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

2 /GE /

Content

1. Introduction & Fundamentals

2. nanotom CT / resolution comparison

3. Scan results for geological samples

4. Conclusion & Outlook

3 /GE /

X-ray tubes Microfocus - nanofocus

Introduction & Fundamentals

4 /GE /

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

Introduction & Fundamentals

5 /GE /

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

Introduction & Fundamentals

6 /GE /

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

Introduction & Fundamentals

7 /GE /

Content

1. Introduction & Fundamentals

2. nanotom CT / resolution comparison

3. Scan results for geological samples

4. Conclusion & Outlook

8 /GE /

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

9 /GE /

Principle of CT

Acquisition

of projections during step-by-steprotation by 360°

Steps < 1°

Nanotom CT / resolution comparison

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

10 /GE /

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

11 /GE /

nanoCT microCT

Image resolution:

nanoCT: < 1 µm microCT: ≈4 µm

microfocus CT vs.nanofocusCTof a dried fern

Nanotom CT / resolution comparison

12 /GE /

nanofocusCT

of a dried fern

• Example for resolving smallest features≤ 1µm

Nanotom CT / resolution comparison

13 /GE /

Content

1. Introduction & Fundamentals

2. nanotom CT / resolution comparison

3. Scan results for geological samples

4. Conclusion & Outlook

14 /GE /

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)

15 /GE /

Bentheimersandstone(Ø 5 mm)

Vx = 1 µm

Scan data of geological samples

Bentheimer sandstone

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

16 /GE /

Bentheimersandstone(Ø 5 mm)

Vx = 1 µm

Scan data of geological samples

Bentheimer sandstone

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

17 /GE /

Bentheimersandstone(Ø 5 mm)

Vx = 1 µm

1 mm

Scan data of geological samples

Bentheimer sandstoneIncreasing inhomogeneity of samples

Representative?

���� Scaleproblem?

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

18 /GE /

Bentheimersandstone(Ø 5 mm)

Vx = 1 µm

Scan data of geological samples

Bentheimer sandstone

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

19 /GE /

Bentheimersandstone(Ø 5 mm)

Vx = 1 µm

Avizofluid flow simulation

Scan data of geological samples

Bentheimer sandstoneoutlook

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

• Preparation of CT data for modelling (pore scale)

20 /GE /

Bentheimersandstone(Ø 5 mm)

Vx = 1 µm

Avizofluid flow simulation

Scan data of geological samples

Bentheimer sandstonevideo

21 /GE /

pyroclastic rock (Ø 1 mm)

Vx = 1 µm

yz-slice

1 mm

Scan data of geological samples

yz-slice with different grains with high porosity or fractures and bigger pores

3mm

zoomedarea

22 /GE /

1 mm

Scan data of geological samples

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

3mm

pyroclastic rock (Ø 1 mm)

Vx = 1 µm

yz-slice

23 /GE /

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

Vx = 5 µm

xy-slice

1 mm

Scan data of geological samples

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

3mm

24 /GE /

1 mm

Scan data of geological samples

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

25 /GE /

1 mm

Scan data of geological samples

3mm

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

Avizofluid flow simulation

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

Etna pyroclastic rock

26 /GE /

1 mm

Scan data of geological samples

3mm

Etna pyroclastic rock

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

27 /GE /

1 mm

Scan data of geological samples

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

Avizofluid flow simulation

28 /GE /

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

Scan data of geological samples

Transparent 3D view

3mm

29 /GE /

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

Scan data of geological samples

Sliced 3D view to show the delicate internal structures

30 /GE /

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

Scan data of geological samples

Xy slice through center plain

zoomedarea

31 /GE /

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

Scan data of geological samples

Zoomed xy slice through center plain with measured pore 2.3 µm

3mm

32 /GE /

Content

1. Introduction & Fundamentals

2. nanotom CT / resolution comparison

3. Scan results for geological samples

4. Conclusion & Outlook

33 /GE /

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

34 /GE /

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

35 /GE /

Contact and further information:

www.phoenix-xray.comor

www.ge-mcs.com/phoenix