Post on 10-Jul-2020
CT in Geology
Marijn Boone Department Geology and Soil Science – UGCT
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t.be
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
en
uat
ion
(cm
-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%
15.00%
20.00%
25.00%
30.00%
35.00%
40.00%
45.00%
50.00%
po
rosi
ty t0
t38
10.00%
15.00%
20.00%
25.00%
30.00%
35.00%
40.00%
45.00%
50.00%
po
rosi
ty t0
t38
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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