TheoriginofsomenaturalgasesinPermianthroughDevonianAgeSystemsintheFredBaldassareAppalachianBasin&therelationshiptoincidentsofstraygasmigrationFredBaldassareSeniorGeoscientistprearedforpTechnicalWorkshopsforHydraulicFracturingStudyChemical&AnalyticalMethodsAnalyticalMethodsFebruary24,20111MethaneisthePrincipalHydrocarbonfoundinPermianthroughDevonianagestrataandinallstraygasinvestigations2STRAYGASINCIDENTS3•Astheallegationsofhydraulicfracturingcausingcontaminationofgroundwatersuppliesreceivedtheattentionofvariousmediaoutlets,thelinktostraynaturalgascontaminationofaquifersystemscreatedbyhydrauliccontaminationaquifersystemscreatedhydraulicfracturingwassimultaneouslymade,inexplicably...I iifli idi•nvestigationsostraynaturagasncentsnPennsylvaniarevealthatNOincidentsofstraygasmigrationwerecausedbyhydraulicmigrationhydraulicfracturingoftheMarcellusshale.4MethaneingasphaseGasmigrationinthesubsurfaceoccursprincipallybyadvectiveffhi hflditransportromareasogpressuretoareasoowpressureansinfluencedbytemporalchangesin:‐Barometricpressure‐Soil/bedrockporosity,permeabilityMethanedissolvedinwater/p y,p y‐Precipitation‐PorewaterMethanedissolvedingroundwaterintheshallowaquifersystemisnotuncommonincertainareasoftheAppalachianBasin...generally,itdoesnotrepresentthesamethreatasgasphasemethane,andh ldbl dhhidsounoteevauatetesameasmetanegasnorarounabuilding.Solubility~26‐32m/latatmoshericpressure,howeversolubilitgp,,yinwaterisproportionaltopressure.Everyfootofwaterexerts.43psior2.31feetofwaterisunder1psi.Withincreasedhydrostaticpressures,dissolvedmethaneconcentrationsinthegroundwatercangreatlyexceeditssolubilityrepresentgreatlysolubility,andmayrepresentathreattoindoorairspaces.5Incidentsofstraycombustiblegasarenotrecentoccurrences.PotentialSourcesInclude:NaturallyoccurringgasseepsAbandoned,recentlydrilled&operatinggaswellsAb d d&lanonedoperatingcoaminesCBMwellsNaturalgasstoragefieldsNaturalgaspipelinesAbandoned&operatinglandfillsllh llf fNaturayoccurringsaowormations/aquifersBuriedorganicmatterDriftgas67Thermogenic:C1– C6hydrocarbonsgenerated.Formedduringthethermalalterationoforganicmaterials.A itd&itdssociatednon‐assocaeTypeI(lacustrine),II(marine),&III(woody)kerogenEarlymatureMatureLateMatureOvermatureMicrobial:C1– C3hydrocarbonsenerated.Formedbythebacterialgdecompositionoforganicmatter.CO2reductionMethl‐typefermentationye e tat o8Variousresearchershavedeterminedbyexaminationofstablehydrogenandcarbonisotopesofmethanethattherearecommonhydrogenandcarbonisotopiccompositionsformethanehydrogenisotopiccompositionsthermogenic gasassociatedwithcoalandnaturalgas,driftgas,andothernear‐surfacemicrobialgases(Craig,1953;Colemanandothers,1977;Deines,1980;Schoell,1980;RiceandClaypool,1981;Schoell,1983;Whiticar,1986;WieseandKvenvolden,1993;Coleman,1994;Baldassare andLaughrey,1997;Kaplanandothers,1997;andRoweandMuehlenbachs,1999,OsbornandMcIntoshMcIntosh,2010).Stablecarbonisotopecompositionsareexpressedastheratioof12Cto13Cofthesamplecomparedwiththatoftheinternationalstandard...expressedaspermil(partsperthousand,o/oo)andexressedasδ13Cvaluesasfollows:pδ13C‰=[(13C/12Csample‐13C/12Cstandard)/(13C/12Cstandard)]*1000Internationalstandards:carbon:PeeDeeBelemnite(“PDB”)hydrogen:StandardMeanOceanWater(“SMOW”)9Ingeneral:Microbialmethaneacetatefermentation(marshgas&landfillgas)δ13C1:‐40to‐62o/ooδD:‐270to‐350o/ooMicrobialmethaneCO2reduction(driftgas)δ13C1:‐62to‐90o/ooδD:‐180to‐240o/ooThermogenic methaneδ13C1:‐26to‐50o/ooδD:‐110to‐250o/oo10Isotopicmass‐balancecalculationstodeterminethefractionsofend‐membergasescanbeusedtodefinemixing11BernardGraphRevesez,etal.,2010Differentiation of thermogenicgases-30-25g-35

δ 13C (o/oo)-45-40d13-C1 d 13-C2 d 13-C3 d 13-nC4A-41.87 -35.04 -29.16B-43.22 -33.39 -30.06C-42.99 -34.03 -31.07D-41.3 -35.98 -30.2345E-41.76 -35.4 -30.49ABCDE12DIC:DissolvedinorganiccarbonIfwehavebackgroundgroundwaterqualityforanaquifer,DICanalysiswillallowustodetermineifmethanehasbeenimpactedbyoxidationord diegraation.MicrobialprocessessuchasCH4productionorCH4consumptionbyoxidationcanimpartuniqueisotopicsignaturestogasesandcomponentsofthtdidtteassociaewaters.Usngacombinegasandwaterapproachisimporantforconstrainingtheoriginofnaturalgasinwaterwells.Whiticar,andFaber,1986,Revesz,et.al,201013Central&NorthernAppalachianBasinRepresentativeisotopegeochemistrydataforh itermogenic gases:14-100ISOTOPE CROSSPLOTMarcellus (NC PA)Themogenic Gas("natural gas" andcoalbed methane)Upper Devonian/Marcellus (SW PA)Marcellus(NCPA)

(% ) oMicrobial Gas -CO Reduction2-200

h ane(drift gas)

D of Metearlythermogenic

δMicrobial Gas -Fermentation(landfillgases)-300y g( g)-90 -80 -70 -60 -50 -40 -30 -2015δ13C of Methane(% )oRepresentative Thermogenic gasesCentral/Northern Appalachian Basin-100ISOTOPE CROSSPLOTThermogenic Gas("natural gas"and

(% ) oMicrobial Gas -CO Reduction2( naturalgasandcoalbed methane)-200

h ane δ(drift gas)2

D of Met hMicrobial Gas -Fermentation(landfill gases)-300-90 -80 -70 -60 -50 -40 -3016δ13o(% )C of MethaneSouthwestern PennsylvaniaPrivate water supply well dataInvestigations revealed methane origin as naturally occurring-100ISOTOPE CROSSPLOTThemogenic Gas("natural gas"and

(% ) oMicrobial Gas -CO Reduction2( naturalgasandcoalbed methane)-200

a neCOReduction(drift gas)2

D of Meth aUpper Devonian Age Strata(Catskill & unknown formations)C1 : C2 55 - 6,900

δMicrobial Gas -Fermentation(landfill gases)-300δ-90 -80 -70 -60 -50 -40 -30 -20C of Methane(% )Pre-Marcellus well activity17δ13CofMethane(%)oPre Marcelluswellactivityprivate water supply wellsBradford County-100ISOTOPE CROSSPLOTThemogenic Gas("natural gas" andcoalbed methane)566'

(% ) oMicrobial Gas -CO Reduction2-200

a neUpper Devonian(Catskill & unknown fm)566' - 916'566'916'770'COReduction(drift gas)2

D of Meth a δMicrobial Gas -Fermentation(landfillgases)-300

Dδ( g)-90 -80 -70 -60 -50 -40 -30 -20(% )1813C of Methane(%)oMarcellus Gas WellCentral Bradford CountyδCMarcellusgaswellBradfordCounty,PA0‐55‐50‐45‐40‐35‐30‐25‐20δC13UpperDevonian20004000Seal?UpperDevonian(Catskillfm?)40006000

e pth (ft)d13C1d13C2Marcellusshale(noteisotopereversal)8000

D e(noteisotopereversal)100001912000δMarcellusgaswellBradfordCounty,PA0‐50.0‐45.0‐40.0‐35.0‐30.0‐25.0‐20.0δC13UD i2000seal?pperDevonian(Catskillfm?)40006000

p th (ft)d13C1d13C28000

De pMarcellusshale(noteisotopereversal)100002012000δMarcellusGasWellBradfordCounty,PA0100‐55‐50‐45‐40‐35‐30‐25‐20δC13200300Shallowthermogenic gasthroughoutsample400500

p th (ft)d13C1d13C2throughoutsampleinterval600700

De pSeal?80090021100022