Well Logging Summary_Master

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WIRELINE LOGGING
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Abbreviations (shown on Logging Program from office)
• BH: Sonic (Bore hole compensated)
• !"I: Dipole Sonic
• AI#: Array Induction Tool (Laterlog resistivity + SP) can !e replaced "ith #$LA
i% use salty mud e&g& '(l
• HRLA: #igh $esistivity Laterlog ($esistivity Laterlog + SP)
• PE$: Plat%orm )*press (+eutron , Density porosity)
• !%a& #L!: Dual density (density at -. degree)
• 'L#B: /icrolog
• ('I: /icrolog resistivity gives color image %or dip
• $)*a&: %or cement volume , hole condition
• $) a&*ER!: can apply e*tra pressure on string i% tool stuc0
• ER!: )lectrical (ontrol $elease Device
Device uses a remotely operated emergency electrical disconnect that ma0es
it possi!le to carry out a controlled release& It leaves a 1%ishing hoo02 !ehind
so that the elogs can !e retrieved a%ter the source sa%ely out o% hole& (an
apply e*tra pressure on string i% tool stuc0&
Logging #oo&s vs+ '%, "-stems
Note. Logging tools are selected !ased on mud system (mud system dictates "hich
tools to run !ecause some tools "or0s in one type o% mud and some in other)
• Air base mud (air drilling): 3$ Induction density , neutron (side "all
porosity: S+P)& ()lectrode $esistivity SP , Sonic4Acoustic (+S (neutron:
compensated neutron Sonde) does not "or0)
$eason: none o% these tools a%%ected !y air
• Oil base mud: 3$ DIL SP Sonic4Acoustic Density , +eutron ((+S) tools
$eason: none o% these tools a%%ected !y oil !ase mud
• Water base mud plus polymer additives: 3$ SP DIL Sonic4Acoustic
+eutron , Density tools
$eason: none o% these tools a%%ected !y "ater !ase mud neither !y polymer
additive
Note. 5ne single log can not provide all in%ormation a!out a %ormation46one o%
interest7 ho"ever a set o% logs help to interpret the 6one4%ormation&
Bac/%0 %rve. "hen curve 8umps out o% scale and remaining curve repeats
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We&& Logging "%mmar-
Logging Ob1ectives
9& (orrelation: "ell to "ell o% %ormation tops ma8or lithologies ma8or
uncon%ormities
:& Locating the porous permea!le reservoir roc0s
;& Locating the hydrocar!on sho"s using <ualitive 1<uic0 loo02 techni<ues
=& >uanti%y reservoir engineering data
a& Thic0ness o% net pay
!& Average porosity
c& Average "ater saturation
d& )stimate o% permea!ility
?& Stratigraphic and structural studies
@& Aell completion
B& 3eophysical application
RESISTIVITY LOGS
!%a& In,%ction Log
Tool measures conductivity o% the %ormation
Cormation evaluation:
• (onductivity is inversely proportional to resistivity& $esistivity is calculated %rom
conductivity value ($ D 94()& $esistivity is used to identi%y hydrocar!ons& #igher
resistivity "ith clean , porous 6one indicates hydrocar!on 6one& Also used to
identi%y lithology&
• ; curves (shallo" medium and deep)& Eou can read directly %rom deep
curve4$ILD is e<ual to %ormation true resistivity
• (an !e presented either on linear or logarithmic scale
• Scale: .&: F :... (le%t to right) in Trac0 : , ; and .&: F :. in Trac0 9
• Gnits: ohmHmeter
• I% resistivity is high either has hydrocar!on "ater tight4dense %ormation4roc0
(no porosity)& I% $ is too high might have Anhydrite 3ypsum Salt (hal0 could
!e tight LS or Dolomite con%irm "ith P) log&
• Cluid contact: I% clean and porous 6one (!ased on 3$ , SP logs) lithology (P)
log) , +4D porosity (+4D Porosity log) is almost constant and resistivity drops
there is %luid contact (oilH"ater)& Lo" resistivity in this 6one is "ater& $esistivity o%
3as is less than "ater , oil&
• Cormation (hanges: resistivity log is a good secondary method o% pic0ing
%ormation tops as many %ormations have %airly characteristic resistivity pro%iles&
Sandstone and coal !eds tend to !e more resistive than shales& Limestone or
dolomite !eds are usually much more resistive than either sandstones or shales
and anhydrite is e*tremely resistive& Shales "hich contain a large amount o%
organic matter (such as the +ordegg and )*sha" and Cish Scales 6ones) sho"
typically high resistivities on the induction log&
)nvironmental )%%ects "hich a%%ect toolIs accuracy:
• 3ap !et"een hole and tools creates pro!lems
• Best "or0s in oil !ase mud and %resh mud "here conductivity o% mud is 6ero
• $eading up to :?. ohmHm accurate a!ove :?. ohmHm starts errors
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• Bed thic0ness = %t or J = %t and hole diameter K inch "or0s good
• #ole damage4caving (s0in e%%ect) e%%ects it accuracy
• Tool is conductivity see0ing device higher the conductivity !etter tool "or0s&
/ain %eatures4components o% tool:
$eceiver coil transmitter coil ground loop a constant po"er direct coupling (or
reverse "ound coil) to eliminate un"anted signals e&g& LHSignals&
Tool mechanism4Principles o% measurement: a constant current is applied to
transmitter coil "hich creates and induces magnetic %ield into %ormation a second
magnetic %ield is created !y ground loop and induces in receiver coil and current is
measured (strength o% %ormation current depends on %ormation conductivity)&
!%a& Later&og Log (!LL)
Tool measures resistivity o% the %ormation
Cormation evaluation:
• $esistivity is used to identi%y hydrocar!on 6one and also used to identi%y lithology
to some e*tent& #igh resistivity "ith clean , porous 6one indicates hydrocar!on
presence
• ; curves (shallo": LLS deep: LLD /SCL: /icroHSpherically Cocused Log used to
measure $*o)
• Presented on logarithmic scale
• Scale: .&: F :... (le%t to right) in Trac0 : , ; and .&: F :. in Trac0 9
• Gnits: ohmHmeter
• $ead last ; points %rom Induction Log: high resistivity Cluid (ontact and
Cormation (hanges:
)nvironmental )%%ects "hich a%%ect toolIs accuracy
• Aor0s good in salty mud not good in oil !ase mud
• Aor0s "ell "hen $t J $o ((ommonly used %or lo" resistivity muds and high
resistivity %ormations)
• #ole dia K inch
• Bed thic0ness and !ad hole conditions e%%ect its accuracy
• Tool is resistivity see0ing device and higher the resistivity !etter the tool "or0s
/ain %eatures4components o% tool:
• Tool uses electrodes to pass current into %ormation and measure drop4change in
voltage4current !et"een : other electrodes
• Deep loo0ing device is hole centered
• Shallo" loo0ing device is mounted on a pad "hich pressed against !ore hole "all
Tool mechanism4Principles o% measurement:
A constant current (I) is %orced into %ormation and measure change in voltage "hich
is related to resistivity o% %ormation
'icro*Resistivit- Log
• Tool indicates permea!ility o% %ormation , measures close to !ore hole ($*o ,
$o)& 5nly tells thic0ness o% permea!le 6one (mud ca0e)
Cormation evaluation:
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• It measures the voltage drop %rom electrodes and resistivities are determined
%rom these voltages drop
• Presence o% mud ca0e is indicated "here microHnormal curve (deep) reads higher
than microHlateral curve (shallo": reads close to !orehole or $mc)
• : curves: give : di%%erent depths o% investigation (+ormal or microHnormal: deep
resistivity , Lateral or microHinverse: shallo" resistivity)
• Also called /LL (/icrolaterolog) or /SCL (/icroHSpherically Cocused Log)
)nvironmental )%%ects "hich a%%ect toolIs accuracy
• /ud ca0e thic0ness
• Bore hole mud , %ugacity on sides o% hole DJ tool does not "or0 (as padIs loose
contact "ith %ormation)
• )%%ected !y !ore hole e&g& caving good %or straight hole
• 5nly "or0 in conductive medium e&g& good in "ater !ase mud (does not "or0 in
oil !ase mud) additives change $esistivity values
/ain %eatures4components o% tool:
(urrent electrodes guard electrodes tool is pad mounted that pressed against !ore
hole "all (8ust li0e density tool sometime used "ith density tool)
Tool mechanism4Principles o% measurement:
• $esistivity measured !ased on guard4electrode method& Bottom electrode emits
current that %lo"s through mud ca0e %ormation and !orehole !e%ore it returns to
tool case& It measures the voltage drop %rom electrodes and resistivities are
determined %rom these voltages&
• /easurements only see mud ca0e and %lushed 6one
Arra- In,%ction #oo& (AI#). ? curves
POROSITY LOGS
!ensit- Porosit- Log
Tool measures !ul0 density o% %ormation
Cormation evaluation:
• It measures electron density "hich is directly related to !ul0 density o% %ormation&
Bul0 density o% %ormation helps to calculate porosity o% %ormation and !ul0 density
also indicates lithology
• Dense %ormations a!sor! more 3amma rays and count rates at detectors is lo"
• Discriminates !et"een gas , oil "hen presented "ith +eutron porosity log
• Presented in Trac0 : , ; Gnits: PG
• Density correction (delta rho) in Trac0 ; sometime in Trac0 :
• Limestone porosity scale presentation: =? F (H9?) (le%t to right) or .&=? F (H.&9?)
• Sandstone porosity scale presentation: @. F . (le%t right) or .&@ F .&.
• Bul0 density scale: : F ; (le%t to right units gm4cc or c;) or :...H;... (0g4m;)
• The rule o% thum! i% the correction curve is greater than +.&9? g4cc (+9?.
0g4m;) the data in the main curve "ill not !e very relia!le& It is the value not
the scale that matters& #o"ever accepta!le range o% the density correction is
%rom H.&.? to .&9? gm4cc (or H?. to 9?. 0g4m;)
• I% !ul0 density is too high (porosity too lo") tight4dense %ormation (no porosity)&
I% BD 8umps out o% scale or close might have Anhydrite 3ypsum Salt could !e
Dolomite con%irm "ith P) log&
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• Bul0 densities o% common roc0s4minerals: (onsult ta!le
• /irror image porosity i% gas e%%ect is mirror image (e&g& cross over) calculate
porosity using %ormula D S>$T (+P
:
+ DP
:
4:)& #o"ever in other cases The rule
o% thum! is D +P + DP4:
• The vast ma8ority o% o%%ice geologists re%er to the density porosity curve "hen
assessing reservoir <uality and it is !est to report 8ust the density porosity values
to the client unless instructed&
• (ross plot SS vs& LS Scale: does not matter either logs porosity on SS or LS
scale !ut "hen using cross plot %or LS compare porosity on *Ha*is and yHa*is
and read accordingly& And %or SS compare porosity directly on SS line and read
accordingly&
• +eutron4Density Porosity: is very high %or (oal and may 8ump out o% scale (le%t o%
the scale)
• 3as )%%ect ((ross 5ver): +eutron porosity tool detects hydrogen atoms and
neutrons are di%%use a%ter collision "ith "ater some counts come !ac0 to tool
(more "ater less counts !ac0 to tool)& 3as has less hydrogen atoms and more
neutron counts !ac0 to tool and tool reads less neutron porosity and +eutron
porosity curve moves to right& Density porosity tool measures !ul0 density (less
density DJ more porosity)& Density o% gas is less than %resh "ater (9&.) and oil
density tool reads more porosity and moves to le%t& This leads to the Mgas e%%ectM
on porosity logs and sho"s Mcross overM& True porosity in a gasH!earing (cross
over) 6one is average o% neutron and density porosities&
• (urves separation: I% neutron density porosity curves come close to each other
there is potential o% oil& #o"ever i% !oth curves start separating %rom each other
(move a"ay) con%irm "ith other logs (e&g& 3$ P) or so) "hat is causing them
to separate may !e change in lithology or shaly 6one&
• Also called (ompensated Density Log ((DL) Spectral Density Log (SDL)
Cormation Density (ompensated (CD() and LithoHDensity Tool (LDT)& +ames
%rom di%%erent logging companies&
)nvironmental )%%ects "hich a%%ect toolIs accuracy:
• (aving4!ad !orehole conditions (rugosity: !orehole "all is rough increase in
density correction)
• #eavy mud e&g& Barite
• Aor0s in all types o% muds and air drilled holes
• Does not "or0 "ell in cased hole
/ain %eatures4components o% tool: 3$ source : detectors (near4short spacing
%ar4long spacing)& Tool is pad device , pushes against !ore hole "all
Tool mechanism4Principles o% measurement: 3ammaHrays are in8ected into
%ormation rays interact "ith %ormation& A%ter (ompton scattering (e%%ect) most are
a!sor!ed some o% scatter4counts come !ac0 and detected& Actually tool measures
electron density "hich is directly related to !ul0 density o% %ormation&
• The num!er o% gamma rays that reach the detectors is a %unction o% the electron
density o% the %ormation !eing logged&
• Presence o% electron in C/ slo"do"n the 3$
• Less gamma ray "e get !ac0 more electrons in Cm , density is lo"& Smaller
reading more porosity
• /ore dense %ormation more 3$ slo"s do"n less return to detector& )&g& LS
• Less dense %ormations less 3$ slo"s do"n more return to detector& )&g& (oal
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Ne%tron Porosit- Log
Tool measures "ater content (hydrogen inde*4atoms) o% %ormation
Cormation evaluation:
• Gsed to identi%y porous %ormations (determine porosity)
• Amount o% +eutrons detected related to %ormation porosity& Less +eutrons
detected more hydrogen content in %ormation , higher %ormation porosity
• Ahen presented "ith !ul0 density uses to identi%y lithology and gas detection
(cross over4gas e%%ect "here neutron porosity reads lo")
• Discriminates !et"een gas , oil "hen presented "ith density porosity log
• Presented in Trac0 : , ; Gnits: PG
• Limestone porosity scale presentation: =? F (H9?) (le%t to right) or .&=? F (H.&9?)
• Sandstone porosity scale presentation: @. F . (le%t right) or .&@ F .&.
• $ead %ollo"ing points %rom Density Porosity log: +eutron4Density Porosity 3as
)%%ect ((ross 5ver) and (urves separation
)nvironmental )%%ects "hich a%%ect toolIs accuracy:
• Borehole rugosity , caving
• /ud salinity
• (+S good in oil !ase mud and S+P good in air4gas !ase mud
• Pressure , temperature
• /ud ca0e and mud "eight
• Stand o%% (space !et"een tool and !orehole)
/ain %eatures4components o% tool:
Cast neutron source : detectors (9 near 9 %ar) !olt spring4s0id "hich pushes tool
against !ore hole "all
Tool mechanism4Principles o% measurement:
Source !om!ardment o% %ast moving neutrons "ith high energy into %ormation& As
they collide "ith hydrogen nuclei they loose energy and slo" do"n through
epithermic to thermic level& Detectors measure their loss o% energy as they pass
through& Some lo" energy neutrons come !ac0 and detected
"onic2Aco%stic Log
Tool measure the %ormationIs capacity to transmit sound "aves
(/easures travel time4deltaHt (reciprocal o% the velocity) o% sound "aves into
%ormation)
Cormation evaluation:
• Delta t (travel time) helps to calculate porosity determine lithology (matri*) and
%racture identi%ication
• Gnits: measured in usec4%t or usec4m
• Plotted at linear scale in porosity trac0 (trac0 : , ;)
• Scale: ?.. F 9.. (le%t to right) usec4m or =. F 9=. usec4%t
• (oal !eds have lo" velocities and high deltaHt values due to their lo" density
"hile limestone dolomite and anhydrite are much denser and have higher
velocities and lo"er deltaHt values&
• Cracture and 3as Identi%ication: I% you see cycle s0ipping in the sonic curve (i&e&
a signi%icant and sudden shi%t in the !ac0ground deltaHt pro%ile "ithin a uni%orm
section o% lithology) this can indicate the presence o% %ractures or gas&
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• (ycle S0ip: %rom !ottom o% spi0e corner is sharp at -. degree see picture
• +oise Spi0e: at top o% spi0e corner is rounded see picture
)nvironmental )%%ects "hich a%%ect toolIs accuracy:
• (aving: cause cycle s0ipping
• #ole rugasity: cause +oise triggering
• I% too tilts in hole travel time !et"een receivers cancel out
• #ydrocar!on does e%%ect travel time some time in homogeneous roc0s i% porosity
J =B&@ N then pro!lem
• 3as in hole: gas !u!!les scatter and a!sor! acoustic energy
/ain %eatures4components o% tool: a sound !ody "ith in tool : transmittersHreceiver
groups& )ach group consist o% 9 transmitter , : receivers (near , %ar)
Tool mechanism4Principles o% measurement: a sound !ody propagates compressional
(sound) "aves into %ormation& 9
st
(A) , :
nd
(B) negative arrival o% compressional
"aves ("ith slo"er velocity) come !ac0 to tool and detected& A F B D Sonic Oelocity
(deltaHt)
(Tool measures the time it ta0es %or a sound pulse to travel !et"een a transmitter
and a receiver mounted a set distance a"ay along the logging tool)&
GA''A RA) LOG (GR)
Tool measures natural radioactivity o% the %ormation (measures the natural gamma
ray emissions %rom radioactive %ormation ('HPotassium GHGranium Th HThorium)
Cormation evaluation:
• Gsed %or lithology identi%ication and correlation
• Caceis identi%ication
• /ineral analysis
• )valuation o% shale content o% %ormation higher radioactive material in %ormation
higher 3$ value and higher S# N& Because it is lithology indicator and used to
calculate S# volume&
• Shales tend to read higher than K. API siltstones %rom P@?HK. API and most
other lithologies (sandstone limestone dolomite limestone coal etc&) less than
@? API& Some shale !eds are highly radioactive and go o%% scale (higher than 9?.
API e&g& +ordegg )*sha" Cish Scales 6one)&
• Presented in trac0 9 on linear grid and scaled in API units (increased %rom le%t to
right)
• Applica!le in open hole and cased hole
• Spectral 3amma $ay Log: one curve o% total gamma ray in trac0 9 and ; curves
in trac0 : , ; (one curve %or each source e&g& G ' , Th)
)nvironmental )%%ects "hich a%%ect toolIs accuracy:
• (aving causes lo"er 3$ values
• #eavy mud (e&g& !arite in mud DJ lo"er value in mud ca0e)
• '(l mud increase in !ac0ground 3$ values
/ain %eatures4components o% tool:
Simple tool consists o% a gamma ray detector and associated electronics %or passing
the gamma ray counts or count rates to the sur%ace& (/odern tool is a sensitive 3$
detector consists o% a scintillation counter (sodium iodide crystal) and a photo
multiplier)
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Tool mechanism4Principles o% measurement:
• 3amma radiation is electromagnetic "aves o% energy similar to light and radio
"aves having no mass& This is the radioactive energy that is measured in the
!orehole !y the gamma ray detector&
• $adioactive source (' G Th DJ i% present in %ormation) emits gamma rays "ith
high energy (GR definition: emission of photons with no mass & no charge but
great energy) "hen they passes through material (%ormation and mud) their
energy is a!sor!ed through (ompton scattering4e%%ect and due to collision
!et"een 3$ , electrons their energy is degraded& #igher the density o% material
they passes through rapid loss4degradation o% energy and continuous spectrum
o% values is o!served4recorded in detector at the sur%ace&
"P ("PON#ANEO3" PO#EN#IAL) LOG
Tool measures the ionic potential !et"een !orehole %luid and %ormation %luid (ion
e*change !et"een : salinities)&
Cormation evaluation:
• Indicates permea!ility (SP de%lects le%t %rom Shale !aseline DJ negative
de%lection)
• Discriminates !et"een porous and non porous 6one
• Indicator o% %ormation "ater salinity
• Gsed to calculate resistivity o% %ormation "ater
• Gsed to identi%y depositional environment
• +o de%lection in SP log (straight line) means drilling "ater and %ormation "ater
has same salinity
• Bigger the di%%erence in salinity !igger the de%lection (i% drill "ith %resh mud no
salinity)
• SP log runs "ith $esistivity Tool
• Presented "ith 3$ in Trac0 9
• Gnits: milli volts (mO)
• #ydrocar!on: I% clean and porous 6one (!ased on 3$ , SP logs) lithology (P)
log) , +4D porosity (+4D Porosity log) is almost constant and SP curve de%lects to
le%t %rom shale !aseline and de%lects little !it to right "ithin negative de%lection
here is hydrocar!on&
)nvironmental )%%ects "hich a%%ect toolIs accuracy:
• To get de%lection need "ater !ased mud (no SP in oil !ase mud and air drilled
hole !ecause there is no conductive %luid in !orehole)
• Collo"ing %actors a%%ect shape o% SP , amplitude: $m%4$" ratio (di%%erence in
resistivities o% : %luids) Salinity di%%erence hydrocar!on presence '(l mud high
resistivity %ormations
• Collo"ing %actors a%%ect validity o% SP i% anyone occurs then SP is useless:
/agnetism Bimetallic e%%ect Telluric currents ("inter a%%ect chec0 logging date)
/ain %eatures4components o% tool:
: electrodes (SP electrode ground electrode) recording voltmeter
Tool mechanism4Principles o% measurement:
/easured !y suspending an electrode in !orehole and measuring the voltage
di%%erence !et"een electrode and a 1ground2 electrode that ma0es the electrical
contact "ith the earth at sur%ace& +o arti%icial currents are applied&
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/ore 3eneral Cacts:
• Gsed to identi%y depositional environment e&g& i% !ell shape curve indicates
Transgrasive4Alluvial point !ars4shoreline depositsH%iner up"ard (ylinder shape
indicates distri!utary channels4tur!iditiesHuni%orm grain si6e %unnel shape
indicates regressive4delta marine %ringe4shoreline deposit4o%%shore !aresHcoarser
grains up"ard
• ; %actors to provo0e an SP current: a) conductive %luid in the !orehole !) a
porous , permea!le !ed surrounded !y an impermea!le %ormation c) and a
di%%erence in salinity !et"een !orehole %luid and %ormation %luid
• SP de%lection could !e negative %rom Shale !aseline i% %ormation "ater is more
saline than mud in !orehole and here resistivity o% %ormation "ater is less than
$m%
• To get %ull SP de%lection and proper !ed resolution as a rule o% thum! a !ed
should !e thic0er than :. times the !orehole diameter& SP "ill not sho" %ull
de%lection i%:
o Bed is not thic0 enough
o Shale in %ormation
o Invasion is very deep
o #ydrocar!ons are present
• De%lection to le%t (Hve) DJ %resh mud in hole , salty "ater in %ormation
• (urve moves4de%lects to"ards less saline "ater (or %resh "ater) or a"ay %rom
more saline "ater
• 5ther %actors "hich a%%ect shape o% SP , amplitude o% SP: Shaliness Bed
thic0ness Bed resistivity Invasion Borehole diameter
• Cactors "hich a%%ect validity o% SP i% anyone occurs then SP is useless: /agnetism
(partial logging truc0 get magneti6e) Bimetallic e%%ect (logging ca!le
touches4!rushes inside casing di%%icult to detect) Telluric currents (natural a%%ect
caused !y "inter i% SP tool sits at !ottom then natural earth current passes
through tool SP curve moves all over chec0 logging date i% logged in "inter)
Photo*E&ectric Effect (PE) or Photoe&ectric (actor Log (Litho*!ensit-)
It is a measure o% the amount o% light re%lected %rom the roc0 layers (actually it
detects the atomic num!er 1Q2 o% %ormation constituents)
Cormation evaluation:
• Lithology indicator (types o% roc0s in %ormation)
• /easured in Barns4electron
• P)C curve is plotted com!ined "ith density and neutron logs (scale: .H9. DJ le%t
to right)
• I% P) value o% t"o roc0s is very close then loo0 at !ul0 density log (i% availa!le)
• (onsult ta!le %or P) values o% roc0s4minerals
)nvironmental )%%ects "hich a%%ect toolIs accuracy:
• $oc0 type !ut "ater in %ormation does not a%%ect
• #eavy mud e&g& Barite in mud (P) value o% Barite: :@B ho"ever common roc0
minerals have P) value R @)& Simply does not "or0 in mud contains Barite
/ain %eatures4components o% tool:
Tool is related to density tools& A high energy gamma ray source : detectors (near ,
%ar)
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Tool mechanism4Principles o% measurement:
The emission o% electrons %rom matter a%ter the a!sorption o% energy %rom
electromagnetic radiation such as *Hrays or visi!le light&
Ahen 3amma rays pass through matter a%ter collision they loose energy& PhotoH
)lectric a!sorption occurs "hen gamma rays loose enough energy to !e captured !y
electrons& (apturing electron gets energy leaves its or!it and ioni6ed& Degree o%
a!sorption depends on atomic num!er (Q) and electron density o% the atoms& This is
related to chemical composition and indirectly to lithology&
#igh energy gamma rays are slo" do"n !y collision or (ompton scattering4e%%ect
(until they are a!sor!ed through photoelectric e%%ect)& Phenomenon is 0no"n as
PhotoH)lectric a!sorption "hen gamma rays loose enough energy to !e captured !y
electrons& (apturing electron gets energy leaves its or!it and ioni6ed& $elated to
average atomic num!er (Q) o% the constituents o% the %ormation&
P) measurement: photoelectric a!sorption occur "hen a gamma ray colliding
"ith an electron trans%er its all energy to electron& This reaction depends on the
energy o% incident gamma ray and the type o% atom& The photoelectric a!sorption
inde* o% an atom is appro*imately related to atomic num!er Q& /easurement o% the
%ormation P) "ill give an indication o% Q o% the %ormation minerals&
!IP 'E#ER
• Tells dip o% !eds (at "hat angles !y calculation)
• Tool "or0s 8ust li0e caliper tool DJ opens up , pushes against !ore hole "all
• 3ives color photograph o% !ore hole "hich sho"s !ed stri0es
('I ((ormation Image)
3ives color photograph o% !ore hole "hich sho"s !ed stri0es& Same as Dip /eter
Higher Archie for Porosit- !etermination from Logs
9& + F D (+eutron , Bul0 Density) very po"er%ul to use %or porosity
determination
:& + F A (+eutron , Acoustic4Sonic)
;& Bul0 Density
=& Sonic4Acoustic: DeltaHt DJ do not use
?& + (+eutron)
@& (ore F only covers certain points
B& D F A (Bul0 Density , Acoustic4Sonic) DJ not good to use even "e do not
use
Log Res0onse to 4ario%s 'inera&s
'inera& PE
4a&%e
B%&/
!ensit-
(gm2cc)
Ne%tron
Porosit-
(L")
"onic
!e&ta*t
Resistivit- Resistivit-
Range
Ohm*m
Sandstone 9&K9 :&@? H:&9 9K9 /od H lo"
Limestone ?&.K :&B9 . 9?B 3en& high Oaria!le
Dolomite ;&9= :&K@ .&? 9;K 3en& high Oaria!le
Anhydrite ?&.@ :&-K H9&: 9BB Oery high 9.... H
in%inity
Salt4#alite =&@ :&.; H9&K ;K. Oery high 9.... H
12
in%inity
3ypsum ;&=: :&;: @. #igh 9...
(oal P .&: P 9&? =.H@. =..H
@..
#igh(varia!le) 9. F
9......
Cresh
Aater
.&;@ 9&.. 9.. @:.
Salt Aater .&K9 9&9=@
Pyrite H; Oery lo" .&...9F.&9
Shale /oderate )*tremely
varia!le
(.&?H9...)
5il .&9; .&K?
3as .&.-? .&...@B
3lauconite ?&;:
Siderite 9=&@- 9:
Barite :@B
Shaly SS :&B
Roc/ #-0e2'inera& PE 4a&%e
SS (S .N porosity)
(S ;?N porosity)
Shaly SS
Sandstone and siltstone !eds
depending on their degree o% shaliness
9&K9
9&?=
:&B
9&K H ;&.
LS (S .N porosity)
(S ;?N porosity)
LS (Dolomitic) depending on the degree
o% dolomiti6ation
?&.K
=&:;
;&: H ?&.
Dolomite
(Pure Dolomite)
;&9=
;&:
Shale (Gsually ranges !et"een :&? and
;&? and can %all outside o% this range)
;&:=
3lauconite ?&;:
Salt4#alite =&@?
3ypsum ;&=:
Anhydrite ?&.@
(oal (Pure coal)
(impure coal)
9&.
.&9@H.&9K
Pyrite 9@&-B
Siderite 9=&@-
Cresh "ater .&;@
Salt "ater .&K9
5il ((#=) .&9; (varia!le)
3as ((#=) .&.-?
Log Res0onse to 4ario%s 'inera&s
'inera& PE 4a&%e B%&/
!ensit-
(gm2cc)
Ne%tron
Porosit-
(L")
"onic. !e&ta*
t
13
>uart6 9&K9 :&@?
(alcite ?&.? :&B9
Dolomite ;&9= :&KB
Anhydrite ?&.K :&-@
Salt (+a(l)4#alite =&@? :&9@?
(oal P .&: P 9&?
Cresh "ater .&;? 9&..
Salt "ater 9&: 9&9=@
#ydrocar!on Less or e<ual
.&9:
R 9
14
RE"I"#I4I#) #OOL"
Later&og 5 In,%ction #oo&s

15
'icro*resistivit- #oo&
16
PORO"I#) #OOL"
!ensit- Porosit- #oo&
17
Ne%tron Porosit- #oo&
18
"onic2Aco%stic Porosit- #oo&
19
GA''A RA) #OOL
"P 5 RE"I"#I4I#) #OOL vs+ LOG"
20
"P ("PON#ANEO3" PO#EN#IAL) #OOL
21
!IP 'E#ER2('I ((OR'A#ION I'AGE)