Re: Gas reserves deep in the Earth? - New research

From: tadchem (thomas.davidson_at_dla.mil)
Date: 09/20/04 

Date: 20 Sep 2004 12:03:03 -0700

Aidan Karley <aidan@abuse.demon.co.uk.invalidated> wrote in message news:<VA.0000018b.00c2b4cc@abuse.demon.co.uk.invalidated>...

<snip>

> Indeed. They got what they expected in that respect. What they
> didn't expect was that the Baltic shield would have a sufficient stress
> field locked into it that the wellbore would elongate to something like
> 2:1 in the direction of maximum stress (they did several multi-arm
> caliper runs) and that the well would take off in that direction at
> something like 25 degrees from the vertical. That put a lot of
> unexpected wear on the casing, slowed drilling, etc.

I imagine that would. Few people appreciate how fluid "solid rock"
can be, but it is exactly that fluidity that permits plate tectonics
to occur.

Since the stress field increases with depth (at least until magma is
reached), drilling technology is limited by this factor from ever
reaching the Mohorovicic Discontinuity. If there *is* significant
methane within the mantle, one could expect it would accumulate at the
Moho (with the crust as a caprock) until it can percolate up through
cracks in the crust. All observed cracks in the crust that reach to
the mantle are sources not of gas but of magma.

As an interesting aside, *Science* is reporting today the following:
"...geophysicist Henry Scott of Indiana University in South Bend used
an apparatus called a diamond anvil cell to heat and squeeze iron
oxide, calcite, and water. The experiment was intended to mimic
conditions 100 km to 200 km deep, in the partially molten layer known
as the mantle. At temperatures between 500° and 1500°C and pressures
between 50,000 and 110,000 atmospheres, methane bubbles formed, the
team discovered by sending x-rays through the sample."
source http://sciencenow.sciencemag.org/cgi/content/full/2004/917/3

(This smells like a research project intended to generate grant money
for further research, pending sale of the idea to gullible
politicians.)

They credit the online edition of Proceedings of the National Academy
of Sciences for the original report. What is *omitted* from the
report is the fact that the composition of the crust is mainly silicon
and aluminum with other metal oxides:
http://www.geo.cornell.edu/geology/classes/geochemdata/CrustalAbundances.html
*not* "iron oxide, calcite, and water."

The Upper mantle is also poor in hydrogen and carbon:
http://www.seismo.unr.edu/ftp/pub/louie/class/plate/composition.html

These elements occur mineralogically in carbonates and hydrates
respectively, which are found in sedimentary and metamorphic rocks -
rocks which originate in the biosphere.

I stand by the conclusion that commercially useful quantities of
methane will not be found "deep in the earth."

Tom Davidson
Richmond, VA

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