Montana oil and mining journal. [volume] (Great Falls, Mont.) 1931-1953, 1940-10-12
MORE ABOUT "CRACKOLOGY,

There is none who seriously disagrees
on theories of oil accumulation in Kelvin
Sunburst field. It's occurrence is err
ratio, as measured by any other theory
than that of vertical migration upward
along cracks in the Madison lime. When
the vast Kevin-Sunburst dome was up
warped by mountain building forces.
the pliable shales bent into the shape
of an overturned bowl. But the mas
sive, hard, brittle Madison lime did
not bend. Instead. 1t cracked and
shattered as. it was appraised bearing
a mantel of everything shales
Along these cracks and assures ground
waters sought escape from the pressure
provided by the porous intake forma-
tions in the mountains, where eternal
rain and snowfall penetrated the porous
rocks and travel basinward, water always
seeking its own level
In the distillation of petroleum from
the shales, oil has accumulated on top
Of the water, since oil always floats
on water Accordingly it is impossible
for oil to travel any direction except
upward when water is present, and oil
travels upward AHEAD of the water,
seeking escape. Thus the Madison lime,
which does not contain the necessary
hydrocarbons to form oil, becomes the
HOST ROCK for oil which comes from
the known oil-bearing formations.
In its upward travel. the oil may pene-
trate any porous spot in the lime. In
the periods of submergence and emer-
gence. during the ages when the Madison
limestone was laid down, strata of ma
terials softer and more porous than
lime, were laid down. and into these
layers the oil frequently penetrates:
notably the Turner Valley horizon.
which is near the base of the Madison
Lime
Where there is crack or fissure
which continues on upward, the oil con-
tinues on upward, penetrating cross
cracks and assures and porous materials
ever seeking escape Where the cracks
are too minute to allow the passage
of oil gas (sometimes bearing a con-
siderable amount of naptha) mounts
onward higher in the lime and it would
find escape on the surface of the ground
except for an everything. impervious cap
ping found just above the Madison lime
That Gaping is the shale base of the
Ellis formation. of Jurassic age. The
bottom of the Ellis is from 40 to 100
feet of hard black shale that is imper-
vious to oil. gas or water, where it is
unbroken. 1t is an ideal caprock. MAX
ing possible the major accumulations
found in Kevin-Sunburst and Pondera
oil fields.
Occasionally. as in the Morton Shaw
Elhngson producer in West Kelvin field.
oil is found in broken portions of the
Ellis fblack lime" near the base In
every such instance it has been later
determined that the presence of this oil
is the result of fracturing, and evidence
of fracturing usually points to a nearby
accumulation of oil, since it likely re-
fleets an unusually large crack or fis-
sure in the Madison lime.
Needless to point out, Kevin-Sunburst
does not conform to any of the school
book rules and the pedagogue married
TO the theory of lateral migration is like
the farmer who saw a camel for the
first time: he merely says, at can't
be; there is no such animal
Then comes the argument:
There is no possible way to know
where to spot a well in Kevin's vast one
lundred-thousand acres. The thigh" of
the structure may be dry, If no lime
racks happen at that point. There may
be oil in the low" of the structure.
lust because there is a lime crack at that
Joint. Therefore there is no rule to go
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