SCM Truncated Gaussian Algorithm Petrel 2010
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Transcript of SCM Truncated Gaussian Algorithm Petrel 2010
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7/27/2019 SCM Truncated Gaussian Algorithm Petrel 2010
1/13
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7/27/2019 SCM Truncated Gaussian Algorithm Petrel 2010
2/13
Petrel is a mark of Schlumberger
4801 Woodway Drive, Suite 150W Houston, TX 77056 www.scminc.com [email protected]
2011 SCM E&P Solutions, Inc.
2
Reefs
BuildingmodelsthatreplicatethisorderlyfaciestransitionhasbeendifficultinPetrel.Analgorithmcalled
TruncatedGaussiansimulationallowstheseorderedtransitionstobemodeledeasily.ThediscussionbelowdemonstratestheuseofthisalgorithmontheAfricantrainingdatasetandondatarepresentingapinnaclereef.
TheauthorshaveusedTruncatedGaussiansimulationonacoupleprojectsandfounditsimplertousethantheTruncatedGaussianwithtrendsalgorigthm(availableinpreviousreleasesandstillavailable)andthatitproducedbetterresultsthantheotherforthatdata.Becauseofthelimitednumberofprojectstheyhave
workedusing
this
tool,
the
authors
are
not
experts,
but
felt
atips
and
tricks
article
was
important
to
make
all
awareofthenewtool.
TruncatedGaussiansimulationTheAlgorithm
TruncatedGaussiansimulationisastochasticalgorithm.Thismeansthatitusesaseedand,iftheseedisallowedtovary,willproduceadifferentresultuponreexecution.
Primaryinputinclude:
Faciesdataasapropertymodelupscaledfromafacieslog Thefaciestobemodeled Theorderthefaciesaretooccur(adjacencyinthemodel) Onevariogram(usedforallfacies) Theglobalfractionofeachfacies(tendstobedominatedbyTrendsiftheyareused)
Optionalinputdatainclude:
VerticalfaciesproportionsfromtheDataAnalysisprocess. Trend(3D,2D,or1D)foreachfacies Smoothingandwhetherdataarehonoredduringsmoothing
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Petrel is a mark of Schlumberger
4801 Woodway Drive, Suite 150W Houston, TX 77056 www.scminc.com [email protected]
2011 SCM E&P Solutions, Inc.
3
Figure:ParametersavailableontheTruncatedGaussiansimulationdialog.
Thealgorithmbasicallymodelstheprobabilityofthefaciesinnormalscorespaceandthenconvertsthat
modeledprobabilitybacktoafaciescode.Althoughtheauthorsdontunderstandexactlyhowthealgoirthm
works,wehavebeenabletopickupenoughfromthedocumentationtoeffectivelyusethetool.Our
interpretationofthemodelingprocessgoessomethinglikethis(seefiguresbelow).GivenWells1and2and
threestacksofcellsinbetweenthem,theprogram:
1. Checkstheprobabilityofeachfaciesandbuildsacumulativeprobabilityfunctionthattotals100%(010=green,10.01to40=red,and40.01to100=yellow).Actuallynormalscorevaluesof0to1are
usedbutpercentsareusedinthisexample.
2. Assignstoeachfaciesthepercentatthecenterofitsportionoftheprobabilityfunctionandthesearethe
values
that
are
used
to
model
that
facies
(5
for
green,
25
for
red,
and
70
for
yellow).
3. Buildsacontinuousmodelfromtheinputdata(probablyusingSGS).4. Convertsthemodeledprobabilityvaluesbacktofaciesspacebycomparingthevalueinthecellto
theprobabilityrangeandassigningtothatcellthefacieswhoseprobabilityrangeitlieswithin.
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Petrel is a mark of Schlumberger
4801 Woodway Drive, Suite 150W Houston, TX 77056 www.scminc.com [email protected]
2011 SCM E&P Solutions, Inc.
4
Figure:Wellswithmidpointprobabilityvalues(displayedas%)thatarepassedtothemodelingprocess.Stacks
ofcells(,,andofwaybetweenwells)withcontinuousprobabilityvaluesmodeled(displayedas%).The
probabilityvaluesareconvertedtofacies(color)basedonwhichfaciesprobabilityrangeitsvaluefallsin.
Thisexampleisbasedononlyoneprobabilitynumberforeachfacies,thatis,notrendsorverticalproportions
wereused.Theprocessgetsmorecomplexastrendsetc.areaddedbutthegeneralapproachissimilar.
AfricanModel
TheAfricandataset,commonlyusedfortraining,showshowthealgorithmworks.Themodelisfirstbuiltusing
SequentialIndicatorsimulationandthenusingtheTruncatedGaussiansimulation.Figure:ThesamedatamodeledwithSequentialIndicatorsimulation(left)andTruncatedGaussiansimulation(right).Thevariogramsweremadeasalikeaspossible(sphericalleftandgaussianright).
Notethehaloofyellowfaciesaroundtheredfacies.TheorderthefacieswereinputtotheTruncatedGaussiansimulationalgorithmwasGrey,Yellow,andRedandthisistheorderthefacieshadtostayinwhenmodeledbecauseofhowthealgorithmworks.Becauseitisastochasticalgorithm,youwillstillgetanumberoffacies
bodiesthatareunsupportedbydatabutthedatawillbehonoredinallcases.
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Petrel is a mark of Schlumberger
4801 Woodway Drive, Suite 150W Houston, TX 77056 www.scminc.com [email protected]
2011 SCM E&P Solutions, Inc.
5
Figure:parametersusedtobuildtheAfricanmodelwithTruncatedGaussiansimulation.
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Petrel is a mark of Schlumberger
4801 Woodway Drive, Suite 150W Houston, TX 77056 www.scminc.com [email protected]
2011 SCM E&P Solutions, Inc.
6
Thelargerthenuggetthemorefuzzyistheboundarybetweenthefacies.
Figure:Modelbuiltwithnugget=.001(left)andnugget=.1(right).
PinnacleReef
InthepastithasoftenbeensaidthatPetrelisnotfriendlytomodelerstryingtobuildcarbonatemodels.Forthis
reason,wehavebuiltaPinnaclereefmodelsimilarinstyletopinnaclesseenintheMichiganBasin.Sincewe
didnthavedataforPinnaclereefswestudiedtheliteratureandmanufacturedourown.
StructuralFrameworkandtheMentalGeologicModel
Thehorizonsmodeledfromtopdownaresummarizedinthetablebelow.Belowarecrosssectionand3Dviews
showingthehorizongeometry,pinnacleform,andlayeringusedinthemodel.Normallythereis40%to60%
compactioninthecarbonates(littleornoneintheevaporates)whichcreatesadrapingeffectoverthe
pinnacles.Wedidnottakethetimetobuildthiscompactionformintothemodelasitwasnotthegoalofthis
study,althoughthedrapewouldhavecreatedamoreelegantandaccuratefaciesmodelatboundariesbetween
reefand
evaporite.
Layering
was
made
proportional
in
the
A
2Carbonate
and
Lower
Niagara
and
made
to
followthetopintheotherzones.
Theshapeofthehorizons,thelayering,andtheapproachusedtomodelfacieswerealldictatedbyourmental
imageofhowthereefshouldlookandthedistributionoftherocksinthatmentalimage.Thementalmodel
usedtoguidethisworkwasderivedfromworkdonebyK.J.Mesolella,K.D.Robinson,L.M.McCormick,andA.R.
Ormiston,1974,CyclicdepositionofSiluriancarbonatesandevaporatesinMichiganbasin:AAPGBulletin,v.58,
P.3462.Modelnumber3fromthispublicationwasused(twoperiodsofgrowthseparatedbyevaporate
deposition.
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Petrel is a mark of Schlumberger
4801 Woodway Drive, Suite 150W Houston, TX 77056 www.scminc.com [email protected]
2011 SCM E&P Solutions, Inc.
7
Figure:Section(left)throughthehorizonsmodeledforthePinnaclereefstudy.ReefisfoundintheNiagaraand
A1Carbonatezones.A3DviewofthetopNiagarawiththecrosssectioncuttingitisshownintherightview.
Figure:Sectionshowingthelayeringusedtoguidethecorrelationsineachzone.
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Petrel is a mark of Schlumberger
4801 Woodway Drive, Suite 150W Houston, TX 77056 www.scminc.com [email protected]
2011 SCM E&P Solutions, Inc.
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Table:Listofhorizonsmodeledanddescriptionofrocklyingbeloweachhorizon.
Horizon Zonerockdescription
A2Carbonate Coarsegrained,densecarbonate,unfossiliferous.
A2Evaporite Halitewithoccasionalthindolomitebedscappedby
fewfeetofdenseanhydrite
A1Carbonate Densefinegrained,unfossiliferous,argillaceous,
thinbeddedcarbonates.
A1Evaporite
Clear,
coarsely
crystalline
halite
thinly
interbedded
withanhydriteanddolomite,commonlycapped
withafootortwoofanhydrite.
Niagara Denseargillaceous,micriticcarbonate,rangingfrom
massivetandolomitetograymicriticcrinoidal
limestonetolightgraynodularlimestone.
TopLowerNiagara SameastheNiagarabutwithouthavinganyreef
development(zoneaddedtoseparatethelower
nonreefNiagarafromtheupperreefbearing
Niagara.
BaseLowerNiagara
(topClinton)
Baseofmodelsonorocksmodeledbeneath.
FaciesModeling
Thefaciesmodeledarelistedinthefigurebelow.Notallfacieswerefoundineachzone.Infactitwasnecessary
tomodeleachzoneseparatelysothatfaciesfromonezonewouldnotblurintoazonetheydidnotbelongin.
OneofthemostimportantaspectsofusingtheTruncatedGaussiansimulationalgorithmistousehorizonsorsomeothermeanstorestrictthemodelingareastohavejustthosefaciesthatmatchthestyle(adjacencyorder)
ofthealgorithm.TheWellsectionbelowshowsthefaciesdistributionineachwellandzone.Basedonthe
distributionandrelationshipofthefacies,thefollowingalgorithmswereusedtomodeleachzone:
A2Carbonate TruncatedGaussiansimulation(limestoneanddolomite)
A2Evaporite SequentialIndicatorsimulation(saltandanhydrite)
A1Carbonate TruncatedGaussiansimulation(reefandcarbonate)
A1Evaporite
Sequential
Indicator
simulation
(salt
and
anhydrite)
Niagara TruncatedGaussiansimulation(reefandcarbonate)
LowerNiagara Assignvalue(Interreefmud)
TheA2CarbonatecouldhavebeenmodeledwitheitherSequentialIndicatororTruncatedGaussianequallywellastherewereonlytwofaciesinthezone.
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7/27/2019 SCM Truncated Gaussian Algorithm Petrel 2010
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Petrel is a mark of Schlumberger
4801 Woodway Drive, Suite 150W Houston, TX 77056 www.scminc.com [email protected]
2011 SCM E&P Solutions, Inc.
10
usedwhichdramaticallyimpactthepercentofeachfacies.Needlesstosay,themodelwasworkeduntilits
geologicfeatures(faciesdistributions)lookedacceptable,andmatchedthementalimageofthegeology.
Figure:DataAnalysisdialogforthetworeefzones(remember,layeringissettofollowtop).
Figure:Trends
used
to
model
the
A
1Carbonate
(top
row):
Reef
Rock,
Reef
Talus,
Dolomite,
Limestone
and
Niagara(bottomrow):ReefRock,ReefTalus,andInterreefMud.
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Petrel is a mark of Schlumberger
4801 Woodway Drive, Suite 150W Houston, TX 77056 www.scminc.com [email protected]
2011 SCM E&P Solutions, Inc.
11
Figure:FaciesmodelingparametersusedtomodeltheA1Carbonate.
Figure:Jindexsectionwitha1:1verticalexaggerationshowingthefinalfaciesmodel.
Figure:Iindexsection(topleft,5:1),Jindexsection(topright,5:1),Kindex(bottomleft,throughA1
Carbonate),and3Dviewofreefrockandtalus(bottomright5:1),allshowingthefinishedmodel.
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Petrel is a mark of Schlumberger
4801 Woodway Drive, Suite 150W Houston, TX 77056 www.scminc.com [email protected]
2011 SCM E&P Solutions, Inc.
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Experiments
Someexperimentsweremadetoseewhattheeffectwouldbeiftrendswerenotused,iftheSequentialIndicatorsimulationalgorithmwasusedwiththesametrends,andifthereefsandtheintermediateevaporatewereallmodeledasonezone.Thefiguresbelowshowthesescenarioscomparedtothebestcasemodel.It
wasfoundthatforthisdata,SISandTGScouldbothbeusedtoproduceacceptableresultsbutthatthetrends
weremore
rigorously
followed
with
TGS.
Figure:ModelsbuiltwithTruncatedGaussiansimulation:withouttrends(left)andwithtrends(right).
Figure:Modelsbuiltwithtrends:SequentialIndicatorsimulation(left)andTruncatedGaussiansimulation(right).TrendstendtobehonoredmorerigorouslywithTruncatedGaussiansimulationbutbothproduceacceptableformswiththisdata.
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Petrel is a mark of Schlumberger
4801 Woodway Drive, Suite 150W Houston, TX 77056 www.scminc.com [email protected]
2011 SCM E&P Solutions, Inc.
Figure:ModelsbuiltwithSequentialIndicatorsimulation:onezonefromtopA1CarbonatedowntoBaseNiagara(left)andseparatezones(right).