Porous rock evaluation with micro ct zacher_ge_copyright

Quantitative investigation of
microstructures within porous rocks
by using very high resolution X-ray
micro-CT imaging
Gerhard Zacher1, Matthias Halisch², Peter Westenberger3 and
Frank Sieker1
1) GE Sensing & Inspection Technologies, Wunstorf, Germany
²) Leibniz Institute for Applied Geophysics, Hannover, Germany
³) FEI Visualization Sciences Group, Düsseldorf, Germany
Copyright General Electric 2014

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Content
1. Introduction & Fundamentals
2. nanotom CT / resolution comparison
3. Scan results for geological samples
4. Conclusion & Outlook

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X-ray tubes Microfocus - nanofocus
Introduction & Fundamentals

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Fundamentals
Geometry and Resolution
Advantage of nanofocus tube:
resolution & Penumbra effect
Focal spot size:
microfocus: F = 3 µm
nanofocus: F = 0.6 µm
M=FDD/FOD ; Vx=P/M
mikrofocus nanofocus
limiting factor for image resolution = F
detail detectability about 1/3 F

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Resolution and Detail Detectability
Detail detectability of the nanofocus tube
Conclusion:
detail detectability
is no measure
for sharpness
Focal Spot 2.5 µm  0.8 µm
500 nm 500 nm
5 µm 5 µm

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Resolution and Detail Detectability
Resolution
2 µm bars 2 µm bars
2.5 µm 
Focal spot size influence:
1.5 µm  0.8 µm 
0.6 µm bars

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Content

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nanotom m
ultra-high resolution
nanoCT system
X-ray tube:
nanofocus < 800 nm spot size
180 kV / 15 W, tube cooling
X-ray detector:
Cooled flat panel, 7.4 Mpixel,
11 Mpixel virtual detector
100 µm pixel size
Manipulator:
5 axis stepper motors,
granite-based,
high-precision air bearing
nanotom CT

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Principle of CT
Acquisition of
(2D) projections
whilst the object
turns through 360°
rotation steps << 1°
nanotom CT
X-ray source CNC Detector
CT / volume reconstruction

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Principle of CT
Acquisition
movie
nanotom CT
Sample rotation + acquisition images

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Principle of CT: Reconstruction Method
Example: spark plug
back-projectionprojection inversion log + filter line
profile
Acquisition of 600 projections 600 back projections 3D visualization
nanotom CT

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resolution comparison
1 mm
Improved sharpness (+80%) & increased CNR (+100%) due to diamond
window and low noise detector
State of the art nanotom m
metallic foam: material development & characterization, automotive
Contrast resolution

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Improved sharpness (+80%) & increased CNR (+100%) due to diamond
window and low noise detector
metallic foam: material development & characterization, automotive
Contrast resolution

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Comparison example (metal alloy*)
CT result close to synchrotron-based CT
State of the art nanotom m
AlMg5Si7 Alloy: material research, University & Industrial metallography labs
Synchrotron-based CT (ESRF
Grenoble/France)
100 µm
* J. Kastner, B. Harrer, G. Requena, O. Brunke, A comparative study of
high resolution cone beam X-ray tomography and synchrotron tomography applied to
Fe- and Al-alloys. NDT&E Int. vol. 43, pages 599-605

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Content

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Cretaceous
reservoir
sandstone
“Bentheimer”
Standard
petrophysical
analysis
Scan data of geological samples
Bentheimer sandstone
Electron microscope images and thin sections with
highly weathered feldspar (left); porosity permeability
cross plot from experimental analysis (right)
38 mm

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Cretaceous
reservoir
sandstone
“Bentheimer”
X-ray CT
(Ø 5 mm)
Vx = 1 µm
1 mm
A
B
AA
BB
A
B
2D slice and 3D volume of CT scan. Quartz (grey), (A)
clay (brown), (B) feldspar (blue) and zirconia (red).
Right: pore space is separated (green)
5 mm

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Cretaceous
reservoir
sandstone
“Bentheimer”
(Ø 5 mm)
Vx = 1 µm
1 mm
Increasing inhomogeneity of samples
Representative?
 Scale
problem?
For different sandstones (Bentheimer, Oberkirchener
and Flechtinger) porosity has been evaluated by
different methods. Range differs a lot.

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Cretaceous
reservoir
sandstone
“Bentheimer”
(Ø 5 mm)
Vx = 1 µm
Comparison of sandstones
average Porosity: ~ 22.5 %
representative scan volume:
1000x1000x1000 Voxel
average Porosity: ~ 7 %
representative scan volume:
> 1750x1750x1750 Voxel
1 mm
Bentheimer Sandstone Flechtingen Sandstone
Porosity (CT) with respect to volume size for different
sandstones

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Digital Rock Evaluation
segmentation percolation test
connectivity test

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quantitative evaluationskeletonization

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Cretaceous
reservoir
sandstone
“Bentheimer”
(Ø 5 mm)
Vx = 1 µm
Avizo
fluid flow
simulation
video

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Pyroclastic
rock
(Ø 1 mm)
Vx = 1 µm
yz-slice
1 mm
yz-slice with different grains with high porosity or
fractures and bigger pores
3 mm
zoomed
area
Etna

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1 mm
Zoom into yz-slice with measurement of thin wall: 1.8 µm
3 mm
Pyroclastic
rock
(Ø 1 mm)
Vx = 1 µm
yz-slice
Etna

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Pyroclastic
rock
(fresh’11)
(Ø 10 mm)
Vx = 5 µm
xy-slice
1 mm
xy-slice through 5x5x5mm cube used later for flow
simulation
3 mm
Etna

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1 mm
3 mm
Pyroclastic
rock
(fresh’11)
(Ø 10 mm)
Vx = 5 µm
3D volume
The surface is composed of 18 Mio. faces and
represents the stone matrix. Shadows enhance the
spatial impression.
SCHEMATIC WORKFLOW FOR POROSITY
AND PERMEABILITY ANALYSIS
Etna

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1 mm
Pyroclastic
rock
(fresh’11)
(Ø 10 mm)
Vx = 5 µm
3D volume
The volume rendering visualizes the separated pore
space, each individual pore has a separate color.
Etna

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1 mm
Pyroclastic
rock
(fresh’11)
(Ø 10 mm)
Vx = 5 µm
Avizo
fluid flow
simulation
The pore space is further skeletonized. Different
colors refer to different throat size.
Etna

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1 mm
The color slice intersects the velocity field calculated
with XLab Hydro and visualizes the vector field.
Colors give the velocity’s magnitude.
pyroclastic
rock
(fresh’11)
(Ø 10 mm)
Vx = 5 µm
Avizo
fluid flow
simulation
Etna

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Content

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Conclusions
• State of the art high resolution tube based X-ray CT with
the phoenix nanotom m offers
• Comparable (or higher) spatial resolution to SRµCT
setups due to nanofocus tube (ease of use, lower cost
and faster analysis)
• Wide variety of geological samples can be analysed
• Data of a whole 3D volume offers numerous qualitative
AND quantitative interpretations
• New insights in rock materials for geo science

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Outlook
• More quantitative data analysis (like permeability, particle
size distribution, density distribution, …)
• More input from geoscientists to better generate the
potential of nanofocus X-ray CT

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Contact and further information:
www.ge-mcs.com/en/phoenix-xray.html
www.ge-mcs.com/de/phoenix-xray/applications/geology-exploration.html
Gerhard.Zacher@ge.com

Porous rock evaluation with micro ct zacher_ge_copyright

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