Chapter 2 2005 Geologic Assessment of Undiscovered Oil and …€¦ · Province, Wyoming and Colorado By Thaddeus S. Dyman and Steven M. Condon Volume Title Page Chapter 2 of Petroleum

Chapter 2

2005 Geologic Assessment of Undiscovered Oil and Gas Resources, Hanna, Laramie, and Shirley Basins Province, Wyoming and Colorado

By Thaddeus S. Dyman and Steven M. Condon Volume Title Page

Chapter 2 of Petroleum Systems and Geologic Assessment of Undiscovered Oil and Gas, Hanna, Laramie, and Shirley Basins Province, Wyoming and Colorado

By U.S. Geological Survey Hanna, Laramie, and Shirley Basins Province Assessment Team

U.S. Geological Survey Digital Data Series DDS–69–K

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

U.S. Department of the Interior DIRK KEMPTHORNE, Secretary

U.S. Geological Survey Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2007

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Suggested citation: Dyman, T.S., and Condon, S.M., 2007, 2005 Geologic assessment of undiscovered oil and gas resources, Hanna, Laramie, and Shirley Basins Province, Wyoming and Colorado: U.S. Geological Survey Digital Data Series DDS–69–K, chap. 2, 62 p.

ISBN 1-4113-2020-8

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iii

Contents

Abstract ……………………………………………………………………………………… 1

Introduction …………………………………………………………………………………… 1

Purpose and Scope …………………………………………………………………… 1

Data Sources ………………………………………………………………………… 7

Acknowledgments …………………………………………………………………… 7

Structural Setting …………………………………………………………………………… 8

Stratigraphy…………………………………………………………………………………… 10

Production Characteristics …………………………………………………………………… 20

Assessment of Oil and Gas Resources ……………………………………………………… 23

System for Numbering Assessed Resources ………………………………………… 23

Links to Data Input Forms and Graphical Data ……………………………………… 24

Data Input Forms ………………………………………………………………… 24

Graphs of Exploration and Discovery Data for Conventional Assessment Units … 24

Phosphoria Total Petroleum System ………………………………………………………… 24

Source Rocks ………………………………………………………………………… 24

Source Rock Thermal Maturity ……………………………………………………… 27

Hydrocarbon Migration ……………………………………………………………… 27

Reservoir Rocks ……………………………………………………………………… 28

Traps and Seals ……………………………………………………………………… 28

Tensleep-Casper Conventional Oil and Gas Assessment Unit (50300101) …………… 29

Estimated Resources ……………………………………………………………… 29

Mowry-Hanna Composite Total Petroleum System …………………………………………… 31

Source Rocks ………………………………………………………………………… 31



Reservoir Rocks ……………………………………………………………………… 42

Sundance Formation ……………………………………………………………… 42

Cloverly Formation ………………………………………………………………… 43

Muddy Sandstone Member of Thermopolis Shale………………………………… 43

Frontier Formation ………………………………………………………………… 43

Mesaverde Group ………………………………………………………………… 44

Lewis Shale ……………………………………………………………………… 44

Medicine Bow, Ferris, and Hanna Formations …………………………………… 45

Traps and Seals ……………………………………………………………………… 45

Mesozoic-Cenozoic Conventional Oil and Gas Assessment Unit (50300201) ………… 46

Estimated Resources ……………………………………………………………… 46

Hanna Basin Continuous Gas Assessment Unit (50300261) …………………………… 46

Niobrara Total Petroleum System …………………………………………………………… 46

Source Rocks ………………………………………………………………………… 49



iv

ReservoirRocks ……………………………………………………………………… 50 TrapsandSeals ……………………………………………………………………… 50 NiobraraContinuousOilAssessmentUnit(50300361)………………………………… 51 EstimatedResources …………………………………………………………… 51 NiobraraBiogenicGasTotalPetroleumSystem……………………………………………… 51 NiobraraBiogenicGasAssessmentUnit(50300461) ………………………………… 53 Hanna-MesaverdeCoalbedGasTotalPetroleumSystem …………………………………… 53 SourceRocks ………………………………………………………………………… 53 SourceRockThermalMaturity ……………………………………………………… 53 HydrocarbonMigration ……………………………………………………………… 55 ReservoirRocks ……………………………………………………………………… 56 TrapsandSeals ……………………………………………………………………… 56 MedicineBow–Ferris–HannaCoalbedGasAssessmentUnit(50300581) …………… 56 MesaverdeCoalbedGasAssessmentUnit(50300582) ……………………………… 56 ReferencesCited……………………………………………………………………………… 56

Figures 1. MapshowingtheHanna,Laramie,andShirleyBasinsProvince,majortopographicand geologicfeatures,subbasins,andborderingpetroleumprovinces………………… 3 2. ColumnarsectionofstratigraphicunitsintheHanna,Laramie,andShirleyBasins Province …………………………………………………………………………… 5 3. MapofpartoftheHanna,Laramie,andShirleyBasinsProvinceshowingmajor tectonicfeatures…………………………………………………………………… 9 4. CrosssectionshowingtheArlingtonthrustandtheCooperCovefield …………… 10 5. Generalizedcrosssectionshowingtrianglezonedevelopmentforstructuresinthe HannaandLaramieBasins ………………………………………………………… 11

6.–19. PhotographsofrockunitsintheHannaBasin ……………………………………… 11 6. TensleepSandstoneoutcropinnorthernpartofHannaBasin ……………………… 11 7. GooseEggFormationoutcropinnorthernpartofHannaBasin……………………… 12 8. BasalconglomerateofCloverlyFormationinnorthernpartofHannaBasin………… 13 9. CloverlyFormation,ThermopolisShale,andMuddySandstoneinwesternpartof HannaBasin………………………………………………………………………… 15

10. MowryShaleinwesternpartofHannaBasin ……………………………………… 15 11. FrontierFormationalongUnionPacificRailroadincentralpartofHannaBasin …… 16 12. NiobraraFormationatSeparationFlatsinwesternpartofHannaBasin …………… 16 13. SteeleShaleatSeparationFlatsinwesternpartofHannaBasin…………………… 17 14. HaystackMountainsFormationinwesternpartofHannaBasin …………………… 18 15. PineRidgeSandstoneinwesternpartofHannaBasin……………………………… 18 16. LowerpartofLewisShaleinwesternpartofHannaBasin ………………………… 19 17. SandstoneinMedicineBowFormationinnorthernpartofHannaBasin…………… 19 18. FerrisFormationincentralpartofHannaBasin …………………………………… 20 19. HannaFormationincentralpartofHannaBasin …………………………………… 21 20. MapofsouthwesternpartoftheHanna,Laramie,andShirleyBasinsProvince showinglocationsofoilandgasfieldsandselectedpilotprojectsandwells …… 22

v

21. Map of Phosphoria Total Petroleum System showing limit of distribution of Phosphoria

Formation source rocks ……………………………………………………………… 25

22. Events chart for Phosphoria Total Petroleum System in the Hanna, Laramie, and Shirley

Basins Province ……………………………………………………………………… 26

23. Diagram of total sulfur in weight percent versus API gravity for oil samples in the Hanna,

Laramie, and Shirley Basins Province ………………………………………………… 26

24. Map showing extent of the Tensleep-Casper Conventional Oil and Gas Assessment

Unit …………………………………………………………………………………… 30

25. Map of the Mowry-Hanna Composite Total Petroleum System showing the distribution of

Mowry-Hanna source and reservoir rocks in the Hanna, Laramie, and Shirley Basins

Province ……………………………………………………………………………… 32

26. Events chart for the Mowry-Hanna Composite Total Petroleum System in the Hanna,

Laramie, and Shirley Basins Province ………………………………………………… 33

27. Regional distribution of total organic carbon in the Mowry Shale in the northern Rocky

Mountains and Great Plains …………………………………………………………… 34

28. Van Krevelen diagram showing oxygen index versus hydrogen index of samples

collected in this study ………………………………………………………………… 34

29. Diagrams of transformation ratio versus time for the Frontier-Hanna Formations in the

Hanna Basin …………………………………………………………………………… 37

30. Cross section showing one-dimensional burial history model with transformation ratio

overlay for generation of oil near the center of Hanna Basin ………………………… 38


overlay for oil-to-gas cracking near the center of Hanna Basin ……………………… 38


overlay for generation of oil along the southern margin of Hanna Basin ……………… 39


overlay for generation of oil in Laramie Basin and Shirley Basin ……………………… 39

34. Map showing extent of Mesozoic-Cenozoic Conventional Oil and Gas Assessment Unit … 47

35. Map of Niobrara Total Petroleum System showing distribution of Niobrara Formation

source and reservoir rocks in Hanna, Laramie, and Shirley Basins Province ………… 48

36. Events chart for the Niobrara Total Petroleum System in the Hanna, Laramie, and

Shirley Basins Province ……………………………………………………………… 49

37. Map showing extent of the Niobrara Continuous Oil Assessment Unit ………………… 52

38. Map showing extent of the Niobrara Formation in the Laramie and Shirley Basins …… 54

39. Map showing outcrops of the Mesaverde Group and the extent of the Medicine Bow

Formation ……………………………………………………………………………… 55

vi

Tables 1. Characteristics of discrete and continuous oil and gas accumulations ………………… 4 2. Assessment results summary—Hanna, Laramie, and Shirley Basins Province (5030)…… 6 3. Oil and gas production from formations that compose assessment units for significant

fields in this study ……………………………………………………………………… 7 4. Depth ranges of formation tops cut by wells in the Hanna, Laramie, and Shirley Basins

Province ………………………………………………………………………………… 31 5. TOC and Ro summary of new samples analyzed in this study …………………………… 35 6. Burial history input parameters for wells used in the Hanna, Laramie, and Shirley Basins

Province ………………………………………………………………………………… 40

Abbreviations Used in This Report AU assessmentunit BCFG billioncubicfeetofnaturalgas BWPD barrelsofwaterperday CFGPD cubicfeetofgasperday MMBNGL millionbarrelsofnaturalgasliquids MMBO millionbarrelsofoil MMBOE millionbarrelsofoilequivalent Ro vitrinitereflectance TPS totalpetroleumsystem USGS U.S.GeologicalSurvey ft foot,feet Ga Giga-annum;billionsofyearsago Ma Mega-annum;millionsofyearsago mi mile,miles m.y. millionsofyears

Edited by Mary-Margaret Coates, Contractor, ATA Layout by Wayne L. Husband, Contractor, ATA

2005 Geologic Assessment of Undiscovered Oil and Gas Resources, Hanna, Laramie, and Shirley Basins Province, Wyoming and Colorado By Thaddeus S. Dyman and Steven M. Condon

Abstract

UndiscoveredoilandgasresourcesoftheHanna, Laramie,andShirleyBasinsProvince,Wyomingand Colorado,wereassessedin2005aspartoftheU.S.Geological SurveyNationalOilandGasAssessmentProject.The provincecontainsfivetotalpetroleumsystems:Phosphoria, Mowry-HannaComposite,Niobrara,NiobraraBiogenicGas, andHanna-MesaverdeCoalbedGas.Reservoirsasoldas thePennsylvanianTensleepSandstoneandasyoungasthe Paleocene-EoceneHannaFormationcomposethestratigraphic sequence.

Withinthesetotalpetroleumsystems,primarysource rocksare(1)phosphaticshalesofthePermianPhosphoria Formation;(2)shalesandcalcareousmudstonesofthe CretaceousThermopolisandMowryShales,Frontierand NiobraraFormations,andSteeleShale;and(3)coalsand mudstonesoftheUpperCretaceousMesaverdeGroupand MedicineBowFormation,UpperCretaceousandPaleocene FerrisFormation,andPaleoceneandEoceneHanna Formation.LacustrinemudstonesoftheFerrisandHanna Formationsmaybeminorsourcerocksinthecentralpartof theHannaBasin.

Oilandgasweregeneratedineconomicquantitiesin differentpartsoftheprovinceatdifferenttimes,primarily relatingtovariationsindepthofburial.Dataforthe Thermopolis-Mowryintervalindicatethat(1)intheHanna Basincenter,peakoilgenerationoccurredabout68million yearsago(Ma)andoil-to-gascrackingoccurredabout 60Ma;(2)alongthesouthmarginoftheHannaBasin, peakoilgenerationalsooccurredatabout68Ma,butno appreciableoil-to-gascrackinghasoccurredtodate;and (3)intheLaramieandShirleyBasins,sourcerocksdidnot reachthermalmaturitiesnecessaryforsignificantoilandgas generation.Mostoftheoilandgascurrentlytrappedinfields intheLaramieBasinmigratedintolocalreservoirsfromthe HannaBasinpriortoLaramidestructuralpartitioning.

Oilandgasmigratedfromsourcerocksintoreservoirs throughasystemoffaultsandfracturesthatarepervasive throughouttheareaandupdipalongbeddingplanesand

withinsandstoneunits.Trappingmechanismsinclude structuresformedinitiallyinassociationwiththelate PaleozoicAncestralRockyMountainsandlaterduringthe LateCretaceoustoearlyTertiaryLaramideorogeny.Structures maybethrustfaults,faultedanticlines,trianglezones,or pop-upstructures.Stratigraphicpinchoutsandcombination stratigraphic-structuraltrapsarealsocommon,especially wheresedimentaryfacieschangeinreservoirrocks.Seals consistofinterbeddedshalesandmudstonesanddiagenetic cements.InsomeinstancesoilfromolderlatePaleozoic structuraltrapsremigratedintoyoungerLaramidetraps.

SevenassessmentunitswereidentifiedfortheHanna, Laramie,andShirleyBasinsProvince:(1)Tensleep-Casper ConventionalOilandGas(50300101),(2)Mesozoic-CenozoicConventionalOilandGas(50300201),(3)Hanna BasinContinuousGas(50300261),(4)NiobraraContinuous Oil(50300361),(5)NiobraraBiogenicGas(50300461),(6) MedicineBow-Ferris-HannaCoalbedGas(50300581),and (7)MesaverdeCoalbedGas(50300582).Onlythreeofthese assessmentunits(Tensleep-CasperConventionalOilandGas, Mesozoic-CenozoicConventionalOilandGas,andNiobrara ContinuousOil)werequantitativelyassessed;lackofdata precludedassessmentoftheothers.

Totalmeanestimatedundiscoveredconventionaland continuousresourcesinthesethreeassessmentunitsare94 millionbarrelsofoil,298billioncubicfeetofnaturalgas,and 14millionbarrelsofnaturalgasliquids.

Introduction

Purpose and Scope

Thepurposeofthisreportistopresenttheresultsofa U.S.GeologicalSurvey(USGS)assessmentofundiscovered

2 Undiscovered Oil and Gas–Hanna, Laramie, and Shirley Basins Province, Wyoming and Colorado

oilandgasresourcesintheHanna,Laramie,andShirley BasinsProvinceofsouth-centralWyomingandnorthern Colorado(fig.1).Theprovincewasaffectedbytwomajor crustalprocesses:bythedevelopmentofanearlyMesozoic forelandbasinthatproducedalarge,asymmetricdepositional troughintheWesternInterioroftheUnitedStatesandCanada andbytheLateCretaceoustoearlyTertiaryLaramideorogeny thatbrokeuptheintracontinentaldepositionalbasinand formedavarietyofdiscretestructuralbasinsandbordering uplifts.TheprovincecontainstheHanna,Laramie,andShirley Laramidestructuralbasins(fig.1).

TheHanna,Laramie,andShirleyBasinsProvince extendsfromtheRawlinsuplifteastwardthroughtheHanna, Laramie,andShirleyBasinstotheLaramieMountains.Onthe northandnorthwest,itisboundedbytheSweetwateruplift andtheWindRiverBasin;onthesouth,itisboundedbythe MedicineBowMountainsandSierraMadreuplift(fig.1). Surroundingpetroleumprovinceshavealsobeenassessedfor oilandgas—theWindRiverBasinProvincetothenorthwest, theSouthwesternWyomingProvincetothewest,andthe ParkBasinsProvincetothesouth(fig.1).Thisprovince includesmostofCarbonandAlbanyCounties,Wyoming, andthenorthernmostpartofLarimerCounty,Colorado.Its areaencompassesmorethan4millionsquaremiles.Subbasin names,suchasPassCreek,Kindt,Carbon,andCooperLake, arecommonlyusedtoidentifyspecificgeologicareaswithin theprovince(fig.1).

Variousoil-andgas-producingregionsoftheUnited StatesarebeingreevaluatedasafollowuptotheUSGS’s1995 NationalAssessmentofUnitedStatesOilandGasResources (Gautierandothers,1996);theresultsofthesestudiesare availableathttp://energy.cr.usgs.gov/oilgas/noga/.Inthe 1995nationalassessment,theHanna,Laramie,andShirley BasinsProvincewascombinedwiththeSouthwestWyoming Province(Gautierandothers,1996;Law,1996).Becausethe Hanna,Laramie,andShirleyBasinsProvincehadnotbeen previouslyassessedseparatelybytheUSGS,estimatesof undiscoveredresourcesfromthecurrentassessmentcannot bedirectlycomparedwiththoseofpreviousUSGSestimates. Law(1996)identifiedandassessedplaysthatlayinallorpart ofthecombinedGreenRiver,Hanna,Laramie,andShirley Basins.AnewassessmentoftheGreaterGreenRiverBasin wasrecentlycompletedbytheUSGS(U.S.GeologicalSurvey SouthwesternWyomingAssessmentTeam,2005).

AnotherdifferencebetweentheU.S.GeologicalSurvey’s 1995nationalassessmentandthisassessmentistheuseofthe petroleumsystemmodel(MagoonandDow,1994).Atotal petroleumsystem(TPS)isdefinedas“allgeneticallyrelated petroleumthatoccurs,orisestimatedtooccur,inshowsand accumulations,bothdiscoveredandundiscovered,whichhave beengeneratedbyapodorbycloselyrelatedpodsofmature sourcerock,”anditconsistsof“essentialgeologicelements [that]controlthefundamentalprocessesofgeneration, expulsion,migration,entrapment,andpreservationof petroleumwithinthetotalpetroleumsystem”(Klett,2004).It consistsofallareastowhichhydrocarbonsfromrelatedsource

rockspotentiallymigratedaftergenerationandexpulsion,and itiscommonlydefinedbythegeographicextentofsource andreservoirrocks.Acompositetotalpetroleumsystemisa mappableentitythatisusedwhenmorethanonesourcerock haschargedtheaccumulations(Klett,2004).

Assessmentunits(AUs)havereplacedplaysasthebasic unitofassessment.Playswereidentifiedprimarilybyusing similaritiesinpetroleumreservoirs,andsourcerockswere notemphasized.Anassessmentunitis“amappablepartofa totalpetroleumsysteminwhichdiscoveredandundiscovered oilandgasaccumulationsconstituteasinglerelatively homogeneouspopulationsuchthatthemethodologyof resourceassessmentisapplicable”(Klett,2004).Itisathreedimensionalentity,consistingofacontiguousgeographicarea andoneormoregeologicformations.TheuseofAUsrather thanplaysdoesnotnecessarilyresultindifferencesinassessed volumesofundiscoveredresources,butapplyingtheconcept ofthetotalpetroleumsystemprovidesaunifyingframework foridentifyingandanalyzingaccumulations(Klett,2004).

AsoneaspectofourstudyoftheHanna,Laramie,and ShirleyBasinsprovince,welookedatthecharacteristics ofknownandpotentialoilorgasaccumulationsto determineiftheyarediscrete(conventional)orcontinuous (unconventional)asclassifiedbySchmoker(1996),a distinctionthatisbasedongeologicparametersratherthan ongovernmentregulationsrelatingtoreservoirclassification. Itisimportanttodistinguishbetweenthetwotypesof accumulationbecausedifferentmethodsareusedforeach typetoestimateundiscoveredresources.Severalfeatures distinguishtheend-memberaccumulationtypes,although aprobablecontinuumbetweenthetypescaninsomecases makeclassificationdifficult.Twolistsofsuchdistinguishing features(table1),weredrawnmainlyfromSpencer(1989), Schmoker(1996),Wilsonandothers(2001),andLaw(2002).

OilandgasfieldsintheHanna,Laramie,andShirley BasinsProvincewereevaluatedwithrespecttothe characteristicslistedintable1.Mostexistingfields,which lieonthemarginsoftheLaramieandHannaBasins,have characteristicsthatclearlyclassifythemasconventional. TwosmallNiobraraoilfieldsonthesouthflankoftheHanna BasinweremodeledaftercontinuousNiobraraoilfields intheSouthwesternWyomingProvince,andacontinuous assessmentunitwasdefinedandquantitativelyassessedfor Niobraraoil.Gasfieldshavenotyetbeendiscoveredinthe deepcentralHannaBasin,andfewdeepwellshavebeen drilledthere.Asaresult,adeep(>20,000foot(ft))basincentergasAUwasdefinedintheHannaBasinbutwasnot assessed.AnevaluationofthefewdeepwellsintheHanna BasinwasbasedondatafromWilsonandothers(2001).

Thegeochemistryofoilsamplescollectedfrom Pennsylvanian,Jurassic,andCretaceousreservoirsinthe LaramieBasinindicatesthatthesourceofsomefieldswasthe PermianPhosphoriaFormation,andthesourceofotherswas marineshalesofCretaceousandlowerTertiaryformations (fig.2)(M.D.LewanandP.G.Lillis,USGS,writtencommun., 2004).Rock-Evalpyrolysisdataindicatesource-rockpotential

Geologic Assessment—Undiscovered Oil and Gas—Hanna, Laramie, and Shirley Basins Province, Wyoming and Colorado �

107° 106°

42°

41°

!(

!(

!(

!(

Hanna

Rawlins

Laramie

ROUTT LARIMERJACKSON

CARBON ALBANY

NATRONA

CONVERSE

17-2

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Figure 4 cross section

0 10 205 MILES

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Basin

Laramie Basin

Hanna Basin Rawlins Uplift

Sierra Madre

Medicine Bow Mountains

Laramie Mountains

Wyoming Colorado

Kindt Basin

CLBCB

PCB

P B P

S W P

W R B P P R B P

Cheyenn

e belt

S W P

Wyoming

Figure 1. Hanna, Laramie, and Shirley Basins Province (outlined in red), major topographic and geologic features, subbasins, and bordering petroleum provinces. Contours are drawn on the top of Precambrian basement in feet relative to sea level (modified from Black-stone, 1989). Thick gray lines are major faults. Red patterned areas are outcrops of Precambrian rocks from Green (1992) and Green and Drouillard (1994). Green lines are seismic profiles used to interpret subsurface structure for this assessment. CB, Carbon Basin; CLB, Cooper Lake Basin; PBP, Park Basins Province; PCB, Pass Creek Basin; PRBP, Powder River Basin Province; SWP, Southwestern Wyoming Province; WRBP, Wind River Basin Province. Green triangle—Anadarko Durante 17–2 well. Green filled circles—BA, Coastal Bates Creek Cattle 1–18–28–79 well; BR, Brinkerhoff Hanna Unit No. 1 well; BU, Buttes Federal 1–18 well; PC, Humble Pass Creek Ridge No. 1 well. Location of the Cheyenne belt from Stone (1995).

� Undiscovered Oil and Gas–Hanna, Laramie, and Shirley Basins Province, Wyoming and Colorado

Table 1. Characteristics of discrete and continuous oil and gas accumulations. [DistinguishingfeaturesfromSpencer(1989),Schmoker(1996),Wilsonandothers(2001),andLaw(2002)]

Characteristic Discrete (conventional)

Type of accumulation

Continuous (unconventional)

Sourcerocks

Maturity

Reservoirrocks

Potentiallydistantfromreservoirs

Accumulationscanoccurinimmaturerocks becauseofmigration

Sourcerocksnearreservoirs;migration distancescommonlyshort Topsofaccumulationscommonlywithina narrowvitrinitereflectance(Ro)rangeof 0.75–0.9percent

Sealsortraps Well-definedstratigraphicandstructuraltraps Lacktraditionalsealsortraps

Porosity Goodreservoirporosity Lowreservoirporosity,commonlylessthan13 percent

Permeability Goodreservoirpermeability Lowreservoirpermeability(

5 Geologic Assessment—Undiscovered Oil and Gas—Hanna, Laramie, and Shirley Basins Province, Wyoming and Colorado

FORMATION/GROUP NAMES

HANNA, LARAMIE ERA PERIOD EPOCH AND SHIRLEY BASINS

NIOBRARA Fm SAGE BREAKS Sh

CEN

OZOI

CM

ESOZ

OIC

PALE

OZOI

CPR

ECAM

BRIA

N

QUATERNARY

TERTIARY

CRETACEOUS

PALEOCENE

EOCENE

OLIGOCENE

MIOCENE

PLIOCENE

PLEISTOCENE

HOLOCENE

JURASSIC

LOWER CRETACEOUS

UPPER CRETACEOUS

TRIASSIC

PERMIAN

PENNSYLVANIAN

MISSISSIPPIAN

DEVONIAN

SILURIAN

ORDOVICIAN

CAMBRIAN

PROTEROZOIC

ARCHEAN

METAMORPHIC

AND

INTRUSIVE

ROCKS

Ar Wh

Wb WIND RIVER Fm

HANNA Fm

FERRIS Fm

LEWIS Sh

STEELE Sh

MEDICINE BOW Fm

Mv

Gp

HM, AR

PR, AL

FRONTIER Fm

MOWRY Sh

THERMOPOLIS Sh

DAKOTA Fm LAKOTA Fm

MORRISON Fm

CLOV

ERLY

Fm

SUN

DAN

CEFm

CH

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Gp

UPPER SUNDANCE

BASAL SUNDANCE

LOWER SUNDANCE

JELM Fm ALCOVA Ls

RED PEAK Fm

GOOSE EGG Fm

TENSLEEP Ss-CASPER Fm

EL DS FL GS ML OS

AMSDEN Fm FOUNTAIN

Fm

Md

Fh

Undivided

Undivided

PR

RR

Upper shale mbr

Muddy Sandstone Mbr

Skull Creek Sh Mbr

Figure 2. Columnar section of stratigraphic units in the Hanna, Laramie, and Shirley Basins Province (modified from Harshman, 1972; Love and others, 1987; and Stone, 1995). Fm, Formation; Gp, Group; Ls, Limestone; Mbr, Member; Sh, Shale; Ss, Sandsonte. Fh, Flathead Sandstone; Md, Madison Limestone; OS, Opeche Shale Member; ML, Minnekahta Limestone Member; GS, Glendo Shale Member; FL, Forelle Limestone Member; DS, Difficulty Shale Member; EL, Ervay Limestone Member; MV Gp, Mesaverde Group; HM, Haystack Mountains Formation; AR, Allen Ridge Formation; PR, Pine Ridge Sandstone; AL, Almond Formation; RR, Rock River Formation; Wb, Wagon Bed Formation; Wh, White River Group; Ar, Arikaree Formation.

Total petroleum Total undiscovered resources system (TPS) MAS Prob. Oil (MMBO) Gas (BCFG) NGL (MBNGL)

and assessment (0-1) F95 F50 F5 Mean F95 F50 F5 Mean F95 F50 F5 Mean unit (AU)

Conventional oil and gas resources Phosphoria TPS

Tensleep–Casper Conventional Oil and Gas AU Oil accums. 0.5 6 19 39 20 6 18 42 20 190 650 1,590 740 1

Gas accums. 3.0 16 47 101 52 460 1,380 3,220 1,550

Total 1 6 19 39 20 22 66 143 72 650 2,030 4,810 2,290

Mowry–Hanna Composite TPS Mesozoic–Cenozoic Conventional Oil and Gas AU

Oil accums. 0.5 7 31 79 36 17 75 208 89 1,620 7,320 21,610 8,910 1 Gas accums. 3.0 25 99 278 118 460 1,920 5,770 2,360

Total 1 7 31 79 36 42 174 486 207 2,080 9,240 27,380 11,270

Total undiscovered conventional oil and gas resources Oil accums. 13 50 119 56 23 94 250 110 1,810 7,970 23,200 9,650

Gas accums. 42 146 379 170 920 3,300 8,990 3,910 Total 13 50 119 56 64 240 629 279 2,730 11,270 32,190 13,560

Continuous oil and gas resources Mowry-Hanna Composite TPS

Hanna Basin Continuous Gas AU—Not quantitatively assessed

Niobrara TPSNiobrara Continuous Oil AU

Oil accums. 0.5 14 33 76 38 6 16 43 19 0 0 0 0 1 Gas accums. 3.0

Total 1 14 33 76 38 6 16 43 19 0 0 0 0

Niobrara Biogenic Gas TPSNiobrara Biogenic Gas AU—Not quantitatively assessed

Mesaverde–Hanna Coalbed Gas TPSMedicine Bow–Ferris–Hanna Coalbed Gas AU—Not quantitatively assessed Mesaverde Coalbed Gas AU—Not quantitatively assessed

Total undiscovered continuous oil and gas resources

Oil accums. 14 33 76 38 6 16 43 19 0 0 0 0 Gas accums.

Total 14 33 76 38 6 16 43 19 0 0 0 0

Total undiscovered oil and gas resources

Oil accums. 28 83 195 94 29 110 292 129 1,810 7,970 23,200 9,650 Gas accums. 42 146 379 170 920 3,300 8,990 3,910

Total 28 83 195 94 70 256 671 298 2,730 11,270 32,190 13,560


Table 2. Hanna, Laramie, and Shirley Basins Province assessment results. [MMBO,millionbarrelsofoil;BCFG,billioncubicfeetofgas;MBNGL,thousandbarrelsofnaturalgasliquids;MAS,minimumaccumulationsize assessed(MMBOforoilaccumulations,BCFGforgasaccumulations);Prob.,probability(includingbothgeologicandaccessibilityprobabilities)ofatleast oneaccumulationequaltoorgreaterthantheMASor,forcontinuous-typeresources,atleastoneadditionalcellequaltoorgreaterthantheminimumestimatedultimaterecovery;Accums.,accumulations.Resultsshownarefullyriskedestimates.Forgasaccumulations,allliquidsareincludedasNGL(natural gasliquids).F95representsa95percentchanceofatleasttheamounttabulated;otherfractilesaredefinedsimilarly.Asinglemajorcommodityandits coproductswereassessedforcontinuous-typeassessmentunits.Fractilesareadditiveundertheassumptionofperfectpositivecorrelation.Resourcetotals maynotbeequaltothesumsofthefractilesormeansbecausenumbershavebeenindependentlyrounded.Totalsreflectroundingtonearestwholenumber. Shadingindicatesnotapplicable]


Table �. Oil and gas production from formations that compose assessment units for significant fields in this study. Data from Hollis and Potter (1984) and IHS Energy Group (2004a). [Meandepth,averagedepthofperforationsforthereservoirinthelistedfield(*,perforationdatanotavailable;averagetotaldepth calculated);MMBO,millionsofbarrelsofoil;BCFG,billionsofcubicfeetofgas(gasvolumeslessthan0.1BCFGroundedtozero)]

Discovery Mean Oil GasPrimary reservoir Field name year depth (MMBO) (BCFG)(ft) Tensleep-CasperConventionalOilandGasAssessmentUnit(50300101) Tensleep AllenLakeEast 1950 3,944 0.6 0 Tensleep BigMedicineBow 1948 *6,838 0.2 0.1 Tensleep Herrick(Dome) 1947 3,654 1.1 0.1 Tensleep LittleLaramie 1948 3,740 1.3 0.1 Tensleep Quealy(Dome) 1947 5,414 5.3 0

Mesozoic-CenozoicConventionalOilandGasAssessmentUnit(50300201) Sundance, Dakota Big Medicine Bow 1935 5,019 7.5 11.1 Dakota, Muddy, Shannon Cooper Cove 1944 4,793 1.9 0.7 Lakota, Dakota, Muddy Diamond Ranch 1957 5,410 1.1 0.2 Muddy, Shannon Dutton Creek 1926 4,775 0.3 0.2 Sundance Elk Mountain 1957 6,520 0.9 0 Sundance, Dakota Quealy (Dome) 1934 3,324 5.3 0 Lakota-Dakota, Muddy, Rex Lake 1923 2,726 1.0 0 Shannon. Sundance through Frontier Rock River 1918 3,021 50.0 11.5 Lakota, Muddy Seven Mile 1947 5,957 0.6 0

TOTALPRODUCTION 77.1 24.0

Data Sources

Primarydatasourcesforourassessmentarecommercial databasesfromIHSEnergyGroup(2004a,b).Wellproduction andcompletiondataarecurrentasofFebruaryandApril2004, respectively.Productionandcompletiondataareavailable fornearly600leasesfortheunitsassessedintheprovince, anddatasuchasformationtops,drill-stemtests,andinitial productiontestsforsome1,350wellshavebeenreported.

Anotherprimarysourceofgasandoilfieldandreservoir datawasNRGAssociates(2003),whichprovidedinformation onthedatesofdiscoveryandsizesofgasandoilfields,trends ofincreasingordecreasingfieldvolumes,gas-oilratios,and APIoil-gravityvalues(seechapterbyKlettandLe(2007) (thisCD-ROM).Manypublishedpapersonthestructure, stratigraphy,andpetroleumgeologyoftheregion,aswellas discussionswithpetroleumindustrypersonnel,alsoprovided importantinformation.

Acknowledgments

WethankDavidDudleyofDudleyandAssociates fordiscussingcoalbedgasintheHannaBasin.Thomas GriffithandDouglasHazlettofAnadarkoPetroleum,and

RogerMatson,consultingpetroleumgeologist,provided insightsintodeepHannaBasinexploration.DonaldStone, consultingpetroleumgeologist,wasespeciallyhelpfulin identifyingstructuralrelationsintheLaramieBasin.E. AllenMerewetherandWilliamPerry,Jr.,providedvaluable informationonthestratigraphicandstructuralgeologyof theregion.WeappreciatethehelpofMichaelLewan,Paul Lillis,andMarkPawlewicz(USGS)fortheirworkonoil sourcerocks,forgeneratingburialhistoryplotsforwellsin thestudyarea,andfordiscussionsthathelpedtoresolvesome ofthecomplexissuesregardinghydrocarbonsourcerocks. TroyCookclarifiedthenatureofseveralgasaccumulations intheHannaBasinbyusingproductioncharacteristics.We thanktheassessmentteamofChristopherSchenk,Timothy Klett,RonaldCharpentier,TroyCook,RichardPollastro, andThomasAhlbrandt,whohelpedguideouranalysisand calculatedthefinalresourceassessmentnumbers.USGS contractorsChristopherAndersonsupervisedgeographic informationsystemprocessingandpreparedworkingmaps, andWayneHusbandpreparedfiguresandformattedthefinal report.LawrenceAnna,JamesOtton,DouglasNichols,and WilliamKeeferreviewedthemanuscript.


Structural Setting

TheHanna,Laramie,andShirleyBasinsProvince experiencedacomplexstructuralhistoryhighlightedbymajor tectoniceventsinthePrecambrian,latePaleozoic,andLate CretaceoustoearlyTertiary.Thesetectoniceventsandstructural styleshavebeendescribedindetailbymanyinvestigators,such asBlackstone(1953,1965,1975,1983,1991,1993,1994, 1996),McGookeyandothers(1972),Stone(1984,1995,2002, 2005),KaplanandSkeen(1985),MerewetherandCobban (1985),Hansen(1986),LeFebre(1988),LillegravenandSnoke (1996),PerryandFlores(1997),Secord(1998),Wroblewski (2003),andLillegravenandothers(2004).Abriefsummary ofthestructuralhistoryoftheregionispresentedhere,drawn largelyfromthesepapersandothersthatarecitedbelow.

Regionalstructuresthatwerecreatedwithinandadjacent totheprovinceinPrecambriantimealsoinfluencedlater tectonics.TheCheyennebeltofStone(1995),alsoknown astheWyominglineament(Ransome,1915;Blackstone, 1953)ortheSybillelineament(MaughanandPerry,1983), trendsfromtheSierraMadreandMedicineBowMountains northeastwardthroughtheLaramieMountains(fig.1).The featurehasbeeninterpretedasasuturezoneofmyloniticand cataclasticrocksthatseparatestheWyomingandColorado basementcrustalterranes.Rocksnorthofthisboundaryare Archeaninage(greaterthan1.8billionyearsold(Ga)),whereas rockssouthoftheboundaryareProterozoicinage(lessthan 1.8Ga)(Simsandothers,2005).Thissuturezoneisevidence ofacollisionbetweenthepaleo-Proterozoicarcterraneofthe ColoradoprovincewithArcheancratonicrocksoftheWyoming province.Thecollisionoccurredabout1.8Gaanddeformed andmetamorphosedrocksonbothsidesofthesuture(Sims andothers,2005).Thepresenceofnumerousfoldsandfaults inyoungerrockswithintheareaoftheCheyennebeltindicates recurrentstructuralactivityduringthePhanerozoic.Within theLaramieBasininparticular,laterLaramidedeformation followstheestablishednortheast-directedtrendoftheearlier Precambrianstructures.

MaughanandPerry(1983)describedasystemoflinear structuralelementsinthenorthernRockyMountainregionthat canbeidentifiedintheHanna,Laramie,andShirleyBasins Province.Theprovinceliesattheintersectionofsixofthese featuresthatmayhavehadtheiroriginsinthePrecambrian; thesefeaturesaffectedsedimentarydepositionalpatternsand faciesdevelopmentduringthePaleozoicandearlyMesozoic (Blackstone,1993).

Asecondepisodeofregionaldeformationoccurredduring thelatePaleozoic.ThesupercontinentPangeacoalescedduring thePennsylvanianandPermianPeriodsandcausedacollision betweentheAfrican,SouthAmerican,andNorthAmerican plates.ThiscollisiondeformedPaleozoicrocksoftheOuachita orogenicbeltandcausedcratonicdeformationasfarnorthas ColoradoandWyomingthatculminatedindevelopmentofthe AncestralRockyMountains(Kluth,1986).

TheaxisoftheAncestralRockyMountainsextended

northwestwardfromtheDenver,Colo.,areaintosouth-central Wyomingobliquetothenorth-southaxisofthepresent-day FrontRangeofColoradoandWyoming.Theancestralfeature wascomposedofaseriesoftiltedandrotatedfaultblocks thatsteppeddownwardalongitsnortheastmarginintoabroad depositionaltroughofmarineandnonmarinesedimentsin southeasternWyoming(MaughanandAhlbrandt,1985).This deformationisreflectedinthePermianthrust-foldcomplex, arotatedblockofnorth-tonortheast-trendingthrust-faulted anticlineslyingnorthoftheCheyennebelt(Stone,1995). Someoftheseanticlinesareassociatedwithoilfieldsinthe LaramieBasinandhavebeenwelldocumentedonseismic profiles.Seismicdatashowthatthrustfaultsterminateinthe PermianGooseEggFormation,whichwasdepositedduring developmentofthethrustfaults(Stone,1995).

Thethirdandmostprominentdeformationepisodeisthe LaramideorogenyofLateCretaceoustoearlyTertiaryage (DickinsonandSnyder,1978;Dickinsonandothers,1988). Commonly,Laramidestructuressothoroughlyoverprinted earlierstructuresthatmanybecamehiddenordifficultto recognize.Today,theHanna,Laramie,andShirleyBasins aredistinctstructuralbasins.PriortotheLaramide,however, theywerepartofabroadforelandbasinthatincludedthe entireHanna,Laramie,andShirleyBasinsProvinceandhad contiguouseastward-flowingfluvialsystems.Thestructural basinswereformedinthelatePaleoceneinconjunctionwith thedevelopmentofbasement-coredupliftstothewest(Rawlins uplift)andeast(FlatTopandSimpsonRidgeanticlines,fig. 3)(Lillegravenandothers,2004).AccordingtoWroblewski (2003),theHannaandLaramieBasinstectonicallyseparated duringthemiddlePaleocene(about58Ma),aneventassociated withtectonicupliftalongthenorthwestmarginoftheLaramie Basin.Dammingofthrough-flowingstreamsresultedina widespreadlacustrinefaciesintheupperpartoftheFerris FormationintheHannaBasin.

ThemodernHannaBasinisoneofthesmallestLaramide structuralbasinsintheRockyMountainregionbutitisalsothe deepest;itsmorethan40,000ftofbasinfillincludesmorethan 15,000ftofUpperCretaceousandlowerTertiarysynorogenic sedimentaryrocks(fig.2).Thebasinisstructurallycomplex andpossessesnumerousLaramidestructuresthatwereformed duringatimespanofabout15m.y.TheLaramieBasin,larger butnotasdeepastheHannaBasin,isalsostructurallycomplex, particularlyalongitswestmargin.Historically,theLaramie BasinhasproducedthemostoilandgasintheHanna,Laramie, andShirleyBasinsProvince.

TheShirleyBasinisabroad,southward-plungingsyncline boundedonthewestandsouthwestbytheShirley,Seminoe, andFreezeoutMountains,ontheeastandnortheastbythe LaramieMountains,andonthesouthbystructuresatthe northendoftheLaramieBasinsuchasComoBluffandFlat Topanticlines(fig.3).Inthisbasin,post-LaramideTertiary sedimentsweredepositedonanerodedsurfaceofUpper Cretaceousstrata.Laramide-agenormalfaultsdisplacerocksas youngasLateCretaceous,butlarge-displacementthrustfaults arerare.

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41


Figure �. Part of the Hanna, Laramie, and Shirley Basins Province showing major tectonic features (modified from Perry and Flores, 1997). AT, Arlington thrust fault; CBA, Como Bluff anticline; FM, Freezeout Mountains; FTA, Flat Top anticline; PCA, Pass Creek anticline; PM, Pennock Mountain; RU, Rawlins uplift; SMA, St. Mary’s anticline; ST, Shirley thrust fault; TB, The Breaks.

Gries(1983a)relatedthetiminganddirectionofregional deformationeventsintheLaramideorogenytocontinentalscaleplatetectonicevents.Sheshowedthattheorientationof Laramideupliftschangedthroughtimeowingtochangesin theregionalstressfield,suchthatLateCretaceousstructures trendnorth-south,Paleocenestructurestrendnorthwestsoutheast,andEocenestructurestrendeast-west.

IntheHanna,Laramie,andShirleyBasinsProvince, LaramidestructurestypicallyarePrecambrian-coreduplifts withboundingthrustsystemswheremountain-frontthrust faultsoverrodebasinmargins,ortheyarethrust-faulted anticlineswithbothinto-basin–andout-of-basin–directed thrustfaultsthatformedpop-upstructuresortrianglezones

(Mountandothers,2004).Inaddition,someLaramide faultshaveaconsiderablestrike-slipcomponentbecausethe provincehasundergonerotation(Stone,1995).

TheRockyMountainregionhasnumerousexamples ofPrecambrian-coredupliftsthatoverrodethemarginsof deepstructuralbasinsalongthrustfaultswiththousandsof feetofdisplacement.Thicksubthrustrocksequenceshave thepotentialforundiscoveredoilandgasaccumulations (Gries,1983b).TheShirleythrust,atthenorthmarginof theHannaBasin,andtheArlingtonthrust(figs.3,4),along thewestmarginoftheLaramieBasin,compriseextensive subthrust(footwall)wedgesofsedimentaryrocksbeneath shallow(hanging-wall)Precambrianrocks.TheShirleyand

Fig._4


ArlingtonthrustshavelongandcomplexLaramidehistoriesof Madre,MedicineBowMountains,LaramieMountains, development(Stone,1995;Lillegravenandothers,2004).

LaramidedeformationintheHannaandLaramie Basinsalsoinvolvedthin-skinned,out-of-basinthruststhat placedyoungerrocksoverPrecambrianbasementandolder sedimentaryrocksandformedtrianglezones(fig.5)(Erslev, 1991;Lillegravenandothers,2004).Theseout-of-basinthrust systemsareassociatedwithfoldingofthethick(>15,000 ft)UpperCretaceousandlowerTertiarybasinfill.Out-ofbasinblindthrustsdisappearintoCretaceousshalesinmany places,suchasthePassCreek,St.Mary’s,andSimpson RidgeanticlinesinthesouthernpartoftheHannaBasin,and “TheBreaks”atthenorthendofthebasin(fig.3;Hitchens, 1999).EarlyLaramidesyntectonicsedimentswereinvolvedin laterLaramidedeformation,creatingacomplexdepositional pattern(Blackstone,1993).

Precambrian-coredsatelliteupliftsborderthesouthend oftheHannaBasinjustnorthoftheMedicineBowuplift (Blackstone,1993).Theseasymmetricstructuresarebounded bythrustfaultsandwereformedbyupliftofPrecambrian coresandconcurrentfoldingofthelessbrittlesedimentary coverrocks(McClurgandMatthews,1978).

Stratigraphy

NorthoftheCheyennebelt(fig.1),thePrecambrian basementisanArcheanmicroplateofmetasedimentary gneissandschistandgraniticrocks,olderthan2.5Ga,that underliesmostoftheHanna,Laramie,andShirleyBasins Province.TheserocksareexposedinthenorthernSierra

SW NE

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Figure �. Generalized southwest-northeast cross section showing the Arlington thrust fault and the Cooper Cove field in the western Laramie Basin. Simplified from Stone (2005). Location of cross section shown on figure 1. pe, Precambrian; J-e, Jurassic through Cambrian ; Km-Ks, Cretaceous Muddy Sandstone Member through Cretaceous Steele Shale; Kmv-Kl, Cretaceous Mesaverde Group through Cretaceous Lewis Shale; T, Tertiary rocks undifferentiated. Vertical scale in thousands of feet. No vertical exaggeration.

andSweetwateruplift(fig.3).SouthoftheCheyenne belt,thePrecambrianbasementrocksconsistofa1.8-Ga metamorphicterraneintrudedby1.5-to1.4-Gagranitic rocks(Petermanandothers,1968).Metasedimentaryand metavolcanicgneissesandcalc-alkalicplutonicigneous rocksareexposedinportionsofthesouthernMedicine BowandSierraMadreuplifts(Houston,1968;Simsand others,2005).Precambrianplutonicandmetamorphicrocks areoverlainbyanunconformitybyCambrianandyounger sedimentaryrocks.

Cambriansedimentaryrocksareabsentthroughout muchoftheprovincebutareexposedontheeastflankofthe Rawlinsuplift(fig.1),wheretheyare450ftthick(Lovering, 1929).IntheCambrianFlatheadSandstone(fig.2),abasal conglomeraticsandstoneisoverlainbyquartzosesandstone orquartziteandbyreddish-brownglauconiticsandstoneand shale.Theformationthinstotheeastandisentirelyabsent atthewestendoftheLaramieBasinandintheShirley Basin(Harshman,1972).RocksofOrdovician,Silurian,and Devonianageareabsentintheprovince.

OntheRawlinsuplift,theMississippianMadison LimestoneunconformablyoverliesCambrianstrata(fig.2). Eastward,wheretheFlatheadisabsent,theMadisonrests unconformablyonPrecambrianrocks.AlongtheRawlins uplift,theMadisonisagraytoredlimestoneorcherty limestone;akarstsurfaceiswelldevelopedintheupper partoftheunit.TheMadisonaverages100ftthickonthe Rawlinsuplift(Lovering,1929)and150ftthickinthe ShirleyBasin(Harshman,1972),butitisthinorabsentin theLaramieBasin.LillegravenandSnoke(1996)identified 98ftofMadisonLimestoneinthenorthernHannaBasin.

Geologic Assessment—Undiscovered Oil and Gas—Hanna, Laramie, and Shirley Basins Province, Wyoming and Colorado 11

ANTICLINALSYNTECTONIC UPLIFTBASIN

PRECAMBRIA

N BASEMENT

SHALLOW OUT-OF-BASIN THRUST

ROCKS

BASEMENT-INVOLVED BLIND THRUST

Figure 5. Generalized cross section showing triangle zone development as described by Lillegraven and others (2004) for structures in the Hanna and Laramie Basins.

Wherepresent,thePennsylvanianAmsdenFormation unconformablyoverliestheMadisonLimestone(fig.2).The Amsden’ssandstone,reddishmudstone,andchertylimestone (Lovering,1929)averages200ftthickontheRawlinsuplift. Itthinsto140ftinthesouthernpartoftheHannaBasin. Harshman(1972)didnotrecognizeAmsdenintheShirley Basinbutidentifiedadistinctivesolutionbrecciaandkarst zonewithreddishshaleandsandstonethatheplacedinthe upperpartoftheMadison.HauselandJones(1984)didnot recognizetheAmsdenFormationintheLaramieBasin,but time-equivalentrocksoftheFountainFormationcropoutin thesouthernpartofthebasinneartheWyoming-Colorado stateline(fig.2).

ThePennsylvanianTensleepSandstoneunconformably overliestheAmsdenFormationandaverages300–400ft thickintheHannaBasin,whereitisdescribedasamediumgrained,crossbedded,quartzosesandstoneandlimestone unit(Mitchell,1961;Stone,1966;figs.2,6).Theequivalent CasperFormationaverages500ftthickintheLaramieBasin andis650ftthickintheShirleyBasin,wheresomerocksin thelowerpartarecorrelativewiththeAmsdenFormationto thewest(Harshman,1972).TheCasperbecomesmorearkosic southeastwardintheLaramieBasinandisinpartequivalent totheFountainFormation.Fusiliniddataindicatethatlithic unitsintheTensleep-Casperdepositionalsystemaretime transgressive.IntheHannaBasin,theTensleepisprimarily Desmoinesianinage,whereasthetopoftheCasperinthe LaramieBasinisWolfcampian(Mitchell,1961).TheTensleep isimportanttothepetroleumgeologyoftheprovincebecause itisaregionalreservoirrock,particularlywheretheeolian sandstonefaciesiswelldeveloped.

ThePermianandTriassicGooseEggFormation unconformablyoverliestheTensleepSandstoneandCasper

Figure �. Tensleep Sandstone outcrop along west side of Seminoe Reservoir (T. 24 N., R. 84 W.) in northern part of Hanna Basin. Sandstones are fine-grained and cross-bedded sublitharenites typical of the Tensleep in the region. Younger Jurassic rocks in background. Hammer for scale in right center of photograph.


Formation(fig.2).IntheHannaBasin,theGooseEgg averages250ftthickandiscomposedofreddish-brown calcareoussandstone,dolomiticlimestone,siltstone,and anhydrite(fig.7).Itaverages400ftthickintheShirley Basin.Namedmembersare,inascendingorder,theOpeche Shale,MinnekahtaLimestone,GlendoShale,Forelle Limestone,DifficultyShale,andErvayLimestoneMembers (Harshman,1972;PiperandLink,2002).TheGooseEgg istimeequivalenttothePhosphoriaFormationinwestern Wyoming(CheneyandSheldon,1959)andrepresentsan easternevaporitefaciesofthePhosphoriathatwasdeposited intheGooseEggembayment(seefig.21)ofthePhosphoria sea(PiperandLink,2002).TheGooseEggisimportant tothepetroleumgeologyoftheprovincebecauseitforms aregionalsealtotheeastwardmigrationofoilgenerated fromPhosphoriasourcerocksinwesternWyomingand southeasternIdaho(seelaterdiscussion).

FormationsintheTriassicChugwaterGroup(fig.2) are,inascendingorder,theRedPeakFormation,Alcova Limestone,andJelmFormation.IntheHannaandCarbon Basins,theChugwaterGroupaverages1,300ftthickand

consistsofcoastalandshallowmarinelimestone,mudstone, sandstone,andgypsum(Dobbinandothers,1929).The Chugwaterischaracteristicallyredbutalsocontainsshades ofgreen,purple,andbrown.Itisconformablewiththe underlyingGooseEggFormationinthenorthernpartofthe HannaBasin(LillegravenandSnoke,1996).TheAlcova Limestoneisathin(10–15ftthick)discontinuousunitofhard, sandylimestonethatlocallyformsridges.TheChugwateris about1,100ftthickatRedMountainatthesouthendofthe LaramieBasin(DartonandSiebenthal,1909)andisabout725 ftthickintheShirleyBasin(Harshman,1972).TheChugwater isimportanttothepetroleumgeologyoftheprovincebecause itformsaregionalsealforpetroleumtraps.Locally,Jelm Formationsandstonesformreservoirsforoilandgasinthe LaramieBasin(Mitchell,1961).

TheJurassicSundanceFormationunconformably overliestheChugwaterGroupinmuchoftheprovince(fig. 2).TheunderlyingJurassicNuggetSandstone(notshownon fig.2)hasbeenidentifiedinthewesternmostHannaBasin, butitpinchesouttotheeastinthecentralHannaBasin (Mitchell,1961).TheSundanceFormationconsistsofgray-

Figure �. Goose Egg Formation outcrop along west side of Seminoe Reservoir (T. 24 N., R. 84 W.) in northern part of Hanna Basin. Red mudrocks interbedded with tan evaporites. Note vertical faults in central part of photograph. Field of view is approximately 30 ft across.

Geologic Assessment—Undiscovered Oil and Gas—Hanna, Laramie, and Shirley Basins Province, Wyoming and Colorado 1�

greenmarineshale,fossiliferouslimestone,andglauconitic sandstone(Mitchell,1961;Harshman,1972).Dobbinandothers (1929)measured350ftofSundancealongComoRidgeinthe northernLaramieBasin(CBAoffig.3),about50percentof whichissandstone.LillegravenandSnoke(1996)identified morethan400ftofSundanceinthenorthernHannaBasin,and Harshman(1972)reportedanaveragethicknessof240ftinthe ShirleyBasin.TheSundanceFormationiscomposedofabasal chert-pebbleconglomerateandsandstoneunit(“basalSundance” offig.2)andatleasttwodistinctsandstoneunitsidentified as“upperSundance”and“lowerSundance.”The“upper,”or younger,sandstoneunitisareallyrestrictedtotheHannaand LaramieBasins,whereasthe“lower,”orolder,sandstoneismore widespread(Stone,1966).TheJurassicMorrisonFormation conformablyoverliestheSundance.Sundancesandstone reservoirsproducebothgasandoilintheLaramieBasin.

TheUpperJurassicMorrisonFormationrangesfrom 150to300ftthickintheprovinceandthickenssouthward intoColorado.Itischaracterizedbygray,green,andmaroon nonmarineshalesandmudstones,lithic-richsandstonesand conglomeraticsandstones,andrarelimestones.Thelowerpart oftheMorrisonisprimarilysandstone,andintheLaramie Basinthisunitis140ftthick.IntheShirleyBasin,however,

thelowersandstoneoftheformationisonlyabout20ftthick (Harshman,1972).Itisnotasignificantoilandgasreservoirin theprovince.

TheLowerCretaceousCloverlyFormation unconformablyoverliesJurassicrocksintheHanna,Laramie, andShirleyBasinsProvince.ThenameCloverlyisusedfor rocksequivalenttotheLowerCretaceousDakotaFormation, FusonShale,andLakotaFormationoftheBlackHills;but becauseeachoftheseunitsisnotcontinuousandconsistently recognizableintheprovince,theyarecombined(fig.2;Stone, 1966).Bowen(1917)identifiedanaveragethicknessof231ft fortheCloverlyFormationintheHannaBasin.AtOilSprings field(fig.20)inthenorthernpartoftheLaramieBasin,the Cloverlyincludesabasal10-ft-thicknonmarineunitofchertpebbleconglomerateandconglomeraticsandstone(fig.8),a 33-ft-thickmiddleunitofgraytogreencarbonaceousshale, andanupper85-ft-thickunitofmarinesandstone(Dobbinand others,1929).TheCloverlythinstothesouthandislessthan 100ftthickinthesouthernpartoftheLaramieBasin(Stone, 1966).Itisasmuchas200ftthickintheShirleyBasinwhere thethickeningisdueprimarilytodevelopmentoftheupper sandstoneunit(Harshman,1972).Bothsandstone-richunitsare knownoilandgasreservoirsintheLaramieBasin.

Figure �. Basal Cloverly Formation conglomerate along west side of Seminoe reservoir (T. 24 N., R. 84 W.) in northern part of Hanna Basin. Clasts are dominantly quartzite and chert. Maximum clast diameter approximately 8 in. Hammer for scale in left center of photograph.

1� Undiscovered Oil and Gas–Hanna, Laramie, and Shirley Basins Province, Wyoming and Colorado

TheLowerCretaceousThermopolisShaleispresent throughouttheprovince(figs.2,9).Itrangesinthicknessfrom 200ftinthenorthernLaramieandHannaBasins(Dobbin andothers,1929)to185ftintheShirleyBasin(Harshman, 1972)andto50ftinthesouthernLaramieBasin(Mitchell, 1966).Itisprimarilydark-graymarineshalewithavariably developedsandstoneunitcalledtheMuddySandstone Memberinthemiddle(Eicher,1960).Thelowershaleunit, commonlyreferredtoastheSkullCreekShale(Burtner andWarner,1984),isAlbianinageandisassociatedwith theinitialCretaceousmarinetransgression.TheMuddy SandstoneMemberisacompositeunitofforeshoreto shorefaceregressivesandstonesthatareincisedinplaces byfine-tocoarse-grainedvalley-filldepositsofsandstone andshalethatare,inturn,overlainbytransgressivemarine sandstones(Dolsonandothers,1991).Owingtoitslithologic heterogeneity,theMuddyisanimportantpetroleumreservoir insomepartsoftheprovincebutisapoorreservoirormay evenbeabsentinotherparts(Stone,1966).Theupperpartof theThermopoliscontainsanunnameddark-grayshalethat isequivalenttotheinformallynamed“ShellCreekshale” memberoftheThermopolisShaleinnorthernandeastern WyomingandcentralMontana(Eicher,1962;Dymanand others,1994;PorterandWilde,2001).

TheMowryShale(figs.2,10)isasequenceofdark-gray toblacksiliceousmarineshalewithinterbeddedporcellanite andbentonite.IntheHannaandLaramieBasins,itrangesin thicknessfrommorethan200ftinthenorthto150ftinthe south(Dobbinandothers,1929).Mitchell(1961)identified 400ftofMowryintheLaramieBasin,buthemayhave includedtheinformal“ShellCreekshale”unit.Harshman (1972)recognizedanaverageMowrythicknessof110ftinthe ShirleyBasin.ThetopoftheMowryisidentifiedbyaregional bentonitebedofCenomanianage,theClaySpurBentonite Bed(BurtnerandWarner,1984;Davisandothers,1989; Obradovich,1993).ByersandLarson(1979),Burtnerand Warner(1984),Davisandothers(1986),andDavisandByers (1989)identifiedregionallithofacieswithintheMowryand designateditamajorsourcerockforpetroleuminthenorthern RockyMountainregion.WediscusstheMowry-Hanna CompositeTPSinalatersectionofthisreport.

TheFrontierFormation(figs.2,11)consistsofalower unitofdark-graycarbonaceousshale,theBelleFourcheShale Member,andanupperunitofsandstoneandinterbedded shale,theWallCreekSandstoneMember.Theformation averagesabout700–900ftthickintheprovince(Stone,1966; Harshman,1972;Mieras,1992;LillegravenandSnoke, 1996);itisLateCretaceous(Cenomanian-Turonian)inage. TheBelleFourcherepresentsregressivemarinedeposition andcontainslesssandstoneeastwardintheLaramieBasin. TransgressivemarinesandstonesoftheWallCreekSandstone Memberaverage10–40ftthick(fig.11)andarefine-grained andglauconitic.Theunitis110ftthickintheShirley Basin(Harshman,1972).WallCreeksandstones,whichare petroleumreservoirsintheprovince,arediscussedinalater sectionofthisreport.

IntheHannaBasin,rocksimmediatelyabovetheFrontier arecalledtheSageBreaksShale(fig.2;Merewether,1990)or NiobraraFormation(LillegravenandSnoke,1996).Dobbin andothers(1929)identified450ftofdark-grayconcretionary shaleasequivalenttotheSageBreaksMemberoftheCarlile ShaleoftheBlackHills.Mitchell(1961)identifiedabout 1,200ftofNiobrara(includingtheSageBreaksShale)in theHannaBasinandabout600ftinthesouthernLaramie Basin.TheSageBreaksShalecontainsammonitesofLate Cretaceous(Turonian)age(Stone,1966).Niobrararocks abovetheSageBreaksShalearecalcareousshales,limestones, andchalkylimestones(fig.12).TheNiobraraisconcretionary andcontainsledge-formingcoquinabeds.Harshman(1972) measuredabout900ftofNiobrara(includingtheSageBreaks Shale)intheShirleyBasin.Limestonesandchalksinthe Niobraragiveoffastrongpetroliferousodorandformthe NiobraraTPSdiscussedlaterinthisreport.

TheSteeleShaleconformablyoverliestheNiobrara Formation(figs.2,13).Itisdark-graymarineshaleand minorinterbeddedsandstone,siltstone,andbentoniteof earlyCampanianage.Apersistent5-ft-thickbentoniteinthe upperpartoftheSteeleinthenorthwesternLaramieBasinis equivalenttotheArdmoreBentoniteBedoftheBlackHills region(Gillandothers,1970;Obradovich,1993).TheSteele rangesinthicknessfrom3,500ftinthenorthernHannaand LaramieBasinsto2,400ftinthewesternHannaBasinand to2,300ftinthesouthernLaramieBasin(Gillandothers, 1970).LillegravenandSnoke(1996)recognized5,500ftof SteelestratainthenorthernHannaBasin.Thindiscontinuous sandstones,referredtoinformallyas“Shannon”sandstones, aregasreservoirsintheHannaandLaramieBasins.The Steelecontainslocallycontinuoussandstonesatornearthe topthatareequivalenttobasalsandstonesoftheMesaverde Groupfartherwest.IntheShirleyBasin,Harshman(1972) estimatedtheSteeletobe1,500–2,000ftthick,butthereit hasbeenpartlyerodedandallyoungerCretaceousstratahave beenentirelyremovedbyerosion.TheSteeleShaleispart oftheMowry-HannaCompositeTPSdiscussedlaterinthis report.

TheoverlyingMesaverdeGroupisconformablewith boththeSteeleShaleandtheoverlyingLewisShaleinthe Hanna,Laramie,andShirleyBasinsProvince.Itisdivided intofourformationsintheHannaBasin—inascendingorder, theHaystackMountainsFormation,AllenRidgeFormation, PineRidgeSandstone,andAlmondFormation(fig.2;Gilland others,1970).IntheLaramieBasin,theMesaverdeconsistsof theRockRiverFormationandoverlyingPineRidgeSandstone owingtoaneastwardfacieschangefromsandstonetoshale. TheRockRiverFormationislargelythetimeequivalent oftheAllenRidgeFormation.TheHaystackMountains Formationconsistsof1,700–2,550ftofinterbeddedmarine sandstoneandshale(fig.14).ThelithologicallydiverseAllen RidgeFormationcontainsaunitofnonmarinesandstoneand carbonaceousshale700–1,200ftthickwhich,intheeastern HannaBasin,isunderlainandoverlainlocallyby350–700 ftofmarinetobrackish-watersandstoneandshale(Gilland


Figure �. Muddy Sandstone Member of Thermopolis Shale and the Cloverly Formation; view looking southwest near Rendle Hill, approximately 15 mi north of Rawlins, Wyo. (T. 24 N., R. 88 W.), in western part of Hanna Basin. Muddy Sandstone Member in lower left, Thermopolis Shale in dark gray middle area, and Cloverly Formation in light gray background forming dip slope. Foreground distance approximately 20 ft across

Figure 10. Mowry Shale near Rendle Hill, approximately 15 mi north of Rawlins, Wyo. (T. 24 N., R. 88 W.), in western part of Hanna Basin. Hammer for scale near center of photograph.


Figure 11. Frontier Formation along Union Pacific Railroad tracks near Como, Wyo. (T. 22 N., R. 78 W.), in central part of Hanna Basin. Upper part of outcrop is sandstone of Wall Creek Sandstone Member. Foreground distance approximately 150 ft across.

Figure 12. Niobrara Formation at Separation Flats, approximately 8 mi northeast of Rawlins, Wyo. (T. 22 N., R. 86 W.), in western part of Hanna Basin. Younger rocks are to left. Foreground distance approximately 30 ft across. Steele Shale and Mesaverde Group form gray hills on horizon at far left.


Figure 1�. Steele Shale at Separation Flats, approximately 10 mi northeast of Rawlins, Wyo. (T. 22 N., R. 86 W.), in western part of Hanna Basin. Looking upsection at concretionary zones that form “knobby” ridges in middle part of Steele, top center of photograph. Foreground distance approximately 10 ft across.

others,1970).ThePineRidgeSandstoneunconformably overliestheAllenRidge.Martinsenandothers(1993) suggestedthatthisunconformityseparatesdifferentsequences derivedfromdifferentdirectionsandwasrelatedtoearly LaramideupliftnorthoftheHannaBasin.IntheHanna Basin,theformationisa100–250-ft-thickunitofnonmarine sandstone,siltstone,carbonaceousshale,andimpurecoal(fig. 15).TheAlmondFormationisamarineandnonmarinecoastal sequenceofsandstone,shale,andcoalranginginthickness from450to600ft.InthewesternHannaBasin,fluvial sandstone,shale,andcoalinthenonmarinelowerpartofthe Almondareabout180ftthick.Itcontainsasmanyasseven coalbedsgreaterthan5ftthick.TheMesaverdeGroupisboth asourceandreservoirrockintheprovinceandisdiscussed aspartofcoalbedgasandcontinuousgastotalpetroleum systemslaterinthisreport.

TheMaastrichtianLewisShale(fig.2)wasdeposited duringthefinaltransgressive-regressivephaseoftheWestern InteriorseawayandduringtheearlypartoftheLaramide orogeny(Perman,1990).Itisathick(2,200–2,600ft)

sequenceofgraymarineshale,fine-tomedium-grained sandstone,andsiltstone.InthewesternpartoftheHanna Basin,itformscoarsening-upwardparasequencesofshale andsandstonethatareasmuchasafewhundredfeetthick (fig.16).The600-ft-thickDadSandstoneMemberofthe Lewisseparatesloweranduppershale-richintervalsofthe Lewis.Numeroussandstonebodiesintheupperpartofthe formationintheeasternpartoftheSouthwesternWyoming ProvincetothewestandinthewesternHannaBasinare laterallyequivalenttotheFoxHillsSandstone,andthat nameisusedinsomeplaces(Gillandothers,1970;Fox, 1971).SandstonesandshalesoftheLewiscontainmarine megafaunaofMaastrichtianagefromBaculites eliasithrough B. clinolobatus(Gillandothers,1970).TheLewisisaknown sourceandreservoirrockintheregion.Itispartofthe Mowry-HannaCompositeTPSdiscussedlaterinthisreport.

TheMedicineBow,Ferris,andHannaFormationsare syntectonicsedimentaryunitsassociatedwiththeLaramide orogeny.TheyareprimarilyrestrictedtotheHannaBasinand northernpartoftheLaramieBasinwheretheyrecordahistory ofperiodicupliftofsurroundingLaramidestructures,sea levelfluctuations,andsubsidence(Knight,1951;W.R.Keefer, writtencommun.,1999;Wroblewski,2003).Theseformations areimportanttoourstudybecausetheycontainnumerouscoal bedsandlacustrinemudstonesthatarehydrocarbonsources. InthedeeperpartsoftheHannaBasin,fluvialsandstone reservoirsmaycontaingasaccumulations.

TheMedicineBowFormation(fig.2)wasdeposited duringthefinalwithdrawaloftheMaastrichtianseafromthe Hanna,Laramie,andShirleyBasinsProvinceduringearly stagesoftheLaramideorogeny.Itisathick(about6,200 ft)nonmarinesequenceoffluvialtoestuarinesandstone, carbonaceousshale,andcoal(fig.17;LandonandHeller, 2000).High-volatileAorBbituminouscoalsareespecially abundantinthelowerpartoftheformation,andintheHanna coalfieldinthecentralHannaBasinasmanyas30individual coalbedshavebeenidentified(fig.1).However,onlythreeof thesecoalbedsexceed5ftinthickness(GlassandRoberts, 1980).TheMedicineBowFormationisconformablyoverlain bytheFerrisFormation(figs.2,18)orislocallyinangular discordancewiththeHannaFormationintheeasternHanna andLaramieBasins(Gillandothers,1970).

TheUpperCretaceoustolowerPaleoceneFerris Formationismorethan6,000ftthickatitstypelocalityinthe HannaBasin,whereitisentirelynonmarine.Itcanbedivided intotwolithicunits:alower1,100-ft-thickUpperCretaceous unitcomposedofconglomeraticsandstone,sandstone,and shaleandanupper5,400-ft-thickPaleoceneunitofsandstone andcoal(Gillandothers,1970).GlassandRoberts(1980) identified28coalbedsinthecentralHannaBasinrangingin thicknessfrom4.5to25ft.

ThePaleoceneandEoceneHannaFormationmaybeas thickas13,000ftinthenorthernpartoftheHannaBasin,but itisgenerallymuchthinner.Itisafluvial-lacustrinecyclic sequenceofconglomerate,sandstone,mudstone,shale,and coal(figs.2,19).Depositionalcyclesaredefinedbythe


Figure 1�. Haystack Mountains Formation along North Platte River, approximately 10 mi north of Sinclair, Wyo. (T. 22 N., R. 85 W.), in western part of Hanna Basin, showing coarsening-upward parasequences in upper part of formation. Approximately 700 ft of formation exposed.

Figure 15. Pine Ridge Sandstone along North Platte River, approximately 10 mi north of Sinclair, Wyo. (T. 22 N., R. 85 W.), in western part of Hanna Basin, showing sandstone, mudstone, and coal interbedded in middle part of formation. Coal bed in middle part of photograph approximately 18 in. thick.


Figure 1�. Lewis Shale, approximately 12 mi north of Sinclair, Wyo. (T. 22 N., R. 85 W.), in western part of Hanna Basin, showing coarsening-upward parasequence of shale and sandstone in lower part of formation. Person for scale at left center.

Figure 1�. Sandstone bed in the Medicine Bow Formation on Snyder Ridge (T. 24 N., R. 83 W.) in northern part of Hanna Basin. Staff in left center portion of photograph is 5 ft tall.


Figure 1�. Ferris Formation, approximately 3 mi west of Hanna, Wyo. (T. 22 N., R. 82 W.), along U.S. Highways 30 and 287 in central part of Hanna Basin, showing interbedded carbonaceous shale, coal, and sandstone. Middle-ground distance approximately 125 ft across.

sedimentaryresponsetoupliftandsubsidenceduringthe mainphaseoftheLaramideorogeny.TheHannacontains morethan30individualcoalbedsatleast5ftthickofhighvolatileCbituminousrankthataredistributedthroughout theformation(GlassandRoberts,1980).Theformation unconformablyoverliestheFerrisFormationinthecentral HannaBasin,butitrestsonolderrocksalongthenortheast marginofthebasin(Gillandothers,1970).

UpperEoceneandyoungerrocksarelimitedmainly totheShirleyBasin.TheEoceneWindRiverFormation, theoldestunit,consistsofabasalconglomerateandarkosic sandstoneoverlainbyinterbeddedcoarse-tomedium-grained sandstone,siltstone,claystone,andminorlignitebeds; maximumthicknessisabout500ft(Harshman,1972).The WindRiverunconformablyoverliestheSteeleShaleinthe ShirleyBasin.TheWagonBedFormationisalsoEocenein ageandconformablyoverliestheWindRiverFormation(fig. 2).Itiscomposedofinterbeddedcoarse-grainedsandstone andclaystonethatreachamaximumthicknessofabout150 ft(Harshman,1972).

TheOligoceneWhiteRiverFormationunconformably overliestheWagonBedorolderrocksintheShirleyBasin. Inmanyplacesitconsistsofabasalconglomerate,overlain bytuffaceoussiltstone,sandstone,andlimestonebedsand localinterbeddedconglomerates.TheWhiteRiverhas beendividedintoalowermemberthatisasmuchas400ft thickandanuppermemberthatisasmuchas350ftthick (Harshman,1972).

TheMioceneArikareeFormationconformablyoverlies theWhiteRiverFormationintheShirleyBasin.Itconsistsof fine-tomedium-grainedtuffaceoussandstone,conglomerate, andlimestonewithamaximumthicknessofabout180ft (Harshman,1972).IntheHannaBasinMiocenerocksare locallypresent.TheyunconformablyoverlietheHanna FormationandareassignedtotheBrownsParkFormation (Blackstone,1993).NoneoftheTertiaryformationsyounger thantheHannaisthoughttohavehydrocarbonpotential.

Production Characteristics

Twelvesignificantfields(cumulativeproductiongreater than0.5millionbarrelsofoilequivalent)havebeendiscovered intheHanna,Laramie,andShirleyBasinsProvince;allare locatedalongthewestmarginoftheLaramieBasin(fig.20), wheretheyproducefrom7differentreservoirs.Table3shows theassessmentunitnumberandname,primaryreservoirs, fieldname,discoveryyear,meandepthofproducinginterval, commodity,andcumulativeproductionforthesefields,as compiledfromHollisandPotter(1984)andIHSEnergy Group(2004a).The12fieldsarefoundin2TPSsthatare discussedinthefollowingsectionsofthisreport.Asshown intable3,productionfromthesefieldshasbeenmorethan 77millionbarrelsofoil(MMBO)and24billioncubicfeetof gas(BCFG)fromatotalofabout79MMBOand31.8BCFG


Figure 1�. Hanna Formation, approximately 2 mi west of Hanna, Wyo. (T. 22 N., R. 82 W.), in a road cut along U.S. Highways 30 and 287 in central part of Hanna Basin, showing interbedded carbonaceous shale, coal, and sandstone. Person (E.A. Merewether) for scale.

fromallfieldsintheprovince.Nearly65percentofthatoil hasbeenproducedfromJurassicandCretaceousreservoirsat RockRiverfieldinthenorthwesternpartoftheLaramieBasin (fig.20).Threefields(RockRiver,Quealy,andBigMedicine Bow)accountformorethan85percentoftheoilproduced intheprovince.Only2ofthe12fieldshaveappreciablegas reservoirs(BigMedicineBowandRockRiver);theirtotal cumulativeproductionis22.6BCFG(table3).Allotherfields produceconsiderablylessgas.

TheHannaBasinhostsonlythreefields,noneofwhichis significant.HugusandOverlandarebothNiobraraoilfields, andCedarRidgehasproducedgasfrom“Shannon”sandstones (straysandstonesintheSteeleShale).Inaddition,twocoalbed gaspilotprojectsareunderwayinthenorthernpartofthe HannaBasin—theSeminoeRoadPilotProject(Mesaverde

Groupcoals)andtheHannaDrawPilotProject(Hanna Formationcoals)(Debruin,2003b;fig.20).Cretaceousrocks intheHannaBasincenterhaveonlyrecentlybeenpenetrated butarenotyeteconomicallyproductive(DeBruin,2003a,b). Severaldeepwellshavebeendrilledinthecentralpartofthe HannaBasinandarediscussedinaseparatesection.

Productionisprimarilyfromstructuraltraps,butthere isapotentialfortrapsformedbyfaciesvariations.Structural trapsmaybethrust-faultedanticlines,trianglezones,and combination(structural-stratigraphic)trapsinwhichfacies variationscontrolthesandstonedistributionacrossstructures. Insomestructures,trappingmechanismsarecomplexowing toremigrationofoilfromlatePaleozoic(AncestralRocky Mountains)trapstoLaramidetraps;forexample,atQuealy fieldPhosphoria-derivedTensleep-Casperoilaccumulatedin thismanner(Stone,1995).

Fiveofthe12significantfields,theAllenLakeEast,Big MedicineBow,Herrick,LittleLaramie,andQuealyfields inthewesternLaramieBasin,produceoilfromreservoirsin theTensleepSandstoneandCasperFormation.Thesefields, whichwerediscoveredinthelate1940sto1950,haveatotal cumulativeproductionof8.5MMBO(table3).

TheexplorationhistoryoftheHanna,Laramie,and ShirleyBasinsProvincecanbedividedintoearly,middle, andlatestages.Duringtheearlystage,from1918totheearly 1940s,fielddiscoverieswerebasedprimarilyonsurface mappingofstructuressuchasatRockRiverandRexLake (Stone,2002).Duringthemiddlephase,inthe1950s,fields werediscoveredusingseismicexplorationmethods,suchas atDiamondLakeandElkMountain.Cretaceousreservoirsat QuealywerethefirstseismicdiscoveryintheRockyMountain region,in1934(table3).Thelateststageofexploration (sincethe1970s)hasbeendominatedbydeepdrillingusing improvedtechnology,butnosignificantfieldshavebeen discovered.

Thelackofdiscoveredoilorgasaccumulationsinthe ShirleyBasinisenigmatic.Theareahasbeenmoderately explored,andsome80wells(alldryandabandoned)were drilled,mostofwhichwerelocatedinthreeareas(fig.1):(1) eastofthe+2000ftcontouronPrecambrianbasementonthe eastsideofthebasin,(2)ontheanticlineinthenorthwestern partofthebasin,and(3)withinthefaultedShirleyMountains areainthesouthwesternpartofthebasin(fig.3).Manyof thesewellspenetratedPaleozoicstrata,andsomereached Precambrianbasement.Therehavebeenabout40drillstemtestsinformationsrangingfromtheMuddySandstone MemberoftheThermopolisShaletotheTensleepSandstone (fig.2),butnonereportedshowsofoilorgas(IHSEnergy Group,2004b).ThislackofhydrocarbonsintheShirleyBasin isdifficulttoexplain,becausePhosphoriaoilshouldhave beenabletomigrateintotheShirleyBasinfromthewestin amannersimilartothatelsewhereintheprovince(seethe discussionofthePhosphoriaTPSlaterinthisreport).Barriers couldpossiblyhaveformedbetweenthisbasinandtheHanna andLaramieBasinstopreventsuchmigration,butdirect evidenceislackingandthequestionremainsunresolved.

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Southwestern part of the Hanna, Laramie, and Shirley Basins Province showing locations of oil (green), gas (red), and oil and gas (yellow) fields, wells used to model thermal history of the southern part of province (green filled circles), locations of the Hanna Draw and Seminoe Road coalbed gas pilot projects (red tracts), and Anadarko Durante 17-2 well (green triangle). Contours drawn on top of Precambrian basement in feet relative to sea level (modified from Blackstone, 1989). Heavy gray lines are major faults. Red patterned areas are outcrops of Precambrian rocks from Green (1992) and Green and Drouillard (1994). Location of Cheyenne belt from Stone (1995). BR, Brinkerhoff Hanna Unit No. 1 well; BU, Buttes Federal 1–18 well. PC, Humble Pass Creek Ridge No. 1 well.

Figure 20.

Undiscovered O

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Assessment of Oil and Gas Resources

System for Numbering Assessed Resources

IntheHanna,Laramie,andShirleyBasinsProvince weassessedthe5TPSsand7AUslistedbelow.Theyare numberedaccordingtoasystemestablishedbytheUSGS tofacilitatepetroleumresourceassessment(U.S.Geological Survey,2000):thefirstdigit(5)referstotheregion,thenext three(030)totheprovince,thenexttwo(01,02,andsoon)to theTPS,andthelasttwodigitstotheassessmentunit.

503001 PhosphoriaTPS

50300101 Tensleep-Casper ConventionalOil

andGasAU

503002

Mowry-HannaComposite TPS

50300201

Mesozoic-Cenozoic ConventionalOil andGasAU

BiogenicGas,MedicineBow–Ferris–HannaCoalbedGas,and MesaverdeCoalbedGasAUswerenotassessedowingtoa lackofgeologicdataandinadequateproductiondata.]

Athoroughanalysisofallavailablegeologicdata,as wellaspetroleumexplorationanddevelopmentinformation, waspresentedtoareviewpanelforafinaldetermination ofthecriteriaandboundariestobeusedforeachAU.In addition,estimatesofthesizesandnumbersofundiscovered conventionaloilandgasaccumulations,basedonatabulation ofexistingfieldandwellrecordsprovidedbyKlettandLe (2007)(thisCD-ROM),werepresentedondatainputforms tothereviewpanel.Theseinput-dataforms(seeKlettand Le,2007,thisCD-ROM)constitutethebasisforestimating hydrocarbonresourcesintheAUs.

Thedefaultminimumaccumulationsizethathaspotential foradditionstoreservesforconventionalaccumulationsis 0.5millionbarrelsofoilequivalent(MMBOE).TheNiobrara ContinuousOilAUwasassessedusingthemethodology describedbySchmoker(1996),whereinthenumberof untestedcellswithpotentialforadditionstoreservesandtotal recoverypercellwereestimated.ForthatAU,theminimum recoveryis1,000barrelsofoilpercell.Otherdatawere compiledorcalculatedforeachAUtoaidinthefinalestimate ofundiscoveredresources:gas-oilratio,naturalgasliquids togasratio,APIgravity,sulfurcontent,anddrillingdepth. Additionally,allocationsofundiscoveredresourceswere calculatedforFederal,State,andprivatelandsandforvarious ecosystemregions.Dataareavailableonthecompleteddata inputformsforthethreeassessedAUsinKlettandLe(2007) (thisCD-ROM).

The“wells”shownontheAUmapsinthisreportare generalizedlocationsofwellscalled“cells.”Cellmapsfor eachoilandgasassessmentunitwerecreatedbytheUSGS toillustratethedegreeofexploration,typeofproduction,and distributionofproductioninanAUorprovince.Eachcell representsaquarter-milesquareofthelandsurface,andthe cellsarecodedtorepresentwhetherthewellslocatedwithin thecellarepredominantlyoil-producing,gas-producing, bothoil-andgas-producing,dry,orofunknownproduction type.Thewellinformationwasinitiallyretrievedfromthe IHSEnergyGroup,PI/DwightsPLUSWellDataonCDROM(IHSEnergyGroup,2004b).Cellsweredevelopedas agraphicsolutiontoovercometheproblemofdisplaying proprietaryPI/DwightsPLUSWellData.Consequently, proprietarydataarenotdisplayedonorusedinthecellmaps.

Forthisstudy,wedefineddryholesforeachAUaswells thatreachedtotaldepthinorthroughtheassessedformations andmoreoverwereclassifiedasdryandabandonedinthewell databaseforformationsinthatAU.Dryholesaredistributed relativelyevenlyintheLaramieBasinbuthavenotpenetrated

50300261 HannaBasinContinuousGasAU (notquantitativelyassessed)

503003 NiobraraTPS

50300361 NiobraraContinuousOilAU

503004 NiobraraBiogenicGasTPS

50300461 NiobraraBiogenicGasAU (notquantitativelyassessed)

503005 Hanna-MesaverdeCoalbed GasTPS

50300581 MedicineBow–Ferris–Hanna CoalbedGasAU

(notquantitativelyassessed)

50300582 MesaverdeCoalbedGasAU (notquantitativelyassessed)

EachAUwasdefinedonthebasisofgeologic characteristicsandconditionsfavorableforhydrocarbon generationandaccumulation—suchassource,reservoir, andsealrocks;burial,thermal,andmigrationhistories;and trappingmechanisms—thatcombinetodistinguishitfrom otherAUs.[Note:HannaBasinContinuousGas,Niobrara


thedeepestpartoftheHannaBasin.Thefollowingsections describethecharacteristicsoftheTPSsandthequantitatively assessedAUswithintherespectiveTPSs.

Links to Data Input Forms and Graphical Data

KlettandLe(2007)(thisCD-ROM)providefilesofinput formsandgraphicaldatathatwereusedintheassessmentof theHanna,Laramie,andShirleyBasinsProvince.Twosetsof exploration-activityanddiscovery-historygraphsareprovided foreachoftheAUs,onesetshowingknownfieldsizes (cumulativeproductionplusremainingreserves)andanother setshowingfieldsizesthatwereadjustedtocompensate forpotentialreservegrowthinthenext30years(labeled “grown”).Withineachsetofgraphs,oilfieldsandgasfields areshownseparately.Thelinks,below,directlyaccessthe materialinKlettandLe’schapterofthisreport.

Data Input Forms:

Tensleep-CasperConventionalOilandGasAU (50300101)

Mesozoic-CenozoicConventionalOilandGasAU (50300201)

NiobraraContinuousOilAU(50300361)

Graphs of Exploration and Discovery Data for Conventional Assessment Units

Tensleep-CasperConventionalOilandGasAU (knownfieldsizes) Tensleep-CasperConventionalOilandGasAU (grownfieldsizes) Mesozoic-CenozoicConventionalOilandGasAU

(knownfieldsizes) Mesozoic-CenozoicConventionalOilandGasAU

(grownfieldsizes)

Phosphoria Total Petroleum System

Thegeographicextentsofbothsourceandreservoirrocks thatconstitutethePhosphoriaTPSareshowninfigure21. TheTPSextendseastwardandincorporatesvirtuallyallof theHanna,Laramie,andShirleyBasinsProvince,butbecause Phosphoriasourcerocksdonotextendintotheprovince,the conceptoflong-distancemigrationofoilisimportanttoour understandingofthisTPS.

KeyelementsofthePhosphoriaTPS:

• Sourcerocksofappropriateorganiccontentandsufficientthermalmaturitytogeneratehydrocarbons,

suchastheMeadePeakandRetortPhosphaticShale MembersofthePhosphoriaFormation.

• Long-distancemigrationpathways,suchasvertical pathsthroughfaultsandfractures,andlateral(updip) pathsalongbeddingplanesanddisconformities.

• Reservoirrocks,inthiscasethesandstonesofthePennsylvanianTensleepSandstoneandCasperFormation.

• Traps,suchasthrust-faultedanticlines,complextrianglezones,sedimentarypinchouts,andcombinationsof thesefeatures,alongwithenclosingshale,mudstone, andevaporiteunitsandothertightlycementedbeds thatactasseals.

Figure22isatotalpetroleumsystemeventschartfor thePhosphoriaTPSandtheTensleep-CasperConventional OilandGasAU.Thischartsummarizestherelativeagesof sourceandreservoirrocks;seals;overburden;trapformation; generation,migration,andaccumulationofoilandgas;and thecriticalmoment(timeofmaximumburialdepth),as discussedindetailbelow.

Source Rocks

Lillisandothers(2003)identifiedseveraloiltypesin Paleozoic,Cretaceous,andTertiarystrataintheUintaand PiceanceBasinsofnortheasternUtahandnorthwestern Coloradoonthebasisofgeochemicalcompositionof sampledoil.TheirPhosphoriaoiltypeiswidelydistributed inPennsylvanianthroughJurassicreservoirsintheUinta-PiceanceandSouthwesternWyomingProvinces.Johnson (2003)recognizedPhosphoriaoilinthePennsylvanian-PermianWeberSandstoneatRangelyfieldinnorthwestern Colorado;thatreportalsoidentifies65oilandgasfieldsinthe SouthwesternWyomingProvincethatproducePhosphoriaoil from18pre-CretaceousreservoirsintheTPS.

Regionally,thePhosphoriaoiltypeischaracterizedby highsulfurcontent(0.5–1.4wtpercentsulfur)andpristanephytanevaluesoflessthan1.0(Lillisandothers,2003).For thecurrentassessment,sampleswereanalyzedfromCasper FormationreservoirsatHerrick,LittleLaramie,AllenLake East,andQuealyfieldsintheLaramieBasin.Sulfurvaluesfor thesefieldsrangedfrom2.5to3.5wtpercent(fig.23).Two TensleepoilsampleshavingmoderatetohighAPIgravity andlowsulfurareatO’BrienSpringsandBigMedicineBow fields(fig.23).Theregionaldifferenceinweightpercent sulfurmaybeduetovariationsinPhosphoriasourcerock faciesandkerogencomposition,themixingofoilsfromother sourcerockswiththePhosphoria,ordifferencesinthermal history(PaulLillis,USGS,oralcommun.,2005).Lowsulfur oilsinJurassicSundanceFormationreservoirs(fig.23)in theLaramieBasinatElkMountain,RockRiver,Quealy,and LittleMedicineBowfieldsareinterpretedasderivedfrom MowryoilsoftheMowry-HannaCompositeTPSratherthan fromPhosphoriaoils.


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Figure 21. Pennsylvanian and Permian source and reservoir rocks in western Wyoming and adjacent areas and the Phosphoria Total Petroleum System in the Hanna, Laramie, and Shirley Basins Province (outlined in red), showing the distribution of Phosphoria source rocks (Sublett Basin, within blue crosshatched area) and a portion of the Thrust belt (modified from Maughan, 1984). Tensleep, Casper, and equivalent potential reservoir rocks (inside dashed brown line) modified from Mallory (1972). [Note: the GIS layer for the Phosphoria TPS shows only that part of the TPS within the Hanna, Laramie, and Shirley Basins Province.]

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Documents

Chapter 2 2005 Geologic Assessment of Undiscovered Oil and …€¦ · Province, Wyoming and Colorado By Thaddeus S. Dyman and Steven M. Condon Volume Title Page Chapter 2 of Petroleum