Two emerging tight oil plays in Utah have gained significant traction in the past few years, renewing interest in two historically productive basins. The Utah Geological Survey is conducting a multi-year, U.S. Department of Energy-funded study of these two distinct tight oil plays, utilizing newly acquired core and associated data. The lacustrine Uteland Butte Member of the Green River Formation records the first major transgression of Eocene Lake Uinta after the deposition of the alluvial Colton Formation in the Uinta Basin. The main horizontal drilling objective, as analyzed in several cores, is a 2- to 7-foot-thick interval of fractured dolomite, with porosities between 14 and 30%, interbedded with organic-rich limestone and shale. TOC values in the adjacent rocks range between 2 and 5%, while Ro values range between 0.7 and 1.1%, indicating the reservoir is most likely self-sourcing. The Cane Creek shale is a transgressive-regressive marine sequence in the lower portion of the Pennsylvanian Paradox Formation, Paradox Basin. The Cane Creek is tens of feet to nearly 200 feet thick, over- and underlain by beds of salt, and divided into A, B, and C intervals (in descending order). The B interval is the primary hydrocarbon source rock and productive zone, consisting of black organic-rich shale, dolomite, dolo-mitic siltstone, very fine sandstone, and some anhydrite. Significant porosity (up to 15%) is found in the dolomitic siltstone and sandstone, but permeability is generally low (roughly 0.1 mD); naturally occurring frac-tures are necessary for economic production. The A and C intervals, mostly dolomite and anhydrite, are the seals for the B interval, helping prevent fracture communication with the adjacent salt beds. A refined geological and reservoir characterization study of these two tight oil plays, using newly acquired core and geophysical logs, is currently underway to help delineate play boundaries, guide resource esti-mates, and inform recovery methods.

ABSTRACT Project funded by: U.S. Department of Energy - National Energy Technology

Laboratory and Utah Geological Survey

Michael D. Vanden Berg, Craig D. Morgan, and Thomas C. Chidsey, Jr. Utah Geological Survey, Salt Lake City, Utah

Analyzing Core from Two Emerging Tight Oil Plays in Utah: The Uteland Butte Member of the Green River Formation in the Uinta Basin and the Cane Creek Shale within the Paradox Formation in the Paradox Basin

BACKGROUND

The Uinta Basin is a topographic and structural trough encompassing an area of more than 9300 square miles (14,900 km2) in northeast Utah. The basin is sharply asymmetric, with a steep north flank bounded by the east-west trending Uinta Mountains and a gently dipping south flank. The Uinta Basin formed in the Late Cretaceous Maastrichtian time, creating a large area of internal drainage that was filled by ancestral Lake Uinta during the Paleocene and Eocene. Deposition in and around Lake Uinta consisted of open- to marginal-lacustrine sediments that make up the Green River Formation (GRF). Alluvial red-bed deposits that are laterally equivalent to, and intertongue with, the GRF make up the Colton (Wasatch) Formation. The southern shore of Lake Uinta was often very broad and flat, which allowed large transgressive and regressive shifts in the shoreline in response to climatic and tectonic-induced rise and fall of the lake. The cyclic nature of the GRF deposition in the southwest Uinta Basin resulted in numerous stacked deltaic deposits. Distributary-mouth bars, distributary channels, and nearshore bars are the primary producing sandstone reservoirs in the area. Recently, companies have targeted the thinner carbonate layers, such as the Uteland Butte Member, as horizontal drilling targets.

Project website: http://geology.utah.gov/resources/energy/oil-gas/shale-oil

UTELAND BUTTE PLAY MAP

DUCHESNEFM.

UINTAFM.

‘transitionbeds’

‘saline facies’&

upper mbr.

middle &lower mbrs.

COLTONFM.

GREEN RIVERFM.

FLAGSTAFFLS

NORTH HORNFM

CRETACEOUSFORMATIONSFrom Keighley

and others (2002). Based

on map of Witkind (1995)

STRATIGRAPHIC NOMENCLATURE -

THIS STUDY modified from

Keighley and others (2002).

Radiogenic dates from 1Remy (1992),

2Smith and others (2008)

‘SALINE FACIES’OF THE

GREEN RIVER FORMATION

54 ma1

CARBONATEMARKER UNIT

COLTON TONGUE

LOW

ER

GR

EE

NR

IVE

R F

MU

PP

ER

GR

EE

NR

IVE

R F

M

UTELAND BUTTELIMESTONE

COLTONFORMATION

SUNNYSIDE DELTA INTERVAL

TRANSITIONAL INTERVALC MARKER

D MARKER

?PALEOCENE-EOCENE

BOUNDARY (55.8 Ma)?

Cashion (1967)modified from

Morgan and others (2003)

Tgde

Twz

LOW

ER

GR

EE

NR

IVE

R F

MM

IDD

LE G

RE

EN

RIV

ER

FM

UP

PE

R G

RE

EN

RIV

ER

FM

Tgdf

MAHOGANY OIL SHALE

DOUGLAS CREEK MEMBER

(tongue A Tgda)

RENEGADE TONGUE

WASATCH (Twx)

HORSEBENCH SANDSTONE

49.3 ma2

48.7 ma2

47.3 ma2

CURLY TUFF

WAVY TUFF

BLIND CANYON TUFF

NINE MILE CANYON/GATE CANYON

OUTCROP

PARACHUTE CREEK MEMBER

EVACUATION CREEK MEMBER

EAST

Morgan and others (2003)

CASTLE PEAK RESERVOIR

LOW

ER

GR

EE

NR

IVE

R F

MM

IDD

LE G

RE

EN

RIV

ER

FM

UTELAND BUTTERESERVOIR

UPPERDOUGLAS CREEK

RESERVOIR

LOWER DOUGLAS CREEK

RESERVOIR

SUBSURFACECORRELATION

D MARKER

MAHOGANY OIL SHALE

C MARKER

S1 MARKER

GARDEN GULCH

RESERVOIR

S2 MARKER

UG

RF

MID

DLE

GR

EE

N R

IVE

R F

M

GENERALIZEDSTRATIGRAPHYS. UINTA BASIN

OIL SHALE ZONESVanden Berg (2008)

PA

RA

CH

UT

E C

RE

EK

MB

R.

L4

R3

R5 L5

R6 B-GROOVE MAHOGANY A-GROOVE

R8

‘SALINE ZONE’

R4 L3

R2 L2

?

?

BASIN CENTER

DO

UG

LAS

CR

K. M

BR

.

MAHOGANY OIL SHALE

EOC

ENE

PALE

OC

ENE

?

Uinta Basin Stratigraphy

The stratigraphic nomenclature used to describe the Green River Formation in the Uinta Basin is as diverse as the rocks themselves. The nomenclature is based on facies, which are often bounded by subtle and interfingering relationships that are difficult to carry with confidence and great distance within the basin. Above are just a few of the different naming conventions from different researchers.

Vernal

Price

GrandJunction

Rifle

RockSprings

Big Piney

Evanston GRE

EN R

IVER

BA

SIN

WASHAKIEBASIN

UINTABASIN PICEANCE

BASIN

Utah

Colorado

Wyoming

10 0 10 20 30

Miles

Dou

glas

Cre

ekAr

ch

Uinta Mountain Uplift

Lake Uinta

Lake Gosiute

Rock

Spr

ings

Upl

ift

San Rafael Uplift Uncompahgre Uplift

Conceptual map of ancient Lake Uinta, which coverd the present day Uinta and Piceance Basins, and ancient Lake Gosiute, which covered the Green River and Washakie Basins.

Uinta Basin Geology and Green River Formation

The Uteland Butte reservoir is the first major transgression of ancient Lake Uinta after deposition of the fluvial Colton (Wasatch) Formation. The Uteland Butte ranges in thickness from less than 60 feet to more than 200 feet in the southwest Uinta Basin. The Uteland Butte is equivalent to the first lacustrine phase of Bradley (1931), black shale facies of Picard (1955), lower black shale facies of Abbott (1957), basal limestone facies of Little (1988) and Colburn and others (1985), the Uteland Butte limestone of Osmond (1992), and the basal limestone member of Crouch and others (2000). The Uteland Butte consists of limestone, dolostone, calcareous mudstone and siltstone, and rare sand-stone. Most of the limestone beds are ostracodal grain-supported or mud-supported grainstone, packstone, or wackestone. Grainstone is more common near the shallow shoreline of the lake, whereas deeper distal depos-its are commonly argillaceous limestone. A cryptocrystalline, dolomitized, compacted wackestone with ostra-cods has been found near the top of the Uteland Butte in some core. The dolomite often has more than 20 per-cent porosity, but is so finely crystalline that the permeability is low (single millidarcy or less). The Uteland Butte reservoir was deposited during a rapid and extensive lake-level rise. The Uteland Butte is distinctive in the abundance of carbonate and the lack of sandstone, which could have been caused by one or both of the following situations: (1) the rapid lake-level rise caused siliciclastic sediments to be depos-ited in the proximal alluvial channels, or (2) the main inflow into the lake was far from the southwest Uinta Basin area, perhaps flowing into the southern arm of the lake south and west of the San Rafael uplift. The Uteland Butte reservoir is oil productive throughout most of the southwest Uinta Basin. The Uteland Butte was a secondary objective in most vertical wells and was usually perforated along with beds in the Castle Peak, lower Douglas Creek, and upper Douglas Creek reservoirs. The cryptocrystalline dolomitic wackestone has only recently been extensively explored. This bed, widely distributed throughout the central and southern Uinta Basin, has become a recent target for extensive horizontal drilling, with limited success in the southern part of the basin, but more success in the over-pressured central basin area.

Uteland Butte Member

Simplified north-south schematic cross section of the Uinta Basin in Duchesne County showing the northward dip of the beds and the relative depths of the major oil fields. The Uteland Butte is the basal member of the Green River Forma-tion and pinches out to the north, towards the deeper basin facies. Modified from Newfield, 2011.

0

2000

4000

6000

8000

10000

12000

14000

16000

Dep

th in

Fee

t

NORTH SOUTH

Duchesne River

Uinta

Green River

Colton / Wasatch

Mahogany Bed

Carbonate Marker Bed

Uteland Butte{Carbonate Marker Unit

Black Shale facies

Castle Peak

Altamont / Bluebell Central Basin Monument Butte

Green River sand lenses

Colton tongue

Near NineMile Canyon

Abbott, W.O., 1957, Tertiary of the Uinta Basin, in Seal, O.G., editor, Guidebook to the geology of the Uinta Basin: Intermountain Association of Petroleum Geologists Eighth Annual Field Conference, p. 102-109.Anderson, J.G., and Roesink, J.G., 2013, Reservoir characterization of the Uteland Butte Formation in the Uinta Basin: AAPG Search and Discovery Article #50888.Bradley, W.H., 1931, Origin and microfossils of the oil shale of the Green River Formation of Colorado and Utah: U. S. Geological Survey Professional Paper 168, 56 p.Cashion, W.B., 1967, Geology and fuel resources of the Green River Formation, southeastern Uinta Basin, Utah and Colorado: U. S. Geological Survey Professional Paper 548, 48 p.Colburn, J.A., Bereskin, S.R., McGinley, D.C., and Schiller, D.M., 1985, Lower Green River Formation in the Pleasant Valley producing area, Duchesne and Uintah Counties, Utah, in Picard, M.D., editor, Geology and energy resources, Uinta Basin, Utah: Utah Geological Association Publication 12, p. 177-186.Crouch, B.W., Hackney, M.L., and Johnson, B.J., 2000, Sequence stratigraphy and reservoir character of lacustrine carbonates in the basal limestone member - lower Green River Formation (Eocene), Duchesne and Antelope Creek fields, Duchesne Co., Utah [abs.]: American Association of Petroleum Geologists Annual Convention Program with Abstracts, p. A34.DOGM (Utah Division of Oil, Gas, and Mining), 2015, Data Research Center – Well Data: Online, oilgas.ogm.utah.gov/Data_Center/DataCenter.cfm, accessed March 2015.Hintze, L.F., Willis, G.C., Laes, D.Y.M., Sprinkel, D.A., and Brown, K.D., 2000, Digital geologic map of Utah: Utah Geological Survey M-179.Keighley, D., Flint, S., Howell, J., Anderson, D., Collins, S., Moscariello, A., and Stone, G., 2002, Surface and subsurface correlation of the Green River Formation in central Nine Mile Canyon, SW Uinta Basin, Carbon and Duchesne Counties, east-central Utah: Utah Geological Survey Miscellaneous Publication 02-1.Little, T.M., 1988, Depositional environments, petrology, and diagenesis of the basal limestone facies, Green River Formation (Eocene), Uinta Basin, Utah: Salt Lake City, University of Utah, M.S. thesis, 154 p.Morgan, C.D., Chidsey, T.C., Jr, McClure, K.P., Bereskin, S.R., and Deo, M.D., 2003, Reservoir characterization of the Lower Green River Formation, Uinta Basin, Utah: Utah Geological Survey 411, 1–140 p.Newfield, 2011, Uinta Basin / Greater Monument Butte area update: Online, www.newfld.com/assets/pdf/uintaupdate.pdf, accessed March 2013.Osmond, J.C., 1992, Greater Natural Buttes gas field, Uintah County, Utah, in Fouch, T.D., Nuccio, V.F., and Chidsey, T.C., Jr., editors, Hydrocarbon and mineral resources of the Uinta Basin, Utah and Colorado: Utah Geological Association Publication 20, p. 143-163.Picard, M.D., 1955, Subsurface stratigraphy and lithology of the Green River Formation in Uinta Basin, Utah: American Association of Petroleum Geologists Bulletin, v. 39, no. 1, p. 75-102.Remy, R.R., 1992, Stratigraphy of the Eocene part of the Green River Formation in the south-central part of the Uinta Basin, Utah: U.S. Geological Survey Bulletin 1787-BB, 79 p.Smith, M.E., Carroll, A.R., and Singer, B.S., 2008, Synoptic reconstruction of a major ancient lake system: Eocene Green River Formation, western United States: Geological Society of America Bulletin, v. 120, no. 1-2, p. 54–84.Vanden Berg, M., 2008, Basin-wide evaluation of the uppermost Green River Formation's oil-shale resource, Uinta Basin, Utah and Colorado: Utah Geological Survey Special Study 128.Witkind, I.J., 1995, Geologic map of the Price 1° x 2° quadrangle, Utah: U.S. Geological Survey Miscellaneous Investigations Series, Map I-2462.

REFERENCES

Well name: 14-1-46 (4301334113)

Operator: Bill Barrett Corp.Location: T4S, R6W, Sec. 1, Duchesne County, UTM E 541444, UTM N 4445336

6640

6645

6650

6655

6660

6665

6670

6675

6680

6685

6690

6695

Dept

h (ft

)

30% 0%Neutron-Density

DPHINPHIGR

CALI

1 1000Resistivity (ohm-m)

LLD

LLS

Permeability (md)0.00001 10

Porosity (%)0 35

0 4

2.2

1.8

1.8

1.6

3.3

1.1

0.9

1.9

2.9

TOC (wt % HC)

6.0

3.2

5.1

4.0

8.8

2.8

1.2

5.9

7.0

0 10S2 (mg HC/g)

276

176

283

246

264

261

135

303

239

0 400HI (S2*100/TOC)

442

447

435

434

446

432

448

435

448

415 515Tmax (⁰C)

0.80

0.89

0.67

0.65

0.87

0.62

0.90

0.67

0.90

0.2 2.6Ro (%)

0.60

0.31

0.68

0.29

0.18

0.57

0.30

0.64

0.19

0 1PI (S1/(S1+S2)

Gas Generation

Imm

ature

Oil Generation Gas GenerationImmature

Oil Gen.

S2 - Oil Potential - >5 mg HC/g = good/excellent

Cored interval: 6647-6669.7, 6672-6707 ft (core shifted up ~7.5 ft to match logs)Core location: Utah Core Research Center

Remarksclay vf

siltstone

wackestone

packstone f

grainstone m c

Core logCore

photosQuartzK FeldsparPlagioclase

CalciteDolomite & Fe-DolomitePyrite

Total Clay

XRD

6647.10 (6639.60)

6650.80 (6643.30)

6655.05 (6647.55)

6658.95 (6651.45)

6663.35 (6655.85)

6667.05 (6659.55)

6672.40 (6664.90)

6675.70 (6668.20)

6679.00 (6671.50)

6681.70 (6674.20)

6684.00 (6676.50)

6686.20 (6678.70)

6688.20 (6680.70)

6690.00 (6682.50)

6692.25 (6684.75)

6694.00 (6686.50)

6696.00 (6688.50)

6698.00 (6690.50)

6699.45 (6691.95)

6699.75 (6692.25)

6702.95 (6695.45)

6706.95 (6699.45)

Gamma Ray (API)0 150

*core depth (log-corrected depth)*

6647.0-6659.3 (6639.5-6651.8) - Interbedded argillaceous dolostone (dark tan to brown)and calcareous shale (medium to dark grey). Mostly planar to wavy laminated with minorsoft-sediment deformation, several near-vertical open and calcite-filled bed-bound (dolostone)fractures. Brecciated dolostone bed with ostracods near base (6657.75-6658.8 [6650.25-6651.30]).

*core depth (log-corrected depth)*

6659.3-6662.0 (6651.8-6654.5) Interbedded calcareous shale (medium to dark grey) andargillaceous dolostone (dark tan to brown). Mostly planar to wavy laminated.

6662.0-6662.8 (6654.5-6655.3) - Argillaceous limestone, medium grey, with gastropods andpelecypods.

6662.8-6666.0 (6655.3-6658.5) - Interbeded argillaceous dolostone and calcareous shale.Mostly planar to wavy laminated with minor soft-sediment deformation, several near-verticalopen and calcite-filled bed-bound (dolostone) fractures.

6666.0-6668.5 (6658.5-6661.0) - Argillaceous limestone, medium grey, with gastropods and pelecypods.

6668.5-6669.7 (6661.0-6662.2) - Top of “C shale”, calcareous shale, medium grey, thin planarto wavy laminations.

6672.0-6678.3 (6664.5-6670.8) - Interbeded argillaceous dolostone and calcareous shale.Mostly planar to wavy laminated with minor soft-sediment deformation, several near-verticalopen and calcite-filled bed-bound (dolostone) fractures. Ostracods present at 6674.2 (6666.7).

6678.3-6678.6 (6670.8-6671.1) - Argillaceous limestone, medium grey, with gastropods and pelecypods.6678.6-6680.2 (6671.1-6672.7) - Dark grey calcareous shale, thin planar to wavy laminations,thin argillaceous dolostone bed near top.6680.2-6681.2 (6672.7-6673.7) - Tan dolostone with chert nodules and minor ostracods. Chert nodules are coated with calcite and pyrite.6681.2-6683.2 (6673.7-6675.7) - Argillaceous limestone, medium grey, with gastropods and pelecypods.

6683.9-6688.9 (6676.4-6681.4) - “PZ-1”, argillaceous dolostone, medium brown. Abundantostracods near top, brecciation near base, chert nodules and styolites throughout. Smallvertical fractures present, some filled with calcite.

6688.9-6691.9 (6681.4-6684.4) - Argillaceous limestone, medium grey, with gastropods and pelecypods.

6691.9-6695.2 (6684.4-6687.7) - “PZ-1`”, interbeded argillaceous dolostone and calcareousshale. Mostly planar to wavy laminated with minor soft-sediment deformation, severalnear-vertical open and calcite-filled bed-bound (dolostone) fractures.

6695.8-6700.7 (6688.3-6693.2) - Argillaceous limestone, medium grey, with gastropods and pelecypods.

6700.7-6703.8 (6693.2-6696.3) - “PZ-2”, argillaceous dolostone, medium brown, with minorinterbedded shale. Multiple, large verticle fractures with smaller calcite-filled vertical fractures.Chert nodules present.

6703.8-6705.3 (6696.3-6697.8) - Argillaceous limestone, medium grey, with pelecypods andminor gastropods.

6705.3-6707.5 (6697.8-6700.0) - Top of “D shale”, calcareous shale, medium grey, thin planarto wavy laminations. Minor ostracods.

Flat/planar lamination

Wavy lamination

Soft-sedimentdeformation

Stylolite

Brecciation

Chert

Fracture

Ostracods

Pelecypods

Gastropods

Argillaceouslimestone

Calcareousshale

Argillaceousdolostone

C-shale

Ro (VR) = 0.97%6656.8 (6649.3)

6683.2-6683.9 (6675.7-6676.4) - Dark grey calcareous shale, thin planar to wavy laminations.

6700

6705

6710

6715

D-shale

Dolomite 3 (PZ-2)

Dolomite 2 (PZ-1`)

Dolomite 1 (PZ-1)

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UINTAH CO.

DUCHESNE CO.

CARBON CO. Ü

0 5 10Miles

Monument Butte

Altamont/Bluebell

Natural Buttes

Newfield - Monument ButteUteland Butte Play

Newfield - Central BasinUteland Butte Play

Cescent Point -Uteland Butte Play

Petroglyph -Uteland Butte Play

LINN -Uteland Butte Play

Bill Barrett -Uteland Butte Play

QEP -Uteland Butte Play

Anadarko -Uteland Butte Play

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Township and Range

Uinta Basin

Active horz. well in Uteland Butte4

surface = colored circle, bottom hole = gray open circle

!

Top of GRF outcrop1

Base of GRF outcrop1

Oil field

Gas field

APD horizontal well in GRF4!

EXPLANATION

1From Hintze and others, 20002From USGS, per. comunication3From Anderson and Roesink, 20134Utah Division of Oil, Gas, and Mining, Dec. 2015

Uteland Butte cores

Active/proposed horz. wells

Appox. area of overpressure2

(from DSTs)

Approx. area of overpressure3

(pg >0.50 psi/ft)(mudweights only)

Newfield XL (~5000 ft)Newfield SXL (~11000 ft)

!

!

UCRC

LINN

Bill Barrett

Newfield

QEP

Anadarko

EOG

Petroglyph

"

"

"

"

"

" "

"

" Crescent Point

UINTAH CO.

DUCHESNE CO.

CARBON CO. Ü

0 5 10Miles

Monument Butte

Altamont/Bluebell

Natural Buttes

Newfield - Monument ButteUteland Butte Play

Newfield - Central BasinUteland Butte Play

Cescent Point -Uteland Butte Play

Petroglyph -Uteland Butte Play

LINN -Uteland Butte Play

Bill Barrett -Uteland Butte Play

QEP -Uteland Butte Play

Anadarko -Uteland Butte Play

Township and Range

Uinta Basin

Top of GRF outcrop1

Base of GRF outcrop1

Oil field

Gas field

EXPLANATION

1From Hintze and others, 20002From USGS, per. comunication3From Anderson and Roesink, 20134Utah Division of Oil, Gas, and Mining, Dec. 2014

Appox. area of overpressure2

(from DSTs)

Approx. area of overpressure3

(pg >0.50 psi/ft)(mudweights only)

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First 3 monthsproduction (BOE)4

! 300 - 10,000

! 10,000 - 20,000

! 20,000 - 40,000

! 40,000 - 60,000

! 60,000 - 80,000

! 80,000 - 110,000

! ~11,000 ft lateral(all others ~5000 ft)

UTELAND BUTTE PRODUCTION MAP

14-1-46

Quartz + Clay

Calcite Dolomite

6647.10

6650.80

6655.05

6658.95

6663.35

6667.05 6672.40

6675.70

6679.00

6681.70

6684.006686.20

6688.20

6690.00 6692.25

6694.00

6696.00

6698.00

6699.45

6699.75

6702.95

6706.95

BBC 14-1-46

argillaceouslimestone

calcareousshale

argillaceousdolostone

shale

>10% porosity

UTELAND BUTTE MEMBER, GREEN RIVER FORMATION

MINERALOGY ANDGEOCHEMISTRY

0

200

400

600

800

1000

400 410 420 430 440 450 460 470 480 490 500

Hyd

roge

n In

dex

(mg

HC

/ g

TOC

)

Tmax (0C)

~ 0.6 % Ro ~ 1.4 % RoImmature Oil Generation Gas Generation

TYPE I KEROGEN

TYPE II KEROGEN

TYPE III KEROGEN

6650.1

6656.8 ft

6665.5

6668.76681.7

6685.3

6689.2

6703.3

6706.4

Bill Barrett 14-1-46 - 6684.4 ft - PZ-1 Dolomite

Lithology Sample ID Depth (ft) Orientation

As Received Bulk Density

(g/cm3)

Confining Pressure (psi)

Peak Effective Compressive Strength

(psi)

Effective Residual Compressive Strength

(psi)

Young’s Modulus (106 psi)

Poisson’s Ratio

tan dolomite

BTR1-1 6684.40 Vertical 2.282 1337 19420 9580 BTR1-6 6684.40 Vertical 2.348 1337 22190 10410 5.390 0.22 BTR1-2 6684.780 Horizontal 2.140 2741 19740 13240 3.829 0.27

Zone 1 Deformation Index: Ratio of Secant E at Peak to E: 1.15 Zone 2 Ductility Index: Amount of Plastic or Strain Hardening Strain: 0.009 Zone 3a: Tang and Kaiser Index (Axial): 0.245 J/tonne Zone 3b: Tang and Kaiser Index (Volumetric): 2.87 J/tonne Zone 4: Peak to Residual Strength Ratio: 1.86

Zone 1 Deformation Index: Ratio of Secant E at Peak to E: 1.23 Zone 2 Ductility Index: Amount of Plastic or Strain Hardening Strain: 0.044 Zone 3a: Tang and Kaiser Index (Axial): 0.69 J/tonne Zone 3b: Tang and Kaiser Index (Volumetric): 3.987 J/tonne Zone 4: Peak to Residual Strength Ratio: 1.59

0

5000

10000

15000

20000

25000

-0.025 -0.015 -0.005 0.005 0.015 0.025

Axi

al S

tress

Diff

eren

ce, p

si

(Radial) Strain (Axial)

404730 UGS, Bill Barrett 14-1-46BTR1-6, 6684.4 ft, Vertical, As-Received

Pc = 1337 psiPp = 0 psi

Peak Axial Stress Difference = 20,853 psiEffective Peak Compressive Strength = 22,190 psi

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

-0.031 -0.021 -0.011 -0.001 0.009 0.019 0.029

Axi

al S

tress

Diff

eren

ce, p

si

(Radial) Strain (Axial)

404730 UGS, Bill Barrett 14-1-46BTR1-2, 6684.70 ft, Horizontal, As-Received

Pc = 2741 psiPp = 0 psi

Peak Axial Stress Difference = 16,995 psiEffective Peak Compressive Strength = 19,736 psi

Bill Barrett 14-1-46 - 6698.3 ft - Argillaceous Limestone

Lithology Sample ID Depth (ft) Orientation

As Received Bulk Density

(g/cm3)

Confining Pressure (psi)

Peak Effective Compressive Strength

(psi)

Effective Residual Compressive Strength

(psi)

Young’s Modulus (106 psi)

Poisson’s Ratio

gray limestone BTR3-1 6698.25 Vertical 2.586 1340 23980 13700 4.038 0.14 BTR3-2 6699.00 Horizontal 2.614 2747 52680 19850 8.657 0.32

Zone 1 Deformation Index: Ratio of Secant E at Peak to E: 1.13 Zone 2 Ductility Index: Amount of Plastic or Strain Hardening Strain: 0.093 Zone 3a: Tang and Kaiser Index (Axial): 0.972 J/tonne Zone 3b: Tang and Kaiser Index (Volumetric): 1.82 J/tonne Zone 4: Peak to Residual Strength Ratio: 1.60

Zone 1 Deformation Index: Ratio of Secant E at Peak to E: 1.12 Zone 2 Ductility Index: Amount of Plastic or Strain Hardening Strain: 0 Zone 3a: Tang and Kaiser Index (Axial): 4.34 Zone 3b: Tang and Kaiser Index (Volumetric): 12.75 Zone 4: Peak to Residual Strength Ratio: 2.58

0

5000

10000

15000

20000

25000

-0.04 -0.02 0 0.02 0.04 0.06

Axi

al S

tress

Diff

eren

ce, p

si

(Radial) Strain (Axial)

404730 UGS, Bill Barrett 14-1-46BTR3-1, 6698.25 ft, Vertical, As-Received

Pc = 1340 psiPp = 0 psi

Peak Axial Stress Difference = 22,639 psiEffective Peak Compressive Strength = 23,979 psi

0

10000

20000

30000

40000

50000

60000

-0.05 -0.03 -0.01 0.01 0.03 0.05

Axi

al S

tress

Diff

eren

ce, p

si

(Radial) Strain (Axial)

404730 UGS, Bill Barrett 14-1-46BTR3-2, 6699.00 ft, Horiztonal, As-Received

Pc = 2747 psiPp = 0 psi

Peak Axial Stress Difference = 49,929 psiEffective Peak Compressive Strength = 52,676 psi

Bill Barrett 14-1-46 - 6706.5 ft - D-shale

Lithology Sample ID Depth (ft) Orientation

As Received Bulk Density

(g/cm3)

Confining Pressure (psi)

Peak Effective Compressive Strength

(psi)

Effective Residual Compressive Strength

(psi)

Young’s Modulus (106 psi)

Poisson’s Ratio

shale BTR5-4 6706.50 Vertical 2.487 1341 14450 9190 1.295 0.18 BTR5-2 6706.65 Horizontal 2.502 2750 17250 13270 3.797 0.26

Zone 1 Deformation Index: Ratio of Secant E at Peak to E: 1.38 Zone 2 Ductility Index: Amount of Plastic or Strain Hardening Strain: 0.48 Zone 3a: Tang and Kaiser Index (Axial): 0.205 J/tonne Zone 3b: Tang and Kaiser Index (Volumetric): 1.576 J/tonne Zone 4: Peak to Residual Strength Ratio: 1.60

Zone 1 Deformation Index: Ratio of Secant E at Peak to E: 1.22 Zone 2 Ductility Index: Amount of Plastic or Strain Hardening Strain: 0.083 Zone 3a: Tang and Kaiser Index (Axial): 0.00527 Zone 3b: Tang and Kaiser Index (Volumetric): 0.196 Zone 4: Peak to Residual Strength Ratio: 1.24

0

2000

4000

6000

8000

10000

12000

14000

16000

-0.05 -0.03 -0.01 0.01 0.03 0.05

Axi

al S

tress

Diff

eren

ce, p

si

(Radial) Strain (Axial)

404730 UGS, Bill Barrett 14-1-46BTR5-4, 6706.5 ft, Vertical, As-Received

Pc = 1341 psiPp = 0 psi

Peak Axial Stress Difference = 13,147 psiEffective Peak Compressive Strength = 14,448 psi

0

2000

4000

6000

8000

10000

12000

14000

16000

-0.04 -0.03 -0.02 -0.01 0 0.01 0.02 0.03

Axia

l Stre

ss D

iffer

ence

, psi

(Radial) Strain (Axial)

404730 UGS, Bill Barrett 14-1-46BTR5-2, 6706.65 ft, Horizontal, As-Received

Pc = 2750 psiPp = 0 psi

Peak Axial Stress Difference = 14,495 psiEffective Peak Compressive Strength = 17,245 psi

Bill Barrett 14-1-46 - 6703.1 ft - PZ-2 - Tan Dolomite

Lithology Sample ID Depth (ft) Orientation

As Received Bulk Density

(g/cm3)

Confining Pressure (psi)

Peak Effective Compressive Strength

(psi)

Effective Residual Compressive Strength

(psi)

Young’s Modulus (106 psi)

Poisson’s Ratio

tan dolomite

BTR4-4 6703.10 Vertical 2.543 1341 23340 14290 6.422 0.28

BTR4-2 6702.90 Horizontal 2.473 2748 26760 11050 6.223 0.26

Zone 1 Deformation Index: Ratio of Secant E at Peak to E: 1.62 Zone 2 Ductility Index: Amount of Plastic or Strain Hardening Strain: 0.902 Zone 3a: Tang and Kaiser Index (Axial): 0.0039 Zone 3b: Tang and Kaiser Index (Volumetric): 0.0132 Zone 4: Peak to Residual Strength Ratio: 1.44

Zone 1 Deformation Index: Ratio of Secant E at Peak to E: 1.06 Zone 2 Ductility Index: Amount of Plastic or Strain Hardening Strain: N/A Zone 3a: Tang and Kaiser Index (Axial): N/A Zone 3b: Tang and Kaiser Index (Volumetric): N/A Zone 4: Peak to Residual Strength Ratio: 3.17

0

5000

10000

15000

20000

25000

30000

-0.04 -0.03 -0.02 -0.01 0 0.01 0.02 0.03

Axi

al S

tress

Diff

eren

ce, p

si

(Radial) Strain (Axial)

404730 UGS, Bill Barrett 14-1-46BTR4-4, 6703.1 ft, Vertical, As-Received

Pc = 1341 psiPp = 0 psi

Peak Axial Stress Difference = 24,998 psiEffective Peak Compressive Strength = 26,339 psi

0

5000

10000

15000

20000

25000

-0.03 -0.02 -0.01 0 0.01 0.02 0.03

Axi

al S

tress

Diff

eren

ce, p

si

(Radial) Strain (Axial)

404730 UGS, Bill Barrett 14-1-46BTR4-2, 6702.90 ft, Horizontal, As-Received

Pc = 2748 psiPp = 0 psi

Peak Axial Stress Difference = 24,007 psiEffective Peak Compressive Strength = 26,755 psi

GEOMECHANICS

0.00001

0.0001

0.001

0.01

0.1

1

10

0 5 10 15 20 25 30 35

Perm

eabi

lity

(mD

)

Porosity (%)

Well Name: 14-1-46Operator: Bill Barrett Corp.

Argillaceous dolostone

Argillaceous limestone

Calcareous shale

shale

Exponential trend in the dolomites

R2 = 0.63

"

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UINTAH CO.

DUCHESNE CO. Ü0 2 4 6 81Miles

PRELIMINARY

UTELAND BUTTE - PZ-1 THICKNESS

! Well with picked tops

Outcrop - Green River Fm. base

Outcrop - Green River Fm. top

Low : 1.6 ft

High : 8.5 ft

PZ-1 isopach

UTELAND BUTTE - C-SHALE TO D-SHALE THICKNESS

UINTAH CO.DUCHESNE CO.

CARBON CO.

Ü0 4 8 12 162

Miles

! Well with picked tops

Outcrop - Green River Fm. base

Outcrop - Green River Fm. top

Isopach betweenC and D shale

High : 45 ft

Low : 13 ft Transition from proximal facies(south) to distal facies (north)

A

A`Shallow (proximal) “Fresher” water >ostracodal grainstones Fish, ooids, >gastropods

Sunnyside delta

Deeper (distal) No sand/silt No ostracodal grainstones

14-1-46

PRELIMINARY

5850

5860

5870

5880

5890

5900

5910

5920

5930

43013338278190

8200

8210

8220

8230

8240

8250

8260

8270

8280

4301351006 4301350156

6970

6980

6990

7000

7010

7020

7030

7040

7050

7060

4301332088

4950

4960

4970

4980

4990

5000

5010

5020

5030

4304731505

4670

4680

4690

4700

4710

4720

4730

4740

4750

4304752584

4820

4830

4840

4850

4860

4870

4880

4890

GRporosity

A A`

0

200,000

400,000

600,000

800,000

1,000,000

1,200,000

Cum

ulati

ve P

rodu

ction

(BO

E)

Average daily production - 1st month (BOE/day)

Normal-pressured

Overpressured

Super-long Laterals -Overpressured

12

20

9

1

1

3

4

2

8

11

4

1

3

3

0

200,000

400,000

600,000

800,000

1,000,000

1,200,000

Cum

ulati

ve P

rodu

ction

(BO

E)

Cumulative production during first three full months (BOE)

25

15

11

1

6

10

6

7

3

12

4

Ro (VR) = 1.00%6706.4 (6698.9)

Core on display

BBC 14-3-45 (7365.1 ft) - Limestone w/ bivalves

replacementcalcite

Dolomiticpeloids

BBC 14-3-45 (7374.5 ft) - PZ-1 zone - Dolomite

Chert

BBC 14-3-45 (7374.5 ft) - PZ-1 - Dolomite

Micropores

replacementcalcite

replacementchert

BBC 14-3-45 (7374.5 ft) - PZ-1 - Dolomite

chert

replacementcalcite

BBC 14-3-45 (7374.5 ft) - PZ-1 - Dolomite (UV light)

micropores in early chert cement

Thin section micrographs from adjacent Bill Barrett core (14-3-45). Photos and interpretations from Core Lab.

Core and data provided by Bill Barrett Corporation

14-3-45

N