Evaluation of rock properties and rock structures in the μ-range with sub-μ X-ray computed...

Evaluation of Rock Properties and Rock Structures in the µ-range with sub-µ X-ray

Computed Tomography

Gerhard Zacher1, Matthias Halisch², Thomas Mayer1

1) GE Sensing & Inspection Technologies, Wunstorf, Germany

²) Leibniz Institute for Applied Geophysics, Hannover, Germany

Avizo Meeting, Bordeaux, May 31, 2012

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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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RequirementsGeometry and Resolution

M=FDD/FOD

U=(M-1)F (on the detector)

Vx=P/M

detector pixel P<< U

F predominates resolution

detector pixel P >> U

Pixel- / Voxelsize predominates resolution


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Resolution and Detail DetectabilityDetail 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 DetectabilityResolution

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 multra-high resolution

nanoCT system

X-ray tube: nanofocus < 800 nm spot size180 kV / 15 W, tube cooling

X-ray detector:Cooled flat panel, 7.4 Mpixel,11 Mpixel virtual detector100 µm pixel size

Manipulator:5 axis stepper motors, granite-based, high-precision air bearing

Nanotom CT / resolution comparison

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Principle of CT

Acquisition

of projections during step-by-steprotation by 360°

Steps < 1°


The acquisition of radiographic data is the elementary measuring process in CT

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Principle of CT: Reconstruction MethodExample: spark plug

back-projectionprojection inversion log + filter lineprofile

Acquisition of 600 projections 600 back projections 3D visualization

nanotom CT / resolution comparison

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nanoCT microCT

Image resolution:

nanoCT: < 1 µm microCT: ≈4 µm

microfocus CT vs.nanofocusCTof a dried fern


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nanofocusCT

of a dried fern

• Example for resolving smallest features≤ 1µm


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Content





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Bentheimersandstone(Ø 5 mm)

Vx = 1 µm

Scan data of geological samples

1 mm

A

BAA

BB

A

B

Bentheimer sandstone

3D volume of CT scan. Quartz (grey), (A) clay (brown), (B) feldspar (blue) and high absorbing minerals (red). Right: pore space is separated (green)

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Vx = 1 µm



Electron microscope images of clay aggregation (left) and highly weathered feldspar (right)

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Vx = 1 µm



1 mm

Comparison of CT result (left) and thin section (right). Histogram shows several peaks for different phases (air, clay (Illite), quartz, feldspar, denser minerals.

feldspar

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Vx = 1 µm

1 mm


Bentheimer sandstoneIncreasing inhomogeneity of samples

Representative?

�� Scaleproblem?

For different sandstones (Bentheimer, Oberkirchenerand Flechtinger) porosity has been evaluated by different methods. Range differs a lot.

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Vx = 1 µm



Mittlere Porosität: ~ 22.5 %Repräsentatives Scan-Volumen: 1000x1000x1000 Voxel

Mittlere Porosität: ~ 7 %Repräsentatives Scan-Volumen: > 1750x1750x1750 Voxel

1 mm

Bentheimer Sandstone Flechtingen Sandstone

Porosity (CT) with respect to volume size for different sandstones

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Vx = 1 µm

Avizofluid flow simulation


Bentheimer sandstoneoutlook

• Further linking CT informationen to rock physik:• inner surface• pore size distribution / NMR

• Preparation of CT data for modelling (pore scale)

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Vx = 1 µm



Bentheimer sandstonevideo

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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

3mm

zoomedarea

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1 mm


Zoom into yz-slice with measurement of thin wall: 1.8 µm

3mm

pyroclastic rock (Ø 1 mm)

Vx = 1 µm

yz-slice

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Etna pyroclastic rock (fresh’11)(Ø 10 mm)

Vx = 5 µm

xy-slice

1 mm


xy-slice through 5x5x5mm cube used later for flow simulation

3mm

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1 mm


3mm

Etna 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.

Etna pyroclastic rock

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1 mm


3mm

Etna pyroclastic rock (fresh’11)(Ø 10 mm)Vx = 5 µm


The colored volume rendering shows the velocity’s magnitude within the pore space. The particle plot shows the actual vector field using cones.


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1 mm


3mm


The pore space is visualized with volume rendering. The matrix’ thickness has been calculated and is visualized on the surface.

Etna pyroclastic rock (fresh’11)(Ø 10 mm)Vx = 5 µm

Avizowall thickness

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1 mm


3mmThe color slice intersects the velocity field calculated with XLab Hydro and visualizes the vector field. Colors give the velocity’s magnitude.

Etna pyroclastic rockEtna pyroclastic rock (fresh’11)(Ø 10 mm)Vx = 5 µm


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3D view of a Nummulite Lower Eocene 53 million years old(Ø 2 mm)

Courtesy of

R. Speijer, K.U.

Leuven, Belgium

Vx = 1 µm

1 mm


Transparent 3D view

3mm

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3D view of a Nummulite Lower Eocene 53 million years old(Ø 2 mm)

Courtesy of

R. Speijer, K.U.

Leuven, Belgium

Vx = 1 µm

1 mm


Sliced 3D view to show the delicate internal structures

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Slice view of a Nummulite Lower Eocene 53 million years old(Ø 2 mm)

Courtesy of

R. Speijer, K.U.

Leuven, Belgium

Vx = 1 µm

1 mm


Xy slice through center plain

zoomedarea

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Slice view of a Nummulite Lower Eocene 53 million years old(Ø 2 mm)

Courtesy of

R. Speijer, K.U.

Leuven, Belgium

Vx = 1 µm

1 mm


Zoomed xy slice through center plain with measured pore 2.3 µm

3mm

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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 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.phoenix-xray.comor

www.ge-mcs.com/phoenix

Evaluation of rock properties and rock structures in the μ-range with sub-μ X-ray computed...

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