Basic Well Logging Design.pdf

Basic Well LoggingDesign
Presented by M Bakhsh
Roll No 2k15-PET-36
NFC IET Multan Pakistan
A One-day Courseon
ConsortiumAlumni Association Presents

Agenda
• Introduction(8:15)
• Lecture‐I Basic Theory/Interpretation
• Break (10 – 10:15)
• Lecture‐II LoggingProgram/Design
• Break (12:00)
• Workshop (1:30 – 4:00)
• Wrap‐up (4:00 – 5:00)

Objectives
 Get to know various logmeasurements
 Recognizefluid type and lithologyof majorreservoirs,
and some practicalapplication of log data
 Familiarizewith factors affecting the logresponse
 Understand the strategy in wellevaluation
 Get to knowvarious approaches to well loggingdesign
 Exercisewith well logdesign

According to
4th Edition of J.A.Jackson’s Glossary of Geology:
Log : A continuous record as a function of depth,
usually graphic and plotted to scale on a narrow
paper strip, of observations made on the rocks
and fluids of the geologic section exposed in
the well-bore.
Definition

WirelineLogging Logging whileDrilling
Cable
T
ools
LWDTools
Mud in
Mud out
Drill Bit

Well LoggingHistory
• The first electrical log was introducedin 1927 in Franceusingstationed
resistivitymethod.
• The first commercialelectrical resistivitytool in 1929 was used in
Venezuela, USA andIndonesia.
• SP was run alongwithresistivityfirst timein 1931
• Schlumbergerdevelopedthefirst continuous recordingin1931
• GR andNeutron logs was startedin1941
• Microresistivity array dipmeter and lateralog were first time introduced
in 1950’s
• The first induction tool was used in 1956 followed by Formation tester
in 1957, Fomation Density in 1960’s, Electromagnetic tool in 1978 and
most of Imaginglogs weredevelopedin1980’s
• Advancedformationtester was commercialized in early1990’s

The “First” Log recorded in 1927
Well in Pechelbronn -France Surface Recording Instrument

Log Measurements
Practical definition of a log
Log is an indirect measurement of formationproperties
exposed by the well‐bore acquiredby lowering a device or
a combinationof devicesin the well bore.
A Formation Evaluation Specialist is essential tounderstand
The theory of measurements, quality control, interpretation
principles, geophysics and petroleum geology as well as
petroleum reservoirs

Advantagesand Limitationsof WellLogging
Advantages:
- Continuous measurements
- Easy and quick to work with
- Short time acquisition
- Better resolution than seismic data
- Economical
Limitations:
- Indirect measurements
- Limited by tool specification
- Affected by environment
- Varying resolution

Logsare ImpliedMeasurements
• Logis not adirect measurementof formationproperties,itis an implied
measurementbasedon one or combinationof thefollowing devices
• Electrical (Resistivity and
Induction)
• Acoustic
• Nuclear
• Electromagnetic
• Magnetic

BasicTheory onResistivity
Current path
Rw
Current path
Unit volume filled with only water
Ro
Unit volume with water and matrix

Typical Formation
Water
Sand grain
Current path
Rt
Measured by thetool
Grain surface water
Oil

Resistivityand MeasurementConcept
Resistivity is the ability of a substance to impade the flow of electrical current
Rw - Formation Water resistivity
E - Voltage difference across theformation
A - Cross sectionalArea
L - Length of brine containerr
I - Current
E *A
Rw =
I * L
I E
A
Rw
L

Resistivityand MeasurementConcept
Schematic diagram of how an induction tool works
Secondarymagnetic field
Created bythe ground loop
Secondarymagnetic field
Inducesa current to flow in the receiver
Magnetic field induces
a current in the ground loop
Primary magnetic field
created by transmitter
Transmitter
Receiver

Resistivity is the key to hydrocarbon saturation determination
Sh = 1 - Sw
Water Saturation Estimation
Archie’s Equation
ResistivityApplication
F * Rw
Rt
Sw = (
SW - Watersaturation
Rw - Formationwater resistivity
Rt - True Formationresistivity
)
1/n
where F =
1.0
Por
m
Resistivity is also used for well to well correlation, and to pick fluid contacts
F - Formationfactor
n - Saturationexponent
m - Cementationfactor

Spontaneous PotentialLog(SP)
• SP measurement is based on Electrical currentsflowingin the
mud from electrochemicaland electrokinetic
• Salinitydifference betweenmud flitrate and formationwaters,
ions movement creates currentsmeasured in mVolt
• Negativeor PositiveSP curve deflectionrepresentswhich fluid,
formationor mud filtrate,has more ionic charge.
• It only works in waterbased mud !
• The use of SP log; bed boundary,distinguishingpermeablefrom
impermeable rock, shalyness indicator
, Rw determinationand
well correlation.

Spontaneous Potential(SP)
SP
Shale
Sand
- - - - - - -
- - - - - - -
Thick clean wet sand
(-) (+)
Thick shaly wet sand
Thick clean Gas sand
Rmf >> Rw in all sands
Thick shaly Gas sand
Hydrocarbon effect

Spontaneous Potential(SP)
SP
40 mV
20
Limitation
SP is not reliable when you have no or very small contrast
Between Formation water salinity and mud filtrate salinity resulting in no
to small SP deflection
7470
Determine Rw ?
7430
Given:
Rmf = 0.51 at 135 F
Rm = 0.91 at 135 F
TD = 8007 ft
Bottom hole temp.= 135 F
Surface temp. = 60 F

Rw calculationfromSPlog
SSP = -Klog
Rmfe
Rwe
Steps of Calculation;
- Determine Temperature at Depth of interval
- Correct Rm and Rmf to this temperature (gen-9)
- Determine SP (log) from shale baseline
- Correct SP to SSP using SP thickness corr.chart
- Determine Rmf/Rwe ratio using SP-1 chart
- Determine Rwe from above equation or SP-1 chart
- Correct Rwe to Rw using SP-2 chart

Gamma Ray Log(GR)
• GR toolmeasures naturalradioactivityoftheformationfrom
theemmision of all these;(T
otalGR)
Potasium,Uranium andThorium
• GR log is usedfor;
‐ Well to well geologicalcorrelation
‐ Bed definition, more accurate than SP log
‐ Shale Volume Indicator (mostreliable)
‐ Lithologyand mineralogyindicator(NGT)
IGR =
GRlog - GRmin
GRsh - GRmin
IGR - Gamma ray index
GRmin - GR clean
GRsh - GR shale baseline

Gamma Ray Log(GR)
Mineral Density DT GR
Quartz 2.64 56 0-15
Calcite 2.71 49 0-15
Dolomite 2.85 44 0-15
Orthoclase 2.52 69 220
Micas 2.82 49 275
Kaolinite 2.41 - 80-130
Chlorite 2.76 - 180-250
Illite 2.52 - 250-300
Montmorillonite 2.12 - 150-200
Anhydrite 2.98 50 low
Pyrite 4.99 39 low
Coal 1.47 high low

Gamma Ray Log(GR)
Well-1 Well-7 Well-2
GR Res
GR Res
GR Res

NaturalGamma Ray Log(NGT)
• NGT tool measures the spectrum of
Potasium,Uranium, and Thorium
• NGT log is used for;
- Study of Depositional Environments
- Geochemical logging
- Shale typing
- Source Rocks
- Diagenetic History
- Vclay content correction
• With combination of Photoelectric curve can be
used for clay and mica type identification

NaturalGamma Ray Log(NGT)
0 0 2 4 6
K, Potasium (%)
8 10
2
4
6
8
10
Pe
Kaolinite
Montmorillonite
Illite
Glauconite
Muscovite
Biotite

DensityLog
• Density tool is one of themost important instrumentsused to
evaluateformationswhich measures formation density and
directly ties to formationporosity
• The density tool measures theelectrondensity
, by emitting
gamma ray from radioactivesource and returning to two
detectors
• The amount of Gamma rays that return depend on the number
of electrons present, electron density is related to bulk density
of mineral orrock
• In most cases environmentalcorrectionforDensity log is not
significant, field log density can be readily used for
interpretation

DensityLog
Main categories in the process of GR energy loss due to
collisions with other atomic particles:
Compton Scattering is selected to be the energy level to
generate GR of the Cesium 137 radioactive source at 662 keV

DensityLog
POR =
• Porositydeterminationfromdensitylog:
RHOBma - RHOBlog
RHOBma - RHOBfluid
RHOBma - Matrix density
RHOBfluid - Formation fluid density
RHOBlog - Log density
PORd - Density derived porosity
Exercise: Determine porosity of limestone with field log
density inicated 2.5 gr/cc.

NeutronLog
• The tool measures theHydrogen Index which is thequantityof
Hydrogen per unitvolume
• The tools emit high energy neutrons eitherfrom radioactive
source or minitron.They are sloweddown by collisionswith
formation nuclei, collisionwill result energy loss,and the
elementmostlyslowed down is H
• Water has high neutron counts,Oilhas a littlelesscounts than
Water
, Gas will havevery low neutron counts
• Neutron log is very sensitiveto environment change; bore hole
size, mud cake,mud weight, temperature, stand‐off, pressure
and formation salinity
, measurement is compensation of far
and near countrates.

NeutronLog
• Neutron tool has a wide rangeof applications
‐ PorosityDetermination
‐ Gas Detection
‐ Borehole and formationsalinity
‐ ReservoirSaturation
‐ ReservoirMonitoring
‐ Borehole Fluid dynamics
• Neutron radioactivesourcein normally usesAm 241
Exercise Neutron Log environmental correction
Given: Uncorrected neutron porosity of 34%, 14” borehole size,
0.25” mud cake, 200 kppm borehole salinity, 12 ppg mud at
170 F, 5000 psi pressure, using water based mud with formation
salinity of 50 kppm.

AcousticLog
• Sonic tool generatesacousticsignalsto measure thetimetravel to
pass through a formation,log measurement in time required to
travel in one foot formation(microsec/foot)
• Rock properties can be implied from sonic measurements;
Porosity
, Lithology
, Gas shows, Compaction and Rockstrength
• Maincurrent use : ‐ SeismicTie
‐ Mechanical properties
‐ Fracture identification
• T
ooltypes; Borehole compensatedsonic
Long spacingsonic
Array sonic tool
Ultrasonic boreholeimage
Dipole shear sonicimage

SpecialTools
• Resistivity Based Imaging Tool
- Pad device on 4 to 6 arm caliper, few mm resolution
- Application: Thin bed Evaluation, Dip meter,
Paleostream direction, fracture evaluation, stratigraphy.
• Nuclear Magnetic Resonance
- Using Permanent magnet to realign hydrogen protons to new
magnetic field, a Lithology dependance porosity, saturartion
and permeability estimation
• Dipole Shear Sonic
- Shear measurement, AVO and Rock mechanics applications
• Borehole sonic imaging
- Acustic based bore hole imaging for 360 deg coverage, lower
resolutionthan resistivity based imaging tools.

SpecialTools continued
• Modular Formation Test
- Very robust formation tester with the capability to take
unlimited pressure tests, pump the fluid into the borehole,
identify the fluid type before sampling
• WellboreSeismic
- VSP: Vertical seismic profile surface guns, wellbore detectors
- SAT:Seismic acquisition tool
- WST: Well seismic tool
- DSA: Downhole seismic array tool (3 axis geophones)

Log and Seismic TieEffort
• Log DataValidation
‐ Checkthe logquality
‐ See if thereis any missing logdata
‐ Determinewhethersonic peaks/anomaliesrepresentingformation
• Logediting
• Velocity CorrectionSonic over VSP (using4‐2 msecresolution)
• SyntheticSeismicGeneration
‐ AcousticImpedance
‐ Convolution Waveletto tie seismicand logpeaks
* Extracted Wavelet‐ to utilize wavelet as seen in theseismic
it is highlyrecommended(similarapperance)
* RickrWavelet‐ commonly used to havezerophase

SyntheticSeismograms
• SyntheticSeismogramsareused to correlate seismicsections
• Theoretically this method uses many simplificationand assumptionsput
intothemodel
• It provides importantlinkto understandthetiebetweenseismicdataand
well log responses

Velocity Survey
• Velocity or check shot surveys areperformedin the wellboreto obtain
vertical travelpaths through the formationsby locatingsourcesand
detectors/receivers at certainconfiguration,normallythe receiversare
placednearthe gelogicalhorizons
• The surveyonly utilize first arrivalto use in the recordedseismictrace
• First arrivalsarethen convertedintovertical travel timeson time‐depth
graphs whichcan be used to calculate averagevelocities
• Sonic log calibrationneeds to be done prior to generationof synthetic
logs,normallyborehole effects arefound veryoften causingdriftwhichis
to be removedto preventshiftingin timeof seismicreflectionsor
pesudoevents

Vertical SeismicProfile
• Vertical Seismic Profiling (VSP) uses both entire recorded seismic trace and
first break. Receivers are spaced at very closed intervals in the wellbore in
order to geta seismicsection in thewellbore
• The seismicwaveand alleffects aremeasured as a function of depth as it
propagates through theformations
• Thr receiversare close to reflectorswhere up‐going and down‐goingwaves
are recorded as a function ofdepth
• The down‐going waveletsareused to design deconvolutionfilters
• In general VSP provide much betterspatialandtemporalresolution,the
signal changes intermof bandwidth and energy loss aremeasured
• Applicatiosof VSP are to correlatetheactualseismiceventswith more
confidence,and with much betterresolution due to shorter travelpathsit
can provide a tool to generatehigh resolution maps,and betterestimateof
rockproperties

Offset VSP
• OffsetVSP areused to detect faultsand pincouts
developedto illuminatestructureaway from thewellbore
Multiple offset and walkaway VSP
• Multiple offset VSP were developed to provide high-resolutionseismic
structuraldetailsin the area where interference from the shallow layers
• The disadvantages is very time consuming, it requiresfew days for the
acquisition by puttingmultiplesourcepositioned in different locations

BasicLogInterpretation
Logs DataApplications
• Determinedepth and thickness
• Identify productive zones
• Distinguishfluid types, gas, oil and water
• Estimatehydrocarbonreserve
• Help geological correlation and subsurface mapping
• Determinefacies and drilling locations

BasicLog Interpretation Continued
Common Tools in the Logging Industry
• GammaRays
• Self Potential
• Resistivity
• Induction
• Density
• Neutron
• Sonic
• Magnetic Resonance
• FormationTest

Typical properties implied or estimatedfrom
the log Measurements:
• Porosity
• Water Saturation
• Permeability
Fluid types
• Fluid contacts
• Lithology
• Dip angle
• Velocity
Basic Log Interpretation Continued

the followings; - Density
- Neutron
- Sonic
Volume of pores
Porosity =
Total Volume of Rock
Porosity= “Storage Capacity”
Porosity is estimated using one or combination of
Combination of three inputs will get better estimate
Density Porosity:
POR = (DENmatrix – DENlog)/(DENmatrix – DENfluid)
Petrophysical Properties

Formation Water in the pores
SW =
Total pore space in the rock
Water Saturation is estimated using combination of
the followings; - Porosity
- Resistivity
It requires formation factor and saturation index
derived from core analysis, and formation water resistivity
Rt
Archie’s Equation
Sw = (
SW - Water saturation
Rw - Formation water resistivity
Rt - True Formationresistivity
)
1/Porm * Rw 1/n
n - Saturation exponent
m - Cementationfactor

Permeability Estimationfrom Logs
K=
93 *Por
Swi
Permeability (K) is a measure of rock property to get the fluid passes through the rock.
The equations are based on empirical study, accurate K estimation can be obtained from
formation test, drillstem test (DST) or from core analysis
( 2.2
) 2
K=
250 *Por
Swi
( 3
)2
Timur’s
Tixier’s
where Swi = Irreducible water saturation

Objectives
 Recognize fluid type and lithology of major
reservoirs,and some practicalapplications of log
data

Fluidand Lithology Identification Fromthe Logs

Fluidand Lithology Identification Fromthe Logs
Gas
Oil
W
ater
Oil-Water Contact
Water filled Sand
Oil Sand
Gas Sand
Gas-Oil Contact
Water filled Sand
Water filled Sand
Coal
Carbonate/Limestone

RES
0.1 100
Fluid and Lithology Identification From the Logs
Oil-Water Contact
Gas-Oil Contact
Oil Sand
Gas Sand
Water filled Sand
Water filled Sand
Water filled Sand
Coal
Carbonate/Limestone

How Can We Remember TheseEasily?
About LithologyInterpretation
• Claystone ‐ has large amount of water, and radioactive materials, is denser when ithas
less water, is not harder than limestone and is very conductive.
• Sandstone‐ is less dense than limestone, has less water than clay
, contain more water
than limestone except when itis saturated with dry gas,its conductivity is depending on
fluid type it contains, has small to none radioactive fragments.
• Limestone‐ is harder than both clayand sand, contains least water of the three, very
resistive,it has low radioactivity materials, fastvelocity
, high density
.
• Coal ‐ Normaly low radioactive,rarely radioactive,lowest density and very resistive

How Can We Remember TheseEasily?
About Fluid Interpretation
• High Radioactivity
• Very Conductive
• High Water
• High Gas
• High Oil
‐ High GR
‐ Low Resistivity
‐ High Neutron and LowResistivity
‐ Low Neutron and HighResistivity
‐Higher Neutron than Gas, denser
than gas Less Neutron than water,
less dense than water, more
resistivethan water, less‐
resistivethan gas when other
properties are the same
‐ Very resistive,largest
density neutron crossover
‐ Largerdensity‐neutron crossover
than oil with low GOR
‐ Reservoir filled with high resistivewater
• Dry Gas
• High GOR
• Fresh Water

Are There Any Anomalies?
About Fluid Interpretation
• In a gaszone
‐Mud filtrateinvasion will causethe neutron‐density
crossover looks like thatof oil zone, the shallowinvestigation
resistivitywill be less resistivethan thatof deeperdepthof
investigation,resistivitydifference is largerwhen conductive
mud isused
‐High Irreduciblewater (water bounds in clays and grains’
surface)will demonstratelittle density‐neutroncrossover
similar tothatofoil or water zonesbut less resistivethan gas
or oil zones withless irreduciblewater
• In an oil zone‐ similarto above

How Is Log Analysis Calibrated?
• Core Data
Routie CoreAnalysis- For Porosity and PermeabilityCalibration
Special Core Analysis - For detailed rock and fluid propertiessuch as
X Ray Diffraction, ScanningElectronMicroscopy, Petrophysical
parameters(a,m and n determination), PVT, Gas Analysis and finger
printsof fluid samples, and etc.
• Formation Test
Fluid Identification from the logs is not direct, when the parametersare
not well established,formation test fluid samples can be used to
calibrate fluid identification using the logs. Formation test is also used
when possible log responseanomaliesencountered to get conclusive
fluid identification.

Modern Formation For Fluid Identification
Electric Power Module
Fluid Description Module
Hydraulic Power Module
Test Probe
MDT StringConfiguration
Large sample Chamber
Multi sample Chambers

Basiccomponentsof thetool
Probe
Multi-sample
Chambers
Resist.
sensor
Pump Out
Module
Pre-Test
Strain Gauge
Quartz Gauge
Isolation
Valve
Optical Fluid
Analyzer
Flowline
Probe
HPGauge
V
alve
Pre-Test
Two Sample Chambers
OLD NEW

OFA Gas Detector Optics
Gas Detector System
Light Emitting Diode
Cylindrical Lens
Polarizer
Fluid Flow Gas
Liquid
Gas
Sapphire
Prism
Photodetector
Array
Sapphire window

OFASpectrometer
How OFA Divice Operates
Fluid flow
Sapphire
Lamp
Filter Lens
Catridge
Light
Distributor
Source
Light path
Solenoids
Chopper motor
Measure
Light Path
Filter lens
Photodiode

OFASpectrometer
How Can We Differenciate Fluid Types ?
Fuel
Oil
Diesel
Mud
Filtrate
Crude OilA
Crude Oil B
Water
Near infra-red
0.0
4.0 Visible
Optical
Density
500 1000 1500
Wave Length - (NM)
2000

Are There Any Other LogsApplications?
➢Selecting Drilling Location
➢Well Completion
➢Subsurface Geological Mapping
➢Reservoir Characterization
All are useful for
The Logs Can Help Us to Determine:
• Volume ofHydrocarbon
• Fluidcontinuity
• ReservoirExtent
• ReservoirRockProperties
• DepositionalEnvirontment
• Diagenesisand Compaction
• Trapping
• Heterogeneity

Hydrocarbon Reserves Estimate
Oil rec =
7758 * (1-Sw) * h * Por * RF *A
Where : RF - Recovery Factor
h - Thickness, A- Area
BoI - Oil Vol. factor
BoI = 1.05 + 0.5 * (Gas Oil Ratio/100)
BoI
(43560 * DEPTH*0.43)* (1-Sw)* h* Por*RF*A
Gas rec =
15

LateralContinuity ?
Well-1 Well-2
Well-7
GR Res
GR Res
GR Res

Objectives
 Recognizefluid type and lithologyofmajor reservoirs,and
some practicalapplications of log data

Depth of Investigation and Resolution
of Logging Tools
2 cm
0 cm
50 cm
200 cm 150 cm 100 cm
Depth of Investigation
250 cm
5 cm
60 cm
20 cm
30 cm
40 cm
80 cm
80 cm
Micro resistivity
Micro log
Dipmeter
Sonic
Density
Radioactivity
Gamma-ray
Neutron
Laterolog
Induction
log
Resistivity
Acoustic
Resistivity
Resolution

AIT SDT LDT CNT SGT LEH TCC AMS
Additional combinable tools:
- Dipmeter
- Magnetic Resonance
- Borehole Imager
- Dipole Sonic
- Formation Tester
- Others
Tools Size and Measuring point for Typical
Oil Based Mud Environment
Induction
Sonic
Density
Neutron
GR
Measuring point from
the bottom of the tool
Tool Length
This slide helps you to configure the tool string that is appropriate for yourwell

Resistivity MeasurementProblems andLimitations
Resistivity measurements are not reliable when you have:
Severe invasion due to overbalanced mud
Large washed-out borehole
Shoulder bed affects
High content of conductive minerals
Some older tool generations have limited vertical resolution

Ri
Effectsof BoreholeEnvironment
Rm
Rxo
Rmf
Sxo
Ri
Rz
Si
Ro
Rt
Rw
Sw
Undisturbed
Formation
Invaded
Zone
Flushed
Zone
Mud Cake
Rmc

InvasionProfile
Fresh Mud Rmf > RW
Salt Mud Rmf < Rw
Rxo
Rxo
Rt
Rt
Rm
Rm
S M D
D M S
Low High

SP LogLimitations
The tool is only for water based borehole environment
SP is not reliable when you have no or very small contrast
between Formation water salinity and mud filtrate salinity resulting in no
to small SP deflection
GR Log Limitations
Standard GR tool is not reliable when you log an interval with radioactive
mineral rich rocks. NGT is recommended to use for this type of
Formation to get reliable GR derived clay volume calculation.
GR measurements in cased hole environment need to be normalized
due to casing, and cement attenuation
Density Log Limitations
Density log is a pad device, it is very sensitive to the pad contact with
The borehole wall, make sure to consult with your petrophysicist prior to
using the data for any other applications.

Neutron LogLimitations
Neutron log is very sensitive to environment change; bore hole size,
mud cake, mud weight, temperature, stand-off, invasion, pressure and
formation salinity, measurement is compensation of far and near count
rates.
Sonic Log Limitations
Sonic log is likely affected by strong attenuation when we log
unconsolidated formation, fractured formation, gas saturated reservoirs,
aerated muds, rugose and enlarged borehole sections. Typically shows
some curve skippings.
Formation Test Log Limitations
Formation test problems normally occur when you don not have a good
Rubber pad seal, causing a communication with the mud giving you much
Higher pressure reading. Depleted and highly invaded zone would cause
long fluid pumping before you get clean sample or fluididentification

Objectives
 Recognizefluid type and thelithologyofmajor reservoirs,
and practicaluses of logdata
 Understand thestrategyof a well evaluation

Why Wireline Welllogging
1. Better Resolution
2. More advanced tools
3. Better depth control
4. Only choice available (certain tools)
5. More certain on data quality

DisadvantagesofWireline
logging
1. Invasion effect
2. Hole condition dependant
3. Unable to log in high angle wells (>60 deg)
4. Acquired after drilling, more rig time
5. More uncertainty in getting data or good
data in problem prone wells

Important Issueswith
Running Wirelinelogs
1. Borehole fluid type
2. Borehole size
3. Welldeviation
4. Tool combination
5. High Mud Weight resulting in over balanced

Why LWD?
• Reduce RigTime
• Real TimeDecisions
• Minimized BoreholeProblems
• High Angle/Horizontal Wells

Disadvantages ofLWD
• Borehole size and rugosity are not known
• Good data collected only when the toolis rotating
• Data qualityis ratedependant
• Log resolution is generally poorer than that of wireline
• Abilitytoconfigurethetools is limited
• Not a good application fora slow drillingrate for cost
considerationespecially for expensiverig.
• Depthcontrolis poorer thanwireline data

LWD and WirelineComparison
X800
X900
Invasion
X800
X900

LWD Real time and RecordedLogs
GR
GR
D. RES
D. RES
DEN DEN
NEU
NEU
X500
X600
X700
X500
X600
X700

Selecting the Tools torun
What tools do you run in the hole?
Itdepends on whattypeof informationyou are about to get
and thecostyou are willing to spend.
Need Want
What is the value of information you are getting?

Ability to Define YourNeed
• Geological
• Geophysical
• Reservoir
• Petrophysical
• Mechanical

Typeof Information toAcquire
• Geology
‐ Sand development and sandthickness
‐ Stratigraphic information
‐ Lateralcontinuity
‐ Hydrocarbonsource
• Geophysics
‐ Velocity uncertainty
‐ Well to seismic tie
‐ Seismic and fluids/lithology correlation

Typeof Information… continued
• Petrophysics
‐ Porosity
‐ Watersaturation
‐ Permeability
‐ Mineralogy
• Reservoir
‐ Compartment
‐ Fluid properties
‐ Reservoirpressure
‐ Reservoirmonitoring
• RockMechanics
‐ Stress direction
‐ Pressure profile
‐ Fracture orientation

Understand the Scales OfObservation
Seismic Section
Wireline Logs
Out-Crops/Core
Thin Sections

Objectives
 Get to know various well loggingdesigns

Well Logging DesignObjective
The objectives of a well logging design should follow
your drilling objectives, if drilling objective is not met,
the objectives of logging program should be adjusted
accordingly.
A logging program would vary depending on drilling
Objectives.

Well LoggingDesign‐1
• Onshorewell
Adevelopmentwell,A‐5, is todrill updip structureofA‐Sand
to accelerate oil production,the A‐4 well has produced this
Reservoir for a year
, and currently produces 80% water
. The
reservoir has a strong aquiverdrivemechanism.

Well LoggingDesign‐1 continued
• Drilling objective is todrill and complete theA‐Sand Level
• Logging program objective for this well is then to locate the
top of theA‐Sand and make sure that theinterval is still in the
oilcolumn.
• Other information:Strong water drive means it has good
pressure maintenance, therefore, no need totake pressure
data.
• Rigtype: Onshore Rig (inexpensive), a vertical well.
• Logging Design :WirelineGR‐Resistivity‐Neutron‐Density

Well LoggingDesign‐2
• Offshorewell
A third appraisal well is proposed on the west flank of the
structure. First two‐wellssuggest that well to well log
correlationis not easy,however pressure data has helpedthe
well to well correlation. This well is to reveal the lateral
continuityand the compartmentissue of the reservoirs.

Well LoggingDesign‐1 continued
• Drilling objective is todrill and tofind out the lateral continuity
of somereservoirs.
• Logging program objective is to collect as much datato
confirmlateral continuityand well towell correlation.
• Otherinformation:Thewell is still in theappraisalphase.
• Rigtype: OffhoreRig (expensive), directional well?
• Logging Design:
‐ LWD GR‐Resistivity‐Density‐Neutron
‐ Wireline GR‐Resistivity‐Density‐Neutronascontigency
in case LWD data is not reliable
‐ Wireline formationtest forpressure correlation
‐ Wireline OBMI forstratigraphic information
to help well to wellcorrelation

Example‐1‐ LoggingProgram
• 26 “Conductor ‐ 3500’to3700’MD
None
• 20”Casing ‐ 3700’to 4100’MD
None
• 17‐1/2”Hole section 4100’to 6000’MD
‐ LWD: GR‐Resistivity
• 12‐1/4”Hole Section 6000’to 9000’MD
‐ LWD: GR‐Resistivity‐Density‐Neutron
‐ Wireline: T
riple combo only when LWDfail
Formationtestasrequired
• 8‐1/2”Hole section 9000’to 12000’MD
‐ LWD: GR‐Resistivity‐Density‐Neutron
‐ Wireline: T
riple combo only when LWD fail
Formationtestas required
Borehole image as required
Nuclear Magnetic tool asrequired

Example‐2Logging Program Continued
• 8‐1/2”Hole Section 9000’to 12000’MD
LWD:
GR‐Resistivity‐Density‐Neutron
Wireline:
T
riple combo as a contingencywhen LWDfail
Wet Case:
T
riple combo as a contingencywhen LWD datais not reliable
Formationtestsfor pressures and watersamples
H.C.Case:
T
riple combo as a contingencywhen LWD datais not reliable
Formationtestsfor pressures and fluidsamples
Borehole image log for dip and stratigraphicinformation
Nuclear Magnetic tool when considerablethick‐shalysand reservoirsare
penetrated
Borehole seismicfor velocitysurvey

Important Aspects ToConsider
• Risk
• Cost
• Environment
• Hole Size
• WellDesign
• ToolSpeed

Some examples
• Risk
‐While we are running in hole with wireline tools, the
tools could not go down at certain depth. Thecompany
representativehas decidedto pull out of hole to run
different toolconfiguration.
‐In case of a risk that we are not able to go down passing
the same depth withnew tool configuration, the
petrophysicisthas asked thelog engineer to log up while
pulling out of hole to get data assurance.

Some examples
• Cost
‐Afterthe well reached TD at 6000 ft, the team found out
that they do not have room to get all log data tothe baseof
the reservoir near TD if they use typical triple combination
wireline tools, to drill additional50 ftwould take24 hour rig
time including RIH andPOOH.
‐The petrophysicisthas then decidedtosplitthe tools into
tworuns, whichonly require additional6 hour rig time for
second wireline run. By doing that it would have saved 18
hour rig time if they drill additional50 ft to have only one
logging run

Some examples
• Environment
‐The well is to drill complex lithology interval in Jurasic
section. Where coal, shale, sand, limestone can be
penetrated in thesamehole section.
‐The geologist and petrophysicisthave suggested their
drilling team to drill the well with oil based mud to help
possible swelling clay problem, formationof limestone
ledges and washed‐out sand section, therefore it would
promotea smooth and successfullogging operationafter
they reach TD.

Some examples
• Hole Size
‐The Drillingengineer has suggested torun only LWD in the
12‐1/4” hole sectionto reducewell cost.
‐The petrophysicisthas argued and suggested to run
wireline becausebased on previous wells in this field where
they havedrilled at average rate of 300 ft/hrresulting in not
reliable data.The team has supported theirpetrophysicistto
run wireline because it would help to support field
certification.

Some examples
• Well Design
‐Afterthe G&G team provide the targets to the drilling
engineer
, theteam has to end up witha well design that it
requires a highly deviated well exceeding 60 deg.
‐LWD log data acquisitionis then put in their logging
programbecausebased on theirexperience in this field 50
deg well was the highest deviated well that they could log
withwireline.

Some examples
• ToolSpeed
‐Based on thestatistics drillingthe Pliocenesectionis very
quick, averaging400 ft/hr
, the company is drilling a
horizontalgas well at about 3000 ftTVD.
‐LWD engineer and the petrophyscisthave worked together
and havegivena recommendationtodo controlleddrillingat
about 200 ft/hrtoget an acceptable log data quality.

What do youhave in mind?
On Shore
Development Well
Off Shore
Deep water
development-well
In respect to Risk, Cost, Environment, Hole Size, Well Design, Tool Speed

ExploratoryWell
• Seismic Information
• Regional GeologyInformation
• Drilling the well using “Learning while doing”
concept
• HighRisk but must be manageable
• Mostly Verticalwell

DevelopmentWell
• In Many cases with littleto no need of seismic
information
• Local GeologyInformation
• Drilling with fullknowledge
• Low Risk mainly mechanical
• Vertical,highly deviated to horizontalwells

An Exampleof rather complexLoggingProgram
DecisionTree
West Seno Data Gathering Strategy
Standard
well
PAY
Fully
Loade d
Wireline
Full
Cor es
SAMPLING
LWD
SAMPLES
LWD
12 1/4 “ WIRELINE
PAY
PRESSURE
P.O
PEX
MD T
CST
Cor es
Special
Logging
Velocity
Uncertainty
UBI or CBL
SAMPLING
Cased HoleGR
CSAT
or VSP
GR to bottom of 13 3/8 “
STOP
STOP
Y
N
Y
Y Y Y
Y
Y
Y
Y
Y
Y N
N
N
N
N
N
N
N
N
N
N
N
LWD
MDT
Objective Objective
driven-logging
De epest
Well
VSP
STOP
N

Another Way ToSaveCost!
• ACQUIRE DAT
A WITHOUT USING COSTL
Y RIG TIME
(PIPE DECISION NOT NECESSARY ‐NO DRY HOLES)
– GATHER DATAREALTIMEWHILEDRILLING
– GATHER DATATHROUGHTUBING AFTERCOMPLETION
– COMBINATION OFBOTH

Project BaseApproach
UOME company has $200 MM programfor
exploratory wells for the year 2004.
As a follow up of their exploration campaign,
UOME Company has $ 600 MM program for
developing a new deepwater field for the year
2005 that willhave peak productionof 100,000
BOPD

Objectives
 Get to knowvarious well logging designs
 Exercisewith welllogdesign

Exercise‐1
• PT Indooil Co.,the sole owner of mineralright on BlockA, on‐shore, 2 km in
adjacenttoa known oil producing areain the Block B.The company is looking ata
prospect to drillthe firstwell, Indoco‐1,in the block targetingforthe same
producing intervalin BlockB atabout 4000 ft depth,and itis estimated50ft down
dip in thisblock.
• The costsfor various availablelog dataacquisitionareas follow:
• Wireline GR ‐ $1/ft,Induction ‐ $4/ft,BHC Sonic ‐ $1/ft,Density‐$2/ft,Neutron‐$2/ft
• Formationtest‐$100/pressure,$1000/fluididentification,$2000/fluidsample
• Depth charge for each Wireline tool isfree.
• LWD GR and Induction ‐ $10,000/day
,Densityand Neutron ‐ $10,000/day
• The rig cost is$5000/day
• 1) What is your recommended datagatheringstrategyand welllogging designfor
the well?
• 2) While drilling, thewellpenetrates5 thicksand units with high mud log gas from
3,000to 4,200ft.How do you recommend the company on the logging design?
• 3)After the wellreached the proposed TD,there were no encouragementseenfrom
the mud log signs,what would you do for your logging program?

Exercise‐2
• The exercise‐1 was seismically to test the amplitudeanomaly
at Orangehorizon,equivalenttothe Berani Clastic Formation.
The Indoco‐1 well encountered 300 ft of Oil column and was
completed and produced from this level for over one year
with cumulative production of 4 mmbo.The company is
looking at similarseismic character 1‐1/2 km away from
Indoco‐1 well, which was connectedby dim event to the
amplitudeat theIndoco‐1 well. It has been interpreted as a
different channel lobe. The companydid low profile and ran
only simplewireline GR,resistivity, density, neutron and sonic
on the Inoco‐1well.
• What is your data gathering strategy forthis Indoco‐2 well?

Exercise‐3
• Asubsurfaceteam is evaluatinga four‐wayclosure structure
offshore East Kalimantan, based on their synthesis,if the
timing of migrationis right, it is a big structurefilled with
hydrocarbon.The water depth around the prospect isabout
4500 ft. T
oproperly evaluate the prospect, the team thinks
that they need at least 8 wells drilled at various locationson
the structure. Some apparent faults due to regional
compressivestress cut the structureinto possible many
compartments.
• Make assessment on options the companyneeds todo and
make recommendationon well evaluationstrategy.

Exercise‐4
• An offshore well is proposed to redrill the A‐5 well
with updip direction fromthis well to get the gas leg
of clean and blocky sand found with gas water
contact in the A‐5 well.The company is trying toget
more gas production. The team is looking at drilling
horizontal well with about 500 ft of producing
section. What is your recommended logging
programfor this well and why?

Basic Well Logging Design.pdf

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