2009 rmag petra tips and tricks short course_working with log data
TRANSCRIPT
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BobCluff
TheDiscoveryGroupInc.
RMAGSpringshortcourse,
20April2009
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ObjectivesWeassumeyoualreadyknowhowtousethe
software,
Ourgoalistopresentaseriesofusertipsandtricks
that
will: Improveworkflows
Letyoudothingsthatmaynothavebeenobvioushow
to
do Workaroundlimitationsinthesoftwareorsubstitute
forfeaturesthatarenotexplicitlydesignedintothe
package Generallysaveyoutime,effort,andmoney
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Loganalysistipsandtricks Petrahasageneralpurpose,flexiblelogcalculationengine
builtinto
it.
ItdoesNOTaimtobeahighendpetrophysicalmodelingormodeldevelopmentpackage
DISCLOSURE:DiscoveryGroup
does
not
attempt
to
force
fit
Petraintothatmold,wehaveseveralspecializedpetrophysicspackagesavailableforourworkflows
WeDOusePetraforbatchprocessingoflargenumbersof
wells,for
computing
pore
volumes
and
HCPV
over
entire
fields,andforitsintegrationwithcrosssections,mapping,andotherwelldata
WeuseitEVERYDAYinourpetrophysicalstudies
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WhatPetradoeswellManageandorganizelogdata,includingsupportfor
logaliases
Allowyoutosplicecurvesorlogruns,editcurves,&performsomebasiccurvenormalization
Computeshaliness,
porosity,
and
fluid
saturations
Computeflagcurvesusingavarietyofcriteria
Computenetpay,netofuserdefinedcutoffs
Runprocessesonlargenumbersofwellsveryquickly
Allowsyoutowriteandsaveflexibleuserequations,
and
to
some
extent
user
programs
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WhatPetradoesnotdo..Runvendorandtoolspecificenvironmental
correctionsSupport1or2pointnormalizationusinghistogram
overlays at
least
without
using
aprinter
and
alight
table
Usestandardcrossplotroutinestocomputeporosityfrommultiplelogs(e.g.neutrondensity)
Computemulti
mineral
volumes
(e.g.
Vdol
Vls
Vqtz)
Linktooutsidecodesinstandardlanguages(e.g.VisualBasic,C++,Java,etc.)
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LeftforanotherdayNormalization
Crossplotting
Multimineralmodels
TheAdvancedUserModels language
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A.How
do
Ibring
log
data
into
Petra,
and
what
are
the
pitfallsofusingthebatchLASimportfunction?
APInumberscritical,cantlivewithem,cantlivewithout
em
WrongAPI=WrongassociationwithawellinPetra.
Youcannot
assume
the
vendor
or
digitizer
got
it
right.
Solutions:
Importwellsoneatatime
Openeach
LAS
file
in
atext
editor
and
add/fix
them
ExtracttheAPInumbersfromtheLASfiles,edittheminaspreadsheet,writethembackintotheLASfiles.
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B.
Howdo
Iimport
LAS
header
data
to
Petra,
and
what
arethedifferencesbetweenLAS1.2and2.0formats?
LAS1.2and2.0headersuseadifferentformatfortheWell
information
block,
including
information
such
astheAPInumber
PETRArecognizesbothformats,andautomaticallyflipsthem
into
the
standard
(2.0)
order
Thecriticaldatatocaptureareanythingusedinlog
calculations
or
useful
for
log
evaluations Loggingdate,runnumber,andservicecompany
Mudtype,weight,Rm@T___,Rmf@T___
Maxrecorded
temperature,
LTD,
base
of
csg
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LAS version 1.2 Well Information Section.~Well Information Section
#MNEM.UNIT Data Type Information#--------- ------------- ------------------------------
STRT.M 635.0000:
STOP.M 400.0000:
STEP.M -0.1250:
NULL. -999.25:
COMP. COMPANY: ANY OIL COMPANY INC.
WELL. WELL: ANY ET AL A9-16-49-20FLD . FIELD: EDAM
LOC . LOCATION: A9-16-49-20W3M
PROV. PROVINCE: SASKATCHEWAN
SRVC. SERVICE CO: ANY LOGGING COMPANY INC.
DATE. LOG DATE: 13-DEC-86
UWI . UNIQUE WELL ID: 100091604920W300
LAS version 2.0.
~Well Information Section#MNEM.UNIT VALUE/NAME DESCRIPTION
#-------- -------------- ---------------------
STRT.M 635.0000 :START DEPTH
STOP.M 400.0000 :STOP DEPTH
STEP.M -0.125 :STEPNULL. -999.25 :NULL VALUE
COMP. ANY OIL COMPANY INC. :COMPANY
WELL. ANY ET AL 12-34-12-34 :WELL
FLD . WILDCAT :FIELD
LOC . 12-34-12-34W5M :LOCATION
PROV. ALBERTA :PROVINCE
SRVC. ANY LOGGING COMPANY INC. :SERVICE COMPANYDATE. 13-DEC-86 :LOG DATE
UWI . 100123401234W500 :UNIQUE WELL ID
Lookat
the
order
of
the
Data
TypeandInformationinanLAS1.2header
vs.theorderinanLAS2.0header. Theorderisnowconsistentinalldatablocks
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Headersareimportedseparately,andtheheaderimport
will
create
anew
well
ifit
cannot
find
an
API
numbermatch
The
mapping
between
header
data
and
zone
data
fieldsisvendorspecificwithafewexceptionstheLASstandarddoesnotspecifyparameterorcurvemnemonics. Loggingcompaniesanddigitizerscookuptheirownabbreviations!
Youcansavethemappingforreuse.
Ithas
to
already
exist
to
be
used
in
abatch
import.
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1.2file
2.0file
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C.How
do
Iuse
curve
name
aliases,
and
how
should
theybeorganized?
Aliasesarepublicandprojectwide.
Aliasesare
NOT
nested.
Youneedtolistcurvesinthehierarchyyouwantthemtobeused. E.g.,ifyouwanttouse2ftresolution
resistivitycurves
in
preference
to
1ft
curves,
put
them
higherinthelist.
Werecommendeither:
Usethe
most
common
curve
names
as
your
aliases
(GR,
NPHI,DPHI),andaliasallthesynonymstothem;or
SetupspecialaliaseslikeALIAS_GR soitisobvious
which
are
the
aliased
curve
names
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SincePetra
uses
the
firstcurveitfindsinanaliaslist,ifyou
havemultiple
runs
withdifferentcurvenamesyouwillneed
tosplice
runs
to
createasinglecurvethatappearshigher
inthe
alias
list
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D.
Ihave
way
too
many
curve
names
how
can
Iclean
itupandsimplifymycurvedatabase?
Deanalreadytalkedaboutthis.
Weexport
the
curve
listing,
with
well
counts,
to
aspreadsheet
before
anyseriousorganizing Ithelpstocategorizecurvesbyloggingvendor,tooltype,vintage,&
datasource Usesuffixesandprefixestosetapartspecialcurveclasses(flags,
aliases,normalized
curves,
etc.)
Consideradjective/nounorder. Thereisareasonthemilitarynamesthingsthewaytheydo!
Weliketopreserveoriginalloggingvendormnemonics,thereisoften
informationin
them
that
might
not
be
obvious
to
anon
specialist
e.g.anAtlasCNCandCNCFaredifferent Porositylogsareonlyusefulwhenyouknowthematrixassumptions
(SS,LS,DOL),makethempartofthename!
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E. Myporositylogsarevariouslyindecimal(v/v)and
percent(pu)
units.
How
do
Iclean
that
up
so
they
plot
correctlyoncrosssectionsandcomputesaturations
right?
Findthemallfirst Easiesttocomputelogstatisticsandthenusewell
select
by
data
criteria
functionConvertthemalltothesamebasis. Mostequations
wantfractionalporosity.
Recomputethe
stats
and
check
your
work
Pitfall:logrunchangeswithdifferentvendors. Thisisacleanupproblemthatneedstobefixedwhencurves
are
spliced.
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F. Someofmywellshavedensityporosity,othershave
bulkdensity,
some
both,
what
should
Iuse
and
how
do
Igetthemallonacommonbasis?
Asbefore,
find
them
first
using
the
well
select
by
data
criteriafunctions.
DensityporositycurvesareALWAYSambiguous,
sincethey
made
amatrix
density
and
fluid
density
assumptioninthefieldwhencurvewascomputed LASheadersrarelyrecordthesevalues.Youhaveto
lookthemuponthepaperlogs/rasters.
Bewareofmidlogscalechanges
Enterthevaluesaszoneparameters;wesetupaspecialpetrophysics orlogging zoneforthisandotherdata.
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G. SomeofmywellshaveneutronporosityinLSunits,
othersare
in
SS,
what
should
Iuse
and
how
do
Iget
themallonacommonbasis?
EqnstoconvertfromLSSSandSS LSarenotpublished
by
the
service
companies
Youcandigitizethechartbooksandfiteqnstothecurvesyourself
LSunitsarethetruebasisofneutronlogging. Othermatrices
are
output
as
aconvenience
for
log
analysis
on
thehoodofaChevy Therelationshipsareallnonlinearexceptinlimestone.
They
vary
from
company
to
company,
tool
to
tool. Findingproblemwellsisdifficultbecausethemnemonics
generallydonotincludethematrix. Lookthemuponthepapercopies
Plotspecial
xsections
and
look
for
distinctive
separation
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20%
25%
Highendpackagescomputebothporosityand%mineralvolumesbasedoninterpolationofisoporositylinesandmineralendpoints
SS
LS
SH
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Usefulresources(outsidePetra)
Didger4.0 onscreendigitizingsoftwarefromGolden
Software
Grapher7.0has11predefinedcurvefittingalgorithmsthatfitmostcommonchartbookcurves
Excelhasverybasiccurvefittingfunctionality;youcanalsopurchaseanaddinthatexpandsonthis
At
the
high
end,
TableCurve2D
and
TableCurve3D
fit
thousandsofpredefinedfunctionstoadataset
Learnsomelinearalgebraifyouwanttodoit
yourself
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H. WhatisthebestwaytobringcoredataintoPetra,
andwhat
should
go
into
the
core
tab
vs.
what
goes
into
thelogcurvedatabase?
Coredata
live
in
two
places
in
Petra:
TheCoresTab,whichstoresinformationoncoretype,coredinterval,datecored,recovery,etc. Thiscanbe
posted
on
logs
and
sections TheLogstab,whereactualnumericalcoredatais
storedwiththelogdata
Coredata
can
be
imported
as
LAS
or
as
ASCII
files,
depthshifted,plotted,andmanipulatedlikeanylogdata
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Coredepth
shifts
can
be
recorded
on
the
Cores
tab,orasremarkstoeachcurveintheLogtab
Theseare
global
remarks
(applies
to
the
curveinallwells
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Thesearelocalremarks
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I. Howdo
Ideal
with
data
on
different
depth
increments(e.g.0.5ftlogdataand1ftcoredata)?
Petraisdatabaseoriented,nottiedtoaspecificframe
incrementlike
an
LAS
file
Itallowsdataondifferentdepthstepstocoexist
TheproblemariseswhenyouEXPORTdatatoanLASfile,becauseLASfilesrequireaspecificstepvalue
Petrawillnotresamplecurvesonthefly,butitwill
allow
you
to
only
export
data
with
a
specific
sample
rate
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Bestsolutionistoresamplecurvespriortoexport
usingLogTransformationsTransformsResample
curves
Note:thisfunctionOVERWRITEStheoriginalcurve,so
youmight
want
to
work
on
acurve
copy
Also,becarefulwhenresamplingcoredata,asinterpolatedvaluesmightnotbewhatyouwant
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Usewithcoredata!
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J.
Whatis
the
easiest
and
cleanest
way
to
splice
curves,nullbaddata,toolpickup,etc.inPetra?
EasiestisintheLogCurvePreviewer,accessedfrom
theLogs
tab
Youcannullsections,smooth,anddespikecurvesallinthispanel
CurvesplicingisdoneinLogs SpliceCurves
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K.
Iwant
to
baseline
shift
all
my
SP
logs
so
they
are
at
~0mValongtheshalebaseline.WhatdoIdo?
Thisisquickifyoujustneedabasicbaselineshift
Startby
cleaning
up
the
curves,
including
nulling
tool
pickupandintervalsbehindcasing
Ifyoudont,thosesectionswillbecountedinthelogstatisticsandcouldskewyourbaseline
Fixanyobviousoffsetsbetweenloggingruns
Compute FromLogs Statistics,
and
calculate
the
95th percentileoftheSPusingthearithmeticmean.Savethisinanappropriatezone(likePetrophysics)
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UsingCompute FromLogsEquationExpression, SP_BLS
=SP
PC95SP
AssingtheappropriatecurvenametoSP,usingaliasesifnecessary,andassignthezoneparametercalculated
beforeto
PC95SP
AllofyourSPlogswillbebaselineshiftedtoavalueofzeroatthe95th percentile.
This
does
not
correct
for
drift
with
depth,
it
is
asimplebaselineshift.
Unlikethenormalizationfunction,thisdoesnot
rescale
the
SP
curves
it
is
just
an
offset
correction.
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L. Whatis
meant
by
net
pay and
how
do
Icompute
it
inPetra?
Petrasnetpay moduleisactuallyageneralpurpose
summation
module,
accessed
via
Compute
FromLogs
Footages(ReservoirProperties). ItisoneofPetrasgreateststrengths.
Definitions:
GROSS=the
total
interval.
Calculated
using
the
Compute
FromZones Isopachfunction. GROSSSAND=sandnetofashaliness(GR)cutoffonly,set
byCondition4intheLogFootageSummationscreen.
NETSAND
=sand
net
of
shaliness
and
porosity
cutoffs,
ignoringfluidsaturation. Thisissetbyconditions1and4inPetra. Engineerswantthistodefinethetotalcontainervolume.
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NETPAY=sandstonenetofshaliness,porosity,and
watersaturation
cutoffs.
Petra
also
adds
aPermeability
conditionandaUserLogcondition,forexampleaflagcurvetoexcludecertainlithologies(e.g.coal)
Because
Petra
defines
net as
passing
ALL
checked
conditions,youneedtobecareful. Ifyouwanttocalculatenetporevolume,irrespectiveofSw,youcannotchecktheSwcondition,orelseyouhaveto
openup
the
cutoff
range.
Weoftenrunthismoduletwice,oncetogetreservoirvolumes,asecondtimetogetnetpay volumes.
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Firstrungetsnetreservoir
properties
Secondruncomputespay properties
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Youcancreateflagcurvesinthismoduleonthe
Capturetab
YoucansavepredefinedsetupscreensastemplatesandruntheminBatchmodetodomorethanonestep,
or
calculate
net
pay
sensitivity
to
some
key
criteria
e.g.netpay>6%,>8%,and>10%
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M.HowdoIcomputeSwonalargenumberofwells
overabig
area
where
some
key
parameter,
like
Rw,
variesfromwelltowell?
You
have
two
choices:
Runeachzoneindividuallyusingequationexpressions,whichcanbesavedinyourequationlist.
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Or,use
the
ComputeFromLogsAdvancedLog
TransformsUserModelLogTransformmodule.
ProgramminglanguageissimilartoBasicandis
undocumented.
Onlythe
examples
provided
with
Petraserveasaguidetowhatcanbedone.
GOTO,IFTHEN,BEGINENDandDONEstatements
Allinput
logs,
constants,
and
output
logs
are
declared
atthestart. Ifthemodelcompiles,yougetascreenthatallowsyoutoassignallofthosetologsorzone
parametersin
Petra.
Youcanrunthemodeloverselectedzonesortheentirewell.
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