Montana oil and mining journal. [volume] (Great Falls, Mont.) 1931-1953, 1944-06-10


Of the federal nineral-leasing La
The area Is covered by overlap
ping nonmarine Tertiary sediments
Ia which there are isolated ex-
posures of upper Crefaceous and
older rocks. The structure of the
oil-bearing rocks In most of the area
is shown by 1O0foof contour lines
drawn on top of the Fall River
sandstone. and by two structure
sections A iarge-scale inset map de
picts by 1OO-foot contour lines the
structure of the Lance Creek oil
and gas field on the top of the Leo
zone of the Hartville formation.
The map also contains columnar
section showing rocks ranging in
age froRn Tertiary TO pre-C ambrian.
The most conspicuous structural
feature IN the area Is the Old
Woman-Hat Creek uplift, which is
a northward prolongation of the
Hartvflle uplift. The structural fea-
ture that Is most important econom-
ically, however, is the long, sinuous
anticline upon which the Lance
Creek and East Lance Greek domes
are superimposed. Smaller discern
ibie upfolds are Ant Hills dome; a
nose near the southwest corner of
twp. "a N, rye. IS w; nose at
the southeast corner of twp. 35 N,
rye IS w; and Magoon dome in and
near the north-cenfral part of twp.
81 n, rye. "a w. Several dry holes
on the northwest flank of Lance
Creek dome indicate major sub
surface faulting in that locality, of
which no surface evidence was
found.
The Lance Greek oil and gas field
was discovered In 1913. and until
1890 the Fall River sandstone was
the principal oil-and-gas-p producing
zone. In 1880 oil was discovered in
a sandstone near the middle of the
Sundance formation, and in 1895
larger amounts of oil were discov-
cred In a sandstone at the base of
the Sundance. The prolific Leo zone
in the Hartville formation was dis
covered in 1887. The field has yield
ed relatively small amounts of oil
from the Newcastle sandstone mem
Der OF the Graneros shale, sand
stone IN the Carlile shale, the La
kota sandstone, the Unkpapa sand.
stone, the Minnekahta limestone,
and sandstones in the upper part
of the Hartville formation To the
end of 1913 the field had produced
about 56,272, 500 barrels of oil.
The East Lance Creek field was
discovered in 1919 with the compile
ton of one relatively small oil vel
In the Fall River sandstone, which
Is still productive One gas we'll In
this field also produces from the
Fall Dtxras4 Commissioners
zones that are productive in the
Lance Creek field have, SO far
failed TO yield oil In the East Lane,
Creek field
A well on Ant Hills dome, which
produced some oil from sandst0n,
In the Inyan Kara group, was deep
eTied almost to the pref Cambria
and then abandoned.
A well drilled in 1917 in the SW1
NWM NWA sec 8, twp. SO NJ, rye
So w, on Old Woman anticline, hal
a strong showing of oil in the LIE
zone A later well drilled almos
to the pref ambrian in the SCI
SW% NWH sec. of the same towr
ship yielded no significant showing
of oil or gas.
Dry holes have been drilled I
the pref ambrian on Hat Cree
dome. and to the Leo zone on Nj;
COON dome and on the structure
nose three miles west
Copies of the map are availabl
at 50 cents each from the Directo
Geological Survey, Washington 2
ID. C.
Send contribution to the SUI
hzxgsxs Uaf40ar