Geophysical neutron logging-tool NNTE for measurements of porosity and rock matrix Sa - numerical simulations A. Drabina1), T. Zorski2) 1) INSTITUTE OF NUCLEAR PHYSICS Polish Academy of Sciences Krak

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Geophysical neutron logging-tool NNTE for
measurementsof porosity and rock matrix Sa -
numerical simulationsA. Drabina1), T.
Zorski2)1) INSTITUTE OF NUCLEAR PHYSICS
Polish Academy of SciencesKraków, Poland2)
AGH UNIVERSITY OF SCIENCE AND TECHNOLOGYFaculty
of Geology, Geophysics and Environmental
ProtectionKraków, Poland
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Well logging
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NNTE logging-tool

• The prototype logging-tool
• made by Polish geophysical prospecting company
• is designed to measure in the borehole
• 2 parameters of a geological formation
• - neutron porosity and
• - thermal neutron absorption cross-section, Sa

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NNTE logging-tool
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NNTE logging-tool Principles of the measurement
interpretation

• neutron porosity evaluation from the readings
  of the NEAR epithermal detector, the NEAR thermal
  detector or from the ratio of the NEAR-to-FAR
  epithermal detector readings
• rock matrix Sa evaluation from the difference
  between the neutron porosity obtained from the
  NEAR thermal detector and the neutron porosity
  obtained from the NEAR epithermal detector

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Calibration of the NNTE tool

• Experimental calibration
• Basic calibration at the calibration facility in
  Zielona Góra (Poland), property of the GEOFIZYKA
  KRAKÓW Sp. z o.o.
• 21 rock models which represent 3 lithologies
  (limestone, sandstone and dolomite)
• 2 borehole diameters (220 mm, 145 mm)
• 3 NaCl concentrations in the borehole fluid
• 4 Sa of the rock matrix

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Experimental calibration
Calibration facility in Zielona Góra (Poland),
property of the GEOFIZYKA KRAKÓW Sp. z o. o.
Rock models
General view
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Calibration of the NNTE tool

• Numerical calibration
• Extension of the calibration onto a wider range
  of such parameters as
• the rock matrix Sa and
• the borehole diameter

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Numerical calibration
Monte Carlo codes used for numerical
calculations MCNP4C and MCNP5 with ENDF/B-V and
ENDF/B-VI neutron libraries

• Steps of numerical calibration
• Modelling of the experimental geometry

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Modelling of the experimental geometry
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Numerical calibration
Monte Carlo codes used for numerical
calculations MCNP4C and MCNP5 with ENDF/B-V and
ENDF/B-VI neutron libraries

• Steps of numerical calibration
• Modelling of the experimental geometry
• Correlation between the calculation and
  experimental results (calculations for the rock
  models of the calibration facility in Zielona
  Góra)

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Correlation between the calculation and
experimental results
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Numerical calibration
Monte Carlo codes used for numerical
calculations MCNP4C and MCNP5 with ENDF/B-V and
ENDF/B-VI neutron libraries

• Steps of numerical calibration
• Modelling of the experimental geometry
• Correlation between the calculation and
  experimental results (benchmark calculations for
  the rock models of the calibration facility in
  Zielona Góra)
• Creation of the standard calibration curves for a
  given standard lithology (here Miocene standard)
  - calculations for theoretical rock models
  representing the lithology standard with porosity
  varying from 0 to 100

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MCNP calculationThe standard calibration curves
Miocene standard
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Numerical calibration
Monte Carlo codes used for numerical
calculations MCNP4C and MCNP5 with ENDF/B-V and
ENDF/B-VI neutron libraries

• Steps of numerical calibration
• Modelling of the experimental geometry
• Correlation between the calculation and
  experimental results (benchmark calculations for
  the rock models of the calibration facility in
  Zielona Góra)
• Creation of the standard calibration curves for a
  given standard lithology (here Miocene standard)
  - calculations for theoretical rock models
  representing the lithology standard with porosity
  varying from 0 to 100
• Creation of nomograms for determining the rock
  matrix Sa - calculations for theoretical rock
  models representing the lithology standard with
  the varying rock matrix Sa and porosity from 0 to
  100

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Nomogram for the rock matrix Sa evaluation upon
the difference between porosity derived from the
NEAR thermal and epithermal detectors
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Prospects for the future

• Depth of investigation of the NNTE logging-tool
• observation of behavior of the detector signal
  while increasing diameter of the rock model

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The end