Montana oil and mining journal. [volume] (Great Falls, Mont.) 1931-1953, 1937-06-26

Passing through Conrad one day this
week we saw the start OF one of the
most historic events in the oil history
of Montana:
THE START OF THE GEOPHYSICAL
SURVEY IN NORTHERN MONTANA.
One Of the most completely equipped
and most modern geOphysical outfits
in the United States this week began a
survey in the center of the Sweetgrass
Arch, on a structure near Conrad known
as Midway structure.
GeOphysicaI methods have brought in a
majority of the new oil fields discovered
in the last decade. GeOphysical methods
have found oil fields In areas in Cali
fOrnia, the MidcOntinent and the Gulf
Coast where ordinary methods of ge-
OlOgy could find no evidence of struc-
ture. just as Montana watched other
states bring in the greatest oil pools In
the world by deep drilling so has Mon
tana watched other states prOfiting by
the use of geOphysics and until now has
done nothing about it. None Of the major
companies, who could afford geOphysical
surveys, which cost from $1,000 to
100000 per month, were interested in
making surveys in this state and the In
dependents had SO much proven ground
available that they have not taken time
to look into the possibilities of geophys-
ical prospecting.
An independent concern has brought
possibility that there may grow up I'm
Montana another great oil company con-
trolling vast reserves of petroleum.
Our organization issued a bulletin
on geOphysical prospecting three years
ago, suggesting that geOphysics might
dOmes as BOwdOfn, POrcupine and the
Sweetgrass Arch. There isn't enough oil
in the world to fill BOwdOin DOME al
though it is q completely enclosed saxuc-
tre, capable of trapping a vast amount
of oil. Shallow wells have found gas
the teIlfaIe stgnboard which points TO
oil in lower hOrtzOns-but some operators
have not been disappointed that deep wells
have not found Oil In formations above
the Madison lime.
The same is true of the Sweetgrass
Arch, which is . three-sided structure
large enough to trap trilliOns of barrels
of oil. But the trap is not filled. In
the Arch it is determined that the OIL is
trapped I'm local pOoIs-''wrinkIes'' ON the
greater upIift. But these localized strHc-
lures are not defined on the surface of
the ground so that a geOEOgist cam
measure the dips and map thena- We
suggested that some day, geophysics
might find these local oil traps and thus
simplify the search for oil in vast areas
where oil is known to exist, but can't
be located by old methods.
Every member OF this organization has
kOOU WOAAAhAK AAOWACukO Oh kSS1NShuHsSs
He could not map structure, perhaps,
but he knows the principle of the bend
ing of the earth's surface in Natures
business of mountain making, to form
traps into which oil migrates, floating
on the top of water. He knows that an
anticIfne is revealed like the roof Of
house, the shingles representing the shale
strata dipping down ON either side of the
crest. He knows that one end OF this
anticIine may be sealed with fault,
which is a break in the earth's surface:
where the formations have actually brOk-
en-, rather than Bonded. Thus when an
oil-beaFing sandstone is so displaced
that it rests against impervious shale,
trap is formed. Likewise, when lime
is folded il more frequently cracks than
it bends, so oil frequently migrates up
ward through limestone fractures, from
lower oiI-bearing formations. But there
is no way of recognizing limestone frac-
lures from the surface of the ground,
under present geological methods.
The geophysicist has arrived at
method of Cooking below the surface
Of the ground, by measurement of the
rate OF vibrations. Our former pubiica-