This document provides an overview of well logging exercises for students. It discusses the importance of various disciplines in exploration and production such as reservoir modeling, drilling and logging, geology and seismic. The ultimate goal of well log interpretation is to calculate water saturation, hydrocarbon saturation and effective porosity in reservoir rock units. Key points are provided about common rock types like sandstone, shale and limestone. The document reviews important well logs like gamma ray, resistivity, neutron and density and how they can be used to interpret lithology, porosity, fluid content and saturation. Formulas like Archie's equation and Indonesian equation are also summarized. Contact information is provided for institutions where students can learn more.

1. Well-Logging Exercise for Students
Dileep.P.Allavarapu
dpa.taeching@gmail.com /or
motherindia.energy@gmail.com
9703070878

2. EACH DISCIPLINE HAS ITS OWN IMPORTANCE & ROLE in E&P
RESERVOIR MODELING
OPEN HOLE LOGGING
(RES, POR, LITH LOGS)
-LWD/WL
MUD LOGGING
CORE ANALYSIS
DRILLING
&LOGGING
STATIC MODEL
INTERPRETATION MODEL
& UNCERTAINITY
CERTAINITY
CORE ANALYSIS
3D & VSP
GEOLOGY
& SEISMIC
CASED HOLE /PL LOGGING
(cement eval,flow rate ,fluid
Tests)
-WL
INJUCTION DATA
FLUID STUDIES
DYNAMIC MODEL
FLUID STUDIES
4D

3. THE ULTIMATE GOAL OF
conventional log INTERPRETATION
Calculation of
S
Hc
*
φe
in each reservoir rock unit
Preparation of a PARA LOG

4. Important Points

5. Sand Stones:
Log Analyst:
Composition (Sand Stone)
Framework of Quartz and Feldspar
Grains(Majority)/
Other Fragments (Non Majority)/
Cement (Quit Limited))
Processing Engineer:
Matrix (Sand Stone)
K-Na, Ca Al Si3 O8
Si O2

6. Shales: Frame work ,Matrix, Cement are Clay Minerals
( Kaolinite,Montmorilllonite,Illite)
Minute percentage of Non Clay Minerals.
90% Clay Minerals
K Feldspar derived Radio Active K rich clays
Rain water derived U,Th Br salts
K (12%),U Th (<500ppm)
Laminar ,Dispersed, Structural
Lime Stone: CaCO3 chemically precipitated calcium
Dolomite: Mg CO3(upto 12%)+CaCO3 chemically precipitated

7. Traps : Structural (tectonics), Stratigraphical (depositional environment), Combinational
What is Local Gravity High(LGH) ?
Anhydrate /Denser minerals in hydrothermal fluids closed to intrusive salt dome remains as top
.
Gravity is low over dome , central part have comparatively high gravity
In past ,North Brazilian sea have potassium rich salts.

8. STUDY THE LOG RECORD
(to take proper action in any stage of interpretation )
UNDERSTANDING LOG
HEADer- MAINfo- TAILer,…. DISPLAY INFORMATION .
TOOL SKETCH ,
CALIBRATION ,
PERFORMANCE & REMARKS ………
MARK THE INTERESTED ZONES
QUICK LOOK
INTERPRETATION
(to take the readings )
POROUS –PERMEABLE ZONES :
WATER /HC BEARING ,OTHER RESERVOIR ROCK UNITS
TAKE READINGS & LIST OUT THE INERPRETATION FORMULA
(to calculate the interpretation parameters)
GR , SP , CALIPER, RESTIVITY ,MICRO RESISTIVITY,
NEUTRON ,BULK DENSITY ,SONIC TRANSIT TIME
DETAILED
INTERPRETATION

9. GR FOR IGR
SP/RESISTIVITY &NEUTRON FOR Rw
RESISTIVITY FOR Rt
NEUTRON , BULK DENSITY ,SONIC TRANSIT TIME FOR φe
CALIPER, MICRO RESISTIVITY FOR k indication
FOR
S w, S hc, S movable , PAY

10. Archie's Equation : Archie's experiment concludes an empirical relationship
between resistivity of the water bearing formation and water, pore volume it
contain and also water saturation.

11. If Sw = 1 ,
means water-bearing formation
Resistivity of water
Resistivity of waterbearing formation
Formation factor

12. Volume of Shale: The percentage of shale present in the rock unit
Response in the
zone of interest
Shale
Clean formation
Indonesian Equation

13. GR: The record of count rate of Natural GAMMA as a result of emission from RADIO ACTIVE
MINERALS present in the ROCK UNITS
RADIO ACTIVE MINERALS are more in the CLAYS & SHALES
GR infer the LITHOLOGY whether rock unit is having CLAYS & SHALES or not
In the first /each run (lowering tool), first track (left side of log paper)
0-100 API (10intervels)
along with CALIPER,BIT SIZE , SP.
GR
around 30 -SAND
up to 50 -SAND SHALE
up to 80 -SHALE SAND
up to 100- SHALE
more than 100-CLAY
Volume of Shale
DEPTH GR
Vsh

14. SP: The record of voltage variation
as a result of electrolytic conduction due to salinity
variation between fluids present in the ROCK UNITS
electrolytic conduction is more across porous –permeable rock unit
SP infer the LITHOLOGY whether rock unit is having porous& permeable SAND or not
In the first /each run (lowering tool), first track (left side of log paper)
0-100 units (10intervels)
along with CALIPER,BIT SIZE ,GR.
SP +Ve : R mf <R w : Shale Base Line is in left side of Sand Deflection Line
SP in the same well either +Ve or –Ve :
crossover indicates the presence of HYDROCARBON

16. OR
K=61+0.133T°F
R we to R w
conversion chart
DEPTH
SSP
K
10 ˆ(SSP/K)
Rwe R w

17. BIT SIZE : size of the drill-bit used
CALIPER: size of the drilled hole
Grater than BIT SIZE : absence of permeable rock units / factures
Less than BIT SIZE : presence of permeable rock units /MUD CAKE
RESISTIVITY : Apparent resistivity of the formation
(can calculate true resistivity by using at least three apparent resistivity values )
Using Resistivity Tool: in saline muds , good contact between annulus electrode and BH wall.
Using Induction Tool : in non saline muds
In the first run (lowering tool), first track (middle of log paper)
0.2-2000 units (log scale)
Configuration :
App resistivity = (Geometrical factor × Observed voltage difference)/ Sending current
Characteristic charts used to calculate true resistivity from apparent resistivity

18. DLL MSFL Invasion
Correction charts
DLL MSFL LOG RECORD
(R t / R LLD )× R LLD = R t
DEPTH
LLD
LLS
MSFL
LLD/LLS
LLD/MSFL Rt/LLD
Rsh = Rt in shale
RO = Rt in WBZ
Rt

19. NEUTRON: The count rate of back scattered neutron/gamma as a result of energizing rock
units with neutrons (source: Am Be -16 curie)
Sending neutron lose total energy and collapse into the nuclei of HYDROGEN and release a
Gamma
Response α Hydrogen Index
In the first run (lowering tool), third track (right side of log paper)
0.54 - -0.06 (10intervels)
along with SONIC ,DENSITY.
NEUTRON :
Gas < Oil <Water in sand
Sand < Shale (bounded water)
Correction for shale:
Φ Nc = ΦN-(Vsh× ΦN in shale)
Neutron Porosity
Φ N = ΦN
corrected
calibration

20. Chemical Sources:
Neutron sources
o Am241-Be9 : emits neutrons with mean energy of 4.2 MeV.
oz Californium(Cf252) : emits neutrons with mean energy of 2.35 MeV.
Gamma sourceso Cesium(Cs137) produce a steady flux of gamma rays at 662 KeV
Electrical Generators:
This device produces 14 MeV neutrons by accelerating deuterium ions into a tritium target
(up to 125,000 V DC).

21. NEUTRON
SOURCE
ENERGY
LEAVING
SOURCE
NEUTRON ENERGY (e V)
106
104
102
10 eV
APPROX.
EPITHERMAL
ENERGY
REGION
1
.4 eV
AVERAGE
THERMAL
ENERGY .
025 EV
CAPTURE
01
1
10
TIM E ( µ s )
100

22. Φ N RT
GR
20
97
24
24
78
23
22
69
25
28
72
26
30
52
23
Will get
Rt =100
Sand Stone
Matrix Point
∆t = 48,
φN =0 ,
ρb =2.65
ΦN = 0
10
20
30
40
50
Choose
Φ=20

23. now mark the point φ=20,Rt=156.25
& draw the 80% saturation line
Rw=4.878
Sw =80% =0.8
Rt = 100/0.64
= 156.25
now replace the 0.64 by
0.36,0.16,0.04 …..to get the
60%,40%,20%,…… saturation lines

24. SW =1=100%
Red Points
GR=23-30
Blue Points
GR=30-40
Yellow Points
GR=40-50

25. Sw=0.8=80%

26. Ro =F Rw
Rt= F Rwa
Different Trend
HC indication
Main Trend
Rwa line WBZ

27. 50 = φ DC
-10
0
10
20
30
40
GAS
-10
0
10
20
30
40
50= φ NC

28. DENSITY : The count rate of back scattered gamma as a result of energizing rock units with
gammas (source : Cs 137)
Sending gamma undergone Compton Scattering
no of collisions α no of electrons in rock unit ρe
ρb = 1.0704 ρe + 0.1883
In the first run (lowering tool), third track (right side of log paper)
2.8 -1.8 (10intervels)
along with SONIC ,NEUTRON.
DENSITY:
Gas < <Oil <Water in sand
Correction for shale:
Φ Dc = ΦD-(Vsh× ΦD in shale)

30. Effective Porosity: Volume of interconnected pores
Neutron Correction for shale:
Φ Nc = ΦN-(Vsh× ΦN in shale)
Density Correction for shale:
Φ Dc = ΦD-(Vsh× ΦD in shale)
DEPTH
Φ N cal
Φ NC
ρb
φD
φDC
Φeff

31. Indonesian Equation
S HC = (1-SW)
DEPTH
Rw
Rt
Φ eff S W
S Hc
S Hc × Φ eff

32. Here our goal need more data from
ROCK PHYSICS LABORATORY,
so it limited to
S hc × φ e

33. Conventional Open hole logs
Lithology logs
(SP,GR with CALIPER)
Porosity logs
(NEUTRON, DENSITY ,SONIC)
Resistivity logs
(RESISTIVITY,
MICRORESISTIVITY)
Lithology
(shale ,sand ,…)
Porous –permeable beds
(no of ,thickness)
Shale volume
Effective porosity
Type of fluid
Contacts
(GSC,GOC,OWC,GWC)
Uncompacted
Formation water
& True resistivity
Saturation
MHI
Permeability indication

34. GSC
GOC
WOC

35. General Information

37. Lithology
GR
Rt
φN
Sand Stone ( more
compacted & dry )
Less=25
Less clay
minerals
More=1000
SiO2 insulator / no
electrolytic
conduction
Less<10
More=2.6
No fluid / no H2 Closed grain
packing
Sand Stone ( less
compacted & wet)
Less=25
Less clay
minerals
Less<100
Saltwater
conductor /
electrolytic
conduction
More=10-30
Having H2
Moderate=2.1
(30% H2O=1
/70% SiO2
=2.6)
Having oil
Less=25
Less clay
minerals
Moderate >100-700
Oil insulator
(at least 5times of
R0 )
More=10-30
Having H2
(less than
water zone)
Moderate=1.9
(less than
water zone)
Having gas
Less=25
Less clay
minerals
More >700
Gas insulator
(at least 5times of
More=10-30
Having H2
(less than oil
Less =1.8
Having water
ρb

38. Lithology
GR
Rt
φN
ρb
Sand-Shale ( more
compacted & dry )
Less=30-50
More or
less clay
minerals
More<100
Dry clay insulator
,bounded water in
composition / not
much electrolytic
conduction
Less=20
No fluid /
bounded water
H2
More=2.5
Closed grain
packing
(30%shale
=2.3,70%sio2=2
.6)
Sand-Shale ( less
compacted & wet)
Less=30-50
More or
less clay
minerals
Less<50
Wet clay
conductor / more
electrolytic
conduction
More=20-40
Having H2
Moderate=2.2
(20% H2O=1
,50% SiO2 =2.6
30%Shale 1.82.6)
Having oil
Less=30-50
More or
less clay
minerals
Moderate >100-700
Oil insulator
(at least 5times of
R0 )
More=20-40
Having H2
(less than
water zone)
Moderate=1.8
(less than
water zone)
Having gas
Less=30-50
More or
less clay
minerals
More >700
Gas insulator
(at least 5times of
oil zone )
More=20-40
Having H2
(less than oil
zone)
Less =1.7
Having water

39. Lithology
GR
Rt
φN
ρb
Shale ( more
compacted & dry )
More =80-100
More clay
minerals (80%)
More<50
Dry clay insulator
/ not much
electrolytic
conduction
Less=30-40
No fluid /
bounded water
H2
More=2.3
Closed grain
packing
Shale ( less
compacted & wet)
More =80-100
More clay
minerals
Less<10
Wet clay
conductor
/ more electrolytic
conduction
More=40-50
Having H2
Moderate=1.9
(30%
H2O=1,70%
shale=2.3)
,
More >100(120)
More clay
minerals
More<50
Dry clay insulator
/Less<10
Wet clay
conductor
Less=30-40
More 2.4
Having water
Clay

40. Dileep.P.Allavarapu
dpa.taeching@gmail.com /or
motherindia.energy@gmail.com
9703070878
Contact any Institution
Dept. of Mathematics, MGR Junior College
Dept. of Chemistry, LAMP Degree College
Dept. of Geophysics , Andhra University
Logging Base ,ONGC –Rajahmundry Asset
Oil and Gas Deliveries, Infotech Enterprises Limited
Gravity Observatory , Gravity Group-NGRI
Seismological Observatory, Warna Canal Division-MERI
UV Physics Academy
Analog IAS Academy
THANK
U