e b . t n CT in Geology e g u . Marijn Boone t c - - PowerPoint PPT Presentation
e b . t n CT in Geology e g u . Marijn Boone t c Department Geology and g Soil Science UGCT u . w w w e Overview presentation b . t n History: review papers e g Applications of CT in geology u 3D
Marijn Boone
Department Geology and Soil Science – UGCT
(Conroy & Vannier, 1984 and Haubitz et al., 1988)
– CT for irreplacable fossil samples (non destructive analysis)
Conroy & Vannier, 1984
Haubitz et al., 1988)
– CT for irreplaceable fossil samples (non destructive analysis)
– One of a kind sample: Allende Meteorite
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
Medical CT in multiple fields of geology by early 90s
Medical CT Spatial resolution of 250 µm
– 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
X-ray source Sample X-ray detector
250 µm
Resolution High resolution
samples
s M M d R 1 1
SOD SDD M
R: resolution d: resolution detector M: magnification s: spot size X-ray source
Grey value µ(x,y,z) : local attenuation coefficient Proportional to mass density quartz - clay Strongly depending on atomic number quartz (Si) – zircon (Zr)
DETERMINING THE GRAINS SIZE, SHAPE AND DISTRIBUTION FROM THE 3D IMAGE
Applications in geology
Grain size distribution:
angularity
Original image Segmentation based on grey scale Maximum opening
Original image Segmentation based on grey scale Watershed separation Maximum opening Maximum opening Equivalent diameter = Diameter of sphere with this volume
DETERMINING THE MINERAL DISTRIBUTION IN 3D
Applications in geology
– Multi-energy scanning: density & atomic number
1 10 100 1,000 20 40 60 80 100 120 140 160
Attenuation (cm-1)
keV Linear attenuation coefficient
Quartz Chalcopyrite Malachite Barite
– Multi-energy scanning: density & atomic number – Data fusion: combining different techniques
~ 3.5 mm
2008 Analytical and Bioanalytical Chemistry
– Multi-energy scanning: density & atomic number – Data fusion: combining different techniques
µCT SEM-EDS
2D µXRF mapping
EDAX EAGLE-III µ- probe on the surfaces of the sample Cu Cu S S Ba Ba Si Si Fe Fe
Quartz SiO2 Malachite Cu2CO3(OH)2 Chalcopyrite CuFeS2 Fe-rich ground mass Barite BaSO4
Quartz SiO2 Malachite Cu2CO3(OH)2 Chalcopyrite CuFeS2 Fe-rich ground mass Barite BaSO4
DETERMINING POROSITY AND PORE SIZE DISTRIBUTION
Applications in geology
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
Porosity calculation Labeling different pores according to:
Pore network extraction Pore throats
Oolithic limestone (resolution 5.6µm) Partially filled with water
Oolithic limestone (resolution 5.6µm) Partially filled with water Analyze distribution of water and air in pore structure
Oolithic limestone (resolution 5.6µm)
Oolithic limestone (resolution 5.6µm) 8,5 % air 6,8 % residual water
Importance of water distribution in rock: Frost weathering
Visualize water uptake in building material Preferential uptake along certain zones in the rock
Applications in geology
single phase flow Lattice Boltzmann method Extracting pore network model
Permeability value in Darcy
Computational intensive: Cluster Computer needed for calculation
More than one fluid: Pore Network Modelling
Mineral grains Pore space
Water displaced by non wetting phase
CCS project in Svalbard (Norway) Underground CO2 storage in a geological reservoir
Porosity = 10% Percolating porosity = 9% Permeability = 11 mD
Pore network model from CT
Pumping CO2 into the underground: Water displaced by CO2 (= 87% CO2)
Pumping CO2 into the underground: Water displaced by CO2 (= 87% CO2) Stop CO2 injection and return water: CO2 displaced by water (= 60% CO2 trapped)
Future Challenges
High resolution = small sample
scan representative for an entire rock or core?
5 mm
Representative ?
Carbonate reservoirs:
Complex texture Very heterogeneous concerning porosity
AAPG, 77
Interparticular & Intraparticular porosity Moldic porosity Intercrystal porosity Fractures Vuggy porosity
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
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)
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)
Future Challenges
Underground CO2 storage in a geological reservoir
CO2 injection Dissolution in the reservoir fluid pH drop Chemical imbalance in reservoir rock
Scan resolution: 5,6 µm
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
Begin After 94 hours After 38 hours Changes in porosity through time:
Changes in porosity through time:
10.00% 15.00% 20.00% 25.00% 30.00% 35.00% 40.00% 45.00% 50.00%
porosity
t0 t38 10.00% 15.00% 20.00% 25.00% 30.00% 35.00% 40.00% 45.00% 50.00%
porosity
t0 t38 t94
Future Challenges
Looking at rock behaviour when exposed to external conditions
development
Specialized add-on modules or cells are needed on the micro-CT setup
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
detail Artificial rock Mixture of quartz (grey) and olivine (green) (porosity 25%)
fluid displacement – residual water (blue) 7.5%
residual water CO2 @ 50 bar
Marijn Boone
Department Geology and Soil Science – UGCT
www.ugct.ugent.be Marijn.boone@ugent.be