I have to disagree with much of what Glen says here.
AG Marketing FC BG JD MP GP BH wrote:
> In regards to the BHP announcement Ken Witherly advised us of on May 18, I
> found it interesting that BHP actually showed nothing which was identified
> as gravity gradient data. Their excellent examples of using gravity data to
> high grade magnetic leads apparently showed simply gravity data of the type
> which Carson Aerogravity has been measuring from S-61 helicopters and DHC-6
> Twin Otters for more than 20 years at 2 to 4 km half wave lengths.
A cursory look at the BHP data shows resolution far better than "2-4 km
half-wavelengths" - I suggest 5x better at least.
> I can
> understand BHP not going out of their way to mention this fact to share
> holders, but it was totally disingenuous of them to claim "Falcon - the
> world's first effective gravimetric surveying tool" (BHP slide 29).
Indeed, management might have been better advised to add the caveat
"for minerals exploration"
> The
> patented Carson Aerogravity survey system has collected more than 1,000,000
> km of aerogravity data in 35 countries for 65 clients (including BHP
> Petroleum PTY). Hats off to BHP for their gradiometer! Now they need to
> show some real gradiometer data
I dont think you are going to see gradients as such in any
presentation. If
you look at the paper
Bodard J.M., Creer J.G. and Asten M.W., 1993.
Next generation high resolution airborne gravity reconnaissance in oil
field
exploration: Energy Exploration and Exploitation 11, p.198�234.
you will see a discussion on some of the problems of artifacts in images
which
appear on gradient data. It was clear early on in the project that
transformation to "equivalent gravity" would be necessary in order to
have data
in a form suitable for geological interpretation. (As a loose analogy,
we routinely put mag data thru a transformation to the pole, in order to
improve interpretability). My association with the BHP
program ended in 1996, but it is evident that they have done just that.
> vs. conventional aerogravity data in order
> to demonstrate that they have actually improved on a system
I'll be charitable here - if you cant see a resolution improvement in
the BHP data vs aerogravity, then you are a powerful advocate for your
own business.
You might also be right if you suggested that the BHP data suffers a
drafting error in that scale bars (mgals, eotvos or whatever), seem to
be missing. Carelessness on the part of very senior management, I
guess.
> contacted at a small fraction of the cost of the Falcon system.
So what did Falcon cost?
>
> Glen Penfield
> Vice President
>Regards,
Michael Asten
Flagstaff GeoConsultants
www.flagstaff-geoconsultants.com.au
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