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CIT-ChE
Wel l Log Analys is .
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SonicLog
(Acoustic Log )
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Contents
1. Introduction
2. Measurement Principle of Sonic Velocity Log
3. Sonic Response to Typical Formation
4. Sonic Porosity
5. Shale Effects
6. An Introduction to MAC
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(1) sonic velocity log ;
(2) Full Waveform Sonic log ;(3) Vertical Seismic Profile (VSP) log ;
(4) sonic amplitude log ;
(5) down hole noise log ;
(6) sonic image logs .
CNLCIntroduction of sonic logs
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Applications of Sonic Log
Determine porosity and lithology (with or without
other logs);
Determine formation mechanical properties which in
turn can be used to estimate hydraulic fracturingpressures and to evaluate sanding problem;
Measure attenuation of sonic energy to evaluate
fracturing and permeability;
Combine sonic and density logs to produce
synthetic seismic traces;
Combine sonic and check shot surveys to calibrate
surface seismic data with borehole log data.
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Propagation of Elastic Waves
An elastic wave travels
through a medium (solid,
liquid, or gas) as slight
disturbances to theparticles in that medium.
The wave energy will move
the particles parallel to
(compressional) and/or
perpendicular to (shear) the
wave propagation direction.
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P-Wave
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S-Wave
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Stoneley Wave
Stoneley wave is a guided tube
wave with velocity and
amplitude determined by:
Borehole fluid elastic
properties
Formation elastic properties
Formation permeability.
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Presentations and scales
Interval transi t t ime
(t, us/ft)---the timerequired for the wave
to travel
a given distance.
Transit time can be
more elegantly calleds lowness.
Most formations have
tc values of 45 to 150
us/ft, and ts values
of 80 to 200 us/ftSonic logs are
presented on a linear
scale, as shown in
right Figure.
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Measurement Principle of Sonic Velocity Log
The simplest sonic tool
has only one transmitters
and two receivers. This kind
of tool can record the sonic
wave that refracts at acritical angle to borehole
wall and travels along the
side wall .The first arrival
compressional waves arerecorded by two receivers .
The interval transit time
(t) can be used to estimateformation porosity .
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Borehole Compensated Sonic (BCS)
The method above
doesnt work well whensidewall is rough and
the sonde is tilted. A
simple means for
overcoming thisproblem is adding a
transmitter on the other
end , newtc
tc =(tu + tl) / (2*L) will be more reliable .
Where L= span, usually
L=0.5~2 ft .
tc is compensatedt .
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Sonic Response to Typical Formation
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The depth of investigation of a sonic tool is
less than 30 in., so it is subject to borehole
effects. These include:
gas in the borehole fluid, large diameter boreholes,
very slow formations, and
the invaded (altered) zone.
Environmental Effects
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Sonic Porosity
Wyllie Time Averge ( WTA )One of the first relationship proposed to
determine fromtc was by Wyllie : ( TimeAverage )
s =
Wheretma is the pure matrix slowness ;tf is the pore fluid slowness ;Cpis a correction,Cp=1 in hard rocks ,but
in unconsolidated formation better results are
found by using Cp =(tshale /100).
Cp(tf tma )(tc tma )
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Shale Effects
Sonic logs will generally have to be corrected forthe presence of shales before estimatingporosity fromtc. The method is to determine
Vsh from some other source (such as theGamma Ray), and reduce tc by some amountwhich depends on Vsh and tsh. The normalmethod for this is:
(tc)shalecorr= tcVsh*tsh
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Shale and Clay Distribution
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Shale Distribution and Effects ont
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Multipole Array Acoustic Log
The conventionalsonic velocity log onlydeterminates the first
arrival compressionalwave. The followingwave (such as shearwave, Stoneley wave )are now be recorded,its amplitude or waveform has been used forrock mechanicsanalyzing.
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Comp.Shear
Stoneley
Compressional Shear Stoneley
Slowness (us/ft)
us
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Un puits for , ncessite d tre
tub et ciment avant sa miseen production .On a alors
besoin de juger de la qualit
de cimentation , de l
tanchit ainsi ralise ainsi
que de l tat du tubage et du (
ou des ) tubing en placeDans ce but une panoplie de
mthodes se basant sur l
tude de la propagation des
ondes , permet d allerjusqu
l obtention d images de la
paroi du trou de sondage , dela colonne de ciment , de la
face interne du tubage , ou du
tubing ou des deux , de
dtecter les endroits corrods
, percs ou autres DIAGRAPHIES SONIQUES
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ANALYSE
STRATIGRAPHIQUE
ANALYSE
STRATIGRAPHIQUE
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Rock Mechanical Properties
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