Petroleum and Natural Gas Fields in Wyoming Page: 29
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REVIEW OF OIL AND GAS FIELDS
from the First Sundance sand at 5,150 to
5,206 feet, and 6,300 barrels of 63 API
gravity oil and 3 million cubic feet of gas
from the Basal or Second Sundance sand at
5,299 to 5,397 feet. The shut-in wellhead pres-
sure of the First Sundance was 1,900 p.s.i.,
and that of the Second sand 1,100 p.s.i.
In 1948 a well in the SE1/NE1/4 sec. 26 had
an initial daily production of 1,920 barrels of
590 API gravity oil from the Tensleep sand
at 6,666 to 6,867 feet. The log of a well in the
SE1/4SE1/4 sec. 23 shows the depth, in feet, to
the following formation tops: Shannon, 1,684;
Niobrara, 3,370; Frontier, 4,137; Muddy,
4,851; Dakota, 4,932; Lakota, 5,000; First
Sundance, 5,267; Second Sundance, 5,403;
and Tensleep, 6,794. Before the discovery of
oil and gas in the Sundance formation, seven
wells were drilled on the Medicine Bow anti-
cline, one of which flowed a small quantity of
oil from 4,003 feet, probably from the Wall
Creek sand. The well was deepened and
The oil in the First Sundance sand was satu-
rated with gas at reservoir pressure, as a gas
cap existed in the sand. Analysis of a sub-
surface oil sample taken in it well at 5,526
feet, opposite the top of the First Sundance
sand, showed that 2,995 cubic feet of gas (cal-
culated at 60 F. and 14.4 p.s.i.a.) was in solu-
tion at 142 F. (reservoir temperature) and
2,370 p.s.i.g. (reservoir pressure) for each bar-
rel of residual or produced oil (measured at
atmospheric pressure and 60 F.). As the
solution gas was composed primarily of heavy,
normally gaseous hydrocarbons, the oil had a
surprisingly high shrinkage factor. It was
indicated thus that 2.77 barrels of oil in the
reservoir at 2,370 p.s.i.g. and 142 F. would be
required to produce 1 barrel of oil at atmos-
pheric pressure and 60 F.
The oil in the Second Sundance sand flowed
from the wells because of the hydrostatic
pressure in the sand. The oil was saturated
with gas at 194 p.s.i.a. and 60 F. Analysis
of a subsurface oil sample taken at a pressure
of 790 p.s.i.g. showed that 375 cubic feet of
gas was liberated from solution when the pres-
sure was reduced from 194 p.s.i.a. (saturation
pressure at 60 F.) to 14.4 p.s.i.a. and 60 F.
for each barrel of residual or produced oil.
The analysis also showed that 1.27 barrels of
oil in the reservoir at 2,330 p.s.i.g. and 1400 F.
was required to produce 1L barrel of oil at
atmospheric pressure and 600 F. High-pres-
sure (250-p.s.i.) and low-pressure (28-p.s.i.)
separators have been used to separate the oil
and gas produced. Analyses of oil from the
First Sundance and Second Sundance sand
and the Tensleep sandstone and of gas from
the First and Second Sundance sands are
given on pages 334 and 335 and in table 8 (p.
287), respectively. Analyses of water from the
Mesaverde, First Sundance, Second Sundance,
and Tensleep formations are given in table
9 (p. 293).
As of January 1, 1958, there were five pro-
ducing oil wells in the field; of these, four
were in the Sundance and one in the Tensleep.
There was one shut-in Tensleep well. During
December 1957, 5,141 barrels of oil was pro-
duced from the Sundance sands and 20,673
barrels from the Tensleep. Water production
for the month was 62,900 barrels, mostly from
the Sundance. The field produced 240,099
barrels of oil and 42.3 million cubic feet of gas
in 1956. The cumulative production through
1956 was 6,289,720 barrels of oil and 11,333
million cubic feet of gas. The oil is trans-
ported through 7 miles of 4- and 6-inch line to
the town of Medicine Bow, where it enters
the Fort Laramie-Salt Lake pipeline. Gas
from the field was delivered into the Allen
Lake-Laramie gas pipeline until 1937. For a
few years after 1937 gas was piped to the Rock
Creek oilfield and injected into the Dakota
sands for storage.
The Big Muddy oilfield (figs. 16 and 17) is
in the north half of T. 33 N., R. 76 W., Con-
verse County. The structure is an anticline
trending east-west. The outcropping sands
dip 2 to 10 on all sides, except on the north,
where they dip about 200. The structure has
a closure of about 500 feet. Many minor trans-
verse faults cut the structure. The Cody shale
is exposed on the surface, which has an aver-
age elevation of about 5,000 feet.
The field was discovered in 1916, when a
well was completed in the NE1/4NE1/4 sec. 9,
with an initial daily production of 26 barrels
of oil from the Shannon sand. Wells com-
pleted later in the Shannon sand averaged 35
barrels daily of 34 API gravity green oil,
although a few produced 300 to 400 barrels
daily. In 1917 a well in the NW1/4SE1/4 sec.
7 was completed, with an initial daily produc-
tion of 128 barrels of oil from the deeper Wall
Creek sands at 3,147 to 3,217 feet. In 1922,
36 API gravity brown oil was discovered in
the Dakota sand. In 1931 a well in the NE1/4
NE1/ sec. 9 was completed in the Lakota sand
at 4,353 to 4,364 feet; the initial daily pro-
duction was 405 barrels of 320 API gravity
brown oil. The Lakota sand also carried
water. About 529 wells were drilled on and
near the Big Muddy structure, of which 306
were either dry or had been abandoned by
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Biggs, Paul & Espach, Ralph H. Petroleum and Natural Gas Fields in Wyoming, report, 1960; Washington D.C.. (digital.library.unt.edu/ark:/67531/metadc38797/m1/43/: accessed July 27, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.