Montana oil and mining journal. [volume] (Great Falls, Mont.) 1931-1953, 1942-08-22

tana with those below the "big lime:
To 500 FEET:
Bearpaw shale. No oil or gas
1850 TO 1850 FEET:
Two Medicine formation. No oil or gas.
800 TO 400 FEET:
Eagle sandstone. Contains gas; no oil
1850 TO 1000 FEET:
Colorado shale. Contains several sands
but with exception of gas In middle and In
bottom sand, seldom shows anything.
$40 TO 1000 FEET:
KOOtenai formation. This is the first "pays
horizon, with oil In the Sunburst sand in
the Cut Bank sand just below it. They are
just below the red beds which were formerly
the stop" sign of Montana oil prOspectOrs.
IS TO 295 FEET:
Ellis shaIe. This formation occasionally
contains a sand which carries oil AS drill
ing depth increases, frequency Of oil show
ings is noted.
In the first 1900 to S. 600 feet of sediments
found in northern Montana there are three
to four horizons which show oil, as a COM
pOsite log OF hundreds Of wells would show
The same is true of eastern Montana where
the nomenclature of formations is different
but there is no difference In the matter of
shOwings Of oil There is gas only In the
formations ABOVE THE BIG LIME, in that
area The same is true in central Montana
excepting in the highly faulted Cat Greek
field where oil Is found in the KOOtenai
sands
In other words, there is little or no en-
cOuragement to the driIIer who would ex-
plOre these horizons above the lime Yet
because oil has been found in commercial
quantities at the base Of these formations,
prospecting has continued over the years
only to stop as soon as white lime appeared
on the bit or when water Is found. There
was once rule that when water was found
In the basal sands Of the Colorado, that
spelled "finiS." The Colorado water bOgy
was abolished by the Cat Creek discovery
well.
Now we look at a composite log OF the
few wells drilled through the Big Lime and
find to our establishment that the number
of shOwings increases with depth
As compared with FOUR encouraging
shOwings ABOVE the lime, in some 1900
feet Of sediments, there are SEVENTEEN
horizons which have shown oil In the vari-
GUS wells drilled 1900 feet BELOW the top
Of the Madison lime.
1875 TO 1860 FEET:
Madison lime; oil at the contact and oil
In three breaks" within a few feet of the
contact break" being any porous part
Of the lime capable Of absorbing oil or act
ing as a host rock Eighty feet below the
top Of the lime Is the O'NeiI-Lashbaugh
horizon of Kelvin field, which gave 5000
barrel well Since water is usually found In
One of the three breaks" above, 1t is sell
dom drilled. Two hundred and twenty-five
feet below the top Of the lime is the Trapp-
Hover horizon In a well drilled south Of
Conrad. Four hundred fifty to $50 feet be-
low the top Of the lime Is the Turner Valley
horizon which gives wells Of from a few
hundred TO 5000 barrels, with acidizatiOn.
The Turner Valley horizon, found In the
Kitchen well in Kelvin field, had a showing
If oil, before acidization was known. Six
hundred thirty-n feet below the top Of
he lime is the Dry Fork wen horizon which
lad a large showing, measurable in several
oarrels per day, Of "a gravity crude Drilled
n a syncline, this well had water in all
he upper horizons.
100 TO 500 FEET:
DevOnian formation; the top of the De-
oman is the horizon of the Athabaska tar
ands; $40 to 1909 feet below the top of the
addison lime the HiIand- VandaIe well near