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 andFrank 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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FundamentalsGeometry and Resolution

Advantage of nanofocus tube:resolution & Penumbra effect

Focal spot size:microfocus: F = 3 µmnanofocus: F = 0.6 µm

M=FDD/FOD ; Vx=P/M


mikrofocus nanofocuslimiting factor for image resolution = Fdetail detectability about 1/3 F


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Resolution and Detail DetectabilityDetail detectability of the nanofocus tube

Conclusion:detail detectabilityis no measurefor 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 resolutionnanoCT 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


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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 CTAcquisition

movie

nanotom CT

Sample rotation + acquisition imagesCopyright General Electric 2014

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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


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resolution comparison

1 mm

Improved sharpness (+80%) & increased CNR (+100%) due to diamondwindow 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 diamondwindow 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 petrophysicalanalysis

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

BAA

BB

A

B

Bentheimer sandstone

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


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


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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Scan data of geological samplesBentheimer sandstoneDigital Rock Evaluation

segmentation percolation testconnectivity test


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Scan data of geological samplesBentheimer sandstoneDigital Rock Evaluation

quantitative evaluationskeletonization


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Vx = 1 µm

Avizofluid flow simulation


videoBentheimer sandstoneDigital Rock Evaluation


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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

zoomedarea

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


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



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 µmAvizofluid 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 µmAvizofluid 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

[email protected]

Documents

Porous rock evaluation with micro ct zacher_ge_copyright