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Well logging

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Well logging

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  1. 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

  2. Well logging

  3. NNTE logging-tool The prototype logging-tool made by Polish geophysical prospecting company is designed to measure in the borehole 2 parametersof a geological formation: - neutron porosity and - thermal neutron absorption cross-section, Sa

  4. NaJ(Tl) natural gamma ray detector FAR epithermal neutron detector (3He) NEAR epithermal neutron detector (3He) NEAR thermal neutron detector (3He) Am-Be neutron source NNTE logging-tool

  5. NNTE logging-tool Principles of the measurement interpretation neutron porosity evaluation – from the readings of the NEAR epithermal detector, the NEAR thermal detectoror 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

  6. Calibration of the NNTE tool Experimental calibration Basic calibration at the calibration facility inZielona 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 Saof the rock matrix

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

  8. 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

  9. Numerical calibration Monte Carlo codes used for numerical calculations: MCNP4C and MCNP5with ENDF/B-V and ENDF/B-VI neutron libraries • Steps of numerical calibration: • Modelling of the experimental geometry

  10. NNTE tool water rock model concrete Modelling of the experimental geometry

  11. Numerical calibration Monte Carlo codes used for numerical calculations: MCNP4C and MCNP5with 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)

  12. Correlation between the calculation and experimental results

  13. Numerical calibration Monte Carlo codes used for numerical calculations: MCNP4C and MCNP5with 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%

  14. MCNP calculationThe standard calibration curves: Miocene standard

  15. Numerical calibration Monte Carlo codes used for numerical calculations: MCNP4C and MCNP5with 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%

  16. Nomogram for the rock matrix Sa evaluation upon the difference between porosity derived from the NEAR thermal and epithermaldetectors

  17. Prospects for the future Depth of investigation of the NNTE logging-tool: observation of behavior of the detector signal whileincreasing diameter of the rock model

  18. The end

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