The Hardin tribune-herald. [volume] (Hardin, Mont.) 1925-1973, 1941-05-15
DYING MARINE LIFE
FORMED SOURCE
BEDS FOR OIL
Exclusive: Tribune Herald
BY: Ray E. Cotton,
Oil and Gas Science

BY: Ray E. Cotton,
Oil and Gas Science
Writer.
Formed Source Beds For
Crude Oil
II, as is now proven that oil
evolved from dying marine and
marine vegetable life, it is to
be assumed that such life
formed oil source beds" in the
form of muds, clays, silicates
and carbonates. The agency
which solidifed this organic
mass of marine life, was prob
ably subteranean heat. The
mass mellowed for countless
millions of years, during which
time it was being constantly
augmented by additional re-
mains. Finally it began its mi
grafton to what are termed as
adjacent porous rocks. lie. such
llmeStoneS, sands, shales and
S~andStaneS as possessed the
physical attraction of perosity
necessary to attract and to hold
imprisoned i'm their strata folds
the oil.
Field engineering in the search
for oil in Montana and other oil
producing states, reveals that
this migration was the result
of one or more of several forces,
such as induration and dehydra-
ton of the mass, earth move
ment during such land mass ad-
juStmentS as erected the nearby
Big Horn and Rosebud noun
tains, or hydrostatic pressure of
accommodating natural gases.
Reservoir Rocks Had To Be
Permeable as Well as Porous
The receiving or reservoir
rocks to which the migrating
oil mass was attracted, had to
be permeable as we'll as porous,
and they had to be encassed in
what it termed as "impermeable
Strata" that is strata which al
lowed the migrating oil to enter
it, have freedom of movement
within the strata, yet have no
escape from it once entombed.
Preliminary investigation of the
sub-Surface of Big Horn county
and studies made of logs OF
wells previously drilled in this
part of Montana, show that
such favorable rocks lie be-
meath the Hardin, Pryor, Grow
Agency and other areas.
Certain Rocks Will Not
Hold Oil
Igneous, metamorphic and
rocks derived from granite
sources, cannot be any source
of rude oil. These types of rocks,
which are in the minority here
in Big Horn county, lack phys
ical attraction of perosity owing
to their tightness. Had these
rocks once contained any oil,
the conditions which have al
tered them to their present
shape, would have long since
diSsipated any peroliferous ma
terial which they might one
time have contained.
False Ideas About Oil
Accumulation
The public thinks of oil as be-
ing found in underground lakes,
caves and rivers, but the true
condition of oils recovery is
quite different. When ever any
one talks of oil occurring in this
manner, he is either ignorant of
the subject which he is discus
sing, or he is using selling talk
to interest the unwarry in some
stock selling scheme. The reser-
voirs in which oil and gas oc-
cur, are in order of their i'm
pOrtance as follows:
l. Porous sands.
2. SandStones.
8. Fractured and whole shales.
4. LimestoneS.
Such sediments may be seen
outcrops in the area to be
drilled, or during core drillings.
A study of oil deposits shows
that most of the large CONNER
cial accumulations are from
porous sands.
Structural Features of Big
Horn County Are Good for
Oil Traps"
Geologic research work in the
past in various parts of Big
Horn county, reveal that the
anticlines offer the best chances
for oil being recovered. One OF
these structures, the Pryor An
ticline between Crown Butte and
West Pryor mountain in western
Big Horn county, is described
gelogicly as an upward arch OF
the beds of the earth'S surface.
Oil and gas generally occur in
structures of this type in the
minute pores of the sand, sand
stone and limestone at the top
of the arch. Water is found in
the same bed as the oil and gas,
but below them on the arch, as
would naturally be expected, gas
and oil being lighter than water.
The gas and oil are generally
held at the top of the arches by
the water pressure, until re-
leased by the drill, when the
natural gas, also held under
pressure, expands and helps
drive out the oil. AS the oil Is
Withdrawn, water usually under
pressure, replaces the gas, and
helps force the oil into the OIL
wells.