wireline logging totarials

7/23/2019 Wireline Logging Totarials

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PetrophysicsMScCourseNotes WirelineLogging

5. WIRELINELOGGING

5.1 Whatisa WirelineLog

A log is a continuous recording of a

geophysicalparameteralongaborehole.

Wireline logging is a conventional form of

logging that employs a measurement tool

suspended on a cable or wire that suspends

the tool and carries the data back to the

surface. These logs are taken between

drilling episodes and at the end of drilling.

Recent developments also allow some

measurements to be made during drilling.

The tools required to make these

measurementsareattached to thedrillstring

behind thebit, and do notuseawirerelying

instead on low band-width radio

communication of data through the

conductivedrillingmud. Suchdataiscalled

MWD (measurement while drilling) for

simple drilling data, and LWD (logging

while drilling) for measurements analogous

to conventional wireline measurements.

MWDand LWDwillnotbecovered bythis

course, although the logs that are produced

inthiswayhaveverysimilarcharacteristics,

even though they have been obtained in a

completelydifferentway.

Figure 5.1 shows a typical wireline log. In

thiscaseitisalogthatrepresentsthenatural

gamma radioactivity of a formation. Note

that depth is arranged vertically in feet or

metres, and theheadercontainsthenameof

the log curve and the range. This example

showsasingletrackofdata. Notealso that

no data symbols are shown on the curve.

Symbols are retained to represent discrete

core data by convention, while continuous

measurements, suchaslogs, arerepresented

bysmoothcurves. Figure5.1 showsonly50

mofborehole, butreallogsareoftenmuch

longer (thousands of metres), and contain

multiple curves on a single track such as

this, and multipletracks.

Fig. 5.1 ExampleofaGammaRayLog

GAMMARAY(GR)

1000

630

620

APIUNITS

640

670

660

650


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Figure5.2 Atypicallogset


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Figure5.3 Land loggingvehicle

Figure5.4 Offshoreloggingcabin

Figure5.5 Insidetheloggingunit


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Datais transmitted to thesurface through the wireand recorded digitally. Modern toolssample the

formation at intervals from 2.5 mm for the high definition imaging tools to about 15 cm for the

simplertools, so foracombinationtoolwithseveraldifferentlogs, theremaybeasmanyas100,000

individual measurements per metre over a log run ofup to say2000 m. Depending on the logging

speed, data transmission rates may be as high as 200 kbits per second. This data is subjected

immediatelyto arudimentaryanalysisbypowerfulprocessorsand displayed so thatthequalityofthemeasurementscanbechecked. Thedataisalso recorded onto digital(DAT)tapeand transmitted to the

controllingofficeoftheloggingcompanybysatelliteforin-depthanalysis.

Atypicaldrillingand logginghistoryforawellmightbeasshowninTable5.1. Notethatthelogsare

runineachsectionbeforecasingtakesplace. Wheneachlogisrun, theoperatorensuresthatsome

measurementsareincluded oppositethepreviouslycased sectionabovethelogrunasatestthatthe

logtoolsareworkingcorrectlyand to providealocaldepthfixed pointto help tiethedepthsforeach

tool together. Whenever a borehole is logged in sections the operator also ensures that there are

overlap sections so that the logs can be tied together accurately, and repeat sections to check log

qualityand consistency.

Table5.1 Atypicaldrillingand logginghistory.

Procedure DrillBitSize

(inches)

Casing Diameter

(inches)

Depth

(msubsea

surface)

Tools

Drill 25 - 300-400

Case 20 300-400

Drill 17.5 - 400-700

Log - - 700-400 ISF-Sonic-GR/1

Case

-

13.375 300-

690Drill 12.25 - 700-1400


Log - - 1400-680 FDC-CN L/1

Log - - 1400-680 HDT/1

Case - 9.625 690-1390

Drill 8.5 - 1400-2100


Log - - 2100-1380 FDC-CN L/2

Log - - 2100-1380 HDT/2

Log - - 2100-1380 DLL/1

NoteinTable5.1 thatthelogsarerecorded duringthewithdrawalofthetoolsfromthewell, thatsome

tools were run several times at different depth intervals and that these runs have been coded

consecutively, thatthereisanoverlap ofdata, and thatthelowerlogrunsincludepartoftheprevious

casingattheirtop. Notealso thatthemosttoolsarerunintheareathatisexpected to beofgreatest

interest(i.e., thereservoir). Fortoolcodesseewirelineoperatorsmanuals.

Effortsaremadeatalltimesto ensurethatthelogsareofthehighestquality. Methodsofensuringthat

loggingqualityishighinclude(a)makingrepeatsectionsoflogmeasurementsovershortsectionsthat

contain both low and high measured values, (b) making overlap measurements of the previous


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Figure5.6 Logpresentationgrids. NotethattheAPIformatdefinesparticulardimensionsforeach

track, and anoverallwidthof8.25 inches.

5.4 Tools

There are a plethora of logging toolsnow available in the oil industry. There can be split into the

followingtypes:

Standardopen-holetools(diameter3 to 4 inches)

Theserangefromthesimplestcalipertoolto thesophisticated imagingand NMRtoolsand have

verticalresolutionsfrom2.5 mmto over30 cm.

Slimholetools(diameter1.6875 to 2 inches)

Theseareslimmerversionsofthestandard tools, and areused wherestandard toolsaretoo thick.

Applicationsofthesetoolsareinspecialistloggingthroughdrill-pipeorcoiled tubing, and in

smallscaleholesused inthewaterindustry.

0 10

3600

361010 200 10

Track1 Track3Track2Depth

0 10

3600

3610100 10001 10

0 10

3600

36100 101 10

Linear

Logarithmic

Hy

brid


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Cement-logging tools

Thesearespecialversionsofthosetoolsthatwork throughcementcasingthatareoptimized to

work undertheseconditions.

Productiontools

Thesearespecialisttoolsforrunningduringtheproductionofhydrocarbonsformeasuring

pressureand flowrate, and arealwaysoftheslim-holevarietyto facilitatetheirinsertioninto aproducingwell.

LWDtools

Thesetoolsaredesigned to connectinto thedrillstringand communicatedatato thesurface

throughthedrillingmud.

Asummaryofsomeofthemainstandard open-holetoolsisgiveninTable5.2.

Drillingrigsareexpensiveand canoftenamount to almost10%ofthe totaldrillingcosts. The time

required to runwirelinelogseffectivelydelays thedrillingoperationleading to greaterexpense. To

minimizethisexpensetoolsarebolted togetherforloweringdowntheborehole. Allwirelinetoolsare

designed to becombined in this wayand therearemanypossiblecombinations, somewhichareas

longas30 m. Eachtoolinthecombinationhasitsownmeasurement-sensitiveregion, whichmeasures

agiven formation at a specific depth at different offset times. The datahas to be depth shifted to

accountforthis. Thisisdoneinthedataacquisitionvehiclewithinformationabouttheinstantaneous

speed and dimensionsofthetoolcombination. Evenusingcombinations, itiscommonforasmanyas

threelogrunsto bemadeinthesamesectionoftheboreholewithdifferentcombinationsoftools. If

thisisthecase, onetoolisincluded inallcombinationsto actasareferenceto whichtheothersmight

becompared fordepthmatchingpurposes. Thistooliscommonlythegammaraytool(GR).

Figure5.7 showsanexamplestandard open-holeloggingtool. Notethatitisaneutronporositytool,

whichiscombined withagammaraytool. Theloopsateachend coverscrewthreadsto enableitto be

combined withothertoolsofsimilardesign.

Onland, wherethegeneralgeologyiswellknownand drillingischeaper, onlyafewlogsmayberun.

Thisisbecauseexpensecanbespared asinformationconcerningthesubsurfaceisnothard to come

by. However, and perhapscounter-intuitively, offshoreafullsetoflogsisoftencarried outevenwhen

there areno hydrocarbonshows. Thisisbecausedrillingisso expensive that relativelyfewerwells

willbedrilled, and hencethemaximumdatamustbesqueezed outofeachwellregardlessalmostof

thecost. Ifthereareno hydrocarbonshows, thewelldatawillstillbeveryusefulforcorrelationwith

otherwellsthatdo showhydrocarbons, willhelp to constraintheextentofneighbouringreservoirs, as

wellasaddingto theinformationaboutthegeneralgeologicalstructureofthearea.


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Figure5.7ACompensated NeutronSonde(CNS)

Length 3.87 m(12.68 ft)

Diameter 95 mm(3.74 in)

Weightinair 109 kg(240 lb)

Range-3 to 100

lpu

Resolution Betterthan0.05 puat20 pu

Vert. Resolution 750 mm(30 in)

InvestigationDepth 260 mm(10.2 in)


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Table5.2 Commonopen-holetoolsand theiruses

Tool PhysicalMeasurement Use Comments

Logging conditions

Temperature(BHT)

Pressure(PRESS)

Caliper(CAL)

Temperature

Fluid pressure

Boreholediameter

Boreholetemperatureforresistivity

calculations.

Fluid pressureforformationvolume

factorcalculations.

Dataquality, insitustresstensor,

lithologyand permeabilityindicator

Corrected withHornerplot

Incorporated inRFT

Availablein2, 4, ormulti-

armversions.

Lithology

GammaRay(GR)

Spontaneous

Potential(SP)

Naturalradioactivityof

theformation.

Sand/shaleinterface

potential.

Shaleindicatorand depthmatching

Permeablebeds

Resistivityofformationwater

Canread throughcasing.

Doesnotwork inconductive

muds, oroffshore.

Porosity

Sonic(BHC, LSS)

Density(FDC,

LDT)

Neutron(SNP,

CN L)

Velocityofanelastic

waveintheformation.

Bulk densityofthe

formation.

Hydrogenconcentration

intheformation.

Effective(connected)porosity

Totalporosity

Totalporosity(shaleincreases

measured porosity, gasreduces

measured porosity)

Compaction, gasand vugs,

calibrationofseismicdata.

Used to calculatesynthetic

seismograms.

Canread throughcasing.

Resistivity

Simpleelectriclog

(SN, LN, Lat)

InductionLogs

(IES, ISF, DIL,

DISF, ILm, ILd)

Laterologs

(LL3, LL7, DLL,

LLs, LLd)

Microlog(ML)

Micro-laterolog

(MLL)

ProximityLog(PL)

Micro-spherically

focussed log

(MSFL)

Resistivityofflushed,

shallowand deep zones

respectively.

Conductivityofthe

formation.

Resistivityofthe

formation.

Resistivityofmudcake

and flushed zone.

Resistivityofflushed

zone.


zone.


zone.

Used inwatersaturationcalculations.

Conductivityand resistivityinoil

based muds, and hencecalculationof

watersaturation.

Resistivityinwaterbased muds, and

hencecalculationofwatersaturation.

Indicatorofpermeability.

Detectorofthinbeds.

MeasuresRXO

MeasuresRXO

MeasuresRXO

Nowobsolete, notfocussed,

cantbeused inoilbased

muds, proneto invasion.

Focussed devices.

Useinoilbased and fresh

watermuds. Rangeofdepths

ofinvestigation. (Vertical

resolution5-10 ft.)

Focussed devices.

Useinsaltwaterbased

muds. Rangeofdepthsof

investigation. (Vertical

resolution2-4 ft.)

(verticalresolutionabout1

ft.)

Notgood withthick

mudcakes.

Notgood ifinvasionis

small.

PartofDLL-RXOtool.

Imaging Logs Thereisarangeofimaginglogsbased uponsonic, visual, electricaland NMRmeasurementsthatare

beyond thescopeofthiscourse.


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wireline logging totarials

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