Montana oil and mining journal. [volume] (Great Falls, Mont.) 1931-1953, 1942-05-09

Devonian was subjected to some fold
ing, due to mountain building, before
the Mississippian, Silurian and Creta-
ceous series, respectively, were laid
down by the subsequent millions of
years of sedimentation. That raises
grave question regarding the location of
a Devonian test in any present produc-
ing oil field
here IS an answer to that problem !:
GEOPHYSICS. But geophysics costs
$3.50 per day and a survey necessary
to shoot" Devonian high on Kelvin
field might run into many weeks and
perhaps months. Who is going to pay
the cost of such a survey?
IS any individual going to make
geophysical survey of Kelvin field for
the benefit of all the other operators.
perhaps to find that his present lease
is not on the high? Would it be pos
sible for him to buy the high" from
someone else, once he had established
it?
Anyone who knows human nature
knows the answer to those questions.
Accordingly, it looks as though it will
be necessary to discover Devonian oil
on a wildcat structure such as Midway
On Midway the Devonian "high" has
been established by magnetometer and
by seismograph methods and so far as
we know, this IS the only structure Tex
cepting one gas structure in the Sweet
grass Hills) which has been thus
checked and re-checked by geophysics,
in addition to plane-table survey bv
competent biologists.
hat there IS a structure present at
Midway, southeast of Conrad, has been
suspected, if not known, by geologists
for many years. At one time all the
leading major companies had leases on
Midway But none could locate the
high" without drilling. One well was
drilled but it told nothing. 1t was neces-
sary to wait until wells were drilled
AROUND Midway to give some. indi-
cation of flexing of the beds. In due
time, wells were drilled which definitely
showed north closure, then west closure
and finally south closure. East closure
remained unproven except that the en-
tire Sweetgrass Arch dips to the east
beyond its own axis.
Midway is said to be closed to the
east by the regional dip, giving a gil
gantic fold resembling an overturned
vegetable bowl. Instead of following
the line of folding of the Rocky noun
tains northwest to southeast) it fol-
lows line of older folding or a dis
tortion of the axis of the Sweeterass
Arch, and the bowl rests with its length
from 7nrfhancf fn II
off east-and-west.
Apparently the Devonian folding fol-
lows lines BEFORE the Rocky noun
tain uplift for the Devonian fold like
wise runs from northeast to southwest.
as revealed by the geophysical survey
of Midway. Accordingly, the Madison
lime high" may coincide with the De
vonian high" A we'll drilled on the
exact high of the fold may thus find
oil in the top of the Madison lime.
Other wells in the area, down on struc-
ture, have had showings of oil-notably
on Conrad Butte fold to the north.
Given structure with some fracturing
in the lime, and Midway may give pro-
duction at the top of the Madison lime
in the well now being started by R. c.
l drrart.
Tarrant is drilling this well, contrary
to the rule, with the Devonian as his
objective. Associated with him are some
refiners who want to insure their flu
lure by greater reserves. They want
CRUDE whether it comes from the
lime or from new horizons below the
big lime" So if Tarrant gets com
nercial production at the top of the
Madison lime, he may halt short of
he Devonian.
But should he go to the Devonian
md get the production that is prom
sed by the showing of the off-structure
Dry Forks we'll north of Conrad, then
he way will be clear to every intelli-
rent operator and investor.
Proof of the existence of Devonian