Transcript Geophysical neutron logging-tool NNTE for porosity and

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
Kraków, Poland
2) AGH UNIVERSITY OF SCIENCE AND TECHNOLOGY
Faculty 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, Sa
NNTE logging-tool
NaJ(Tl)
natural gamma ray
detector
FAR
epithermal neutron
detector (3He)
NEAR
epithermal neutron
detector (3He)
Am-Be
neutron source
NEAR
thermal neutron
detector (3He)
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
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 Sa of the rock matrix
Experimental calibration
Calibration 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 Sa and
the borehole diameter
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:
1. Modelling of the experimental geometry
Modelling of the experimental geometry
NNTE tool
water
rock model
concrete
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:
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)
Correlation between the calculation and
experimental results
1200
900
2500
measurement [cps]
[cps]
measurement
800
1000
2000
700
800
600
1500
500
600
400
1000
300
400
NNTE
logging-tool
MCNP
calculations
vs.vs.
measurements.
NNTE
logging-tool
MCNP
calculations
measurements.
NNTE
logging-tool
"far"
epithermal
detector
(B10 admixture
admixture
to the
the rock
rock
matrix
"near"
thermal
detector
(B10
to
matrix
"near"
epithermal
detector
(B10 admixture
to the
rock
for tarnamid)
tarnamid)
and S(alpha,
beta) scaterring
for
matrix
and S(alpha,
beta) scaterring
for tarnamid)
far
epithermal
detector
near
epithermal
detector
near
thermal detector
91082116,18847x + 5,44365
y y=y=1917400162,90309x
= 462776722,73826x+- 16,68745
61,34043
22
R
2 0,98297
RR=
=
=0,98182
0,96129
200
500
200
100
0 00
0,E+00
2,E-06
3,E-06
4,E-063,E-07
5,E-06 3,E-06
6,E-06
7,E-064,E-06
8,E-06
9,E-065,E-06
1,E-05
0,E+00 1,E-06
5,E-07
1,E-06 2,E-06
3,E-06
4,E-06
0,E+00
1,E-07
2,E-07 2,E-06
4,E-07
5,E-075,E-06
6,E-07
MCNP
[number
of neutron
MCNP
absorptions
perper
starting
particle]
MCNP
[number
of neutron
absorptions
starting
particle]
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:
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 %
MCNP calculation
The standard calibration curves: Miocene standard
120
120
standard
calibration
curve
for the
epithermal
TheThe
standard
calibration
curve
for the
nearnear
thermal
detector
detector
logging-tool,
Miocene
Standard
216mm,
15 c.u.;
NNTENNTE
logging-tool,
Miocene
Standard
216mm,
15 c.u.;
MCNP simulation
simulation
MCNP
5
4
y y= =-2,457125629181000E-13x
-2,626160364831620E-10x5++1,170906518531030E-09x
4,145969098393270E-07x4- 3
2
2,229645827333610E-06x
2,587863188993960E-04x3++2,165280121324750E-03x
8,028579857542850E-02x2- 1,131978616455080E+00x
1,256943006003870E+01x++2,784379741757920E+02
8,217206293776270E+02
100
100
porosity [%]
porosity
[%]
80
80
near
thermal detector
near
epithermal
detector
60
60
40
40
20
20
00
-20
-20
100
200
150
400
200600
250 800 300 1000350
countrate
countrate[cps]
[cps]
400
1200
450
1400
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:
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 Sa calculations for theoretical rock models representing the lithology
standard with the varying rock matrix Sa and porosity from 0 to 100 %
Nomogram for the rock matrix Sa evaluation upon
the difference between porosity derived from the
NEAR thermal and epithermal detectors
Nomogram for the Miocene rock matrix S a evaluation. NNTE logging-tool.
PorPozBter [% jsm] is the curve parameter . Borehole diameter is 216 mm.
MCNP simulation.
40
4 [% jsm]
8 [% jsm]
35
12 [% jsm]
16 [% jsm]
S a of the Miocene rock matrix [cu]
30
20 [% jsm]
25 [% jsm]
30 [% jsm]
25
35 [% jsm]
40 [% jsm]
20
45 [% jsm]
50 [% jsm]
55 [% jsm]
15
60 [% jsm]
70 [% jsm]
10
80 [% jsm]
90 [% jsm]
5
-10
-5
0
5
DporSigA [% ]
10
15
20
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