This was posted on the grav-mag listserver. Mr. Soule is attempting to establish the validity of this company and its use of "Electro-Kinetic Seismics". Any comments or experiences?
"Several weeks ago I posted a query to the list seeking information on the EKS
method. I received a number of interesting responses. I recently sent a query
to "GROUNDFLOW", the company that is promoting the use of this method. Below
is the query and their response:"
My query:
The Geological licensing board of the state of Oregon (U.S.) has requested
that I investigate your methods and claims. Apparently an individual in this
State is using your methods and equipment. I have talked to several SEG
geophysicists and exchanged e-mail with several others regarding EKS or
seismo electric methods. The consesus seems to be that this technique is
still in the R&D stage and not ready for routine use in geophysical
applications. However your web site suggestes otherwise. Please respond.
Their response:
Dear Mr Soule
Groundflow's electroseismic (or "electrokinetic") equipment is in routine
use around the world. Our customers include research groups as well as
commercial operators. We have sold approximately 45 units in Australia and
New Zealand, Africa, The Middle East, Europe, the USA and Mexico during the
past few years. It is true that most academics have no experience of the
technique and it is not usually taught in college geophysical courses.
However, some of the best universities and institutes (MIT, USGS Colorado,
ANSTO Australia, Imperial College London, Belfast, Delft, University of BC,
Schlumberger,etc) have taken an active interest in the topic.
Most of the technical review papers published in the past decade have
expressed surprise that geophysicists have been so reluctant to take up the
technique and make something of it. I think the reason has to do with the
enormous poularity of seismic reflection surveying in the oil industry,
which has grabbed most of the talent, and with the need to grasp two
branches of physics, acoustics and electromagnetics, to make sense of the
method; not easy for some.
Fundamental work was done by a MIT researcher called Bihan Nourbehecht
over forty years ago (his PhD is available from MIT library). He collected
basic data, conducted key experiments and created physical models of the
electrokinetic phenomenon. His key insight was that the electrical response
to a seismic impulse travelling across an interface (eg bedding plane) will
be focussed back to the source of the seismic wavefront. This is true
whatever the inclination of the beds.That is what allows our equipment to be
so simple and effective. Unfortunately Nourbehecht died shortly after
returning to Iran and only an outline of his work was ever published, by
David Fitterman (USGS, Colorado). Prof. Madden at MIT has helped supervise
numerous research workers at MIT since Nourbehecht. More recently their
results have included work on the transfer function governing the signal
generating process (Steven Pride), massive computer models of the
electrokinetic process (Matthew Haartsen), and development of a tube wave
logging device (Mikhailov). Groundflow has taken full use of such published
research in the development of its own equipment and technique.
Numerous groups have published experimental data showing the characteristics
of electrokinetic signals. Unfortunately it is apparent that the
experimenters have, by and large, ignored or not read the basic physics work
done mostly at MIT and Schlumberger. As a consequence most of the field work
has been badly designed. The fieldwork also reveals a second issue that has
hindered acceptance of the technique. Signals are collected with a grounded
dipole antenna. Correct use of such an antenna requires that the designer of
the experiment knows enough electronics to connect up the antenna to his
recording device correctly. This seldom happens. Most researchers have
treated the dipoles as if they are geophones! The result is that most
experiments generate poor data and projects are usually dropped after the
"best" results have been published.
Groundflow has collected several thousand EKS soundings during the course of
commercial surveys, probably more than anyone else. We have found that
despite the variation in geology from place to place, certain simplifying
assumptions can be drawn. These include:
1. Permeability generally decreases downwards, consequently it is not
essential to search for aquifers deeper than a few hundred metres.
2. If there is no permeability in the rocks underlying an EKS sounding site
there will be no signal. EKS is possibly unique in this respect among
geophysical techniques.
3. If the water in a permeable layer is salty there will be no EKS signal.
4. Where a fresh water-filled aquifer does occur EKS signals are seen. The
strongest signal may be from the air/water interface if the aquifer is truly
unconfined but usually (approximately 90% of the time) the aquifer is
confined and the overall signal will represent the convolution of several
signals from interfaces between different water-saturated rock layers. The
bandwidth of such signals can yield useful permeability data when any noise
has been treated properly.
5. Numerous studies have shown an empirical correlation between the "EKS
permeability" results and actual borehole yields. Similarly, our customers
tell us that using the EKS equipment to locate water wells improves their
yield. Exactitude is impossible because every driller has a different
technique and some undoubtedly do more damage than others.
You can see our description of the technical basis for designing our
equipment in the paper which you can download from our web site. That paper
includes references and from them you can� access the technical literature.
If you have any specific questions regarding theory or technique I will do
my best to answer them.
Richard Clarke
Groundflow Ltd
Kirby Mills
MAG-1 Geoscience
[EMAIL PROTECTED]
