shale gas.docx

shale gas.docx

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shalegas

Shalegas is naturalgas thatisfoundtrappedwithin shale formations. ShalegashasbecomeanincreasinglyimportantsourceofnaturalgasintheUnitedStatessincethestartofthiscentury,andinteresthasspreadtopotentialgasshalesintherestoftheworld.In2000shalegasprovidedonly1%ofU.S.naturalgasproduction;by2010itwasover20%andtheU.S.government's EnergyInformationAdministration predictsthatby2035,46%oftheUnitedStates'naturalgassupplywillcomefromshalegas.

Someanalystsexpectthatshalegaswillgreatlyexpandworldwideenergysupply.China isestimatedtohavetheworld'slargestshalegasreserves. AstudybytheBakerInstituteofPublicPolicy at RiceUniversity concludedthatincreasedshalegasproductionintheUSandCanadacouldhelppreventRussiaandPersianGulfcountriesfromdictatinghigherpricesforthegastheyexporttoEuropeancountries.

The Obama administrationbelievesthatincreasedshalegasdevelopmentwillhelpreducegreenhousegasemissions （in2012,UScarbondioxideemissionsdroppedtoa20-yearlow）.Humanand publichealth willbothbenefitfromshalegasdisplacingcoalburning.

A2013reviewbytheUnitedKingdom DepartmentofEnergyandClimateChange notedthatmoststudiesofthesubjecthaveestimatedthatlife-cyclegreenhousegas（GHG）emissionsfromshalegasaresimilartothoseofconventionalnaturalgas,andaremuchlessthanthosefromcoal,usuallyabouthalfthegreenhousegasemissionsofcoal;thenotedexceptionwasa2011studybyHowarthandothersof CornellUniversity,whichconcludedthatshalegasGHGemissionswereashighasthoseofcoal. Morerecentstudieshavealsoconcludedthatlife-cycleshalegasGHGemissionsaremuchlessthanthoseofcoal, amongthem,studiesby NaturalResourcesCanada （2012）,andaconsortiumformedbytheUS NationalRenewableEnergyLaboratory withanumberofuniversities（2012）.

Some2011studiespointedtohighratesofdeclineofsomeshalegaswellsasanindicationthatshalegasproductionmayultimatelybemuchlowerthaniscurrentlyprojected. Butshale-gasdiscoveriesarealsoopeningupsubstantialnewresourcesof tightoil /"shaleoil".

History

US

Shalegaswasfirstextractedasaresourcein Fredonia,NewYork,in1821, inshallow,low-pressurefractures.Horizontaldrillingbeganinthe1930s,andin1947awellwasfirst fracked intheU.S.

Federalpricecontrolsonnaturalgasledtoshortagesinthe1970s. Facedwithdecliningnaturalgasproduction,thefederalgovernmentinvestedinmanysupplyalternatives,includingtheEasternGasShalesProject,whichlastedfrom1976to1992,andtheannual FERC-approvedresearchbudgetoftheGasResearchInstitute,wherethefederalgovernmentbeganextensiveresearchfundingin1982,disseminatingtheresultstoindustry. Thefederalgovernmentalsoprovidedtaxcreditsandrulesbenefitingtheindustryinthe 1980EnergyAct. TheDepartmentofEnergylaterpartneredwithprivategascompaniestocompletethefirstsuccessfulair-drilledmulti-fracturehorizontalwellinshalein1986.ThefederalgovernmentfurtherincentivizeddrillinginshaleviatheSection29taxcreditforunconventionalgasfrom1980-2000.Microseismicimaging,acrucialinputtoboth hydraulicfracturing inshaleand offshoreoildrilling,originatedfromcoalbedsresearchat SandiaNationalLaboratories.TheDOEprogramalsoappliedtwotechnologiesthathadbeendevelopedpreviouslybyindustry,massivehydraulicfracturingandhorizontaldrilling,toshalegasformations. thatledtomicroseismicimaging.

AlthoughtheEasternGasShalesProjecthadincreasedgasproductionintheAppalachianandMichiganbasins,shalegaswasstillwidelyseenasmarginaltouneconomicwithouttaxcredits,andshalegasprovidedonly1.6%ofUSgasproductionin2000,whenthefederaltaxcreditsexpired.

GeorgeP.Mitchell isregardedasthefatheroftheshalegasindustry,bymakingitcommerciallyviableinthe BarnettShale bygettingcostsdownto$4permillion BritishThermalUnits. MitchellEnergyachievedthefirsteconomicalshalefracturein1998usingslick-waterfracturing. Sincethen,naturalgasfromshalehasbeenthefastestgrowingcontributortototalprimaryenergyintheUnitedStates,andhasledmanyothercountriestopursueshaledeposits.AccordingtotheIEA,shalegascouldincreasetechnicallyrecoverablenaturalgasresourcesbyalmost50%.

Geology

Becauseshalesordinarilyhaveinsufficient permeability toallowsignificantfluidflowtoawellbore,mostshalesarenotcommercialsourcesofnaturalgas.Shalegasisoneofanumberofunconventionalsourcesofnaturalgas;othersinclude coalbedmethane, tightsandstones,and methanehydrates.Shalegasareasareoftenknownas resourceplays （asopposedto explorationplays）.Thegeologicalriskofnotfindinggasislowinresourceplays,butthepotentialprofitspersuccessfulwellareusuallyalsolower.

Shale haslow matrix permeability,sogasproductionincommercialquantitiesrequiresfracturestoprovidepermeability.Shalegashasbeenproducedforyearsfromshaleswithnaturalfractures;theshalegasboominrecentyearshasbeenduetomoderntechnologyinhydraulicfracturing （fracking）tocreateextensiveartificialfracturesaroundwellbores.

Horizontaldrilling isoftenusedwithshalegaswells,withlaterallengthsupto10,000feet（3,000 m）withintheshale,tocreatemaximumboreholesurfaceareaincontactwiththeshale.

Shalesthathosteconomicquantitiesofgashaveanumberofcommonproperties.Theyarerichinorganicmaterial（0.5%to25%）, andareusuallymaturepetroleum sourcerocks inthethermogenicgaswindow,wherehighheatandpressurehaveconvertedpetroleumtonaturalgas.Theyaresufficientlybrittleandrigidenoughtomaintainopenfractures.

Someofthegasproducedisheldinnaturalfractures,someinporespaces,andsomeis adsorbed ontotheorganicmaterial.Thegasinthefracturesisproducedimmediately;thegasadsorbedontoorganicmaterialisreleasedastheformationpressureisdrawndownbythewell.

Shalegasbycountry

Althoughtheshalegaspotentialofmanynationsisbeingstudied,asof2013,onlytheUS,Canada,andChinaproduceshalegasincommercialquantities,andonlytheUSandCanadahavesignificantshalegasproduction.

Thetablebelowisbasedondatacollectedbythe EnergyInformationAdministration agencyofthe UnitedStatesDepartmentofEnergy. Numbersfortheestimatedamountof"technicallyrecoverable"  shalegasresourcesareprovidedalongsidenumbersfor provennaturalgasreserves.

TheUSEIAhadmadeanearlierestimateoftotalrecoverableshalegasinvariouscountriesin2011,whichforsomecountriesdifferedsignificantlyfromthe2013estimates. ThetotalrecoverableshalegasintheUnitedStates,whichwasestimatedat862trillioncubicfeetin2011,wasreviseddownwardto665trillioncubicfeetin2013.RecoverableshalegasinCanada,whichwasestimatedtobe388TCFin2011,wasrevisedupwardto573TCFin2013.

FortheUnitedStates,EIAestimated（2013）atotal"wetnaturalgas"resourceof2,431tcf,includingbothshaleandconventionalgas.Shalegaswasestimatedtobe27%ofthetotalresource. "Wetnaturalgas"is methane plus naturalgasliquids,andismorevaluablethandrygas.

Fortherestoftheworld（excludingUS）,EIAestimated（2013）atotal wetnaturalgas resourceof20,451 trillioncubicfeet（579.1×1012 m3）.Shalegaswasestimatedtobe32%ofthetotalresource.

Europehasestimatedshalegasreservesof639 trillioncubicfeet（18.1×1012 m3）comparedwithAmerica's862 trillioncubicfeet（24.4×1012 m3）,butitsgeologyismorecomplicatedandtheoilandgasmoreexpensivetoextract,withawelllikelytocostasmuchasthree-and-a-halftimesmorethanoneintheUnitedStates.

Environment

Theextractionanduseofshalegascanaffecttheenvironmentthroughtheleakingofextractionchemicalsandwasteintowatersupplies,theleakingofgreenhousegases duringextraction,andthepollutioncausedbytheimproperprocessingofnaturalgas.Achallengetopreventingpollutionisthatshalegasextractionsvarieswidelyinthisregard,evenbetweendifferentwellsinthesameproject;theprocessesthatreducepollutionsufficientlyinoneextractionmaynotbeenoughinanother.

In2013the EuropeanParliament agreedthat environmentalimpactassessments willnotbemandatoryforshalegasexplorationactivitiesandshalegasextractionactivitieswillbesubjecttothesametermsasothergasextractionprojects.

Climate

BarackObama'sadministrationhassometimespromotedshalegas,inpartbecauseoftheirbeliefthatitreleasesfewer greenhousegas （GHG）emissionsthanotherfossilfuels.Ina2010lettertoPresidentObama, MartinApple ofthe CouncilofScientificSocietyPresidents cautionedagainstanationalpolicyofdevelopingshalegaswithoutamorecertainscientificbasisforthepolicy.Thisumbrellaorganizationthatrepresents1.4millionscientistsnotedthatshalegasdevelopment“mayhavegreaterGHGemissionsandenvironmentalcoststhanpreviouslyappreciated.”

Inlate2010,theU.S.EnvironmentalProtectionAgency issuedanewreport,thefirstupdateonemissionfactorsforgreenhousegasemissionsbytheoilandgasindustrybytheEPAsince1996.Inthisnewreport,theEPAconcludedthatshalegasemitslargeramountsof methane,apotent greenhousegas,thandoesconventionalgas,butstillfarlessthancoal.Methaneisapowerfulgreenhousegas,althoughitstaysintheatmosphereforonlyonetenthaslongaperiodascarbondioxide.Recentevidencesuggeststhatmethanehasaglobalwarmingpotential（GWP）thatis105-foldgreater