Utah’s Oil Shale Deposits: Stratigraphy and Resource EvaluationMichael D. Vanden Berg (801-538-5419, michaelvandenberg@utah.gov) and David E. Tabet (801-537-3373; davidtabet@utah.gov)

Utah Geological Survey, Salt Lake City, Utahgeology.utah.gov

With the recent increase in crude oil prices and concerns over diminishing conventional re-serves, the Utah Geological Survey has been re-examining the state’s oil shale resource. Past assessments concentrated on the Eocene Green River Formation’s Mahogany zone in the southeastern part of the Uinta Basin. This lithologic horizon holds the richest oil shale depos-its in Utah, but other significant stratigraphic zones, as well as other areas within the basin, warrant further study. We have broadened our investigation to include the entire Green River Formation’s Parachute Creek Member, which is found throughout much of the Uinta Basin. Over 100 density and sonic logs from oil and gas wells in the basin have been digitized and tops to key oil shale horizons have been picked. Structure contour and isopach maps were cre-ated for each zone, including the R-8, R-7 (Mahogany zone), R-6, R-5, and R-4 rich zones and the A-groove, B-groove, L-5, and L-4 lean zones. Cores from selected rich and lean oil shale horizons will be on display with the poster. In addition, we have correlated available Fischer assay analyses to geophysical logs as a way to produce high-resolution shale oil yield logs. This technique provided data to map oil shale thickness and richness throughout the basin and create structure contour and isopach maps with shale oil yields of 25, 35, and 50 gallons per ton of rock.

ABSTRACTABSTRACT

METHODS FOR EVALUATING OIL SHALE RESOURCESMETHODS FOR EVALUATING OIL SHALE RESOURCES

Step 1:Step 1: Digitized density and sonic logs from oil shale wells

Step 2:Step 2: Compared digitized density and sonic logs to Fischer assay analyses (measures shale oil yield in gallons per ton (GPT))

Step 3:Step 3: Derived equations using a reduced major axes fit relating GPT to the sonic or density logs (see graphs below)

Step 4:Step 4: Digitized density and sonic logs from oil and gas wells throughout the Uinta Basin

Step 5:Step 5: Calculated shale oil yield logs for oil and gas wells using derived equations

Step 6:Step 6: Determined maximum thickness of oil shale averaging 25, 35, and 50 GPT

1.4 1.6 1.8 2.0 2.2 2.4 2.6

Density (g/cm3)

Shal

e O

il Yi

eld

(gal

lon

s p

er to

n)

0

10

20

30

40

50

60

70

80

90

y = -80.894x + 203.996

Reduced major axes fit relating density to shale oil yield

- Data from 8 oil shale wells (R2 ranging from 0.71 to 0.87)

50 70 90 110 130 150

Sonic (ft/sec)

Shal

e O

il Yi

eld

(gal

lon

s p

er to

n)

0

10

20

30

40

50

60

70

80

90

y = 0.7656x - 49.237

Reduced major axes fit relating sonic to shale oil yield

- Data from 4 oil shale wells (R2 ranging from 0.64 to 0.77)

72

Duchesne

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CARBON

EMERY

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UINTAH

5E

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25E24E

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7W 6W

5W 4W 3W 2W 1W

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8S

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100 to 120 ft

120 to 130 ft

80 to 100 ft

60 to 80 ft

40 to 60 ft

20 to 40 ft

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10E 11E 12E

13E

Ua Ub

*White River Oil Shale Mine

1000 ft

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Structure contour - top of 25 gpt zone

25 GPT ISOPACH25 GPT ISOPACH

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15 to 20 ft

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Ua Ub

*White River Oil Shale Mine

1000 ft

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Duchesne

50 GPT ISOPACH50 GPT ISOPACH

Structure contour - top of 50 gpt zone

UGS Open-File Report 469 (2006)Collaboration between the Utah Geological Survey,U.S. Geological Survey, and the U.S. Bureau ofLand Management

Contents:1) Fischer assays for 581 wells - Excel and Text files - Limited pdf files of original reports2) Lithologic logs for 168 wells - Pdf or Tiff files3) Geophysical logs for 173 wells - Tiff files - An inventory of paper logs for an additional 290 wells available in the UGS library4) Formation tops data for over 1000 wells - Excel or Text files

5) Extensive Utah oil shale bibliography - 981 references6) Preliminary Utah oil shale resource map - New Mahogany bed outcrop coverage - Location of wells in database

UTAH OIL SHALE DATABASEUTAH OIL SHALE DATABASE

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30 to 40 ft

40 to 55 ft

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Ua Ub

*White River Oil Shale Mine

1000 ft

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35 GPT ISOPACH35 GPT ISOPACH

Structure contour - top of 35 gpt zone

Mahogany bed outcrop

Mahogany bed outcropMahogany bed outcrop

Mahogany bed outcrop digitized from 30’ x 60’ geologic mapMahogany bed outcrop digitized from 7.5 minute geologic map

Mahogany bed outcrop digitized from other map

County

Township and Range (Salt Lake Base Line and Meridian, Uintah Base Line and Meridian)

Well with core located at the Utah Core Research CenterWell with density log used to calculate resourceWell with sonic log used to calculate resourceWell with Fischer assays used to calculate resource

County Seat

20 0 20 40 Kilometers

10 0 10 20 Miles

Duchesne

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U.S. Forest ServiceState Park or Wildlife Area

Tribal Land

U.S. Bureau of Land ManagementState Land

National Wildlife RefugeWater

Private Land

Wilderness Study Area

Ua

Ub

P-4P-4

Outcrop of the Green River Formation along the White River, Uintah County, Utah.

The White River oil shale mine located south of Bonanza, Uintah County, Utah. This is the location of the BLM R&D oil shale lease which was awarded to Oil Shale Exploration Company (OSEC).

Utah oil shale sample from the White River mine.

Oil shale stockpile at the White River underground mine. Shale was mined from the Mahogany Zone roughly 1000 feet below the surface.

Bird’s nest features near the top of the Green River Formation (top of R-8) along Evacuation Creek, Uintah County, Utah. These cavities were created by the dissolution of nahcolite.

Outcrop of the upper Green River Formation, Parachute Creek Member, Evacuation Creek at Hell’s Hole, eastern Uintah County, Utah.

Mahogany ZoneMahogany Zone

AAPG-RMS - Snowbird, Utah - October, 2007

South UintaSouth UintaBasin 12Basin 12

Map showing landownership in the Uinta Basin and the location of wells used in this study

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