106
T126 Last Resource
itself deep into the ocean—oor sediments. This ‘near the bottom’
pinger also provides additional information about the nature of the
sea oor—hard rock gives a weak signal, with irregular side eehoes,
because it rarely presents a at surface perpendicular to the pinger,
whereas mud with its at surface has a strong signal.
At some point in any survey some kind of quantitive estimate
must be made. In the case of surface deposits samples can be taken
fairly conveniently with dredges, grabs, corers and, in recent times,
by manned submersibles. But once deposits below the immediate—
surface sediment are considered, the diiculty of making such
assessments assumes quite a different scale. Oil and natural gas do
not present too much of a problem; the size of the eld can be
estimated from the results of comparatively few test drillings and
evaluation of the gas or oil ow. On the other hand, mineral ores
can be mapped only after a considerable number of samples have
been collected.
Unfortunately at present satisfactory drilling
techniques for investigating ore bodies just do not exist—the kind
of rig used by the oil companies is far too costly because of the loss
of drilling time during the necessarily frequent shifting. To assess
an ore deposit would involve drilling shallow holes 100 to 700 feet
in solid rock at intervals of hundreds of feet rather than miles.
According to one expert, the evaluation of a large ore body would
require a minimum of 50,000 feet of drilling in the form of approxim—
ately twenty holes, and to maintain exploration at a viable level this
_
would have to be done at a cost below JÇ50,000. ln fact, unless a
cheap drilling system is devised, the prospects for exploring in
search of marine ore bodies must remain very poor indeed.
This discussion has concentrated on the geological detective
work which goes into nding and assessing mineral resources, but
it must be remembered that such activities have to be located
accurately on the Earth’s surface. On the land, the production of
maps, aerial photographs and the like, enable results from surveys
to be accurately located, but this kind of aid is not always available
out at sea. ln fact, before any survey or exploration can commence,
a
navigational grid may have to be established so that results
can be pinpointed and related one to another over the entire area
under study.
Natural gas and oil bommza
Some 200 drilling rigs are at this very moment pr0bing the
T126 Last Resource
itself deep into the ocean—oor sediments. This ‘near the bottom’
pinger also provides additional information about the nature of the
sea oor—hard rock gives a weak signal, with irregular side eehoes,
because it rarely presents a at surface perpendicular to the pinger,
whereas mud with its at surface has a strong signal.
At some point in any survey some kind of quantitive estimate
must be made. In the case of surface deposits samples can be taken
fairly conveniently with dredges, grabs, corers and, in recent times,
by manned submersibles. But once deposits below the immediate—
surface sediment are considered, the diiculty of making such
assessments assumes quite a different scale. Oil and natural gas do
not present too much of a problem; the size of the eld can be
estimated from the results of comparatively few test drillings and
evaluation of the gas or oil ow. On the other hand, mineral ores
can be mapped only after a considerable number of samples have
been collected.
Unfortunately at present satisfactory drilling
techniques for investigating ore bodies just do not exist—the kind
of rig used by the oil companies is far too costly because of the loss
of drilling time during the necessarily frequent shifting. To assess
an ore deposit would involve drilling shallow holes 100 to 700 feet
in solid rock at intervals of hundreds of feet rather than miles.
According to one expert, the evaluation of a large ore body would
require a minimum of 50,000 feet of drilling in the form of approxim—
ately twenty holes, and to maintain exploration at a viable level this
_
would have to be done at a cost below JÇ50,000. ln fact, unless a
cheap drilling system is devised, the prospects for exploring in
search of marine ore bodies must remain very poor indeed.
This discussion has concentrated on the geological detective
work which goes into nding and assessing mineral resources, but
it must be remembered that such activities have to be located
accurately on the Earth’s surface. On the land, the production of
maps, aerial photographs and the like, enable results from surveys
to be accurately located, but this kind of aid is not always available
out at sea. ln fact, before any survey or exploration can commence,
a
navigational grid may have to be established so that results
can be pinpointed and related one to another over the entire area
under study.
Natural gas and oil bommza
Some 200 drilling rigs are at this very moment pr0bing the