Geophysical neutron logging-tool NNTE
for measurementsof porosity and rock matrix a
- numerical simulations
A. Drabina1), T. Zorski2)
1) INSTITUTE OF NUCLEAR PHYSICS Polish Academy of Sciences
Kraków, Poland
2) AGH UNIVERSITY OF SCIENCE AND TECHNOLOGYFaculty of Geology, Geophysics and Environmental Protection
Kraków, Poland
Well logging
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, a
NNTE logging-tool
FAR epithermal neutron detector (3He)
NEARthermal neutron detector (3He)
NEARepithermal neutrondetector (3He)
Am-Be neutron source
NaJ(Tl) natural gamma raydetector
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 matrixa evaluation – from the difference between the neutron porosity obtained from the NEAR thermal detector and the neutron porosity obtained from the NEAR epithermal detector
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.:
1) 21 rock models which represent 3 lithologies (limestone, sandstone and dolomite)
2) 2 borehole diameters (220 mm, 145 mm)
3) 3 NaCl concentrations in the borehole fluid
4) 4 a of the rock matrix
Experimental calibrationCalibration facility in Zielona Góra (Poland), property of the GEOFIZYKA KRAKÓW Sp. z o. o.
General view
Rock models
Calibration of the NNTE tool
Numerical calibration
Extension of the calibration onto a wider range of such parameters as
the rock matrix a and
the borehole diameter
Numerical calibration
Steps of numerical calibration:
1. Modelling of the experimental geometry
Monte Carlo codes used for numerical calculations:
MCNP4C and MCNP5 with ENDF/B-V and ENDF/B-VI neutron libraries
Modelling of the experimental geometry
NNTE tool
water
rock model
concrete
Numerical calibration
Steps of numerical calibration:
1. Modelling of the experimental geometry
2. Correlation between the calculation and experimental results (calculations for the rock models of the calibration facility in Zielona Góra)
Monte Carlo codes used for numerical calculations:
MCNP4C and MCNP5 with ENDF/B-V and ENDF/B-VI neutron libraries
Correlation between the calculation and experimental results
MCNP calculations vs. measurements. NNTE logging-tool "near" thermal detector (B10 admixture to the rock matrix
and S(alpha, beta) scaterring for tarnamid)
y = 462776722,73826x - 61,34043
R2 = 0,96129
0
500
1000
1500
2000
2500
0,E+00 5,E-07 1,E-06 2,E-06 2,E-06 3,E-06 3,E-06 4,E-06 4,E-06 5,E-06 5,E-06
MCNP [number of neutron absorptions per starting particle]
mea
sure
men
t [c
ps]
near thermal detector
MCNP calculations vs. measurements. NNTE logging-tool "near" epithermal detector (B10 admixture to the rock
matrix and S(alpha, beta) scaterring for tarnamid)
y = 91082116,18847x + 5,44365
R2 = 0,98297
0
100
200
300
400
500
600
700
800
900
0,E+00 1,E-06 2,E-06 3,E-06 4,E-06 5,E-06 6,E-06 7,E-06 8,E-06 9,E-06 1,E-05
MCNP [number of neutron absorptions per starting particle]
mea
sure
men
t [c
ps]
near epithermal detector
MCNP calculations vs. measurements. NNTE logging-tool "far" epithermal detector (B10 admixture to the rock matrix
and S(alpha, beta) scaterring for tarnamid)
y = 1917400162,90309x + 16,68745
R2 = 0,98182
0
200
400
600
800
1000
1200
0,E+00 1,E-07 2,E-07 3,E-07 4,E-07 5,E-07 6,E-07MCNP [number of neutron absorptions per starting particle]
mea
sure
men
t [c
ps]
far epithermal detector
Numerical calibration
Steps of numerical calibration:
1. Modelling of the experimental geometry
2. Correlation between the calculation and experimental results (benchmark calculations for the rock models of the calibration facility in Zielona Góra)
3. 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 %
Monte Carlo codes used for numerical calculations:
MCNP4C and MCNP5 with ENDF/B-V and ENDF/B-VI neutron libraries
MCNP calculationThe standard calibration curves: Miocene standard
The standard calibration curve for the near thermal detector NNTE logging-tool, Miocene Standard 216mm, 15 c.u.;
MCNP simulation
y = -2,457125629181000E-13x5 + 1,170906518531030E-09x4 -
2,229645827333610E-06x3 + 2,165280121324750E-03x2 - 1,131978616455080E+00x + 2,784379741757920E+02
-20
0
20
40
60
80
100
120
200 400 600 800 1000 1200 1400countrate [cps]
po
ros
ity
[%
]
near thermal detector
The standard calibration curve for the near epithermal detector NNTE logging-tool, Miocene Standard 216mm, 15 c.u.;
MCNP simulation
y = -2,626160364831620E-10x5 + 4,145969098393270E-07x4 -
2,587863188993960E-04x3 + 8,028579857542850E-02x2 - 1,256943006003870E+01x + 8,217206293776270E+02
-20
0
20
40
60
80
100
120
100 150 200 250 300 350 400 450
countrate [cps]
po
rosi
ty [
%]
near epithermal detector
Numerical calibration
Steps of numerical calibration:
1. Modelling of the experimental geometry
2. Correlation between the calculation and experimental results (benchmark calculations for the rock models of the calibration facility in Zielona Góra)
3. 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 %
4. Creation of nomograms for determining the rock matrix a - calculations for theoretical rock models representing the lithology standard with the varying rock matrix a and porosity from 0 to 100 %
Monte Carlo codes used for numerical calculations:
MCNP4C and MCNP5 with ENDF/B-V and ENDF/B-VI neutron libraries
Nomogram for the rock matrix a evaluation upon the difference between porosity derived from the
NEAR thermal and epithermal detectorsNomogram for the Miocene rock matrix a evaluation. NNTE logging-tool.
PorPozBter [% jsm] is the curve parameter . Borehole diameter is 216 mm. MCNP simulation.
5
10
15
20
25
30
35
40
-10 -5 0 5 10 15 20DporSigA [%]
a
of
the
Mio
ce
ne
ro
ck
ma
trix
[c
u]
4 [% jsm]
8 [% jsm]
12 [% jsm]
16 [% jsm]
20 [% jsm]
25 [% jsm]
30 [% jsm]
35 [% jsm]
40 [% jsm]
45 [% jsm]
50 [% jsm]
55 [% jsm]
60 [% jsm]
70 [% jsm]
80 [% jsm]
90 [% jsm]
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
The end
