CT in Geology

Marijn Boone Department Geology and Soil Science – UGCT

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Overview presentation

• History: review papers

• Applications of CT in geology

• 3D grain analysis

• 3D petrography

• Pore analysis

• Fluid flow analysis

• Future innovations

• REV - multiscale

• Dynamic imaging

• In situ scanning

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First Geological applications

• Paleontology

(Conroy & Vannier, 1984 and Haubitz et al., 1988)

– CT for irreplacable fossil samples (non destructive analysis)

Conroy & Vannier, 1984

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First Geological applications

• Paleontology (Conroy & Vannier, 1984 and Haubitz et al., 1988)

– CT for irreplaceable fossil samples (non destructive analysis)

• Meteorites (Arnold et al., 1982)

– One of a kind sample: Allende Meteorite

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First Geological applications

• Petroleum engineering (Wellington and Vinegar, 1987 and WithJack, 1988)

2 phase fluid flow experiments on cores (high temporal resolution)

After Wellington and Vinegar, 1987 After Wellington and Vinegar, 1987

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First Geological applications

Medical CT in multiple fields of geology by early 90s - Porosity of soils

- Sediment morphology in cores

- Faulting in rocks

- …

Medical CT Spatial resolution of 250 µm

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First Geological applications

• End of the 90s: higher resolution

– shape and size of individual pores, minerals, grains and factures

– Mainly synchrotron facilities (cost and availability)

– Around 2000: lab based micro-CT systems in geology

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X-ray source Sample

X-ray detector

First Geological applications

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First Geological applications

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First Geological applications

2D 3D www.ugct.

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First Geological applications

2D 3D www.ugct.

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First Geological applications

250 µm

Resolution High resolution only for small samples

sMM

dR

11

SOD

SDDM

R: resolution d: resolution detector M: magnification s: spot size X-ray source

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First Geological applications

Grey value µ(x,y,z) : local attenuation coefficient Proportional to mass density quartz - clay Strongly depending on atomic number quartz (Si) – zircon (Zr) www.ug

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GRAIN SIZE ANALYSIS: DETERMINING THE GRAINS SIZE, SHAPE AND DISTRIBUTION FROM THE 3D IMAGE

Applications in geology

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Applications: grain size analysis

Grain size distribution: - Sieving

- Measuring on thin section

- Sorting

- Determine shape and angularity

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Applications: grain size analysis Original image Segmentation based on grey scale

Maximum opening

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Applications: grain size analysis Original image Segmentation based on grey scale

Watershed separation Maximum opening

Maximum opening

Equivalent diameter = Diameter of sphere with this volume

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Applications: grain size analysis

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3D PETROGRAPHY: DETERMINING THE MINERAL DISTRIBUTION IN 3D

Applications in geology

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Applications: 3D petrography

• X-ray CT: no direct chemical information

– Multi-energy scanning: density & atomic number

• Synchrotron: mono-energetic

• Lab based microCT : poly energetic (challenging)

0

1

10

100

1,000

0 20 40 60 80 100 120 140 160

Att

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-1)

keV

Linear attenuation coefficient Quartz

Chalcopyrite

Malachite

Barite

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Applications: 3D petrography

• X-ray CT: chemical information

– Multi-energy scanning: density & atomic number

– Data fusion: combining different techniques

• XRF (synchrotron & lab system)

~ 3.5 mm

B. De Samber et al, 2008 Analytical and Bioanalytical Chemistry www.ug

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Applications: 3D petrography

• X-ray CT: chemical information

– Multi-energy scanning: density & atomic number

– Data fusion: combining different techniques

• XRF (synchrotron & lab system)

• SEM(SEM-EDS)

µCT SEM-EDS

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Applications: 3D petrography

2D µXRF mapping EDAX EAGLE-III µ-probe on the surfaces of the sample

Cu

Cu

S

S

Ba

Ba

Si

Si

Fe

Fe

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Applications: 3D petrography

Quartz SiO2

Malachite Cu2CO3(OH)2

Chalcopyrite CuFeS2

Fe-rich ground mass

Barite BaSO4 www.ugct.

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Applications: 3D petrography

Quartz SiO2

Malachite Cu2CO3(OH)2

Chalcopyrite CuFeS2

Fe-rich ground mass

Barite BaSO4 www.ugct.

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3D PORE CHARACTERIZATION: DETERMINING POROSITY AND PORE SIZE DISTRIBUTION

Applications in geology

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Applications: 3D pore characterization

Before CT: 3D pore structures based on 2D thin sections or SEM images

µCT & image analysis: visualize and analyze complex pore structure and its connectivity

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Porosity calculation Labeling different pores according to: - size - orientation - surface - … Pore network extraction Pore throats

Applications: 3D pore characterization

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Applications: 3D pore characterization Oolithic limestone (resolution 5.6µm) Partially filled with water

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Applications: 3D pore characterization Oolithic limestone (resolution 5.6µm) Partially filled with water

Analyze distribution of water and air in pore structure

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Applications: 3D pore characterization Oolithic limestone (resolution 5.6µm)

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Applications: 3D pore characterization Oolithic limestone (resolution 5.6µm)

8,5 % air 6,8 % residual water www.ugct.

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Applications: 3D pore characterization

Importance of water distribution in rock: Frost weathering

Visualize water uptake in building material Preferential uptake along certain zones in the rock

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Applications: 3D pore characterization

Frost weathering

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FLUID FLOW ANALYSIS: MODELLING FLUID FLOW THROUGH THE PORES

Applications in geology

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Fluid flow analysis

single phase flow Lattice Boltzmann

method

Extracting pore network model

Permeability value in Darcy

Computational intensive: Cluster Computer needed for calculation

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Fluid flow analysis

More than one fluid:

Pore Network Modelling Mineral grains

Pore space

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Fluid flow analysis

Water displaced by non wetting phase

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Fluid flow analysis

CCS project in Svalbard (Norway) Underground CO2 storage in a geological reservoir

Porosity = 10% Percolating porosity = 9% Permeability = 11 mD www.ugct.

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Fluid flow analysis

Pore network model from CT Pumping CO2 into the underground: Water displaced by CO2 (= 87% CO2)

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Fluid flow analysis

Pumping CO2 into the underground: Water displaced by CO2 (= 87% CO2)

Stop CO2 injection and return water: CO2 displaced by water (= 60% CO2 trapped)

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REV: REPRESENTATIVE ELEMENTARY VOLUME AND UPSCALING

Future Challenges

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REV and upscaling

High resolution

= small sample

scan representative for an entire rock or core?

or even for a quarry or reservoir?

5 mm

Representative ? www.ugct.

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REV and upscaling Carbonate reservoirs:

Complex texture Very heterogeneous concerning porosity

AAPG, 77

Interparticular & Intraparticular porosity

Moldic porosity

Intercrystal porosity

Fractures

Vuggy porosity

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REV and upscaling Upscaling

Combining information from different sample sizes and resolutions to capture all the different porosity types

Larger core – medical CT (500 µm³) Subsample – micro CT (12 µm³)

Capture large vugs and fractures www.ugct.

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REV and upscaling Upscaling

Combining information from different sample sizes and resolutions to capture all the different porosity types

Subsample – micro CT (12 µm³)

Capture Inter-, Intraparticular and moldic porosity

microplug – micro CT (4 µm³)

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REV and upscaling Upscaling

Combining information from different sample sizes and resolutions to capture all the different porosity types

Capture micro porosity

microplug – micro CT (4 µm³) SEM imaging (nm)

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DYNAMIC IMAGING: FOLLOWING A PROCESS THROUGH TIME

Future Challenges

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Dynamic Imaging

Underground CO2 storage in a geological reservoir

CO2 injection Dissolution in the reservoir fluid pH drop Chemical imbalance in reservoir rock oolithic limestone sample of 5 mm diameter

Scan resolution: 5,6 µm

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Dynamic Imaging

First tests: Simulating a flow of CO2 saturated flow in the underground HCl solution with a pH 3 Flow speed: 30 cm³/h Exposed for a period of 94 hours www.ug

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Dynamic Imaging

Begin After 94 hours After 38 hours

Changes in porosity through time: -Dissolution -Transport of loose grains through the pore network

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Dynamic Imaging

Changes in porosity through time: -Dissolution -Transport of loose grains through the pore network

10.00%

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t94

38 hours 94 hours

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Future: Dynamic Imaging

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IN-SITU ANALYSIS: FOLLOWING A PROCESS UNDER EXTERNAL CONDITIONS

Future Challenges

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In-situ analysis

Looking at rock behaviour when exposed to external conditions - Water uptake and displacement of fluids - Cooling and heating of the sample - Climatic control - Uniaxial/triaxial pressure tests and fracture

development

Specialized add-on modules or cells are needed on the micro-CT setup www.ug

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In-situ analysis

A custom designed pressure cell for the High resolution X-ray computed tomography (HRXCT) setup at the UGCT Pressures up to 120 bar Temperatures up to 70 °C

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Future: In-situ analysis

detail

Artificial rock Mixture of quartz (grey) and olivine (green) (porosity 25%) - Full saturation with water (enriched in CsCl)

- Addition of CO2 under 50 bar of pressure fluid displacement – residual water (blue) 7.5% - Dissolution/precipitation are limited to zones with residual water

CO2 @ 50 bar

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Thank you Marijn Boone Department Geology and Soil Science – UGCT www.ugct.ugent.be

Marijn.boone@ugent.be

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