1. 2.2- Basics of Logging
History of logging, Modern logging tools, Multi-well correlations ,
the logging process, porosity and lithology, the Archie Equation,
rock permeability, the invasion process, vertical resolution and
enhanced vertical resolution.
2. History of logging
First well logs recorded in 1927
The recording system
The cable winch
The stationary point-
by-point log
3
3. History of logging
Old Current
V3
Resistivity Tools
V1 emits a current from a surface
generator.
The voltage measured at V2 is
proportional to the formation resistivity.
V2 is measured relative to a return at
V2
the surface ( V3 ).
V1 This electrode configuration is the
Normal tool.
The distance between the V1 and V2
electrodes determines the depth of
investigation and hence the resistivity
being read.
4
4. Modern logging Tools
Maxis (MCM) acquisition system
Wireline Engineer Acquisition Equipment
Unit Engine
Client
(“Witness”)
Winch man
Cable drum
Wireline cable to
downhole tools
5
5. Modern logging Tools
Modern Logging Truck
Modern Surface equipment :
High powered computers
Controls downhole logging
Changes signal configuration
to obtain acquisitions
Includes surface database to
optimise results and for well-
to-well correlations
Used also for forward-
modelling
Includes also all the well
configurations- depth, casing,
formations, etc..
6
6. Modern logging Tools
Logging Tools Modern Tools
Sensors used in modern logging:
Electrical
Electromagnetic
Magnetic Flux Induction
Acoustic
Ultrasonic
Nuclear: Neutron
Nuclear: γ- Rays
Nuclear: Nuclear Magnetic
Resonance Imaging (MRI)
Every potential signal source have been used in modern-day logging
7
7. Modern logging Tools
Modern Logs
Modern logs have
more measurements
but the principle is the
same
1600
Shading is often
added to make the log
curves easier to read.
Additional outputs can
be made:
1700
Invasion Profiles
Facies
Layering
Gamma Ray (GR)
(GAPI)
1:220 Ft Pad
-180
Rt from HALS
RX18
0 150
200
0
180 1
1
1000
1000
0
5
1
2
5
2
SP (SP)
(MV)
0
FXND
(PU)
Rt from AITH
(OHMM)
1
43
51
08
00
50 1 1000
Mud Resistivity from HALS
1
1
1000
1000
0
Mud Resistivity from AITH
(OHMM)
8
9. Logging Cables
Armour
Conducting
cable
Insulator
• 1 Conductor cable
• Diameter: 0.5 cm
• 7 Conductor cable
• Diameter: 2.5 cm
• Used mainly for cased hole logging
• Cable sends power to the tool
• 1000’s of signal can be sent back
to the surface on the same line
• Used mainly for open hole logging
• Cable sends power to the tool
• 1000’s of signal can be sent back
to the surface
10
10. The Logging Process
Open Hole Measurements :
Wireline Logging.
LWD (Logging While Drilling)
Logging on Drill Pipe (TLC)
Logging Using Tractor
Wireline
LWD
TLC
Tractor
11
13. As the tool moves, the recording of
data is also made at a pre-determined
sampling rate (e.g. every ½ ft.)
The Logging Process
500
600
700
14
14. Porosity and Lithology
Petroleum System: Reservoir
Areservoir rock is any rock that has
enough porosity and permeability to
both store and allow the production
of hydrocarbons
The vast majority of reservoir rocks
worldwide are either sandstone or
carbonate rocks
15
15. Porosity and Lithology
Why we log ?
• Lithology (reservoir rock?)
• Resistivity (HC,water,both?)
• Porosity (how much HC?)
• What type of HC
• Formation mech. properties
• Permeability / cap pressure
• Shape of the structure
• Geological information
• Geothermal
• Unconventional applications
16
16. Porosity and Lithology
1- Definition of Porosity
Hydrocarbon
Sand
The Matrix could be complex
ϕ. Sw=
Carbonate
Shale
Anhydrite Volume of Water
ϕ . (1-Sw) = Volume of oil
17
17. Porosity and Lithology
Porosity (Continued)
A rock can be made up of small grains or large grains but have the
same porosity
Porosity depends on grain packing, not the grain size
18
18. the Archie Equation
Water saturation (dimensionless)
Connate water (or water saturation)
refers to the water that exists in the
reservoir when it is discovered
Water saturation is a measure of
how much water is in the reservoir
Hydrocarbon saturation Shc = 1 – Sw
Sw calculated from wireline
resistivity data usingArchie’s
equation
19
19. Permeability
Permeability Definition
Parameters
Area: A K = permeability, in Darcies.
L = length of the section of
rock, in centimeters.
P2
L
Q = flow rate in centimeters /
sec.
P1
P1, P2 = pressures in bars.
A = surface area, in cm2.
µ = viscosity in centipoise.
K = Q. µ . L / { A . ( P1 - P2 ) }
22
20. Invasion Profile
Resistivity of zone
Resistivity of the water in the zone
Water saturation in the zone
Mud
Rm
Adjacent bed
Rs
. The invasion
process creates a
zone where the
main water is
filtrate
Uninvaded
zone
h
mc Flushed
zone Zone of
transition
or
R
t
R
mc
dh
(Bed
thickness)
Rw
annulus
Mudcake Rxo
Sw
. This invaded zone
also has less HC
than the virgin
zone
h Rmf
S
xo
Rs
d
d
i
j
Adjacent bed
. This fluid
(Invasion diameters)
displacement is an
indication of fluid
mobility
rj
d
h
Hole
diameter
23
22. The Invasion Process
The Invasion process
Progressive invasion
Mudcake is formed from solids in mud
This creates an impermeable barrier
Although Phydraustatic > Pformation little
no invasion will take place
Progressive filtrate invasion and mud-cake build-up
25
