14 SonRegistro sonicosic Logging
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Transcript of 14 SonRegistro sonicosic Logging
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Lecture Presentations
PGE368Fall 2003 Semester
November 13 and 18
Principles and Interpretation of Borehole Sonic Measurements
Carlos Torres-Verdn, Ph.D.Assistant Professor
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Bulk Density Logging
Neutron Logging
Sonic Logging
Electrical Resistivity of Rocks
Electrical Resistivity Tools:Induction and Laterolog
Course Plan, II
Saturation
Invasion
Active NuclearLogging
Porosity
GasLithology
Invasion
CoreData
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Objectives:
To understand the physical principles behind the operation of sonic logging tools,
To understand the principles behind the interpretation of sonic logs, and
To understand the limitations of sonic borehole measurements.
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Complementary Reading Assignment:
1. Bassiouni, Z., 1994, Theory, Measurement, and Interpretation of Well Logs, Chapter 3: Acoustic Properties of Rocks.
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APPLICATIONS:
Mechanical Property Analysis
Formation Evaluation
Geophysical Prospecting (Seismic Exploration)
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Stress and Strain
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Stress and Strain
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Mechanical Properties and Petrophysics
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Units and Conversions
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P and S WAVES
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BASIC PRINCIPLES
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250 cm 200 150 100 50 0 cm
80 cm
80 cm
40 cm30 cm 20 cm
60 cm
5 cm 2 cm 0 cm
INDUCTION LOG
LATEROLOG
NEUTRONGAMMA RAY
DENSITY
SONICMICRO RESISTIVITY
MICROLOGDIPMETER
DEPTH OF INVESTIGATION
RES
OLU
TIO
NRESISTIVITY
RADIOACTIVITY
RESISTIVITY
ACOUSTIC
Logging Tools
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Traditional Monopole Tool
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Single Transmitter-Single Receiver Tool
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Single Transmitter-Dual Receiver Tool
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EARLIER TOOLSSingle Transmitter Dual Receiver
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EARLIER TOOLSDual Transmitter Dual Receiver(Borehole Compensation)
Synthetic Compensation
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Monopole in a Fast Formation
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Different Waves, Different Velocities
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MONOPOLE WAVEFORM
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BOREHOLE WAVES
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HARD FORMATION, MONOPOLE EXCITATION
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SOFT FORMATION, MONOPOLE EXCITATION
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CYCLE SKIPPING
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Typical Ranges of Velocities
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P-WAVE VELOCITIES OF GASES
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P- and S-WAVE VELOCITIES OF SEDIMENTARY ROCKS
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Typical Ranges of Velocities
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Relationship with Depth
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Relationship with Pressure
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Formation Over-Pressure
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Influence of Saturating Fluids
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Influence of Gas and Water Saturation
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Qualitative Summary
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DIPOLE FLEXURAL WAVE
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Sonic Porosity
1. The porosity from the sonic slowness is different from that of
the density or neutron tools.
2. Sonic porosity reacts to primary porosity only, i.e. it does not
see the fractures or vugs.
3. The difference between the sonic porosity and the neutron-
density porosity gives a Secondary Porosity Index (SPI) which
is an indication of how much of this type of porosity there is in
the rock.
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Intuitive Model
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tlog = t f + 1 ( )t ma
= tlog t mat f t ma
This is very simple with the inputs of a matrix slowness and a fluid slowness
The basic equation for sonic porosity is the Wyllie Time Average Formula (strictly speaking, an empirical formula):
Sonic Porosity
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Theory and Measurements
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Compaction Effects
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Sonic Porosity
=Ctlogtma
tlogC is a constant usually taken as 0.67
There is another possibility for transforming slowness to porosity, called Raymer Gardner HuntThis formula tries to take into account some irregularities seen in the fieldthe basic equation is
a simplified version used on the CSU and Maxis is
1t c
=1( )2t ma
+
tf
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Synthetic Seismogram (cont.)
Applications Well Tie & Correlation Allow to correlate log
data with surface seismic data
Surface Seismic
Acoustic ImpedanceSynthetic
Seismogram
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BOREHOLE DIPOLE SOURCE
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SOFT FORMATION, DIPOLE EXCITATION
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DIPOLE WAVEFORMS: Fast Formation
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DIPOLE SONICARRAY TOOL
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EXAMPLE:Ultra Slow Compressional Wave
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EXAMPLE:Ultra Slow Dipole Shear Response
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STONELEY PERMEABILITY
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FRACTURE EVALUATION
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LOGGING FOR MECHANICAL PROPERTIES
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CROSS-DIPOLE:In-Situ Stress
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In-Situ Stress
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SANDING MODEL DIAGRAM
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ACKNOWLEDGEMENTSBaker Atlas
Schlumberger