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PorosityMineralogy Logs

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PorosityMineralogy LogsObjectives:

Density Logging Gamma Ray Back Scattering

Compensated Density 2 or 3 detectors

Neutron Logging Slowing Down Length

Neutron Thermalization and AbsorptionCompensated Neutron Ratio Effect of Gas

Sonic Logging Slowness of Wave TravelBorehole Compensation

Depth of Investigation

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Density Logging

Gamma Ray Back

Scattering

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DensityTool

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Gamma RayInteractions

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Density of Common Minerals

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Correction

for

Standoff

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Density

Correction by

Spine and Ribs

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Log of

CorrectedBulk

Density

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Compensated Density Log

Gamma Ray bombardment

multiple collisions with electrons

energy loss due to Compton scattering

size of Gamma Ray cloud inversely

proportional to electron density

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Density Summary

bombardment by medium energy GRs

interactions with electrons in formation

Compton scattering

size of cloud of GRs inversely

proportional to electron density

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NeutronInteractions

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Neutron Nuclei Interaction

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Thermal Neutron Annihilation

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Neutron

Slowing Down Length

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Neutron Logging Technologies Emission Detection

Fast Neutron Thermal Neutron

Fast Neutron Capture Gamma

Fast Neutron Epithermal Neutron

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NeutronLog

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Simple Neutron Logging bombardment by 5 MeV neutrons elastic coll isions with nuclei

energy lost per collision depends onrelative mass of nucleus

hydrogen is most effective

size of neutron cloud inversely proportional tohydrogen content

population of neutron cloud is a function ofabsorption qualit ies

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Neutron

CalibrationPit

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Compensated Neutron Logging

reduces borehole effects

reduces salinity effects

increases depth of investigation

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Comp.

Neutron

Log

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Compensated Neutron Calibration

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Depth of Investigation

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Density

NeutronLog

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Neutron Logs are Hydrogen Logs

Neutron Logs are sensitive to . . .porosity

matrix material

gas saturation

clay

light oil

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Factors Affecting Neutron Logs

anything withHydrogen

WATER

clay

oil

gas

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Clay Minerals Contain Hydrogen

in OH ion in crystal lattice

in electrostatically bound water

on platelet surfaces

therefore clay strongly impactsNeutron logs

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Neutron Response in Gas

Hydrogen concentration in gas is low

compared to water or oil

apparent Neutron porosity isanomalously low

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D-N

Combo

Gas

Indicator

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D-N GasDetection

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Neutron Logging

greater H content

larger N absorption

cross section

smaller N cloud size lower count rate

higher N

lower N population lower count rate higher N

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Neutron Summary bombardment by 5 MeV neutrons

elastic coll isions with nuclei

energy loss per collision

size of neutron cloud inversely

proportional to Hydrogen content

population of neutron cloud related

to absorption qualities

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Sonic / Acoustic Logging

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Sonic Logging

1. Send out pulsefrom magnetostrictive transmitter

2. Listen for received signal at two ormore different distances

3. Record acoustic signal waveformand differences in arrival time

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from the Sonic Transmitter . . .

Energy spreads spherically

Velocity differences distort sphere

S di T itt E

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Spreading Transmitter Energy

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Transmission Modes

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Rough HoleEffect

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BoreholeCompensation

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BHCSonic

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SonicErrors

Long

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Long

SpacingCure

BHC for

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BHC for

LongSpacing

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Unscrambling SonicTransmission Modes

Longer spacingvelocity differences separate P, S, T

Array of receivers

semblance processing coherency plot

Dipole shear imaging tool

generates flexural wave directly

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Array Sonic Tool

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ArraySonic

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Soft RockShear Absent

Flexural

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Wave fromDSI

Dipole

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p

ShearImager

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Sonic Summary

Initiate acoustic wave and measureslowness

Compressional, Shear, and Stoneleytransmission modes

Compressional is fastest