Petroleum and Natural Gas Fields in Wyoming Page: 61
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REVIEW OF OIL AND GAS FIELDS
mately 8 to 9 miles long and 3 to 4 miles wide,
with the main axis trending north-south.
Data from the wells drilled :indicate a possible
closure of more than 300 feet. The Bridger
formation, which covers the surface of the
Church Buttes area, shows very little evidence
of the folded structure in the Cretaceous beds
below. Seismic study in 1941 located the
structure. The elevation of wells in the field
ranges between 6,700 and 7,200 feet above
mean sea level.
The discovery well in the Church Buttes
field was completed in April 1946 with an ini-
tial flow of 12.5 million cubic feet of gas and
146 barrels of condensate a day. The well was
in the C SW1/4NW1/4 sec. 8, T. 16 N., R. 112
W., and was drilled to a total depth of 12,894
feet. Gas production was from the Dakota
formation at a depth interval of 12,550 to
12,666 feet; the shut-in surface pressure was
The Dakota formation is divided into three
main zones by relatively thin shale sections.
The three main sands are very well consoli-
dated and range from 115 to 173 feet aggre-
gate net thickness. The average porosity of
the reservoir sands in the wells drilled ranges
from 8 to 21 percent, and the permeability
variation is appreciable, with individual values
ranging from 14 to 750 millidarcys in the pro-
ducing sections. It is very difficult to correlate
the three main sands stratigraphically because
of lenticularity in the Dakota formation and
variation in porosity and permeability.
The original fluid saturation in the Dakota
sands ranges from 41 to 56 percent water and
from a trace to 3-percent oil saturation. The
fluids, as recovered at the plant, range from
6 to 8 barrels condensate and 1 to 2 barrels
water per million cubic feet of gas produced.
The condensate has a "tank" gravity of 530
API. At the time of the discovery, the pres-
sure in the reservoir was about 7,040 p.s.i.a. at
the datum depth of minus 5,835 feet, and the
temperature 2500 F. After completion of unit
well No. 1, surface samples of the liquid and
gas were studied for the purpose of determin-
ing the properties of the samples when re-
combined in the produced ratio and under the
pressure and temperature of the reservoir. It
was found from these tests that the reservoir
gas is a retrograde gas and that no hydrocar-
bon liquid is present in the reservoir.
The Frontier and. Nugget formations have
been cored and tested without finding commer-
cial production. From data obtained from the
wells drilled, the following formation thick-
ness, in feet, exists at the Church Buttes field:
Bridger, 1,235; Green River shale, 1,735;
Wasatch, 2,090; Fort Union, 1,890; Adaville,
1,498; Blair, 739; Hilliard shale, 2,923; Fron-
tier sandstone, 75; Aspen shale, 375; Dakota
sandstone, 224; Morrison, 700; Curtis, 103;
Entrada, 140; Carmel, 612; and Nugget sand-
stone, 129. Analyses of oil, gas, and water
from the Dakota formation are given on page
351, and in tables 8 and 9 (pp. 288 and 293,
A total of 17 wells had been drilled in the
Church Buttes field by January 1957, of which
11 were producing gas wells. The initial daily
production of the wells ranged from 3 to 45
million cubic feet of gas. These do not repre-
sent maximum open-flow gages, as many of the
wells were tested through a 1/2-inch choke.
Initial shut-in surface pressures were 5,400
p.s.i., and the flowing pressures were 3,000 to
4,500 p.s.i., depending upon the rate of flow.
The first reduction in the wellhead pressure is
taken after the gas travels a short distance
and through one side of a two-pass indirect
heater. After the gas expands through the
adjustable choke, it is again reheated as it
travels through the second pass of the heater.
It then enters the meterhouse on the down-
stream side of the heater. The heaters must
be installed near the well to prevent the forma-
tion of hydrates in the flowlines due to cooling
on expansion to the flowline pressures.
Pressure on the flowlines to the plant is 950
p.s.i., and the hydrate point at this pressure is
approximately 650 F. On the longer flow-
lines intermediate heaters must be installed to
prevent too large a drop in the temperature
of the gas. All flowlines are buried 6 feet,
and accurate records are kept of the daily
temperatures at critical points to maintain the
temperature of the gas above the hydrate-
formation temperature. Regular checks are
made for possible corrosion in the wells and
flowlines. The gas enters the plant at 950
p.s.i., the hydrocarbons and water are removed,
and then the gas enters the main pipeline to
northern Utah at 450 p.s.i.
Gas was produced at the field for 3 months
late in 1948, and production was resumed late
in 1949. Production at the field in 1956
amounted to 13.7 billion cubic feet to bring
the cumulative total of gas produced to the
end of 1956 to 90.7 billion cubic feet. Con-
densate or oil production at the field amounted
to 109,062 barrels in 1956 to bring the cumu-
lative total to the end of 1956 to 701,380 barrels.
Gas from the field enters the main distribu-
tion system serving the area from Rock
Springs, Wyo., to Salt Lake City, Utah.
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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/m1/75/: accessed March 20, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.