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Open Hole Well Logging: Tools,
Utility and
How to Interpret the Chart
Miftahul Firdaus
Petroleum Engineering UPNVeteran Yogyakarta
Yogyakarta, 19 July 2008
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The Short Course
What you should know
Basic hydrocarbon geology
Basic reservoir engineering
Basics of drilling a well
Basic Logging tools?
What you should learn..?
What logging means
Understanding of log analysis
Simple log analysis (Quick Look)Comparison to core
Introduction to computer (S/W) based interpretation
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The Logging Environment & Evaluation of HCPermeable Zone Logs.
Spontaneous Potential Log (SP)
Gamma Ray Logs (GR)
Resistivity Logs.
Induction Logs
Lateral Logs
Porosity Logs.
Neutron Logs
Densitas Logs
Sonic Logs
Clean Formation Interpretation
Shaly Formation Interpretation
Contents :
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Logging Environment &
Evaluation of Hydrocarbon
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Definitions
Log
Sampling rate / logging speed
Vertical resolution
Depth of investigation
Invasion
Logging truck/unit
Logging tools
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THE LOGGING ENVIRONMENT
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Maxis acquisition system
Winch man
Wireline /field Engineer Acquisition Equipment
Wireline cable to
downhole toolsCable drum
UnitEngineClient (Witness)
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Logging Truck
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Type of Logging
Open hole
logging
Perforation &
Productionlogging
Cased hole
logging
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What does logging mean?
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What does logging mean?
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Tool string is moving at a certain logging
speed, and data are recorded at certain
intervals called sampling rate.
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What does logging mean?
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What does logging mean?
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What does logging mean?
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What does logging mean?
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And we get a group ofwiggly lines called a log
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First well logs recorded in 1927
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Modern logs have
more measurements
but the principle is the
same
Gamma Ray (GR)
0 (GAPI) 150
SP (SP)
0 (MV) 200
FXND
50 (PU) 0
1:220 Ft Pad
-180 180
Rt from HALS
RX18
1 1000
1 1000
Rt from AITH
1 (OHMM) 1000
Mud Resistivity from HALS
1 1000
Mud Resistivity from AITH
1 (OHMM) 1000
AHTPR
5.00
7.75
12.01
18.62
28.85
44.72
69.81
107.43166.51
258.08
400.00
90 0 90
1700
1600
Gamma Ray (GR)
0 (GAPI) 150
SP (SP)
0 (MV) 200
FXND
50 (PU) 0
1:220 Ft Pad
-180 180
Rt from HALS
RX18
1 1000
1 1000
Rt from AITH
1 (OHMM) 1000
Mud Resistivity from HALS
1 1000
Mud Resistivity from AITH
1 (OHMM) 1000
AHTPR
5.00
7.75
12.01
18.62
28.85
44.72
69.81
107.43166.51
258.08
400.00
90 0 90
1700
Gamma Ray (GR)
0 (GAPI) 150
SP (SP)
0 (MV) 200
FXND
50 (PU) 0
1:220 Ft Pad
-180 180
Rt from HALS
RX18
1 1000
1 1000
Rt from AITH
1 (OHMM) 1000
Mud Resistivity from HALS
1 1000
Mud Resistivity from AITH
1 (OHMM) 1000
AHTPR
5.00
7.75
12.01
18.62
28.85
44.72
69.81
107.43166.51
258.08
400.00
90 0 90
1700
1600
Some times a large group of
log curves are grouped andcolor coded into an Image.
Shading is often added to
make the log curves easierto read.
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Vertical Resolution + Sampling Rate
Coarse sampling rate Fine sampling rate
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Volume of measurementdepth of investigation
Depth of investigation of different measurements J-curves
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Invasion Process
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The Process of Invasion
Mud pressure in the annulus (Pm)
Hydrostatic pressure of fluid in the formation pores (Pr)
Pm must be kept greater than Pr
Prevent a well blowout
Forces drilling mud into the formation
Invasion happens solid particles on the formation wall & form a mud cake
Liquid that passes into the formation and pushes back some of reservoir
fluids , mud fi l t rate
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Invasion
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Invasion Profile
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Nomenclature:
Borehole:Rm = Resistivity of mud.
Rmc = Resistivity of mud cake.
Flushed Zone:Rmf= Resistivity of mud filtrate.
RXO = Resistivity of flushed zone.SXO = Water Saturation of flushed zone.
Uninvaded or Virgin Zone:RT = True resistivity of formation.
RW = Resistivity of formation water.
SW = Formation Water Saturation.
RS = Resistivity of adjacent bed or shoulder bed resistivity.di = Diameter of invasion.
dh = Borehole diameter.
h = Bed thickness.
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Impact of Invasion on Resistivity Measurement
1. Flushed zone diameter (df.)Containing only Mud Filtrate (Rmf)Residual HydrocarbonResistivity of Flushed Zone (Rxo).Water Saturation of Flushed Zone (Sxo).Thickness ~ 6 inches.
2. Transition zone diameter (dj.)
May extend several feet.
3. Undisturbed zone:
Resistivity of Formation Water (Rw)
True Resistivity of Formation (Rt)
Water Saturation (Sw) .
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Fundamental Interpretation Relations
Definition of Resistivities
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Definition of Resistivities
A. Resistivity of Formation Water (Rw).
First, the tank is filled with water containing 10 % NaClto simulate an formation water.
The ratio V / I1 (volts/amperes) is Rw
VRw = ----- [ ohmm]
I1
B. Resistivity of Formation (Ro).Sand is poured into the water filled tank.The voltage is applied and a current I2 is measured.
VRo = ----- [ ohmm] Ro > Rw
I2
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Formation Factor, F
The Resistivity, Ro must be proportional to Rw since only the water conducts.
Ro1 = F Rw1Ro2 = F Rw2Ro3 = F Rw3
Thus,Ro = F Rw (1)
The proportionality constant F is termed the Formation Factor
Dimana F = Formation Resistivity Factor.
On general principles, F must be related to porosity by relation of the form :
1F = ----------- (2)
m
m = Cementation exponent, m = 1.3 - 2.2
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Archies Plot, Formation Factor (F) Vs Porosity () & Permeability (K)
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Definition of Resistivities
C. True Resistivity (Rt).Fraction of the pore water is replaced by oil (Sw < 1)
The same voltage, V, and current I3VRt = ----- [ ohmm] Rt > Ro
I3Rt = I Ro
(3)
where, I = Resistivity Index
1I = ----------- (4)
Sw nwhere, n = Saturation exponent ( 2)
Knowing Ro and Rt (from eq. 1,2,3&4), Water saturation (Sw) can be calculated :
Ro F. RwRt = ----------- , Sw n = ------------
Sw n Rt
This is the basic equation of log interpretation
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Logging Tools
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Standard Logging String (Triple Combo)
Formation Gamma Ray
Neutron Porosity
Density (Porosity)
Caliper (hole size)
Pad Resistivity (good v.resolution)Resistivity (good depth investigation)
Spontaneous Potential
Mud Resistivity
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Conveyance
Open Hole Measurements :
Wireline Logging.
LWD (Logging While Drilling)
Logging on Drill Pipe (TLC)
Tractor
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Why we log ?
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Why we log ?
Lithology (reservoir rock?) Resistivity (HC,water,both?)
Porosity (how much HC?)
What type of HC
Multiwell Plots
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Multiwell Plots