Montana oil and mining journal. [volume] (Great Falls, Mont.) 1931-1953, 1941-03-08
OIL IN DEVONIAN

Continued from PAGE Onel
shaley and siliceous material which
is inseparately mixed with 1t in
dicate an origin in very muddy
water. The lime becomes more
pure toward the base.
Here also were found two beds
of very fine. hard. black shale six
and Is feet thick, respectively,
which produced the best showing OF
oil found below the Ellis. Despite
the, pressure OF a 2,45O-foot column
of water in the hole, considerable
quantity of free oil, light brown in
color, and evidently of high grade,
rose to the top OF the well and COW
cred the slush pit. The limestone
also, while they apparently had no
oil saturatiOn when brought to the
surface. upon release of pressure.
literally sweat out oil and became
shattered with It in a few minutes
time. No formation was present
which possibly could act as a re-
servoir for accumulation. The lime
between 1888 and 2445 was filled
with minute, rounded grains OF
sand, but was too tightly cemented
to be at all porous.
Right at the base of the De-
vonian a greenish shale was en-
countered which was richer in fos- |
sils than any other in the whole |
we'll section. These fossils were |
identified by DR.. Geo. H. Giry, |
paleontologist OF the U. s. Geolo-
gical Survey and authority on the |
formations of the Paleozoic Era,
as being undoubtedly of upper De-
vonian age On this connection, it i
might be added that rock and fossil
specimens of the whole rock core Il
were submitted to the U.S.G.S. and |
were carefully examined by Drs.
Girty and Stanton, who have con-
firmed the classtfications as shown
in the log.
THE well was abandoned after
drilling at the base 1872 feet of
white, brown massive anhydrite.
AS far as can be ascertained, such
a bed does not outcrop anywhere
In the state and hence 1t cannot be
definitely classified. The chemical
of anhydrite Is practi-
cally the same as gypsum calcium
and II may be this for
nation corresponds to the Canadian
deposits of gypsum and anhydrite
which are designated as being of
Silurian age. In the Cascade well
near Great Falls a bed reported in
he log between 2,102 and ais
Is resembling marble sounds SUI {
piciously like this formation which J
llso showed markings characters
lie of marble. This Is merely a I
Imposition however. For the pre- '
ent it will be placed in the '
{
ut has been clearly shown that
he lower rocks are sufficiently
aturated with oil in places to 9
ield commercial production provid- G
ID a porous bed should anywhere s
'e encountered and it is reasonable /
o suppose that like conditions will t
.btain as far as saturation is con- C
erned, at still lower depths. a
From the geological viewpoint.
is extremely unfortunate that no i
ection Of the Lower Paleozoic
ocks is to be found close in to the
Ievin-Sunburst field. The Sweet II
rass Hills are disappointing in this
aspect as they show the section
My as far down as the Madison
me. There are no lower exposures
1thin the entire Sweetgrass Arch. II
hree wells, the Troy-Sweetgrass
Kevin-Sunburst, the Cascade
ear Great Falls, and the Agawam III
ear Choteau show partial sections
ut none known absolutely to con-
lin rocks lower than those Of
evonian age. Consequently, the
lvestigator is compelled to look to-