英文版油藏工程名词解释

ACopyright?1984-97SPWLA,Allrightsreserved.MaynotbereproducedinanyformwithoutpermissionfromSPWLA

abandon

Toceaseproducingoilorgasfromawellwhenitbecomesunprofitable.Awildcatmaybeabandonedafterithasbeenprovednonproductive.Sometimes,beforeawellisabandoned,someofthecasingisremovedandsalvaged.Usually,oneormorecementplugsareplacedintheboreholetopreventmigrationoffluidsbetweenthevariousformations.Inmanystates,abandonmentmustbeapprovedbyanofficialregulatoryagencybeforebeingundertaken.

abnormalpressure

Anyporepressurewhichdiffersfromnormalporepressure.Itmaybeeitherhigherthannormalporepressure(super-normal)orlowerthannormalporepressure(subnormal).Seeoverpressureandunderpressure.

absolutepermeability

Thepermeabilityofarockmeasuredwhenonlyonefluidphaseispresentintherock.Usuallymeasuredinmillidarciesordarcies.Seepermeability.Compareeffectivepermeabilityandrelativepermeability.

absolutepressure

Pressurerelativetoanidealvacuum.Gagepressureplusatmosphericpressure.

absolutetemperaturescale

Ameasureoftemperatureinwhichzerodegreesisabsolutezero.TemperaturemeasuredindegreesKelvin(°K)fromabsolutezero(–273.16°C)ordegreesRankine(°R)fromabsolutezero(–459.69°F).

°K

=

°C

+

273.16

°R

=

°F

+

459.69

absolutezero

Ahypotheticaltemperatureatwhichallthermalmotionofatomsceases.Atotalabsenceofheat.

absorption

(1)Theprocessofsoakinguportakinginbycapillary,osmotic,chemical,orsolventaction.

(2)Theprocessbywhichradiationlosessomeorallofitsenergytoanymaterialthroughwhichitpasses.Seealsophotoelectricabsorption.

accelerator

Adeviceusedforacceleratingthevelocityofelectrons,ornuclearparticlestohighenergies.Forexample,anacceleratorisusedinpulsedneutronloggingwheredeuteriumisacceleratedtostrikeatritiumtargettoproduceneutrons.

acid

Anychemicalcompound,oneelementofwhichishydrogen,thatdissociatesinsolutiontoproducefreehydrogenions.Seeion.Forexample,hydrochloricacid,HCl,dissociatesinwatertoproducehydrogenions,H+,andchlorideions,Cl–.ThisreactionisexpressedchemicallyasHCl

H+

+

Cl–.Seedissociation.

acidstimulation

Acidizingofawell.Processofintroducingacidintoawelltodissolveacidsolublematerials,inthewellboreorinreservoirrocknearthewellbore,whichmightberestrictingfluidflow.Acid-solublematerialsinthereservoirrockmightoccurnaturallyormighthavebeenintroducedduringthedrillingorcompletionprocessofthewell.Commonlyusedacidsarehydrochloricandmixturesofhydrochloricandhydrofluoric;althoughothermineralacidsandorganicacidshavebeenused,notablycitricacidandaceticacid.

acidtreatment

Seeacidstimulation.

acidize

Seeacidstimulation.

acre-foot

Aunitofvolumeoftenusedinoil-reservoiranalysis.Equivalenttothevolume(asofoilorwater)necessarytocover1

acretoadepthof1

foot.

acre-ft.

acre-foot.

acoustic

Oforpertainingtosound.

acousticlog

Arecordofawell-loggingmeasurementofoneormorespecificcharacteristicsofacousticwavespropagatedinandaroundtheliquid-filledwellbore.

(1)Theintervaltransittime,usuallyofthecompressionalwave,isrecordedonsuchlogsasthesoniclog,continuousvelocitylogs,andboreholecompensatedsonicandAcoustilogs.

(2)Theamplitudeofpartofthepropagatedacousticwave,suchasthecompressionalwaveorshearwaveisthemeasurementrecordedonotherwelllogs.Thesearetheamplitudelog,cementbondlog,andfracturelogs.

(3)Theacousticwavetrainofthepropagatedacousticwaveisdisplayedintheamplitude-timemodeonfullwavetrainlogssuchassignaturelogsorcharacterlogs;whereasthewavetrainisshownintheintensitymodulated-timemodeonvariabledensitylogs,variableintensitylogs,3-DVelocityLogs,orMicro-SeismogramLogs.

(4)Includeslogsresultingfromthemeasurementsoftraveltimeandamplitudeofreflectedacousticenergy.Toolsmakingsuchmeasurementsaretheboreholeteleviewerandsonarcaliper.

(5)Alsoincludeslogsproducedbydeviceswhichdetectandmeasuretheamplitudeofsoundwavesintheaudiblefrequencyrange.Audiblesoundmightemanatefromliquidorgasmovementsinthewellboreenvironment.Toolsdevelopedtomakesuchmeasurementsareusedinaudioornoiseloggingtechniques.

acoustictraveltime

(1)Thetotaltimerequiredforaspecificacousticwavetotravelfromonepointtoanother.

(2)intervaltransittime.Thetimerequiredforacompressionalwave(usually)totravelfromonepointtoanotherseparatedbyadistanceofunitlength(usuallyonefoot).

acousticvelocitylog

AVL.Seeacousticlogpart(1).

acousticwave

Anelasticwave,seismicwave.Asoundwaveinwhichthedisturbancepropagatedthroughamediumisanelasticdeformationofthemedium.Thewavetrainwhichresultsfromtheemissionofanacousticpulsebyawellloggingdeviceisdetectedbyoneormoredetectorsmountedonthesondeandvariousaspectsofitaremeasured(seeacousticlog).Thewavetrainisacompositeofvariousmodesofenergytransfer.Thefirstarrivalusuallyresultsfromcompressionalwavestravelingintheformation;theinverseofitsvelocityismeasuredbysonictools.Asecondarrivalissometimesidentifiedasshearwavestravelingintheformation.Thevelocityofthecompressionalwavestravelingthroughthemudisfrequencydependentandhasrelativelyhighfrequencycontent.Ontheotherhand,surfacewavesofrelativelylowfrequencytravelalongtheboreholewallatlowervelocitiesandareusuallycalledtubewavesorpseudo-Stoneleywaves.Seealsowavetrain.

Acoustilog

Asoniclog.Seeacousticlog.AcoustilogisaDresserAtlastrademark.

activation

Seeneutronactivation.

activationlogging

Awell-loggingtechniqueinwhichtheformationinthenearenvironmentoftheirradiatingtoolsisirradiatedwithneutronswhichtransformsomenucleiintoradioisotopes.Thespecificradioactiveisotopeswhichareproducedbyactivationofthenucleicanbedetectedbytheircharacteristicinducedradioactivityenergylevelsanddecay-timeschemes.Thisprovidesameansforidentifyingtheelementsoriginallypresent.Seealsoinducedspectralgamma-raylogandneutronactivation.

activity

Theactivityofanionspeciesisitsthermodynamicequivalentconcentration;i.e.,theionconcentrationcorrectedforthedeviationfromidealbehaviorcausedbytheinterionicattractionofions.Itisthisinteractionbetweenionswhichtendstocausetheelectricalconductivityofasolutiontobelessthanthatpredictedfromthenumberofionspresent.Onlyatinfinitedilutionaretheionscompletelyfreeoftheinfluenceofotherionsinsolution.

Ionicactivityisusedinexpressingthevariationofelectrodepotentialsandotherelectrochemicalphenomena(e.g.,SP).Atlowconcentrations,thechemicalactivityofasolutionofagivensaltisroughlyproportionaltoitssaltcontent;i.e.,roughlyproportionaltoitsconductivityorinverselytoitsresistivity.Inconcentratedsolutions,therelationbetweenconductivityandconcentrationiscomplexanddependsonindividualsoluteproperties.

adapter

Ashort,threadedpieceorcouplingusedtoadaptpartsoftheloggingtoolthatcannototherwisebecoupledtogetherbecauseofdifferenceinthreadsizeordesign.

adiabatic

Anadiabaticprocessisoneinwhichthereisnoexchangeofheatwiththesurroundings.Therelationshipofpressureandvolumewhenagasorotherfluidiscompressedorexpandedwithnolossorgainofheat.Inanadiabaticprocess,compressioncausesanincreaseintemperatureandexpansionadecreaseintemperature.

adsorption

Atypeofadhesionwhichtakesplaceatthesurfaceofasolidoraliquidincontactwithliquidorgases.Adsorptionresultsintheaccumulationofmoleculesofgases,orionsormoleculesofliquids,atthesurfacesofcontactingsolidsorliquids.

Aelectrode

Thecurrent-emittingelectrodeintheconfigurationofcurrentandpotential-measuringelectrodesofaresistivity-measuringdevice.CompareBelectrode.Seenormalandlateraldevices.

aeratedzone

Seezoneofaeration.

AIME

TheAmericanInstituteofMining,Metallurgical.andPetroleumEngineers.TheNewYorkCity-basedparentgroupoftheSocietyofPetroleumEngineers.TheSPE,headquarteredinDallas,Tex.,publishesthe"JournalofPetroleumTechnology."

airdrilling

Amethodofrotarydrillingthatusescompressedairasitscirculationmedium.Thismethodofremovingcuttingsfromthewellboreisasefficientormoreefficientthanthetraditionalmethodsusingwaterordrillingmud.Inaddition.therateofpenetrationisincreasedconsiderablywhenairdrillingisused.Aprincipalprobleminairdrillingisthepenetrationofformationscontainingwater,sincetheentryofwaterintothesystemreducesitsefficiency.

alkaline

(1)Havingthepropertiesofabase.

(2)Containingsodiumand/orpotassiuminexcessoftheamountneededtoformfeldsparwiththeavailablesilica;e.g.,analkalinerock-inthissensesometimeswrittenalkalic.

(3)Containingionsofoneormorealkalimetals.

(4)Waterscontainingmorethanaverageamountsofcarbonatesofsodium,potassium,magnesium,orcalcium.

alpha

Theratioofthepseudo-staticSP(PSP)tothestaticSP(SSP).Alphabearsaninverserelationshipwithclayiness.

alphaparticle

Aparticleidenticaltotheheliumnucleuswhichhasbeenejectedfromthenucleusofanatomasaformofradiation.Whenthealphaparticleslowsdownitpicksuptwoelectrons,becominganatomofhelium.Thepenetratingpowerofanalphaparticleislow;athinsheetofpaperwillstopmostalphaparticles.Thereadjustmentwhichtakesplacewithintheparentnucleusresultsingammaradiation.

alpharing

AcommonWelexnameforguardedelectrode.

allogenic

Descriptiveofdetritalrockconstituentsandmineralsderivedelsewherefromolderformationsandredeposited.Compareauthigenic.

AmericanPetroleumInstitute

API.Foundedin1920,thisnationaloiltradeorganizationistheleadingstandardizingorganizationonoil-fielddrillingandproducingequipment.Itmaintainsdepartmentsoftransportation,refining,andmarketinginWashington,D.C.,andadepartmentofproductioninDallas.

amorphous

Withoutform.Atermappliedtorocksandmineralshavingnodefinitecrystallinestructure.

AMspacing

Thenotationusedtorefertothedistancebetweenthecurrentelectrode(A)andthepotential-measuringelectrode(M)ofthenormaldevice.

amplifiedcurve

Acurverecordedonamoresensitivescale;e.g.,theamplifiedshortnormalcurve.

amplitudelog

Arecordoftheamplitudeofthecompressionwaveorshearwaveportionoftheacousticwavepropagatedthroughtheboreholeenvironmentinacousticlogging.Seealsocementbondlogandfracturelog.

amplitude-time

Anacousticwavetraindisplaymode.AtraceoftheacousticwavetrainintheX-Yplaneinwhichtheamplitudeofeachpointonthewavetrainisrepresentedasafunctionoftime.Seeacousticlog.Compareintensitymodulated-timeorvariabledensity.Seeillustrationatwavetraindisplay.

anhydrite

Thecommonnameforthenaturallyoccurringcalciumsulfate.Anhydriteiscalciumsulfate(CaSO4)existingintheorthorhombiccrystallineform.Theanhydritecrystalcannotbecomeagypsumcrystal(monoclinicform)inasinglehydrationstep.Anhydritemustfirstbecomedissociatedinsolutionbeforeitcancrystallizeasgypsum(orrecrystallizeasanhydrite).Comparegypsum.

anion

Anegativelychargedion.

anisotropic

Oforpertainingtoanisotropy.Seeanisotropy.

anisotropy

Thepropertyofarockwhichallowsittoshowdifferentresponsesormeasurementswhenmeasuredalongdifferentaxes.Microscopicanisotropyrelatestothevariationofapropertymeasuredperpendiculartothebeddingfromthatmeasuredparalleltothebeddingbecauseplate-likemineralgrainsandintersticestendtoorientthemselvesparalleltothebedding.Macroscopicanisotropyrelatestothevariationresultingfromthinbedsandfractureplaneswhosepropertiesdifferappreciablyfromthoseoftheremainingvolumeoverwhichameasurementismade.

annularspace

Seeannulusparts(1)and(2).

annulus

(1)Thatspacebetweenadrillpipeandtheformationsthroughwhichthedrillingfluid(mud)returnstothesurface.

(2)Thespacebetweentubingandcasingorbetweencasingandformation.

(3)Aringofinterstitialwaterproducedbyinvasionprocessesinhydrocarbon-bearingbedswhenbothhydrocarbonandinterstitialwaterphaseshavemobilityandtheirmobilitiesaredifferent.

WhenRxo

>

Rotheannuluswillbemoreconductivethantheflushedzone(Rxo)ortheuninvadedoil-bearingzone(Rt).WhenRxo

<

Ro,theresistivityoftheannuluswillbeintermediatebetweenthatoftheflushedzone(Rxo)andtheuninvadedoil-bearingzone(Rt).

anticline

Asubsurfacefoldstructureinwhichbedsdipinoppositedirectionsfromacommonridgeoraxis.Afoldthatisconcavedownwards.Seeillustrationinfold.

AOspacing

Thisnotationreferstothedistancebetweenthecurrentelectrode(A)andapoint(O)midwaybetweenthepotential-measuringelectrodes(MandN)ofthelateraldevice.Onthereciprocalsonde,itisthedistancebetweentheMelectrodeandapoint(O)midwaybetweenthecurrentelectrodes(AandB).

API

SeeAmericanPetroleumInstitute.

APIgravity

ThemeasureofgravityofliquidpetroleumproductsontheNorthAmericancontinent,derivedfromspecificgravityinaccordancewiththefollowingequation:

APIgravityisexpressedindegrees,aspecificgravityof1.0beingequalto10

°API.

APIloggrid

TheAPIloggridisthestandardformatusedbyallloggingcompaniesforrecordingwell-loggingmeasurementsinthepetroleumindustry.Thisloggridhasonetrackontheleftsideofthedepthcolumnandtwoontheright.Thetracksare2.5

incheswideandthedepthcolumnis0.75

incheswide.Thetracksmaybedividedintolinearscaleorlogarithmicscale.Seescaleforillustration.

APItestpits

Calibrationpits,locatedattheAPInuclearlogcalibrationfacilityattheUniversityofHouston,usedforthecalibrationorstandardizationofgamma-rayloggingresponsesandneutronloggingresponsesintoAPIunits.

APIunit

Aunitofcountingrateusedforscalinggamma-raylogsandneutronlogs.

(1)Forgamma-raycurves.ThedifferenceincurvedeflectionbetweenzonesoflowandhighradiationintheAPIgamma-raycalibrationpitis200

APIgamma-rayunits.Onetwo-hundredthofthisdeflectionisoneAPIgamma-rayunit.

(2)Forneutroncurves.ThedifferencebetweenelectricalzeroandthecurvedeflectionoppositeazoneofIndianalimestone(19%porosity)intheAPIneutroncalibrationpitis1,000

APIunits.Oneone-thousandthofthisdeflectionisoneAPIneutronunit.

apparentresistivity

Resistivityrecordedonaresistivitywelllogwhichmaydifferfromtrueresistivitybecauseoftheinfluenceonthemeasuredresponsecausedbythepresenceofthemudcolumn,invadedzone,adjacentbeds,boreholecavities,etc.Thesevaluesmayneedcorrectionpriortouseinanycomputation.

apparentvalue

Theuncorrectedvalueofacurverecordeddirectlyonalog.

aquicide

Arelativelyimpermeablestratumthatdoesnottransmitwaterfastenoughtosupplyawellorspring.

aquifer

(1)Awater-bearingstratumofpermeablerock,sand,orgravelcapableofproducingwater.

(2)Inapetroleumreservoirwithanaturalwaterdrive,theaquiferisthatpartofthereservoircontainingwater.

arch

Sandarch.Thearchofsandcreatedoutsideofanorificeorperforationontheformationsideofcasingorliner.Forexample,inunconsolidatedsandstonetherockmusthavethepropertyofdilatancy,orthepropertytoexpand,beforethearchwillform.Theresultingarch,causedbytheinterlockingandwedgingtogetherofsandgrains,preventstheflowofsandthroughaperforation.Cohesionisimpartedtotheloosegrainsformingthearchwhenthewettingphaseisatirreduciblesaturation.

Archie'sformulas

EmpiricalrelationshipsbetweentheformationresistivityfactorF,porosity,watersaturationSw,andresistivitiesincleangranularrocks.

where

m

=

porosityexponent,

Ro

=

resistivityoftheformationwhen100%

saturatedwithformationwater,

Rw

=

formationwaterresistivity,

Rt

=

trueresistivityoftheformation,

n

=

saturationexponent.

arenaceous

Pertainingtosandorsandyrocks(as,aranaceousshale).

argillaceous

Rocksorsubstancescomposedofclayminerals,orhavingnotableproportionofclayintheircompositionsuchasshaleandslate.

arkose

Asandstonecontaining25%ormoreoffeldspars,usuallyderivedfromsilicicigneousrocks.

arm

(1)Abowspringorleveronadownholetoolwhichpressesagainsttheboreholewalltocentralizethetool,topushthetooltotheoppositesideoftheborehole,ortoholdasensorpadtotheboreholewall.

(2)Toprepareaperforatinggunsothatitwillfirewhenthefiringswitchatthesurfaceisoperated.Thisusuallyrequiresconnectingthedetonatorand/orcompletingtheelectricalwiringinthegun.

armor

Layersofsteelwirewrappedaroundinsulatedelectricalconductorsofasurveycable.Thestrengthofthecableundertensionisrelatedtothenumberofwirestrandsinthearmorandtheircondition.Seealsoweakpoint.

aromatic

Pertainingtohydrocarbons,aliquidorsolidhydrocarbonhavingtheformulaCnH2n–6.Suchcompoundscontainthebenzenering.Compareparaffinic.

arrowplot

Adisplayofdipmeterordriftmeasurements.Seetadpoleplot.

artesianwater

Groundwaterthathassufficienthydraulicpressuretoriseaboveitsaquifer.Thiswatermightormightnothavesufficienthydraulicpressuretoriseaboveitsaquifer.Thiswatermightormightnothavesufficientpressuretorisetoorabovethesurfaceoftheground.

artificiallift

Anymethodusedtoraiseoiltothesurfacethroughawell,afterreservoirpressurehasdeclinedtothepointatwhichthewellnolongerproducesbymeansofnaturalenergy.Sucker-rodpumps,hydraulicpumps,submersiblepumps,andgasliftarethemostcommonmethodsofartificiallift.

asphalt

Adarkcoloredbitumenfoundasanaturaldeposit.Crudeoilofhighasphalticcontentwillleaveasphaltasaresiduewhensubjectedtodistillationtoremovethelighterfractions.Asphaltisdarkbrownorblackincoloransatroomtemperaturesusuallyissolid.

atmosphericpressure

Thepressureexertedoverthesurfaceoftheearthbytheweightoftheatmosphere.Atsealevel,thispressureisapproximately14.7

psia.

atom

Thesmallestparticleofanelementwhichcanexistalone,orincombinationwithsimilarparticlesofthesameofdifferentelements.

atomicnumber

Thenumberofprotonswithinanatomicnucleus,orthenumberoforbitalelectronsina"neutral"atom.

atomicweight

Atomicmass.Therelativeweightofanatomonthebasisthatcarbonis12.Forapureisotope,theatomicweightroundedofftothenearestintegerequaltothetotalnumberofneutronsandprotonsintheatomicnucleus.

attenuation

Whenaformofenergyispropogatedthroughamedioum,itsamplitudeisdecreased.Thisdecreaseistermedattenuation.Seealsowavetrain.

audiologging

Seenoiselogging.

authigenic

Descriptiveofrockconstituentsandmineralswhichareformedorgeneratedinthelocationwheretheyarefound.

Authigenicmaterialsussuallyareformedsubsequenttodeposition,butmightbeformedatthetimeofdeposition.Compareallogenic.

azimuth

(1)Inwelllogging.Inahorizontalplane,itistheclockwiseangleofdeparturefrommagneticnorth.Seealsomagneticdeclination.

(2)Curverecordedindipmetersurveys.Lookingdownthehole,itistheclockwiseanglefrommagneticnorthtothereferenceelectrodenumber1onthesondeortool.

(3)Inlandsurveying.Itistheclockwiseangleofdepartureinahorizontalplanefromtruenorth.

azimuthfrequencyplot

Adiagramonpolarchartpaperwhichpresentsonlyacountofthenumberofdipazimuthmeasurementswhichfallwithineachten-degreesector,withinagivengroupofdips.Dipmagnitudeisignored.Seeillustrationinazimuth.

backgroundradiation

Theradiationintensityexistingintheenvironmentwhichisinadditiontothespecficradiationunderconsideration.Onthesurface,thisistheionizingradiationproducedbycosmicirradiationandnaturallyoccurringtraceamountsofradioactiveelements.Inthesubsurface,thisisthenaturallyoccurringradiationpriortotheintroductionofradioactivetracermaterialsoractivation.

back-pressure

Thepressuremaintainedonequipmentorsystemsthroughwhichafluidflows.

back-upcurve

Acurverecordedbyaback-upgalvanometer.

back-upgalvanometer

Agalvanometerwhichbeginstorecordwhentheprimarygalvanometerhasreachedthelimitofavailabletrackwidthorgoesoffscale.Theback-upgalvaometerwillbeeitherlesssensitivethantheprimarygalvanometerorhaveashiftedscale.

ballsealers

Ballsmadeofnylon,hardrubber,orboth,andusedtoshutoffperforationsthroughwhichexcessivefluidislost.

barefootcompletion

Seeopenholecompletion.

barite

BaSO4.Anaturalmineralusedasweightingmaterialindrillingmud.

barn

10–24

cm2.Aunitofmeasureforcapturecrosssection.

barrel

Petroleumbarrel.Aunitofmeasureforcrudeoilandoilproductsequalto42

U.S.gallons.

basalt

Afine-grainedigneousrockdominatedbydark-coloredminerals,consistingofplagioclasefeldspars(acalcium-sodium-aluminum-silicate,usuallypresentinamountsover50%),andferromagnesiumsilicates.Basaltsandandesitesrepresentabout98%ofallextrusiveigneousrocks.

base

Asubstancecapableofcombiningwithchargedhydrogenatoms(ions)toformasalt.Atypicalbaseissodiumhydroxide(caustic),withthechemicalsymbolNaOH.

baseexchange

Seeionexchange.

base-lineshift

(1)Generallyreferstoanaturallyoccurringshiftofthebaselineofanyspecificcurve;e.g.,theSPcurve.Usuallythebaselinereferredtoistheshalebaseline,butcouldbethesandbaselineorotherbaseline.

(2)Sometimesreferstoamanualorelectricalshiftinthecurveproducedbytheloggingengineer.Seemanualshift.

basement

Acomplexofundifferentiatedrocksthatunderliestheoldestsedimentaryrocks.InmanyplacestherocksofthecomplexareigneousandmetamorphicandofPrecambrianage,butinsomeplacestheyarePaleozoic,Mesozoic,orevenCenozoic.Intermsofpetroleumexploration,basementisthesurfacebelowwhichthereisnocurrentexplorationinterest.

basin

Asynclinalstructureinthesubsurface,oncethebedofanancientsea.Basins,inwhichsedimentshaveaccumulated.areregardedasgoodprospectsforoilexploration.

bearing

Seerelativebearing.

bed

Asubdivisionofastratifiedsequenceofrocks,lowerinrankthanamemberorformation,internallycomposedofrelativelyhomogeneousmaterialexhibitingsomedegreeoflithologicunity,andseparatedfromtherocksaboveandbelowbyvisuallyorphysicallymoreorlesswelldefinedboundaryplanes.

beddingplanes

Insedimentaryorstratifiedrocks,thedivisionplanesthatseparatetheindividuallayers,beds,orstrata.

bedrock

Ageneraltermfortherock,usuallysolid,thatunderliessoilorotherunconsolidated,superficialmaterial.

bedthickness

(1)Truebedthicknessisthethicknessofthestratigraphicunitmeasuredalongalinenormaltothedirectionofextensionoftheunit.Truethicknesscanbederivedfrominformationdeterminedbythedipmeter.

(2)Thebedthicknessdeterminedfromsomewelllogsisanapparentbedthicknesscorrespondingtothedistancetheboreholeremainedinthebed.Theboreholemaynothavepenetratedthebednormaltoitsupperorlowerboundarysurfacebecauseofholedeviationandformationdip.Seealsotrueverticaldepth.

Belectrode

Acurrent-returnelectrodeinthecurrentandmeasureelectrodeconfigurationofaresistivitymeasuringdevice.CompareAelectrode.Seealsonormalandlateraldevice.

bentonite

Acolloidalclay,composedofmontmorillonite,whichswellswhenwet.Becauseofitsgel-formingproperties,bentoniteisamajorcomponentofdrillingmuds.Seegelandmud.

betaparticle

Ahighspeeddisintegrationelectron(i.e.,negatronorpositron)spontaneouslyemittedfromanatomicnucleusasaformofradiation.Electrons(negativeorpositive)donotexistinnuclei;theyarecreatedatthemomentofemissionandareaccompaniedbythetransitionofaneutronintoaproton,oraprotonintoaneutron.Theatomicnumberofthenuclideischangedbya+1ora–1withnosignificantchangeinatomicweight.Abetaparticlecanpenetrateonlyafewmillimetersofrock.

BHT

Bottomholetemperature,usuallyobtainedbymaximumreadingthermometers.

bi-metallism

Existenceofcontactbetweentwodissimilarmetalsinthelogginginstrumentwhichresultsinaspuriousemf.Ifelectricalleaksexistbetweenthemetalsandtheboreholefluid,acircuitwillbecompletedintheboreholefluidthroughwhichelectricalcurrentwillflow.Oppositeresistivebeds,thelinesofcurrentaredistortedandcurrentflowisconfinedtotheborehole.WhenthiscurrentcrossestheSPelectrodeitdistortstheSPcurve.

bit

Acuttingdeviceattachedtothebottomendofthedrillpipe.Itsfunctionistoperformtheactualboringordrillingoftherockformations.

blastingcap

Electricalblastingcap,adetonator.Anelectricallyactivatedexplosivedeviceusedtodetonatehighexplosives(e.g.,shapedcharges).

blindram

Anintegralpartofablowoutpreventer,servingastheclosingelement.Itsendsdonotfitaroundthedrillpipebutsealagainsteachotherandshutoffthespacebelowcompletely.Seerams.

blindzone

Shadowzone.Commonlyobservedoncurvesrecordedbyalateraldevice.Azonewhereintherecordedresistivityistoolow.ThiszonecorrespondstothedepthintervalloggedwhileathinresistivebedofthicknesslessthantheAOspacingisbetweentheAelectrodeandthemid