Chapter 2 The Southwestern Wyoming Province · Chapter 2 The Southwestern Wyoming Province —...

Chapter 2

The Southwestern Wyoming Province —Introduction to a Geologic Assessment of

Undiscovered Oil and Gas ResourcesBy USGS Southwestern Wyoming Province Assessment Team

U.S. Department of the InteriorU.S. Geological Survey

Sandstone, Frontier Formation, Muddy Gap, Wyoming. (Photograph by Chris Schenk)

U.S. Geological SurveyDigital Data SeriesDDS–69–D

U.S. Department of the Interior Gale A. Norton, Secretary

U.S. Geological Survey Charles G. Groat, Director

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Manuscript approved for publication May 10, 2005.

ISBN= 0-607-99027-9

U.S. Geological SurveyNational Oil and Gas Assessment Project

Purpose

The purpose of the U.S. Geological Survey’s (USGS) National Oil and Gas Assessment is to develop geologically based hypotheses regarding the potential for additions to oil and gas reserves in priority areas of the United States. The focus of the project is to determine the distribution, quantity, and availability of oil and natural gas resources, with an emphasis on quantifying undiscovered natu-ral gas resources that may underlie Federal lands. The South-western Wyoming Province of Wyoming, Colorado, and Utah is a priority province for the National Oil and Gas Assessment because of the potential for significant natural gas resources. The approach, as in all priority provinces, was to establish the framework geology, define the total petroleum systems, define assessment units within the total petroleum systems, and assess the potential for additions to reserves in each assessment unit. This volume documents the framework geology and oil and gas assessment of nine total petroleum systems in the Southwestern Wyoming Province.

Triassic and Jurassic strata in the Flaming Gorge area of Utah.

U.S. Department of the InteriorU.S. Geological Survey 1

Teton

Sublette

Lincoln

Sweetwater

Carbon

Uinta

SummitDaggett

Duchesne

Carbon

Uintah

Moffat

Rio Blanco

Garfield

Eagle

RouttJackson

Grand

Freemont

Natrona

PinedaleLander Casper

Evanston

Rock Springs

Rawlins

Duchesne

Vernal

Craig SteamboatSprings

Price

Meeker

GlenwoodSprings

40

20

WY

UT CO

0 50 Miles

25

80

70

UTAH COLORADO

WYOMING

191

26

287

191

40

FlamingGorgeReservoir

Location of Southwestern WyomingProvince The Southwestern Wyoming Province is located in southwestern Wyoming, northwestern Colorado, and northeastern Utah, encompassing all or parts of (1) Moffat and Routt Counties in Colorado; (2) Carbon, Fremont, Lincoln, Sublette, Sweetwater, and Uinta Counties in Wyoming; and (3) Daggett and Summit Counties in Utah (fig. 1). The main population centers within the study area are Craig, Colorado, and Rock Springs, Wyoming. The main highways, I–80 and U.S. 40, generally traverse the area from east to west; U.S. 191 traverses the prov-ince from generally south to north. The Green River and its tributaries drain the area.

Figure 1. Southwestern Wyoming Province of southwestern Wyoming, northwestern Colorado, and northeastern Utah.


Carbon

Grand

Garfield

Fremont

Daggett

Eagle

Jackson

Lincoln

Moffat

Natrona

Rio Blanco

Routt

Sublette

Summit

Sweetwater

Teton

Uinta

UintahDuchesne

50 0 25

Miles

Southwestern Wyoming Province Boundary

Mox

a ar

ch

BasinGreat

Divide

Gree

nRi

ver

Basi

n

WYO

MIN

GTH

RU

ST

BEL

T

Rock

Sprin

gsup

lift

Wamsutter

Cherokee

Sand Wash Basin

RANGE

RIVER

WIND

GRANITE MOUNTAINS

RAWLINSUPLIFT

MADRE

SIE

RR

A

PAR

KRAN

GE

AXIAL BASIN UPLIFT

UINTA MOUNTAINS

RockSprings

Rawlins

Craig

HobackBasin

La Barge platform

Was

hakie

Ba

sin

ridge

arch

Intrabasin uplift

Pinedale anticline

Geologic Structure in the Southwestern Wyoming Province

In this assessment, the Southwestern Wyoming Province was defined to approximate the outline of the Greater Green River Basin (fig. 2). The Greater Green River Basin contains a number of subbasins including the Green River, Great Divide, Hoback, Sand Wash, and Washakie Basins. The province is bounded on the north by the Wind River Range and Granite Mountains; on the east by the Rawlins uplift, Sierra Madre, and Park Range; on the south by the Axial Basin uplift and Uinta Mountains; and on the west by the Wyoming and Utah portions of the Wyoming thrust belt. The province also contains the Rock Springs uplift and four major intrabasinal anticlines, the Cherokee ridge, Moxa arch (and La Barge platform), Pinedale anticline, and Wamsutter arch.

Figure 2. Major structural features in the Southwestern Wyoming Province.


Burial-historylocations

UTCOWY

Southwestern WyomingProvince boundary

Eagles Nest

Bear 1

Bruff 2

Currant Creek

WagonWheel

Adobe Town

Federal 31-1

Ro

ckSp

rings

Upl

ift

Age (Ma)100 0

0

5,000

10,000

15,000

20,000

25,000

31,956

BURIAL

DEPT

H(FEET)

MESOZOIC CENOZOICCRETACEOUS PALEOGENE NEOGENE & QUATERNARY

Gas generation - Type III% Ro Range

StartPeakEnd

0.50 - 0.80

0.80 - 2.00

Eocene rocks

Fort Union Fm.

Lance Fm.

Lewis Sh.

Baxter Sh.

Niobrara Fm.

MesaverdeGp.(upper)MesaverdeGp.(lower)

Mowry Sh.

Phosphoria Fm.

A

B

Burial History, Thermal Maturity, and Oil and Gas Generation History in the Southwestern Wyoming Province

Characterizing the level of thermal maturity and extent of petroleum generation of a potential source rock is critical in defining a total petroleum system and its associated assessment units, and in assessing the oil and gas resources of that system. The burial history, thermal maturity, and timing of petroleum generation were modeled at seven locations (fig. 3A) for eight key petroleum system source-rock horizons throughout the Southwestern Wyoming Province. The horizons are (1) the base of the Lower Permian Phosphoria Formation, (2) the base of the Upper Cretaceous Mowry Shale, (3) the base of the Upper Cretaceous Niobrara Formation, (4) the base of the Upper Cretaceous Baxter Shale (and equivalents), (5) the base of the upper part of the Upper Cretaceous Mesaverde Group, (6) the base of the Upper Cretaceous Lewis Shale, (7) the base of the Upper Cretaceous Lance Formation, and (8) the base of the Tertiary (Paleocene) Fort Union Formation (fig. 3B). See Chapter 3 by Roberts and others (this CD–ROM) for a discussion of the thermal maturation of petroleum source rocks.

Figure 3. A, locations of wells used in burial-history reconstructions. B, an example of burial history for the Adobe Town well location showing petroleum generation windows for a Type-III kerogen.


110˚ 108˚111˚ 109˚

41˚

43˚

42˚

107˚

40˚

Lance, Fort Union, Wasatch,and related formationsUpper Cretaceous and Tertiary

Maximum pressure gradient (psi/ft)

0.433 - 0.460.46 - 0.500.50 - 0.550.55 - 0.60Greater than 0.60

0.3 - 0.433

UT CO

WY

50 0 25

Miles

PRESSURE (PSI)

0 2,000 4,000 6,000 8,000 10,000 12,000

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

Fox Hills SandstoneLance FormationFort Union Formation (includes Almy Fm.)Wasatch FormationTertiary undifferentiated

0.3 0.433 0.50.6

0.7

0.8

Lance, Fort Union, Wasatch,and related formationsUpper Cretaceous and Tertiary

DEPTHTOTOPOFTESTINTERVAL(FEET)

Subsurface Pressure Data

Pressure and gas-flow rate data from the Southwestern Wyoming Province have been extracted from a commercial data base, edited, and organized into seven strati-graphic groups. As pressure increases with depth (fig. 4), most points plot between 0.3 psi/ft (the minimum retained value) and 0.433 psi/ft (the freshwater hydrostatic gradi-ent). A large number of points also plot between 0.433 and 0.5 psi/ft, representing normally pressured to slightly overpressured conditions. Pressure gradients exceeding 0.5 psi/ft, which represents significant overpressuring, tend to be more prevalent at depths greater than 9,000 ft as, for example, in the strata of the Lance, Fort Union, and Wasatch Formations. In addition to plots of pressure versus depth, maps of maximum pressure gradient (fig. 5) and maximum gas-flow rate, plots of completion date versus depth, and plots of gas-flow rate versus depth provide a broad perspective on development drilling in the province as a function of time, stratigraphic unit, and geographic location. (See Nelson and Kibler, Chapter 17, this CD–ROM.)


Figure 5. Drill-stem test data points.

Figure 4. An example of pressure data from wells with drill-stem tests in the Upper Cretaceous Lance, and Tertiary Fort Union, Wasatch Formations, and related formations in the Southwestern Wyoming Province, Wyoming, Colorado, and Utah. Lines of constant pressure gradient give ratio of pressure to depth in pounds per square inch per foot (psi/ft).

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

–5.0 –4.0 –3.0 –2.0 –1.0 0 1.0 2.0 3.0 4.013

PRISTA

NE/PH

YTANE

Phosphoria

Mowry

Niobrara

Mesaverde

Fort Union

C CANONICAL VARIABLE

Petroleum Geochemistry As a part of the petroleum resource assessment of the South-western Wyoming Province by the USGS in 2002, oils were characterized geochemically and divided into genetic types that were named on the basis of their presumed source-rock units. Recognized petroleum systems based on these data include the Phosphoria, Mowry, Niobrara, Mesaverde (includes Almond), and Fort Union (includes Almy). Oil data were compiled from a proprietary database (Geo-Mark Research), unpublished USGS data, and from published data (Sofer, 1984; Lillis and others, 2003). Pour point, API gravity, and sulfur-content data were also derived from the U.S. Department of Energy Crude Oil Analysis database version 2.0 (Sellers and others, 1996). Pristane/phytane values, stable carbon isotope values, and the related canonical variable (CV) devised by Sofer (1984), and sulfur content are the most useful geo-chemical parameters for the characterization of oil types. Figure 6 is a graph of the canonical variable (CV equal to –2.53 13Csat + 2.22 13Caro –11.65) versus pristane/phytane of oils in the prov-ince. Phosphoria oils generally have CV values less than –1.3, pristane/phytane values less than one, and sulfur content greater than 0.5 weight percent. Mowry and Niobrara oils have sulfur contents less than 0.5 weight percent and pristane/phytane values between 1.8 to 2.1 but can be distinguished based on CV values (fig. 6) and pour point (Mowry oil greater than 10°F, Niobrara less than 10°F). Mesaverde and Fort Union oils generally have pristane/phytane ratios greater than 3.0 and CV values greater than 0.5, indicating that the source-rock kerogen is dominantly nonmarine organic matter (Sofer, 1984; Hughes and others, 1995).


Figure 6. Graph of the canonical variable (CV equal to –2.53 13Csat + 2.22 13Caro –11.65) versus pristane/phytane of oils in the province.

Southwestern Wyoming Province Boundary

50 0 25

Miles

Fort UnionMesaverdeNiobraraMowry

Phosphoria

La Bargearea

Powder Washarea

Oil types

Rock

Springs

uplift


Petroleum Geochemistry—(continued) The Phosphoria and Mowry petroleum systems are widely distributed throughout the Southwestern Wyoming Province (fig. 7), and the Mesaverde system extends throughout the province except in the south-western part. The Niobrara system is limited to the eastern portion of the province. The Fort Union/Almy samples are restricted to three areas—La Barge area, the eastern flank of the Rock Springs uplift, and the Powder Wash area (fig. 7).

Figure 7. Distribution of oil samples throughout the Southwestern Wyoming Province.

OilshowsTar sands

on outcrop

Hypotheticalstratigraphic oilassessment play

Structural oilassessment play

Pod of maturesource rock

Structural gasassessment play

Oilfields

Gasfields

Geographical extentof petroleum system

Thrustfault

Migrationpaths

Total Petroleum System Concept

A total petroleum system (TPS) is a mappable entity encompassing genetically related petroleum that occurs in seeps, shows, and accumulations (discovered or undiscovered) that have been gener-ated by a pod or by closely related pods of mature source rock (fig. 8). On this basis, we defined the various total petroleum systems in the Southwestern Wyoming Province. We also mapped the reser-voirs, seals, and traps that contain or are projected to contain the petroleum within each TPS. The largest likely geographic extent of a TPS can then be mapped by integrating the areal distribution of known petroleum accumulations with potential migration fairways for oil and gas. Assessment units (AU) are defined within each TPS. An AU is defined as a mappable volume of rock within a TPS that encompasses accumulations (discovered and undis-covered) that share similar geologic characteristics and may be identified as conventional or continuous accumulations. (See fig. 27 for discussion of “con-ventional” and “continuous” hydrocarbon accumula-tions.)

Figure 8. Schematic plan view of a total petroleum system, showing a pod of mature source rock, the distribution of known petroleum occurrences, and the boundaries of assessment units.


AGESTRATIGRAPHIC UNITS

WEST EASTWEST-

CENTRALEAST-

CENTRALTERTIARY

CRETACEOUS

JURASSIC

Eocene

Paleocene

Late

Late

Middle

Early

Early

TRIASSIC

PERMIAN

DEVONIAN

SILURIAN

ORDOVICIAN

PENNSYLVANIAN

MISSISSIPPIAN

CAMBRIAN

Late

Early

Middle

FormationBridgerGreen River Formation

Fort Union FormationHanna andFerris Fms.

Lance Formation

Cloverly Formation

Sundance Formation

Dinwoody Formation

Phosphoria Formation

Ankareh FormationNugget Sandstone

Morrison

Frontier Formation

Baxter Shale Steele Shale Niobrara

Fox Hills Sandstone

Lewis Shale

Mesaverde Group

Hilliard Shale

Aspen Shale Mowry Shale

Thermopolis ShaleMuddy Sandstone

BearRiver

Formation DakotaSandstone

PreussFormation

Twin CreekLimestone

Entrada Sandstone

Carmel Formation

Gannett GroupStump Sandstone Formation

ThaynesLimestone Woodside

FormationChugwater Group

Goose EggFormation

CasperFormationTensleep

Sandstone

AmsdenFormation

Amsden Fm.MorganFormation

TensleepSandstone

WeberSandstone

Madison Limestone

Darby Formation

Unnamed

UnnamedBighorn Dolomite

Gallatin Limestone

Gros Ventre Formation

FlatheadSandstone

BuckSpringFormation

FlatheadSandstone

FountainFm.

Darwin Ss.

�

�MesaverdeGroup

3

1

2

4

57 6

9

8

Wasatch FormationHoback andAlmy Fms. Total Petroleum Systems in the

Southwestern Wyoming Province

Nine petroleum systems named for their source rocks were determined for the Southwest-ern Wyoming Province. Some are composite sys-tems because the exact source of the hydrocarbons or production information of some units were commingled and therefore could not be readily separated. The nine systems are listed below and highlighted by numbered markers on the columnar section (fig. 9).

1. Wasatch–Green River Composite TPS2. Lance–Fort Union Composite TPS3. Mesaverde–Lance–Fort Union Composite TPS4. Lewis TPS5. Mesaverde TPS6. Niobrara TPS7. Hilliard–Baxter-Mancos TPS8. Mowry Composite TPS9. Phosphoria TPS

Figure 9. Generalized stratigraphic column of the Southwestern Wyoming Province.


FlamingGorgeReservoir

Arapahoe Creek

Baggs South

Baxter Basin South

Bell Springs

BisonBasin

BlackButte Creek

Browning

Buck Peak

ButcherKnife Springs

ChurchButtes Cow

Creek

CrooksGap

Espy

Greater Ferris

Golden GooseHappySprings

HiawathaHiawatha

West

HigginsBrady

Jackknife Springs

Kinney

Kirk

Lamont

Lost Soldier

Meander

MoxaUnit

OakCreek

O'BrienSprings

Pagoda

Pine Canyon

Pinnacle

Pioneer

Pretty WaterCreek

Raptor

Riley Ridge

Big Piney-La Barge Area

La BargeDeep

RimRobin

Sheep Creek

Shell Creek

Sherard

Greater Table Rock

Tip Top Deep

Twin Rocks

Williams Fork

Baxter Basin Middle

Baxter Basin NBaxter BasinCrooked Canyon

Iles Dome

Hatfield

MoffatHorseGulch Sage Creek

BaileyDome

GreaterMahoneyDome

Wertz

110°111° 109° 108° 107°

40°

41°

42°

43°

500 25

Miles

WYOMING

UTAH COLORADO

Phosphoria Total Petroleum System

Black marine shales of the Lower Permian Phospho-ria Formation generated a substantial amount of hydro-carbons during the latter part of the Mesozoic Era that are now contained in a wide variety of lithostratigraphic units in the north-central Rocky Mountains (see for example, Claypool and others, 1978). Sixty-eight oil and gas fields in the Green River Basin, containing some 700 wells, are reported to pro-duce from one or more of the 18 formations of Cambrian through Jurassic age included in this TPS (fig. 10).

Figure 10. Approximate location of oil and gas fields in the Green River Basin with reported sub-Cretaceous production (NRG Associates, 2001; IHS Energy Group, 2001).


Maroon Fm

System

SeriesStage

Eon

Era

Triassic

Permian

Jurassic

LU

Middle

Phanerozo

ic

Meso

zoic

Pennsylvanian

Mississippian

Devonian

Silurian

Ordovician

Paleozo

ic

LMiddle

Upper

Cambrian

Preca

mbrian

Arch.

Proter.

Green River Basin

North and west East and south

Morrison Fm. Morrison Fm. Morrison Fm. Morrison Fm.

Stump

Sandstone Curtis Fm.

Sundance Fm. Sundance Fm. Sundance Fm.

Curtis Fm.Entrada Ss.Sundance Fm.Preuss Ss. Entrada Ss.

Twin Creek Ls. Carmel Fm.

Gypsum SpringFormation

Nugget Ss. Nugget Ss. Nugget Ss.

AnkarehFormation

AnkarehFormation

Thaynes Ls.Woodside Fm. Woodside Formation

Weber Ss.

Morgan Fm.

Round Valley Ls.

Dinwoody Fm. Dinwoody Fm. Dinwoody Fm.

Chugwater

Gp.

Phosphoriaand

ParkCityFormations

Thaynes Ls.

Darby Fm.

Tensleep Ss.

Amsden Fm.

Madison Ls. Madison Ls. Madison Ls.

DarbyFormation

Great Divideand

Washakie BasinsSand Wash Basin

Carmel Fm.

Glen CanyonSandstone

Chinle Fm.Shinarump Mbr.

Popo Agie Fm.

Crow Mountain Fm.

Alcova Ls.

Red Peak Fm.

Phosphoria Fm.

Phosphoria Fm.Park City Fm.

Phosphoria Fm.


Phosphoria Fm.


MoenkopiFm.

StateBridgeFm.

Tensleep Ss.

Weber Ss.

Amsden Fm.

Darwin Ss. Mbr.

MinturnFm.Morgan

Fm. BeldenShale

Doughnut Sh.Humbug Fm.

Leadville Ls.

ChaffeeFormation

Manitou Ls.

Peerless Fm.

Lodore Ss.

Bighorn Dolo.

Gallatin Ls. GallatinLs.

Gros VentreFormation

Gros VentreFormation

Flathead Ss.Flathead Ss.

BuckSpring Fm.

Flathead Ss.

Uinta MountainGroup

Metamorphic and intrusive rocks

? ?

State Bridge Fm

Darwin Ss. Mbr.1

Franson Mbr.2

1 of Amsden Formation 2 of Park City Formation

Phosphoria TPSpetroleum source rock

Phosphoria TPS units withreported petroleum production

EXPLANATION

Figure 11. Generalized stratigraphic column showing distribution of reservoir rocks in Green River Basin containing oil and gas derived from Phosphoria Formation (modified from Ryder, 1988).


Southwestern Wyoming Stratigraphic Column

Eighteen units produce oil and gas thought to be sourced from the Phosphoria Formation. Of these, the most productive reservoirs are in the Tensleep Sandstone, Sundance Formation, Nugget Sandstone, Madison Limestone, and Morrison Forma-tion. Of the 700 wells producing from this TPS, nearly 80 percent produce from these five formations.

110°111° 109° 108° 107°

40°

41°

42°

43°

UTAH

WYOMING

COLORADOGlenwoodSprings

Craig

GreenRiver

Jackson

Rawlins

Vernal

Evanston

RockSprings

Prospect thrust

Hogsbackthrust

Moxa

arch

GreenRiverBasin

Rock

Sprin

gs

uplift

Wamsutter

arch

Cherokee ridgeSand

Wash Basin

Basin

Basin

Washakie

Great

Divid

e

Uinta Mountains

Pinedaleanticline

Hoback

Basin

��

��

SE

NW� �

�

�

�

��

Outcrop of Mowry Composite TPS units

Producing wells from TPS units

EXPLANATION

Wells used in cross section fig. 13

Anticlines

Synclines

Assessment Unit 261(Continuous)

Assessment Unit 201(Conventional)

TPS boundary

�

500 25

Miles

Mowry Composite Total Petroleum System

A conventional oil and gas assessment unit (AU) and a continuous gas AU were defined for the Mowry Composite TPS. The Mowry Conventional Oil and Gas AU covers the entire province (fig. 12) and includes mainly intrabasinal and basin margin structures and stratigraphic traps, but also includes traps located strati-graphically below the basin-centered accumulations of the Mowry Continuous Gas AU. The continuous gas AU underlies an area of about 11.5 million acres where the approximate limit of gas saturation is defined by: (1) areas of overpressure, (2) bottom hole temperature greater than 200°F, (3) vitrinite reflectance greater than 0.8 percent, (4) low permeabilities, and (5) absence of gas/water contacts in the reservoirs. See Chapters 5 and 15 by Kirschbaum and Roberts (this CD–ROM) for geologic discussions of the Mowry Composite TPS.

Figure 12. Geographic extent of the Mowry Composite Total Petroleum System in the Southwestern Wyoming Province.NW-SE cross section shown in figure 13.


ShellCreek

Mowry Shale

Muddy Ss

Hilliard Shale (part)

Frontier Fm

Marine

Shoreface

Continental

Depositional environments

NW SE

G = natural gammaC = conductivityR = resistivity

72 Miles

ThermopolisShale

CloverlyFm

DakotaSs

R

C

G

G

CGCGCGRG

RGRGRGC CG G


Figure 13. The Total Petroleum System is defined as a composite system because it contains hydrocarbons generated from multiple source rocks, including marine shale units of the Mowry and Thermopolis Shales and their equivalents, and coaly and lacustrine facies in the Bear River (not shown on cross section) and Frontier Formations and Dakota Sandstone. Oil and gas migrated into fluvial, tidal, deltaic, and shoreface sandstone reservoirs of the Bear River, Frontier, and Cloverly Formations and the Dakota and Muddy Sandstones. The hydrocarbons were trapped in structural, stratigraphic, and basin-centered accumulations. Seals include thick continuous marine shale sequences and in some cases terrestrial to estuarine mudstone units, diagenetic seals, and capillary-pressure seals. Location of cross section shown in figure 12.

24,000

24,000

20,000

20,000

20,000

16,000

12,000

8,000

4,000

16,000

12,000

8,000

4,000

16,000

SandyBend arch

HobackBasin

Sand WashBasin

WashakieBasin

Great DivideBasin

Green

River

Basin

Cherokee ridge

Wamsutter arch

Moxa

arch

Rock

Springs

uplift

110°111° 109° 108° 107°

40°

41°

42°

43°

UTAH

WYOMING

COLORADO

Outcrop of Niobrara Formationand equivalent strata

Niobrara TPS 503703

La Bargeplatform

anticline

Pinedale

W

E

Location offigure 15

cross section

500 25

Miles

Niobrara Total Petroleum System

This map shows the extent of the Niobrara TPS, major structural elements, and location of cross section (fig. 14). Contours represent the approximate depth in feet to the base of the Niobrara Formation (modi-fied from Kirschbaum and Roberts, Chapter 5, this CD–ROM). Contour interval is 2,000 ft. The Niobrara TPS is a self-sourced system that produces oil and natural gas from fractured carbonate-rich reservoirs in the Upper Cretaceous Niobrara Formation and equiva-lent rocks. The Niobrara TPS encompasses parts of the Great Divide, Sand Wash, and Washakie Basins. See Chapter 6 by Finn and Johnson (this CD–ROM) for a geologic discussion of the Niobrara TPS.

Figure 14. Geographic extent of the Niobrara Total Petroleum System in the Southwestern Wyoming Province.


?

Buck Peak bench

Tow Creek bench

Wolf Mountain bench

basal Niobrara

NiobraraFormation

MancosShale

oil show

oil

oiloil

oil

oil

oil

oil

Frontier Formation

W E

Figure 15. Generalized stratigraphic cross section of the Niobrara Total Petroleum System, modified from Haskett (1959).


Cross section of the Niobrara Formation in northwestern Colorado

In figure 15, marine sandstones are shown in yellow and clay-rich marine shale in gray; calcareous-rich zones that are more prone to fracturing are highlighted in light blue; and oil-producing zones are indicated by heavy vertical black bars. The Niobrara TPS produces primarily oil from fractured, calcareous-rich shales, shaley limestones, and marls from the Upper Cretaceous Niobrara Forma-tion and equivalent rocks in the eastern portions of the Greater Green River Basin. Location of cross section shown in figure 14.

SandyBend arch

HobackBasin

Sand WashBasin

WashakieBasin

Great DivideBasin

Riv

erB

asin

Cherokee ridge

Wamsutter arch

Moxa

arch

Roc

kS

prin

gsup

lift

Gre

en

Pinedaleanticline

110°111° 109° 108° 107°

40°

41°

42°

43°

Outcrop of Baxter Shale andequivalent rocks

Hilliard-Baxter-MancosTPS 503704

UT CO

WY

EXPLANATION

500 25

Miles

Hilliard-Baxter-Mancos Total Petroleum System

The Hilliard-Baxter-Mancos TPS covers an area of 22,448 mi2 and includes all of that part of the Southwestern Wyoming Province where this marine shale interval is present (fig. 16). The shales were deposited in offshore to nearshore environments during an extended period in which the Late Cretaceous shoreline was predomi-nantly west of the TPS. The stratigraphic interval included in the TPS ranges in thickness from about 3,500 to 6,000 ft (see fig. 19). The thick organic-rich shales are potential source rocks, and thick nearshore to offshore silty and sandy strata are potential reservoir rocks. See Chapter 7 by Finn and Johnson (this CD–ROM) for a geologic discussion of the Hilliard-Baxter-Mancos TPS.

Figure 16. Geographic extent of the Hilliard-Baxter-Mancos Total Petroleum System in the Southwestern Wyoming Province.


110°111° 109° 108° 107°

40°

41°

42°

43°

UT

WY

CO

Teton

SandyBend arch

HobackBasin

Sand WashBasin

WashakieBasin

Great DivideBasin

River

Basin

Cherokee ridge

Wamsutter arch

Moxa

arch

RockSprings

uplift

Green

Outcrop of Mesaverde Group

Mesaverde TPS 503705

Western limit ofLewis Shale

anticline

Pinedale

Wyomingthrustbelt

Rawlinsuplift

SierraMadre

ParkRange

Uinta Mountains

Axial Basinuplift

Wind

River

Mountains

EXPLANATION

500 25

Miles

Mesaverde Total Petroleum System

The Mesaverde TPS in the Southwestern Wyo-ming Province produces hydrocarbons from sandstone and coal reservoirs in the Upper Cretaceous Mesaverde Group (fig. 17). Coals and terrigenous organic-rich shales within the Mesaverde Group are believed to be the primary source. The TPS includes most strata in the Mesaverde Group east of the pinch-out of the Lewis Shale. The TPS is subdivided into three continuous gas assessment units—the Almond Continuous Gas AU, the Rock Springs–Ericson Continuous Gas AU, and the Mesaverde Coalbed Gas AU—and one conventional assessment unit, the Mesaverde Conventional Oil and Gas AU. See Chapter 8 by Johnson, Finn, and Rob-erts (this CD–ROM) for a geologic discussion of the Mesaverde TPS.

Figure 17. Geographic extent of the Mesaverde Total Petroleum System in the Southwestern Wyoming Province.


SandyBend arch

HobackBasin

Sand WashBasin

WashakieBasin

Great DivideBasin

River

Basin

Cherokee ridge

Wamsutter arch

Moxa

arch

RockSprings

uplift

Green

Pinedaleanticline

Outcrop of Mesaverde Group

Mesaverde–Lance–Fort UnionComposite TPS 503706

Western limit ofLewis Shale

110°111° 109° 108° 107°

40°

41°

42°

43°

UT

WY

CO

500 25

Miles

EXPLANATION

Mesaverde–Lance–Fort Union Composite Total Petroleum System

The Mesaverde–Lance–Fort Union Composite TPS is a predominantly gas-prone system within the westernpart of the Southwestern Wyoming Province, west of the pinch-out of the Lewis Shale (fig. 19). The composite TPS is considered here as one system because all of the units were deposited in a terrestrial setting, contain similar gas-prone source rocks, and have no regional seal within the the entire stratigraphic succession to inhibit the vertical migration of gas. Coals and carbonaceous shales are pre-sumed to be the primary source rocks. See Chapter 10 by Finn and others (this CD–ROM) for a geologic discussion of the Mesaverde–Lance–Fort Union Composite TPS.

Figure 18. Geographic extent of the Mesaverde–Lance–Fort Union Composite Total Petroleum System in the Southwestern Wyoming Province.


GR

Res.

?

?

?

?

?

?

?

?

?

?

?

?

?

UT CO

WY

Line of section

Continental sandstone, siltstone, shale,and coal of Tertiary age

Marine carbonates, marls, andcalcareous shales

Marine sandstone, siltstone, and shale

Marginal marine or coastal sandstone

Coastal plain and alluvial plain sandstone,siltstone, shale, and coal

Marker bed

Predominantly fluvial sandstone

Explanation

Restored

140 MilesMoxa arch Green River

BasinRock Springs

upliftWashakie Basin

Lance Fm

Lewis Shale

Fort Union Fm

Fort Union Fm Lance Fm

Wasatch Fm

Hilliard Sh

Baxter ShFrontier Fm

Mowry ShNiobrara Fm

Steele Sh

Mesaverde Gp Mesaverde Gp

W E

WE

5,000

2,500

0(FEET)


Figure 19. Generalized stratigraphic cross section of the Cretaceous and Tertiary rocks across the Greater Green River Basin. For detailed well-log cross section, see Finn and Johnson, Chapter 14 (this CD–ROM).

Green

River

Basin

SandWash

Basin

Washakie

Basin

Great Divide Basin

Wamsutterarch

Hoback

Basin

Cherokee ridge

Rock

Springs

uplift

WY

CO

COUT

111°

40°

41°

42°

43°

110° 109° 108° 107°

Lewis Continuous GasAssessment Unit

Lewis Conventional Oil andGas Assessment Unit

Area where theassessment units overlap

Lewis TPS boundary

Explanation

SouthwesternWyoming Province

Fields producing from Lewis Shale

500

Miles

Lewis Total Petroleum System

Natural gas accumulations generated from marine mudrock in the Upper Cretaceous Lewis Shale define the limits of the Lewis TPS in the Southwestern Wyoming Province (fig. 20). Accumulations are confined to the Lewis Shale, which is distributed throughout the Great Divide, Sand Wash, and Washakie Basins. The TPS contains two assessment units: (1) the Lewis Continuous Gas AU, which includes the deeper basin areas characterized by an overpressured, gas-saturated, basin-centered accumu-lation (fig. 21); and (2) the Lewis Conventional Oil and Gas AU, which includes shallower basin areas where gas accumulations are within conventional-type traps. Principal reservoirs are sandstones deposited in laterally extensive turbidite systems (fig. 22). See Chapter 9 by Hettinger (this CD–ROM) for a geologic discussion of the Lewis TPS.

Figure 20. Geographic extent of the Lewis Total Petroleum System in the Southwestern Wyoming Province.


SANDWASH BASINWASHAKIE BASINWAMSUTTER ARCH CHEROKEE RIDGE

GREAT DIVIDE BASIN

N S

FEET

8,000

6,000

4,000

2,000

–4,000

–2,000

Sea level

–6,000

–8,000

–10,000

–12,000

–14,000

–18,000

–16,000

20 MILES

Lewis Shale above top of overpressuring

Lewis Shale below top of overpressuring

Top of gas-bearing overpressured rocks(Law and others,1989)

N

S


Figure 21. Relations of Lewis Shale to structure and to top of overpressured zone. Modified from Law and others (1989, their figure 8).

GGRB

WY

COUT

S

N

Line of N-S in GGRB.Area of Lewis Shaleshown in blue.

N S

LewisSha

le

LewisSha

le

LewisSha

le

Dad

Ss.Mbr.

Asqui th

marker zone

Fox Hills Ss.

LanceFm. Lance

Fm.LanceFm.

Almond Fm.

Williams Fork Fm.

Fox Hills Ss.

ExplanationCoastal plain; sandstone,si l tstone, carbonaceousshale and coal

Upper and middleshoreface; predominant lysandstone

Offshore; includes lowershoreface sandstone andmudrock

Deep-basin turbidi tedeposi ts; predominant lysandstone

vertical scale (feet)

500

0


Figure 22. Stratigraphy and lithofacies of the Upper Cretaceous Lewis Shale in the eastern part of the Greater Green River Basin (GGRB), Colorado and Wyoming (Hettinger, Chapter 9, this CD–ROM).

110°111°

43°

42°

41°

40°

39°

44°109° 108° 107° 106°

Casper

HannaRawlins

Lander

Kemmerer

Riverton

Thermopolis

Saratoga

Craig

RifleGlenwoodSprings

GreenRiver

Jackson

RockSprings

Vernal UT

WY

CO

Western limit ofthe Lewis Shale

ExplanationLance–Fort Union CompositeTotal Petroleum SystemSouthwestern WyomingProvince boundary

Lance Formation outcrops

Interstate highway

U.S. or State highway

I-80

Uinta Mountains

Axial Basinuplift

Wyomingthrustbelt

Wind

River

Mountains

GraniteMountains

SierraMadre

ParkRange

Great DivideBasin

Sand WashBasin

Green RiverBasin

HobackBasin

WashakieBasin

Wamsutter arch

Cherokee ridge

Rock

Springs

upliftI-80

I-80

I-80

I-70

I-25

500 25

Miles

Lance–Fort Union CompositeTotal Petroleum System

The Lance–Fort Union Composite TPS in the South-western Wyoming Province is a genetically related system of source rocks and hydrocarbon accumulations contained within the Upper Cretaceous Fox Hills Sandstone and the Lance Formation and the lower Tertiary Fort Union and Wasatch Formations. The petroleum system encom-passes about 6,112,000 acres (9,550 mi2) in Wyoming and Colorado and includes the Great Divide, Washakie, and Sand Wash structural basins and intervening Wamsutter and Cherokee ridge arches (fig. 23). See Chapter 11 by Roberts (this CD–ROM) for a geologic discussion of the Lance–Fort Union Composite TPS.

Figure 23. Geographic extent of the Lance–Fort Union Composite Total Petroleum System in the Southwestern Wyoming Province.


0.8

0.8

0.6

0.6

0.6

1.1

0.8

1.1

1.1

Thermal maturity (Ro) values at thebase of the Lance Formation

Lance Formation outcrops

Explanation

Area of mature source rock (Ro > 0.6 %at the base of Lance Formation)

42°

41°

109° 108°

Rawlins

Baggs

Craig

GreenRiver

RockSprings

UT

WY

CO

0 25 50 Miles

Southwestern WyomingProvince

Lance–Fort UnionComposite Total

Petroleum System

Great DivideBasin

WashakieBasin

Sand WashBasin

I-80

Lance–Fort Union Formations Source Rock

Coalbeds and associated carbonaceous strata (shale, siltstone, and sandstone) within the Lance and Fort Union Formations are considered to be the primary source rocks for hydrocarbon generation within the Lance–Fort Union Composite TPS. These source rocks contain humic, Type-III organic matter and thus are considered to be gas-prone. The extent of mature source rocks is defined as that area in which thermal maturity (R

O) values at the base of the Lance

Formation are estimated to be 0.6 percent or greater. This R

o value was used to define the primary “pod” of mature

source rock within the TPS (fig. 24).


Figure 24. Lance–Fort Union Composite Total Petroleum System source rock thermal maturity (Ro) map.

110°111°

43°

42°

41°

40°

39°

44°109° 108° 107°

Casper

HannaRawlins

Baggs

Lander

Riverton

Thermopolis

Saratoga

Craig

Rifle

GlenwoodSprings

GreenRiver

Kemmerer

Jackson

RockSprings

Vernal UT

WY

COExplanation

Wasatch–Green River CompositeTotal Petroleum System

Southwestern Wyoming Province

Interstate highway

U.S. or State highway

I-80

Uinta Mountains

Axial Basinuplift

Wyomingthrustbelt

Wind

River

Mountains

GraniteMountains

SierraMadre

ParkRange

Great DivideBasin

WashakieBasin

Sand WashBasin

Green RiverBasin

HobackBasin

I-80

I-80I-80

I-70

I-25

106°

500 25

Miles

Figure 25. Wasatch–Green River Composite Total Petroleum System.



Two hypothetical gas assessment units have been delineated within the Wasatch–Green River Composite TPS (fig. 25)—the Wasatch–Green River Continuous Gas AU and the Wasatch–Green River Coalbed Gas AU (fig. 26). Definition of the continuous gas AU is based on the extent of exploration activities and pro-duction tests of gas in the Wilkins Peak Member of the Green River Formation. This potential gas resource is considered to represent a self-sourced, biogenic shale-gas accumulation. The coalbed gas AU addresses the potential for gas accumulations in coals of the Wasatch and Green River Formations in western Washakie and central Great Divide Basins. Currently, there is no commercial production of gas from either assessment unit. See Chapter 12 by Roberts (this CD–ROM) for a geologic discussion of the Wasatch–Green River Com-posite TPS.

110°

42°

41°

109° 108°

MARawlins

Baggs

Craig

GreenRiver

Kemmerer

RockSprings

Explanation

Wasatch–Green River ContinuousGas Assessment Unit 50370961

Wasatch–Green River CoalbedGas Assessment Unit 50370981

0 25 50 Miles

Southwestern WyomingProvince

Wasatch–Green RiverComposite TotalPetroleum System

WashakieBasin

Sand WashBasin

Great DivideBasin

Green RiverBasin

Fold axis

Wrench fault(right lateral offset)

Fault

UintaMountains

WindRiver Mountains

I-80

UT

WY

CO

WA

SBA

CRA

RSU


The Wasatch–Green River Composite TPS in the Southwestern Wyoming Province includes source rocks and potential hydrocarbon accumulations within Tertiary (Eocene) strata in the Wasatch and Green River Forma-tions. The petroleum system encompasses about 7,850,000 acres (12,265 mi2) in Wyoming, Colorado, and Utah and includes areas within the Green River, Great Divide, Washakie, and Sand Wash structural basins (fig. 26). Two assessment units are defined in the TPS: (1) Wasatch–Green River Continuous Gas AU and (2) Wasatch–Green River Coalbed Gas AU.

Figure 26. Geographic extent of the Wasatch–Green River Total Petroleum System in the Southwestern Wyoming Province showing areas included with the Wasatch–Green River Continuous Gas and Coalbed Gas Assessment Units. Abbreviations: CRA, Cherokee ridge; MA, Moxa arch: RSU, Rock Springs uplift; SBA, Sandy Bend arch; WA, Wamsutter arch.


Land surface

Conventionalstructural gasaccumulation

Coalbed gas

Conventionalstratigraphic gas

accumulation

Conventionalstructural oilaccumulation

Continuousbasin-centered

gas accumulationContinuouschalk or shale gas

accumulation

Continuouschalk or shale

oil accumulation

Transitionzones

Tens of miles

Water

Water

Oil

Gas

Water

Gas generation window

Oil generation window

Conventional and Continuous Hydrocarbon Accumulations

Hydrocarbon accumulations can be broadly defined into two categories: conventional and continuous (fig. 27). A conventional oil or gas accumulation is defined as a discrete accumu-lation with a well-defined hydrocarbon/water contact. Conventional accumulations commonly have high matrix permeabilities, obvious seals and traps, and high recovery factors. In contrast, continuous accumulations (also called uncon-ventional) are regional in extent; commonly have low matrix permeabilities; do not have obvious seals, traps, or hydrocarbon/water contacts; are abnormally pressured; are in close proximity to source rocks; and have very low recovery fac-tors. Continuous-type accumulations include basin-centered gas, tight gas, shale gas, shale oil, fractured-reservoir gas and oil, coalbed gas, and gas hydrates. The USGS assessed undiscovered conventional oil and gas accumulations and undiscovered continuous oil and gas accumulations in the Southwestern WyomingProvince.

Figure 27. Categories of oil and natural gas accumulations (Pollastro and others, 2003).


for each assessment unit

Assessment procedure for conventional accumulations

Geologic definition of total petroleumsystem and assessment unit

Coproduct ratios

Select minimum accumulation size

Assign access risk

Geologic-basedprobability distribution

for number ofundiscovered accumulations


for sizes ofundiscovered accumulations

Assign geologic risk

Probability distributionsfor undiscovered

conventional resources

Allocations ofassessed resources by

land entity andby offshore

Conventional Accumulations—Assessment Methodology

The assessment of undiscovered conventional oil or gas accumulations depends entirely upon a geologic understanding of the framework geology and total petroleum system within which the undiscovered accumulations are interpreted to reside. The geologist must therefore have an understanding of hydrocarbon source-rock quality, maturation, timing of generation and hydrocarbon migration, and timing of structural development and trapping, as well as understanding either of the genesis of hydrocarbon accumula-tions that exist within an assessment unit or of the hydrocar-bon accumulations in a geologic analog. An understanding of historical hydrocarbon accumulation types and sizes to construct a probability distribution for sizes and numbers of undiscovered accumulations (fig. 28) is also essential. These geologic-based probability distributions, combined with coproduct ratios, produce the probability distributions for undiscovered hydrocarbon resources that have the potential to be added to the reserve base of the United States over some specified time period. For details see Chapter 19 by Schmoker and Klett (this CD–ROM).

Figure 28. Major steps in the assessment of conventional hydrocarbon accumulations.


Assessment procedure for continuous accumulations

Geologic definition of total petroleumsystem and assessment unit

Select minimum cell EUR


for number ofundiscovered cells


for EURs ofundiscovered cells

Coproduct ratios

Probability distributionsfor undiscovered

continuous resources

Allocations ofassessed resources by

land entity andby offshore

for each assessment unit

Assign access risk

Assign geologic risk

Continuous Accumulations — Assessment Methodology

The assessment of undiscovered continuous accumulations, as with conventional accumulations, depends entirely upon a geologic understanding of the framework geology, total petroleum system, and engineering properties of the sequence that hosts the accumulation. In the United States, the locations of many continuous accumulations are known, but the goal of an assessment is to determine that part of the continuous accumulation that has the potential to be added to the reserve base of the United States over the next few decades. The methodology is as follows: the geologist develops a probability distribution of cell sizes in the continuous accumulation, a cell being the area drained by a well; the historical production data are used as a guide to develop a probability distribution of estimated ultimate recoveries (EUR) for cells. The probability distributions are combined with coproduct ratios to produce a probability distribution for undiscovered resources that have the potential to be added to the reserve base in the United States over the next few decades (fig. 29). Emphasis is given to the recognition of geologic “sweet spots” of production, as these areas are the most likely to be developed within continuous hydrocarbon accumulations. For details see Chapter 13 by Schmoker (this CD–ROM).

Figure 29. Major steps in the assessment of continuous hydrocarbon accumulations. EUR, estimated ultimate recovery.


Federal Surface Ownership in the Southwestern Wyoming Province

In the Southwestern Wyoming Province study area, about 63 percent of the land surface is adminis-tered by the Federal Government, about 4.4 percent is administered by the States, and about 32.3 percent is held by private owners (fig. 30). Of the 63 percent of federally administered lands, the Bureau of Land Management is responsible for about 55 percent, the Forest Service about 6.5 percent, and the National Park Service less than 1 percent. National Forests include Medicine Bow–Routt and White River in Colorado; Wasatch-Cache and Ashley in Utah, and Bridger-Teton, Wasatch-Cache, Ashley, and Medicine Bow in Wyoming. National Recreation Areas include Flaming Gorge in Utah and Wyoming.

Figure 30. Distribution of Federal surface land ownership in the Southwestern Wyoming Province.


3.80 12.70 43.60 16.60 6.70 24.00 85.90 32.20 0.20 0.80 3.20 1.20

0.00 0.00 0.00 0.00 206.20 1,069.00 3,480.00 1,350.70 5.90 31.20 107.20 40.60

1.70 5.70 14.80 6.60 2.70 9.40 25.90 11.20 0.30 1.30 3.70 1.60

85.80 196.30 301.40 195.10 1.60 3.80 6.70 3.90

4.60 13.80 31.90 15.50 0.30 0.90 2.10 1.00

0.90 2.10 4.00 2.30 7.40 17.30 34.80 18.80 0.30 0.60 1.40 0.70

8.80 58.20 164.60 13.40 34.00 69.40 36.90 0.10 0.40 0.90 0.40

0.90 2.10 4.00 2.30 3.80 9.10 18.30 9.80 0.20 0.40 0.90 0.40

8.80 58.20 164.60 101.40 297.70 558.80 310.40 4.20 13.00 26.90 14.00

0.90 2.10 4.00 2.30 103.70 188.90 304.00 194.60 3.70 7.40 13.30 7.80

8.80 58.20 164.60 75.00 229.20 465.90 245.60 0.70 2.20 5.00 2.50

7.30 22.60 66.40 27.80 610.70 2,088.70 5,376.30 2,420.80 17.50 62.00 171.30 74.10

Total undiscovered resourcesTotal Petroleum Systems(TPS)and Assessment Units (AU)

Fieldtype

Oil (MMBO) Gas (BCFG) NGL (MMBNGL)

Gas

Oil

Gas

Gas

Oil

Gas

Oil

Gas

Oil

Gas

Gas

Phosphoria TPS

Total conventionalresources

Sub-Cretaceous ConventionalOil and Gas AU

Mowry Composite TPS

Mesaverde TPS

Lewis TPS

Hilliard–Baxter–Mancos TPS

Mesaverde–Lance–Fort Union Composite TPS

Mowry ConventionalOil and Gas AU

Hilliard–Baxter–MancosConventional Oil and Gas AU

Mesaverde ConventionalOil and Gas AU

Mesaverde–Lance–Fort UnionConventional Oil and Gas AU

Lewis ConventionalOil and Gas AU

Lance–Fort Union ConventionalOil and Gas AU

Lance–Fort Union Composite TPS

Table 1. Southwestern Wyoming Province assessment results—Conventional oil and gas resources.[Assessment results of undiscovered oil and gas resources by assessment unit. Results shown are fully risked estimates.For gas fields, all liquids are included under the NGL (natural gas liquids) category. Undiscovered gas resources are thesum of nonassociated and associated gas. F95 represents a 95-percent chance of at least the amount tabulated. Otherfractiles are defined similarly. Fractiles are additive under the assumption of perfect positive correlation. MMBO, millionbarrels of oil; BCFG, billion cubic feet of gas; MMBNGL, million barrels of natural gas liquids. Gray shading indicates"not applicable."]


8.80 58.20 164.60 6,745.90 8,461.90 10,614.40 8,542.80 110.90 165.80 247.90 170.90

66.90 100.50 151.00 103.60 34.90 59.10 99.90 62.20 1.90 3.50 6.50 3.70

66.90 100.50 151.00 103.60 4,895.10 10,542.00 22,703.40 11,753.20 286.50 661.10 1,525.20 752.20

10,013.50 100.50 151.00 103.60 10,013.50 13,166.10 17,311.30 13,349.70 113.50 190.60 319.90 200.20

66.90 100.50 151.00 103.60 8,768.90 11,962.80 16,320.00 12,178.00 89.20 140.70 221.70 146.10

66.90 100.50 151.00 103.60 126.10 232.10 427.30 248.70 0.00 0.00 0.00 0.00

66.90 100.50 151.00 103.60 8,320.10 13,122.00 20,695.40 13,635.20 329.20 578.60 1,016.90 613.60

66.90 100.50 151.00 103.60 13.70 25.40 47.30 27.30 0.00 0.00 0.00 0.00

66.90 100.50 151.00 103.60 35.30 73.20 151.90 80.80 0.00 0.00 0.00 0.00

66.90 100.50 151.00 103.60 8,764.90 13,132.80 19,677.40 13,535.70 305.00 514.70 868.70 541.40

66.90 100.50 151.00 103.60 4,450.60 7,255.80 11,829.10 7,583.30 39.40 71.10 128.40 75.80

66.90 100.50 151.00 103.60 78.20 152.00 295.50 165.00 0.00 0.00 0.00 0.00

66.90 100.50 151.00 103.60 513.90 891.20 1,545.40 942.50 0.00 0.00 0.00 0.00

66.90 100.50 151.00 103.60 27.80 58.40 122.60 64.70 0.00 0.00 0.00 0.00

66.90 100.50 151.00 103.60 52,788.90 79,134.80 121,830.90 82,169.10 1,275.60 2,326.10 4,335.20 2,503.90

Total undiscovered resourcesTotal Petroleum Systems(TPS)and Assessment Units (AU)

Fieldtype

Oil (MMBO) Gas (BCFG) NGL (MMBNGL)

Oil

Gas

Gas

Gas

Gas

CBG

CBG

CBG

Gas

CBG

CBG

CBG

Gas

Gas

Gas

Gas

Total continuousresources

Mowry Composite TPS

Niobrara TPS

Hilliard–Baxter–Mancos TPS

Mesaverde TPS

Lewis TPS

Lance–Fort Union Composite TPS

Wasatch–Green River Composite TPS

Mesaverde–Lance–Fort Union Composite TPS

Mowry Continuous Gas AU

Niobrara Continuous Oil AU

Niobrara Continuous Gas AU

Almond Continuous Gas AU

Rock Springs–EricsonContinuous Gas AU

Mesaverde–Lance–Fort UnionContinuous Gas AU

Mesaverde Coalbed Gas AU

Mesaverde Coabed Gas AU

Fort Union Coalbed Gas AU

Lewis Continuous Gas AU

Lance–Fort Union Continuous Gas AU

Lance Coalbed Gas AU

Fort Union Coalbed Gas AU

Wasatch–Green RiverContinuous Gas AUWasatch–Green RiverCoalbed Gas AU

Hilliard–Baxter–MancosContinuous Gas AU

Not quantitatively assessed

Not quantitatively assessed

Table 2. Southwestern Wyoming Province assessment results—Continuous oil and gas resources.[Assessment results of undiscovered oil and gas resources by assessment unit. Results shown are fully risked estimates.For gas fields, all liquids are included under the NGL (natural gas liquids) category. Undiscovered gas resources are thesum of nonassociated and associated gas. F95 represents a 95-percent chance of at least the amount tabulated. Otherfractiles are defined similarly. Fractiles are additive under the assumption of perfect positive correlation. MMBO, millionbarrels of oil; BCFG, billion cubic feet of gas; MMBNGL, million barrels of natural gas liquids. Gray shading indicates"not applicable." CBG is coalbed gas]


References Cited

Claypool, G.E., Love, A.H., and Maughan, E.K., 1978, Organic geochemistry, incipient metamorphism, and oil generation in black shale members of Phosphoria Formation, Western Interior United States: American Association of Petroleum Geologists Bulletin, v. 62, no. 1, p. 98–120.

Haskett, G.I., 1959, Niobrara Formation of northwest Colorado, in Haun, J.D., and Weimer, R.J., eds., Symposium on Cretaceous rocks of Colorado and adjacent areas: Rocky Mountain Association of Geologists 11th Field Conference, p. 46–49.

Hughes, W.B., Holba, A.G., and Dzou, L.I.P., 1995, The ratios of dibenzothiophene to phenanthrene and pristane to phytane as indicators of depositional environment and lithology of petroleum source rocks: Geochimica et Cosmochimica Acta, v. 59, p. 3581–3598.

IHS Energy Group, 2001, [includes data current as of December, 2000] PI/Dwights Plus U.S. Production and Well Data: Englewood, Colo., database available from IHS Energy Group, 15 Inverness Way East, D205, Englewood, CO 80112, U.S.A.

Law, B.E., Spencer, C.W., Charpentier, R.R., Crovelli, R.A., Mast, R.F., Dolton, G.L., and Wandrey, C.J., 1989, Estimates of gas resources in overpressured

low-permeability Cretaceous and Tertiary sandstone reservoirs, Greater Green River Basin, Wyoming, Colorado, and Utah, in Eisert, J.L., ed., Gas resources of Wyoming: Wyoming Geological Association Fortieth Field Conference Guidebook, p. 39–61.



Lillis, P.G., Warden, Augusta, and King, J.D., 2003, Petroleum systems of the Uinta and Piceance Basins geochemical characteristics of oil types, in U.S. Geological Survey, Uinta-Piceance Assessment Team, United States, compiler, Petroleum systems and geologic assessment of oil and gas in the Uinta-Piceance province, Utah and Colorado: USGS Digital Data Series DDS–69–B, 25 p.

NRG Associates, 2001, [includes data current as of 1999], The significant oil and gas fields of the United States: Colorado Springs, Colorado, NRG Associates, Inc.; database available from NRG Associates, Inc.; P.O. Box 1655, Colorado

Springs, CO 80901, U.S.A.

Pollastro, R.M., Hill, R.J., Jarvie, D.M., and Henry, M.E., 2003, Assessing undiscovered resources of the Barnett-Paleozoic Total Petroleum System, Bend Arch–Fort Worth Basin Province, Texas: CD-ROM Transactions of the Southwest Section, American Association of Petroleum Geologists Convention, Fort Worth, Texas, American Association of PetroleumGeologists/Datapages, 18 p., one CD–ROM.

Ryder, R.T., 1988, Greater Green River Basin, in Sloss, L.L., ed., Sedimentary cover−North American craton, U.S.: Geological Society of America, The geology of North America, v. D–2, p. 154–165.

Sellers, Carolyn, Fox, Beverly, and Pautz, James 1996, Bartlesville Project Office crude oil analysis user’s guide: U.S. Department of Energy DOE/BC–96/3/SP, 23 p.

Sofer, Zvi, 1984, Stable carbon isotope compositions of crude oils—Applications to source depositional environments and petroleum alteration: American Association of Petroleum Geologists Bulletin, v. 68, p. 31–49.

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