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1 Basics of Geophysical Well Logs_Lithology&Resis7vity

Basics of Geophysical Well Logs Lithology&Resis7vity 1 · E l =− R θ Fn ln C 1 C 2. Basics of Geophysical Well Logs_Lithology&Resis7vity 4 ... While Drilling resisvity logging

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Page 1: Basics of Geophysical Well Logs Lithology&Resis7vity 1 · E l =− R θ Fn ln C 1 C 2. Basics of Geophysical Well Logs_Lithology&Resis7vity 4 ... While Drilling resisvity logging

1BasicsofGeophysicalWellLogs_Lithology&Resis7vity

Page 2: Basics of Geophysical Well Logs Lithology&Resis7vity 1 · E l =− R θ Fn ln C 1 C 2. Basics of Geophysical Well Logs_Lithology&Resis7vity 4 ... While Drilling resisvity logging

2BasicsofGeophysicalWellLogs_Lithology&Resis7vity

Whenthewellboreisfilledbyawaterbasedmudandinpresenceofanalterna7onofpermeableandimpermeablelayers,duetoelectrochemicalphenomena,electricalcurrentsarespontaneouslygeneratedattheinterfacesbetweenmudandforma7onandbetweenimpermeableshalesandreservoirsands.TheSPlogisthemeasurementofthepoten7alofadownholeelectrodewithrespecttoasurfacereferenceelectrodewhichispropor7onaltotheintensityofthecurrentsgenerated.

SpontaneousPoten7al

Page 3: Basics of Geophysical Well Logs Lithology&Resis7vity 1 · E l =− R θ Fn ln C 1 C 2. Basics of Geophysical Well Logs_Lithology&Resis7vity 4 ... While Drilling resisvity logging

3BasicsofGeophysicalWellLogs_Lithology&Resis7vity

ThemagnitudeoftheSPgeneratedisafunc7onofthesalinitycontrastbetweenmudandforma7onwater.TwoarethemainSPgenera7onmechanisms:• membranepoten7al,• liquid-junc7onpoten7al.

TheSPlogisprimarilyapermeabilitycontrastindicatoraswellas

afundamentallithologylogespeciallyinshalysandsequences

SpontaneousPoten7al

Flushed zone

Virgin zone

+ -

Flushed zone

Virgin zone

+ -

Membranepoten7al

Liquid-junc7onpoten7al €

Em = −RθFn

Ia − IcIa + Ic

ln C1C2

El = −RθFnln C1C2

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4BasicsofGeophysicalWellLogs_Lithology&Resis7vity

SpontaneousPoten7al(freshmudandsaltyforma7onwater)

SPsh

SPsd

Vsh = A / B Vsh = (PS-PSsd)/(PSsh-PSsd)

SPlog

A

B

Page 5: Basics of Geophysical Well Logs Lithology&Resis7vity 1 · E l =− R θ Fn ln C 1 C 2. Basics of Geophysical Well Logs_Lithology&Resis7vity 4 ... While Drilling resisvity logging

5BasicsofGeophysicalWellLogs_Lithology&Resis7vity

SPloginterpreta7onproblems

MainproblemsofSPloginterpreta7onaremostlylinkedto:–  lackofpermeabilitycontrast

–  lackofmud/forma7onwatersalinitycontrast

– thinbeds– hydrocarbonoccurrence

Low permeability limestones

Marls

Marls

mV

Lowpermeabilitycontrast

Page 6: Basics of Geophysical Well Logs Lithology&Resis7vity 1 · E l =− R θ Fn ln C 1 C 2. Basics of Geophysical Well Logs_Lithology&Resis7vity 4 ... While Drilling resisvity logging

6BasicsofGeophysicalWellLogs_Lithology&Resis7vity 6 mV

Shales

Gas bearing sands

Water bearing sands

Shales

HydrocarboneffectontheSPlog

High permeability sandstones

Shales

Shales

Rm > Rw Rm = Rw Rm < Rw SSP = -K log (Rmf/Rw)

SPlogbehaviorasafunc7onofmud/forma7onwatersalinitycontrast

mV

SPloginterpreta7onproblems

Page 7: Basics of Geophysical Well Logs Lithology&Resis7vity 1 · E l =− R θ Fn ln C 1 C 2. Basics of Geophysical Well Logs_Lithology&Resis7vity 4 ... While Drilling resisvity logging

7BasicsofGeophysicalWellLogs_Lithology&Resis7vity 7

Rmf > Rw Rmf = Rw

SP SP

Page 8: Basics of Geophysical Well Logs Lithology&Resis7vity 1 · E l =− R θ Fn ln C 1 C 2. Basics of Geophysical Well Logs_Lithology&Resis7vity 4 ... While Drilling resisvity logging

8BasicsofGeophysicalWellLogs_Lithology&Resis7vity

InvertedSP:

Rmf<<Rw

Page 9: Basics of Geophysical Well Logs Lithology&Resis7vity 1 · E l =− R θ Fn ln C 1 C 2. Basics of Geophysical Well Logs_Lithology&Resis7vity 4 ... While Drilling resisvity logging

9BasicsofGeophysicalWellLogs_Lithology&Resis7vity 9

High permeability sandstones

Shales

Shales

mV

inflexion point

SP log

Boundaryloca7onbymeansoftheSPlogVer7calresolu7onoftheSPlog

SPloginterpreta7onproblems

inflexion point

Page 10: Basics of Geophysical Well Logs Lithology&Resis7vity 1 · E l =− R θ Fn ln C 1 C 2. Basics of Geophysical Well Logs_Lithology&Resis7vity 4 ... While Drilling resisvity logging

10BasicsofGeophysicalWellLogs_Lithology&Resis7vity

Geologicalapplica7onoftheSPlog

InabsenceofSPanomalies,whendealingwithwatersaturatedforma7onsandwithmudsofconstantsalinityinallthewellsunderevalua7on,theSPlogmaybeusedforgeologicalcorrela7onamongwellsandtodefinethedifferentsedimentaryfacies(inordertodefinelateralandver7calevolu7onofthesedimentaryenvironments).

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11BasicsofGeophysicalWellLogs_Lithology&Resis7vity

GammaRaylogThenaturalradioac7vityofgeologicalforma7onsisduetothepresenceinrockformingmineralsoftheradioac7veisotopesofelementssuchasUranium(U),Thorium(Th)andPotassium(K).TheseisotopesaremostlyrelatedtoclaymineralswhosecontentinThandKisgenerallyhigherthanassociatedsandandsandstones.Incarbonateforma7onstheradioac7vityismostlyduetothepresenceofUandtheGammaRaylevelisnotdirectlyrelatedtoforma7onshalyness.

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12BasicsofGeophysicalWellLogs_Lithology&Resis7vity

Low activity Cement

High activity Cement

Low activity Cement

K = 4% Th = 24 ppm U = 12 ppm

200 GAPI

Typical responses Of GR log

GammaRaylog

Gamma Ray American Institute Test Pit

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13BasicsofGeophysicalWellLogs_Lithology&Resis7vity 13

(GR-GRsd) Vsh = -----------------

(GRsh-GRsd)

GRsh

GRsd

GR

Caliper - GR Resistivity Density/Neutron

ShalevolumefromGRlogBS, CALI, SP, GR LLD, LLS, MCFL TNPH, RHOB, DT

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14BasicsofGeophysicalWellLogs_Lithology&Resis7vity

GammaRay:environmentalcorrec7onsMain factors affecting GR measurements are: •  hole diameter •  sonde position in the well •  mud loaded with radioactive material

BS

CAL

Measured GR

Corrected GR

Shale

Shale

Sand

Sand

Sand γ

γγ

γ

γ

γ

γ

γ

γ γ

γ

γ

γ

γ

γ γ

Tool eccentered Tool centered

mud

mud

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15BasicsofGeophysicalWellLogs_Lithology&Resis7vity

GammaRay:environmentalcorrec7ons

Page 16: Basics of Geophysical Well Logs Lithology&Resis7vity 1 · E l =− R θ Fn ln C 1 C 2. Basics of Geophysical Well Logs_Lithology&Resis7vity 4 ... While Drilling resisvity logging

16BasicsofGeophysicalWellLogs_Lithology&Resis7vity

GammaRaySpectrometry

Gamma Ray emission spectra

WLLServicesSLB NGSSLB HNGS(PEX)BA SL

Page 17: Basics of Geophysical Well Logs Lithology&Resis7vity 1 · E l =− R θ Fn ln C 1 C 2. Basics of Geophysical Well Logs_Lithology&Resis7vity 4 ... While Drilling resisvity logging

17BasicsofGeophysicalWellLogs_Lithology&Resis7vity

GRincasedhole

GR

Neutron

GRcorrela7onLogincasedhole Forma7onEvalua7onlogginginCH

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18BasicsofGeophysicalWellLogs_Lithology&Resis7vity

Single arm caliper

Two arm caliper

Three arm caliper Four arm caliper

Caliperlog

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19BasicsofGeophysicalWellLogs_Lithology&Resis7vity

Comparisonamongdifferentcalipermeasurements

0

6

6

GR 200

16

16 BS

CAL 0.2 2000 LLD

0.2 2000 MCFL

0.2 2000 LLS RHOZ 1.95 2.95

NPHI 45 -15

0 10 PEF

Mudcakeresul7nginaholediameterrestric7on

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20BasicsofGeophysicalWellLogs_Lithology&Resis7vity

BoreholeGeometryTool(BGT)

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21BasicsofGeophysicalWellLogs_Lithology&Resis7vity

“Noisy”logsduetopoorboreholewall

quality.

CALIPER

DRHO

RHOB

TNPH

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22BasicsofGeophysicalWellLogs_Lithology&Resis7vity

Classifica7onofResis7vitylogs

Inrela7ontodepthofinves7ga7on

•  Macro-devicestomeasureRt•  Micro-devicestomeasureRxo

Inrela7ontotoolphysics•  Nonfocused,galvanicdevices(WLL)•  Focused,galvanicdevices(WLLeLWD)

•  Lowfrequencyinduc7ondevices(WLL)•  EMwavepropaga7ondevices(LWD)

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23BasicsofGeophysicalWellLogs_Lithology&Resis7vity

Environmentaleffectsaffec7ngresis7vitymeasurements

Rt

Rs

Rs

Rt

Rt

1D VERTICAL (shoulder bed)

Rt

Rxo

1D RADIAL (invasion effect)

Rt2

Rs

Rs

Rt3

Rt1 Rxo1

Rxo3

Rxo2

2D

Rs

Rs

Rt3

Rt1 Rxo1

Rxo3

Rxo2 Rt2v

Rt2HMAX Rt2hmin

2D +dip (dipping beds)

Rm

Rt

Rs

Ro

Rm

Rs

Borehole

3D

Rv

Rh

Anisotropy

Page 24: Basics of Geophysical Well Logs Lithology&Resis7vity 1 · E l =− R θ Fn ln C 1 C 2. Basics of Geophysical Well Logs_Lithology&Resis7vity 4 ... While Drilling resisvity logging

24BasicsofGeophysicalWellLogs_Lithology&Resis7vity

Invasion effects and formation parameters

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25BasicsofGeophysicalWellLogs_Lithology&Resis7vity

Sw = Sxo = 100%

Ro= F Rw = (1/Φ^m) Rw Rxo= F Rmf = (1/Φ^m) Rmf

Sw < 100%, Sxo <100%

Rt =(1/Φ^m)(Rw)/Sw^n) Rxo=(1/Φ^m)(Rmf)/Sxo^n)

Page 26: Basics of Geophysical Well Logs Lithology&Resis7vity 1 · E l =− R θ Fn ln C 1 C 2. Basics of Geophysical Well Logs_Lithology&Resis7vity 4 ... While Drilling resisvity logging

26BasicsofGeophysicalWellLogs_Lithology&Resis7vity

Invasionandrelatedresis7vityprofiles

Page 27: Basics of Geophysical Well Logs Lithology&Resis7vity 1 · E l =− R θ Fn ln C 1 C 2. Basics of Geophysical Well Logs_Lithology&Resis7vity 4 ... While Drilling resisvity logging

27BasicsofGeophysicalWellLogs_Lithology&Resis7vity

Fresh mud and salty formation water

Page 28: Basics of Geophysical Well Logs Lithology&Resis7vity 1 · E l =− R θ Fn ln C 1 C 2. Basics of Geophysical Well Logs_Lithology&Resis7vity 4 ... While Drilling resisvity logging

28BasicsofGeophysicalWellLogs_Lithology&Resis7vity

Caliper - GR Resistivity Density/Neutron

Rmf very close to Rw

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29BasicsofGeophysicalWellLogs_Lithology&Resis7vity

Nonfocusedelectricalresis7vitytools

Page 30: Basics of Geophysical Well Logs Lithology&Resis7vity 1 · E l =− R θ Fn ln C 1 C 2. Basics of Geophysical Well Logs_Lithology&Resis7vity 4 ... While Drilling resisvity logging

30BasicsofGeophysicalWellLogs_Lithology&Resis7vity

OldE(electrical)logs

Track 1 Track 2 Track 3

Dep

th

SP (mv) SN (ohmm)

Ampl. SN (ohmm)

LN (ohmm)

IN (ohmm)

Conventional Electrical Log (ES)

SN = Short Normal (spacing 16”) Ampl. SN = Amplified Short Normal

LN = Normal (spacing 64”) IN = Inverse or Lateral (spacing 18’ 8”)

Linear scale

Linear scale

Linear scale

Page 31: Basics of Geophysical Well Logs Lithology&Resis7vity 1 · E l =− R θ Fn ln C 1 C 2. Basics of Geophysical Well Logs_Lithology&Resis7vity 4 ... While Drilling resisvity logging

31BasicsofGeophysicalWellLogs_Lithology&Resis7vity

OldE(electrical)logs

Track 1 Track 2 Track 3

Dep

th

SP (mv) SN (ohmm)

Ampl. SN (ohmm)

6FF40 R (ohmm)

6FF40 C (ohmm)

Induction Electrical Log (IES)

SN = Short Normal (spacing 16”) Ampl. SN = Amplified Short Normal

6FF40 R = Induction log deep (40”) resistivity 6FF40 C = Induction log deep (40”) conductivity

Linear scale

Linear scale

Linear scale

Page 32: Basics of Geophysical Well Logs Lithology&Resis7vity 1 · E l =− R θ Fn ln C 1 C 2. Basics of Geophysical Well Logs_Lithology&Resis7vity 4 ... While Drilling resisvity logging

32BasicsofGeophysicalWellLogs_Lithology&Resis7vity

Normalandlateralresis7vitylogs

Page 33: Basics of Geophysical Well Logs Lithology&Resis7vity 1 · E l =− R θ Fn ln C 1 C 2. Basics of Geophysical Well Logs_Lithology&Resis7vity 4 ... While Drilling resisvity logging

33BasicsofGeophysicalWellLogs_Lithology&Resis7vity

Normalelectricallogresponses:normal

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34BasicsofGeophysicalWellLogs_Lithology&Resis7vity

Lateralelectricallogresponses:lateral

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35BasicsofGeophysicalWellLogs_Lithology&Resis7vity

WellSecala1SP/ILD/SN/MLLFDC/CNL/BHC

ILD (Rt)

MLL (Rxo)

SN (Ri)

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36BasicsofGeophysicalWellLogs_Lithology&Resis7vity

Resis7vitytools:WireLine(WLL)

&WhileDrilling

(LWD)

Page 37: Basics of Geophysical Well Logs Lithology&Resis7vity 1 · E l =− R θ Fn ln C 1 C 2. Basics of Geophysical Well Logs_Lithology&Resis7vity 4 ... While Drilling resisvity logging

37BasicsofGeophysicalWellLogs_Lithology&Resis7vity

DualLaterolog0

6

6

GR 200

16

16 BS

CAL 0.2 2000 LLD

0.2 2000 MCFL

0.2 2000 LLS

Page 38: Basics of Geophysical Well Logs Lithology&Resis7vity 1 · E l =− R θ Fn ln C 1 C 2. Basics of Geophysical Well Logs_Lithology&Resis7vity 4 ... While Drilling resisvity logging

38BasicsofGeophysicalWellLogs_Lithology&Resis7vity

SfericallyFocusedLog

Page 39: Basics of Geophysical Well Logs Lithology&Resis7vity 1 · E l =− R θ Fn ln C 1 C 2. Basics of Geophysical Well Logs_Lithology&Resis7vity 4 ... While Drilling resisvity logging

39BasicsofGeophysicalWellLogs_Lithology&Resis7vity

Environmentaleffectsonfocused

galvanictools

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40BasicsofGeophysicalWellLogs_Lithology&Resis7vity

Induc7onlogging

Induction log principle

Page 41: Basics of Geophysical Well Logs Lithology&Resis7vity 1 · E l =− R θ Fn ln C 1 C 2. Basics of Geophysical Well Logs_Lithology&Resis7vity 4 ... While Drilling resisvity logging

41BasicsofGeophysicalWellLogs_Lithology&Resis7vity

ILD/SFLexample• blackcurveILD• redcurveSFLU

NorthAdria7cfreshWBM

Page 42: Basics of Geophysical Well Logs Lithology&Resis7vity 1 · E l =− R θ Fn ln C 1 C 2. Basics of Geophysical Well Logs_Lithology&Resis7vity 4 ... While Drilling resisvity logging

42BasicsofGeophysicalWellLogs_Lithology&Resis7vity

Rxologging:theMSFLtool

0

6

6

GR 200

16

16 BS

CAL 0.2 2000 LLD

0.2 2000 MCFL

0.2 2000 LLS

Page 43: Basics of Geophysical Well Logs Lithology&Resis7vity 1 · E l =− R θ Fn ln C 1 C 2. Basics of Geophysical Well Logs_Lithology&Resis7vity 4 ... While Drilling resisvity logging

43BasicsofGeophysicalWellLogs_Lithology&Resis7vity

Caliper-GR Resis7vity Density/Neutron

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44BasicsofGeophysicalWellLogs_Lithology&Resis7vity

WhileDrillingresis7vityloggingWhileDrillingresis7vityloggingareoftwotypes:• galvanic;• EMwavepropaga7on.WhileDrillingGalvaniclogs(AnadrillRABonly)canbeusedonlyinpresenceofWaterBasedconduc7veMuds.EMwavepropaga7onlogs,duetothepresenceofmetallicbodyofthesystem,canbeobtainedonlyusinghigherfrequencieswithrespecttotheWireLineinduc7ononeswithadvantagesanddisadvantages.

Page 45: Basics of Geophysical Well Logs Lithology&Resis7vity 1 · E l =− R θ Fn ln C 1 C 2. Basics of Geophysical Well Logs_Lithology&Resis7vity 4 ... While Drilling resisvity logging

45BasicsofGeophysicalWellLogs_Lithology&Resis7vity

LWDPropaga7onResis7vity

T

R1

R2

PS

B

PS (deg.)= f (ε)

Segnale a R1

Segnale a R2

t A

mp

iezz

a

A

AT(dB) = K Log (B/A) = f (σ)

θ

180° 360°

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46BasicsofGeophysicalWellLogs_Lithology&Resis7vity

LWDresis7vi7es:Real7mevsmemory

RealTime Memory