Lecture Presentations PGE368 Fall 2003 Semester November 13 and 18 Principles and Interpretation of Borehole Sonic Measurements Carlos Torres-Verdín, Ph.D. Assistant Professor
Oct 02, 2015
Lecture Presentations
PGE368Fall 2003 Semester
November 13 and 18
Principles and Interpretation of Borehole Sonic Measurements
Carlos Torres-Verdn, Ph.D.Assistant Professor
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
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.
Complementary Reading Assignment:
1. Bassiouni, Z., 1994, Theory, Measurement, and Interpretation of Well Logs, Chapter 3: Acoustic Properties of Rocks.
APPLICATIONS:
Mechanical Property Analysis
Formation Evaluation
Geophysical Prospecting (Seismic Exploration)
Stress and Strain
Stress and Strain
Mechanical Properties and Petrophysics
Units and Conversions
P and S WAVES
BASIC PRINCIPLES
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
Traditional Monopole Tool
Single Transmitter-Single Receiver Tool
Single Transmitter-Dual Receiver Tool
EARLIER TOOLSSingle Transmitter Dual Receiver
EARLIER TOOLSDual Transmitter Dual Receiver(Borehole Compensation)
Synthetic Compensation
Monopole in a Fast Formation
Different Waves, Different Velocities
MONOPOLE WAVEFORM
BOREHOLE WAVES
HARD FORMATION, MONOPOLE EXCITATION
SOFT FORMATION, MONOPOLE EXCITATION
CYCLE SKIPPING
Typical Ranges of Velocities
P-WAVE VELOCITIES OF GASES
P- and S-WAVE VELOCITIES OF SEDIMENTARY ROCKS
Typical Ranges of Velocities
Relationship with Depth
Relationship with Pressure
Formation Over-Pressure
Influence of Saturating Fluids
Influence of Gas and Water Saturation
Qualitative Summary
DIPOLE FLEXURAL WAVE
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.
Intuitive Model
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
Theory and Measurements
Compaction Effects
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
Synthetic Seismogram (cont.)
Applications Well Tie & Correlation Allow to correlate log
data with surface seismic data
Surface Seismic
Acoustic ImpedanceSynthetic
Seismogram
BOREHOLE DIPOLE SOURCE
SOFT FORMATION, DIPOLE EXCITATION
DIPOLE WAVEFORMS: Fast Formation
DIPOLE SONICARRAY TOOL
EXAMPLE:Ultra Slow Compressional Wave
EXAMPLE:Ultra Slow Dipole Shear Response
STONELEY PERMEABILITY
FRACTURE EVALUATION
LOGGING FOR MECHANICAL PROPERTIES
CROSS-DIPOLE:In-Situ Stress
In-Situ Stress
SANDING MODEL DIAGRAM
ACKNOWLEDGEMENTSBaker Atlas
Schlumberger