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Sonic Log

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Theorytical Background

Schlumberger Film

http://localhost/var/www/apps/conversion/tmp/scratch_7/Schlumberger%20-%20Acoustic%20Wave%20Propagation.exehttp://localhost/var/www/apps/conversion/tmp/scratch_7/Schlumberger%20-%20Acoustic%20Wave%20Propagation.exe

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Sonic Log Format Display

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Porosity from Sonic Log

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Porosity from Sonic Log

Wyllie Time-Average Equation:

mafl DtDtDt )1(

mafl

ma

DtDt

DtDt

Wyllie, M., Gregory, A., and Gardner, G., 1956, Elastic wave velocities in heterogeneous and porous media:

Geophysics, 21, 41-70.

Wyllie, M., Gregory, A., and Gardner, G., 1958, An experimental investigation of factors affecting elastic wave

velocities in porous media: Geophysics, 23, 459-493.

Wyllie, M., Gardner, G., and Gregory, A., 1963, Studies of elastic wave attenuation in porous media: Geophysics,

27, 569-589.

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Porosity from Sonic Log

Dt Matrix

Sandstone: 56 uS/ft

Limestone: 49 uS/ft

Dolomite: 44 uS/ft

Dt Fluid

Water, water-base mud: 180 190 uS/ft

Oil, oil-base mud: 190

250 uS/ft

Dt Steel 57 uS/ft

Wyllie Time-Average Equation:

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Porosity from Sonic Log

Interval Transit Time

Porosity

Chart Por-3

Dt = 88

= 24 p.u.

Dt matrix = 56

Dt fluid = 189

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Porosity from Sonic Log

Measured formation slowness is 80 uS/ft.Compute porosity, using Chart Por-3 or a hand

calculator, assuming fluid slowness of 189 uS/ft, for the

following matrix slownesses:

1: Dt Matrix = 55.5 uS/ft

2: Dt Matrix = 48.0 uS/ft

3: Dt Matrix = 37.5 uS/ft

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Porosity from Sonic Log

Measured formation slowness is 80 uS/ft.Compute porosity, using Chart Por-3 or a hand

calculator, assuming fluid slowness of 189 uS/ft, for the

following matrix slownesses:

1: Dt Matrix = 55.5 uS/ft

2: Dt Matrix = 48.0 uS/ft

3: Dt Matrix = 37.5 uS/ft

1. 18 p.u.

2. 23 p.u.

3. 28 p.u.

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Porosity from Sonic Log

Interval Transit Time

Porosity

Chart Por-3

Dt fluid = 189

Dt = 80 uS/ft

23 p.u.

18 p.u.

28 p.u.

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Unconsolidated Sands

Interval Transit Time

Porosity

Chart Por-3

Dt = 100 uS/ft

33.3 p.u.

1.4Compaction Factor, Bcp

23.8 p.u.

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Unconsolidated Sands

cpmafl

ma

BDtDt

DtDt 1

Compaction-corrected porosity