Montana oil and mining journal. [volume] (Great Falls, Mont.) 1931-1953, 1935-11-30

Although the accumulation Of oil and
gas In pools OF the Rocky mountAlli,
states doubtless has been influehceu
by many geological factors the move
ment of ground water appears 70 nave
PLAYED an important part. Evidences that
such is the case are eSPecihly Apui' l.a-
in structural basins wherp the reser-
voir rock containing the oil pools Is
REASONABLY continuous and whose poro-
sity Is such to permit the move
ment OF fluids over great distances. IN
parfs OF Wyoming the comparison OF
results In the Frontier sands, which are
not continuous over large areas and the
Dakota horizons below. which are con-
tinuOus, afford an opportunity 10 com
pare results In the two types OF reser-
vior rock occurring in the same stfuc-
lures.
some Pools Destroyed
Present distribution or cummercial
pools OF oil and gas In structures al
iaeent to equally prominent hut barren
ones that are Of the same apparent
age, invites tho speculation that many
other pools may once have existeg . put
have since been destroyed The relation
If barren and productive structures
suggests that the agent which may have
removed the oil In some OF them Is
ground water.
second method Of destroying an oil
pool is however suggested. Change IN
the hydrostatic conditions In pool
might be so altered as to permit the
oil once accumulated 70 move more or
n
reeeding water table. possibly NOV
ing under the influence OF an actual wa
ter drive The peculiar structural posi-
ton Of some large deposits OF bitumen-
bearing sandstOnes suggests this pro-
cess has been operative IN the destruc-
ton Of some oil pools. The present To-
cation Of many such deposits does not
permit Of them having been formed In
the location IN which they are now
found.
The general movement Of ground wa
Ter Is basnwards from the point OF out.
erop Of the beds into which the ground
water may find access. But It Is sug-
gested that under some conditions depths
arr reached by these moving ground
waters beyond which their Eastward
ments become parallel to the edge Of the
basin,
The relative elevations OF onterOpping
beds on the rim Of structural basins
aud the elevations Of the same beds at
the lowest point OF Outcrop predicts the
possible direction of movement OF water
through them. The fact that numerous
mineral springs are situated at the
points where the main drainage enters
Into or passes from a structural basin
being the lowest point OF the outcrop Is
evidence that movements OF water arc
toward such points The thermal charac-
ter OF such springs is doubtless due 10
the depths reached by the water in
circumstances however. does not. nee
essitate movement to depths far below
those already reached in drilling known ,
structures.
Moves Through Saddle
The relation of some structural basins
to adjoining ones In often such that, |
in theory. water might move from one
% the other through n structural sad
die without appearing at the surface. In
such cases the direction Of movement Of
ground water can again be suggested
whore the regional structural contours
OF the basins can be drawn.
The fitting OF Oil-water contacts in |
numerous producing fields confirms TO |
the direction predicted for movement of
ground waters in these structural basins |