It differs
from traditional seismic in how the soundwaves are recorded. Traditional
seismic records them on a single microphone, called either a geophone when we
are recording on land, or a hydrophone when we are recording in water.
Multicomponent seismic records them on three microphones, orientated
perpendicular to each other. It means that as well as recording the amplitude
of the soundwave that comes to the surface of the Earth, we can also record its
particle motion.
Particle motion is important because
several different types of waves travel through the Earth. Two really important
types are compressional (P) waves and shear (S) waves, and because each of
these waves has a different particle motion orientation, by recording the
direction of particle motion at the surface we can try to distinguish the
compressional waves from the shear waves. When we are looking for natural gas
or oil, our target is often a gas or a liquid. And because the two wave types
respond differently to travelling through gas, liquid or solid, in seismic
exploration we want to use the two wave types in partnership to help us
determine whether we are actually looking at an oil or gas reservoir.
Did
you have many field trips during your PhD?
There were not a lot of field trips for my
research in particular, because most of it is computational programming.
However, I have always been involved in the field trips for undergraduate
students. I enjoy getting out and helping the undergrads realise the practical
applications of what they’re learning in the field of geophysics, the reasons
for learning these things. So that was my release.
Also, Steve Hearn has been
really great in putting me in contact with people around the world. True, I’ve
worked and studied at the University of Queensland, but in my research I
network with people all over the world. I talk with young researchers in
Europe, and I have contacts in America who provide data for my experiments and
offer me technical assistance whenever I need it.
Tracking a different seam: seismic exploration for coal
You
recently returned to full-time work, while still finishing off your PhD. Where
are you working now?
I started full-time work in April of this
year, working in coal seismic as a senior geophysicist for MIM Exploration.
Seismic exploration for coal is a relatively new application. It has a slightly
different emphasis from oil and gas applications, primarily because coal is
only a few hundred metres below the surface of the Earth, whereas oil and gas
is typically a few thousand metres below the surface.
The other difference is that whereas we
tend to have to go and find oil and gas, in general we already know where the
coal is, and what we’re doing with seismic in the coal environment is trying to
map the coal seam. Mapping any discontinuities in the seam is going to make for
more efficient mining, with better mine plans before the miners get
underground. It’s also going to improve the safety of the mining environment,
helping to avoid roof collapses and so forth.
I
suppose some of the machinery used in coalmining will rely heavily upon these
sorts of techniques, as well.
Yes, certainly. One of the techniques that
MIM Exploration, in particular, uses in mining coal is longwall mining, in
which an automated shearing machine mines a panel about 250 metres across.
It is set up to follow the coal seam, and because coal is a much softer rock
than the sandstone and shales sitting around it, the machine needs to stay on
line and track along the seam. If the coal seam suddenly disappears or jumps up
or down, and the shearing tool is suddenly cutting harder rock, you can damage
a lot of equipment. It is also unsafe when that happens.
My work with MIM involves the type of
research I really enjoy not purely theoretical but very much applied. I get
to take the theory of things that have worked before in the oil and gas
industry, and manipulate them and modify techniques to make them work for the
coal industry. This is research to help design practical solutions, using
theory that probably already exists but manipulating it to make a new
application.
An edited transcript of the full interview can be found at http://www.science.org.au/scientists/nh.htm.
Focus questions
- Why can seismic data help reveal what type of rock is below the surface?
- What physical properties of the Earth might geophysicists study in addition to seismic characteristics?
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