New U.S. Geological Survey Publications Warehouse - U.S. … · 2010. 12. 15. · U.S. GEOLOGICAL SURVEY Vitrinite reflectance data for the Paleocene Fort Union and Eocene Wind River

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

Vitrinite reflectance data for the Paleocene Fort Union and Eocene Wind River Formations, and burial history of a drill hole located in central Wind River Basin, Wyoming

by

Vito F. Nuccio 1

Open-File Report 94-220

This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards (or with the North American Stratigraphic Code). Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

1 USGS, Denver, CO

Vitrinite reflectance data for the Paleocene Fort Union and Eocene Wind River Formations, and burial history of a drill hole located in central Wind River Basin, Wyoming

by Vito F. Nuccio

INTRODUCTION

Recent discoveries of oil in the Paleocene Fort Union Formation, and oil shows in the Eocene Wind River Formation, have sparked an interest in the burial and thermal history of these units in the Wind River Basin, Wyoming (fig. 1). The purpose of this report is to present new vitrinite reflectance data, and burial and thermal information for these and other units for a recently- drilled well in the central part of the Wind River Basin. By knowing the burial and thermal history of an area, one can characterize the petroleum potential of source rocks present, and develop an intelligent petroleum exploration strategy.

METHODS

Vitrinite, a maceral derived from woody plant material, is common in coal and carbonaceous shale. Vitrinite reflectance (Ro) is a measurement of the proportion of light reflected from a polished vitrinite grain. It is related to the degree of metamorphism of the vitrinite grain and can be directly converted to coal rank. Ro values have been correlated with oil and gas generation for potential source rocks (Dow, 1977; Waples, 1985). For example, Waples (1985) stated that oil generation begins over a range of RO values depending on the type of kerogen; onset of oil generation ranges from about 0.45 percent Ro to 0.50 percent Ro for high-sulfur kerogen, to 0.60 percent Ro for type II kerogen, to 0.65 percent Ro for type III kerogen. The end of oil generation also occurs over a range of RO values, but 1.35 percent RO is commonly accepted as the value at which oil begins to break down into shorter chain hydrocarbons. Dow (1977) states that oil generation by liptinitic-rich (Type I) source rocks occurs between 0.50 and 1.35 percent RQ. Wet gas is generated from mixed (Types I, II, and III) organic matter and from the breakdown of oil between Ro values of 0.80 percent and 2.0 percent. Dry gas, or thermogenic methane, is generated from humic organic matter and from the breakdown of wet gas between Ro values of about 1.0 percent and 3.0 percent. Biogenic gas can be generated at levels of maturity as low as those for peat (0.20 percent Ro). For this study, "mature" for oil occurs at 0.60 percent Ro (see fig. 2).

Eighteen coal samples were collected from cleaned cuttings from the Paleocene Fort Union and Eocene Wind River Formations (fig. 3) from the Larry Barnes Petroleum, Inc., Carvner Fed. no. 22-15 well in sec. 15 - T. 37 N. - R. 94 W. (fig. 1). The samples were prepared for R0 analysis by crushing, mounting in epoxy on a microscope slide, planing off when hardened, and polishing. The mean random Ro (from randomly oriented indigenous vitrinite grains) was determined using plane-polarized incident white light and a 546 nm monochromatic filter, in immersion oil, on a reflected light microscope with a nonrotating stage (Bostick, 1979; Bustin, 1986). Thirty measurements were made for each sample, and a mean Ro value calculated (see Appendix 1 for individual data sheets).

A burial curve and thermal history model (fig. 4) were constructed for the well using information from several sources. The thickness of the Fort Union and Wind River Formations were measured directly from a geophysical log of the well (see fig. 3). Ages of the Fort Union Formation members were adapted from Nichols and Flores (1993). Thicknesses and ages of post lower Eocene, Oligocene and Miocene strata were estimated using data from Love (1988), Keefer (1970), and Van Houten (1964). The basin modeling computer program BasinMod (Platte River Associates) was used for construction of the burial history, and in modeling the vitrinite reflectance. For this well, a heat flow of 45 mWm~2 was used. This agrees with present-day heat flow values for the Wind River Basin (range from 36 to 48 mWm~2) and also in the range of values that likely existed as far back as Late Cretaceous (Barker and Crysdale, 1993).

DISCUSSION

Mean RO values for samples from the well studied range from 0.61 percent (uppermost sample collected, 3240-3300 ft) in the Eocene Wind River Formation to 0.90 percent (lowermost sample collected, 9050-9060 ft) in the Paleocene lower member of the Fort Union Formation (fig. 5, Appendix 1). Assuming that 0.60 percent RO represents the beginning of oil generation, the lower part of the Wind River River Formation, and the entire Fort Union Formation are in the oil window. The major Tertiary oil source rock in the Wind River Basin is the Waltman Shale Member of the Fort Union Formation (Palacas and others, 1993). Katz and Liro (1993) characterized the Waltman Shale as containing types II and III kerogen, with total organic carbon content values as high as 7.0 percent. Based on these geochemical parameters, and the level of thermal maturity (0.75 to 0.80 for the Waltman zone; fig. 5) from this study, the Waltman would have to be considered an excellent source rock, and the likely source of the oil produced in this well. It is also probable that some of the coals, as well as carbonaceous shales that occur throughout the entire well, may have generated some gas.

Figure 4 illustrates the burial and temperature history of units in the well. Assuming that the burial reconstruction at the well site is accurate, a heat flow of 45 mWm~2 was required to match the modeled maturity with the measured Ro values (fig. 5). Using this heat flow, the base of the Fort Union (base of the Paleocene) was buried to around 12,300 ft, and reached temperatures exceeding 250°F at maximum burial 15 Ma. RO values of 0.90 percent characterize this horizon. The top of the Waltman Shale Member was buried to 10,200 ft, and achieved a temperature of around 250°F at maximum burial 15 Ma. As mentioned above, RO values are around 0.75 to 0.80 percent at the Waltman level. The Paleocene-Eocene boundary was buried to approximately 8,000 ft, and reached temperatures of nearly 200°F at maximum burial and temperature 15 Ma. RO values cluster around 0.60 to 0.65 at this stratigraphic horizon.

Based on the information presented in this report, the Waltman Shale Member of the Fort Union Formation has reached the proper thermal maturity to be in the oil window. It is more than likely that the oil produced from the Fort Union reservoirs, as well as oil shows in the Wind River Formation were sourced from the Waltman.

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sec. 15 -T. 37 N

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STAGEPRIMARY PRODUCT

HYDROCARBONS GENERATED

PERCENT Ro

HIrrID

rrHI Q.2HI

LJJ

IMMATURE

MATURE

POST-

MATURE

DRY GAS

OIL

WET GAS-

CON DENSATE

DRY GAS

HIGHER

HYDROCARBONS

0.60

0.75

1.0

1.35

FIGURE 2-Generalized scheme for oil and gas generation as a function of thermal maturity (expressed as RQ) of source rocks.

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FIGURE 5 Graph showing measured vitrinite reflectance data [(+) and dashed line], and themodeled maturity line (solid line). A constant heat flow of 45 mWm~2 was used to match the measured and modeled lines.

REFERENCES

Barker, C.E., and Crysdale, B.L., 1993, Burial and temperature history of gas generation from coaly organic matter in the Late Cretaceous Mesaverde Formation and associated rocks in the deeper portions of the Wind River Basin, Wyoming, in Stroock, Betty, and Andrew, Sam, eds., Jubilee Anniversary field conference: Casper, Wyoming Geological Association, p. 235-258.

Bostick, N.H., 1979, Microscopic measurements of the level of catagenesis of solid organic matter in sedimentary rocks to aid in exploration for petroleum and to determine former burial temperatures a review, in Scholle, P.A., and Schluger, P.R., eds., Aspects of diagenesis: Society of Economic Paleontologists and Mineralogists, Special Publication Number 26, p. 17-43.

Bustin, R.M., 1986, Organic maturity of Late Cretaceous and Tertiary coal measures, Canadian Arctic Archipelago: International Journal of Coal Geology, v. 6, p. 71-106.

Dow, W.G., 1977, Kerogen studies and geological interpretations: Journal of Geochemical Exploration, v. 7, p. 79-99.

Katz, B.J., and Liro, L.M., 1993, The Waltman Shale Member, Fort Union Formation, Wind River Basin: A Paleocene clastic lacustrine source system, in Keefer, W.R., Metzger, W.J., and Godwin, L.H., eds., Oil and gas and other resources of the Wind River Basin, Wyoming: Casper, Wyoming Geological Association Special Symposium, p. 163-174.

Keefer, W.R., 1970, Structural geology of the Wind River Basin, Wyoming: U.S. Geological Survey Professional Paper 495-D, 35 p.

Love, J.D., 1988, Geology of the Wind River Basin, Central Wyoming, in Sloss, L.L. ed.,Sedimentary Cover-North American Craton: U.S.: The Geological Society of America, Decade of North American Geology, p. 196-200.

Nichols, D.J., and Flores, R.M., 1993, Palynostratigraphic correlation of the Fort UnionFormation (Paleocene) in the Wind River Reservation and Waltman area, Wind River Basin, Wyoming, in Keefer, W.R., Metzger, W.J., and Godwin, L.H., eds., Oil and gas and other resources of the Wind River Basin, Wyoming: Casper, Wyoming Geological Association Special Symposium, p. 175-189.

Palacas, J.G., Flores, R.M., Keighin, C.W., and Anders, D.E., 1993, Organic geochemical typing of oils in the Wind River Basin, Wyoming: [abst] American Association of Petroleum Geologists 1993 Annual Convention Program, p. 162.

Van Houten, F.B., 1964, Tertiary geology of the Beaver Rim area, Fremont and Natrona Counties, Wyoming: U.S. Geological Survey Bulletin 1164, 99 p.

Waples, D.W., 1985, Geochemistry in petroleum exploration: Boston, International Human Resources Development Corporation, 232 p.

APPENDIX 1

Vitrinite reflectance data

Each data sheet represents the mean random vitrinite reflectance data for the individual coal

samples. The File Name is the project name. The Channel Name is the name of the analyst, and

Comment 1 is information regarding the quality of the sample. For each coal sample several

vitrinite grains were measured. These are listed on the data sheet in the Pi. column, and

correspond to the values in the Meas 1 column. The minimum reading (Min), maximum reading

(Max), mean value of all readings (Mean), and standard deviation (StDev) are given. The Mean is

the R0 value for the sample, and is the value plotted in fig.5 and discussed in the text. The

histogram for measurements of the sample are also given.

File Name: RFVN Channel Name: Nuccio Description: 3240-3300

Comment 1: Good sample,Comment 2:Comment 3:Comment 4:Comment 5:Comment 6:

Min:Max:Mean:StDev:

Pt. X-Pos Y-Pos

1 23456789

101112131415161718192021222324252627282930

Clean and consistent

Measl Meas2 Ratio Cone

0.540.680.610.04

Z-Pos Measl Meas2 Ratio Cone.

0.64 0.670.620.630.590.640.660.590.640.570.580.610.600.580.580.590.610.640.600.600.590.570.550.590.540.560.680.660.670.54

10

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Comment 1: Good sample, Clean and consistentComment 2:Comment 3:Comment 4:Comment 5:Comment 6:


Min: Max: Mean: StDev:

Pt. X-Pos

123456789

1011121314151617181920212223242526272829303132

0.58 0.76 0.67 0.05

Y-Pos Z-Pos Measl Meas2 Ratio Cone.

0.670.640.610.640.590.580.670.680.650.620.620.670.730.590.690.680.650.690.620.690.710.760.670.710.700.710.610.750.720.740.710.73

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123456789

101112131415161718192021222324252627282930

sample, Clean and consistent


0.61 0.760.670.04


0.640.650.640.670.630.660.640.660.680.640.630.650.650.670.760.750.700.730.690.680,670.660.610.710.680.620.630.630.670.65

14

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0.590.720.640.03


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0.530.740.660.06


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Pt. X-Pos

1 23456789

101112131415161718192021222324252627282930

0.57 0.76 0.68 0.05


0.60 0,670.670.590.590.570.620.670.660.660.650.720.710.760.730.690.660.680.700.750.680.720.640.680.740.670.680.650.710.72

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Pt. X-Pos Y-Pos

1 23456789

101112131415161718192021222324252627282930

0.54 0.67 0.62 0.03


0.58 0.570.570.630.640.630.650.660.650.640.540.600.570.590.630.640.630.670.640.650.640.620.600.600.610.610.620.630.610.60

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Comment Comment 2: Comment 3 Comment 4: Comment 5 Comment 6

5700-5710Good sample, clean grains large



Pt. X-Pos Y-Pos

123456789

101112131415161718192021222324252627282930

0.56 0.71 0.63 0.04


0.560.580.700.700.640.650.710.640.640.620.670.650.590.580.580.640.640.590.650.630.640.630.640.620.640.560.600.680.570.56

24

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Pt. X-Pos Y-Pos

1 23456789

101112131415161718192021222324252627282930



0.650.750.710.02


0.69 0.750.720.720.700.730.750.730.720.730.700.730.750.700.680.710.720.730.710.740.650.700.710.700.700.690.700.710.730.70

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Min:Max:Mean:StDev:

Pt. X-Pos Y-Pos

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101112131415161718192021222324252627282930



0.560.780.670.07


0.740.740.700.730.720.740.730.720.690.700.580.560.600.640.650.630.650.640.650.630.570.580.570.730.770.780.760.580.610.63

28

Frequency

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File Name: RFVNChannel Name: NuccioDescription: 7740-7750


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Pt. X-Pos Y-Pos

1 23456789

101112131415161718192021222324252627282930



0.720.770.750.01


0.76 0.770.750.750.740.720.760.760.770.770.770.760.740.730.750.740.720.750.750.750.740.740.760.750.750.720.750.750.750.72

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Pt. X-Pos

1 23456789

101112131415161718192021222324252627282930

0.79 0.97 0.90 0.05


0.93 0.960.960.930.820.840.820.910.910.940.790.920.950.970.950.950.950.920.960.830.870.870.880.890.850.930.930.890.860.83

32

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Pt. X-Pos Y-Pos

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101112131415161718192021222324252627282930



0.81 0.970.900.04


0.89 0.900.960.950.860.860.870.960.890.960.880.970.910.920.890.860.930.930.920.910.940.950.880.880.810.850.870.890.850.90

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Pt. X-Pos

1 23456789

101112131415161718192021222324252627282930



0.730.870.800.04


0.76 0.740.800.860.870.840.750.850.780.740.770.830.810.760.730.850.840.850.740.760.770.740.850.830.750.810.780.780.810.81

36

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Min:Max:Mean:StDev:

Pt. X-Pos Y-Pos

1 23456789

101112131415161718192021222324252627282930



0.821.000.890.04


0.88 0.890.920.890.900.910.910.870.850.930.890.910.870.890.890.840.860.880.830.891.000.880.940.850.870.820.860.930.940.92

38

FrequenceO Oi

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Comment 1 : GoodComment 2:Comment 3:Comment 4:Comment 5:Comment 6:

Min:Max:Mean:StDev:

Pt. X-Pos

1 23456789

101112131415161718192021222324252627282930



0.800.990.890.06


0.30 0.800.950.970.970.960.970.940.990.870.960.960.830.850.850.880.890.890.870.870.900.810.860.890.920.910.890.890.840.84

40

Frequency

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Pt. X-Pos

123456789

101112131415161718192021222324252627282930



0.81 0.940.900.03


0.880.930.900.910.880.920.890.930.910.820.920.870.820.810.920.930.920.890.870.890.890.920.920.930.940.940.930.920.910.92

42

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Documents

New U.S. Geological Survey Publications Warehouse - U.S. … · 2010. 12. 15. · U.S. GEOLOGICAL SURVEY Vitrinite reflectance data for the Paleocene Fort Union and Eocene Wind River