Applications of X-ray Computed Tomography in the Geosciences (Geological Society Special Publication) (No. 215)

X-ray computed tomography (CT) is a technique that allows non-destructive imaging and quantification of internal features of objects. It was originally developed as a medical imaging technique, but it is now also becoming widely used for the study of materials in engineering and the geosciences. X-ray CT reveals differences in density and atomic composition and can therefore be used for the study of porosity, the relative distribution of contrasting solid phases and the penetration of injected solutions. As a non-destructive technique, it is ideally suited for monitoring of processes, such as the movement of solutions and the behaviour of materials under compression. Because large numbers of parallel two-dimensional cross-sections can be obtained, three-dimensional representations of selected features can be created. In this book, various applications of X-ray CT in the geosciences are illustrated by papers covering a wide range of disciplines, including petrology, soil science, petroleum geology, geomechanics and sedimentology. Also available: Mapping Hazardous Terrain using Remote Sensing - Special Publication no 283 - ISBN 1862392293 Contents......Page 6 Applications of X-ray computed tomography in the geosciences......Page 8 Table 1. General classification of X-ray computed tomography......Page 14 Fig. 1. Isosurface image of garnet (rendered violet) and staurolite (rendered yellow-brown) .........Page 16 Fig. 3. Three-dimensional reconstruction from X-ray CT data of a 15mm cube .........Page 17 Fig. 5. (a) Three-dimensional reconstruction from X-ray CT data of a 1 cm .........Page 18 Fig. 6. Three-dimensional reconstruction from X-ray CT data of porosity dominated by .........Page 19 Fig. 7. (a) Perspective view of X-ray CT images of lodranite meteorite GRA95209 .........Page 20 Fig. 9. Three-dimensional representation of shapes, sizes and positions of metal-troilite particles......Page 21 Fig. 11. (a) Three-dimensional volumetric reconstruction from X-ray CT data of the skull .........Page 22 Fig. 12. (a) Co-evolution of the mammalian mandible and middle ear (in right .........Page 23 Fig. 14. Three-dimensional volumetric rendering from X-ray CT data of the embryonic .........Page 24 Fig. 15. Two computer-generated models of the face of the Archaeoraptor slab .........Page 25 Fig. 18. High-resolution X-ray CT image of the coral Diploria strigosa (edge .........Page 26 Fig. 19. X-ray CT images of trabecular bone of the femoral head .........Page 27 Computed tomography in petroleum engineering research......Page 30 Table 1. CT numbers for common materials......Page 32 Fig. 2. Example of an X-artefact in scanning a homogeneous diatomite core. .........Page 33 Fig. 3. Scans of an imbibition cell that allows imaging of the .........Page 34 Fig. 4. Scans of a carbonate core at 1 cm spacing. Dark .........Page 37 Fig. 5. CT-derived water saturation (S[sub(w)]) images of spontaneous imbibition in diatonaite, .........Page 38 Fig. 6. 3D reconstruction of water saturation in a sandpack undergoing hot-water .........Page 39 Study of the microgeometry of porous materials using synchrotron computed microtomography......Page 46 Fig. 1. X-ray brilliance produced at the Brookhaven National Synchrotron Light Source .........Page 47 Fig. 2. Schematic diagram of the major components in the SCMT apparatus .........Page 48 Fig. 3. A SCMT volume of sandy sediments from the New York/New .........Page 49 Fig. 4. Distribution of elements found in a single grain of sediment .........Page 50 Table 1. Average porosities ε and correlation lengths L[sub(x)], L[sub(y)] and L[sub(z)] .........Page 51 Fig. 8. SCMT sections taken through samples of Darley Dale sandstone in .........Page 52 Fig. 9. Sections through Berea sandstone in its natural state (top) and .........Page 54 Fig. 11. CT image obtained at the APS showing the Wood's metal .........Page 55 Porosity measurements of sedimentary rocks by means of microfocus X-ray computed tomography (μCT)......Page 58 Fig. 1. Plots of the total linear attenuation coefficient of calcite and .........Page 59 Fig. 2. Macroscopic view of a turbiditic carbonate sample used to compare .........Page 60 Fig. 3. Evaluation of porosity measurements by μCT and classical reflected light .........Page 61 Fig. 5. 3D visualization of the distribution of macroporosity for a turbiditic .........Page 62 Fig. 6. 3D visualization of heterogeneous Westphalian sandstone samples (8 mm in .........Page 63 Fig. 8. Results of mean porosity measurements of sequential slices by μCT .........Page 64 Table 1. Comparison of the results of different porosity measurements (in %) .........Page 65 Quantitative characterizations of fracture apertures using microfocus computed tomography......Page 68 Fig. 2. Convolution of a rectangular profile (fracture) with a PSF, resulting .........Page 69 Fig. 3. Fit of Gaussian and sine function through the fracture attenuation .........Page 70 Fig. 5. Comparison between the performance of PH and MA calculated from .........Page 71 Fig. 6. Coefficient of variation versus fracture aperture for peak height and .........Page 72 Fig. 8. Segment of the fractured sample as determined using microfocus X-ray .........Page 73 Fig. 9. Apertures determined by optical microscopy compared to those determined by .........Page 74 Three-dimensional visualization of fractures in rock test samples, simulating deep level mining excavations, using X-ray computed tomography......Page 76 Fig. 1. (a) Schematic plan view of a South African longwall gold mining .........Page 77 Fig. 2. Cubic sample with mine layout tested in a poly-axial cell .........Page 79 Fig. 4. Fractures observed within a tested Elsburg quartzite sample having a .........Page 80 Fig. 6. CT scans of rock sample showing how the fracture traces .........Page 82 Fig. 9. Three-dimensional reconstruction of the fracture pattern in a Marble Bar .........Page 83 Fig 10. Combination of automatic and manual delineation methods for reconstructing three-dimensional .........Page 84 Fig 11. Example of numerical prediction of the fracture pattern in the .........Page 85 Geostatistics and the representative elementary volume of gamma ray tomography attenuation in rock cores......Page 88 Fig. 1. Orientation of the cores.......Page 91 Table 1. Attenuation statistics of samples......Page 92 Table 2. Component content by percent volume in samples......Page 93 Fig. 4. Computer tomography images and semivariograms of (a) core C1AV and (b) core C2AV.......Page 94 Fig. 5. Semivariograms of computer tomography images for core C2AV with different .........Page 97 Fig. 6. Voxel volume versus range for core C2AV.......Page 99 Table 4. Anisotropy of samples......Page 95 Table 5. Parameters of standardized semivariograms for core C2AV using different aggregations .........Page 98 Porosity and fluid flow characterization of granite by capillary wetting using X-ray computed tomography......Page 102 Fig. 1. Radiological density of minerals occurring in granite, inferred using Eq. 2 .........Page 103 Fig. 3. 3D images of the mineral content. The three sets of .........Page 104 Fig. 4. Radiological density variation induced by different fluids saturating the porosity. .........Page 105 Fig. 5. Radiological density profiles along the core sample. Profiles are built .........Page 107 Fig. 7. (a) Mineral network in section 1 with two K-feldspar phenocrystals, and .........Page 108 Table 1. Capillary parameters inferred from radiological measurements for the different studied volumes......Page 109 Fig. 9. Capillary curves for section 1 and mineral zones D1 to .........Page 110 Fig. 10. Fluid location after 142 and 172 minutes, illustrated by 3D .........Page 111 Direct imaging of fluid flow in fault-related rocks by X-ray CT......Page 114 Fig. 1. Experimental arrangement of the medical X-ray CT scanner W2000.......Page 115 Fig. 2. (a) Schematic diagram of the permeameter cell, (b) Photo image of .........Page 116 Fig. 3. Calibration of CT numbers under different conditions: black symbols – 120kV, .........Page 117 Fig. 4. Photo images of the examined fault-related rocks, (a) IPF-F; (b) CF-P; (c) CF-V.......Page 118 Table 2. Intrinsic permeabilities and compensated permeabilities for the used KI solution......Page 119 Fig. 6. Three-dimensional flow image of sample IPF-P, 150 minutes after initiation .........Page 120 Fig. 7. (a) Converted 8-bit CT image of sample CF-P at the initial .........Page 121 Rock drying tests monitored by X-ray computed tomography – the effect of saturation methods on drying behaviour......Page 124 Fig. 2. Capillary absorption: by-pass of the macropores and trapping of air.......Page 125 Fig. 3. Standard drying kinetic of a porous medium. dW=weight variation; .........Page 126 Fig. 4. CT images of the Fontainebleau sandstone sample Ftx2a2. 1 to 36: .........Page 127 Fig. 5. CT aquisitions plotted on drying curves obtained after total saturation .........Page 128 Fig. 6. RD profile of the dry matrix (RD matrix) and ARD .........Page 129 Fig. 7. (a) Profiles of the mean saturation for each cross-section at the .........Page 130 Fig. 8. (a) Profiles of the mean saturations for each cross-section at the .........Page 131 Characterization by X-ray computed tomography of water absorption in a limestone used as building stone in the Oviedo Cathedral (Spain)......Page 134 Fig. 2. Mercury porosimetry curves showing differences in pore radius between the .........Page 135 Fig. 5. CT image of the vertical central plane of the sample .........Page 136 Fig. 6. Evolution over time during the free absorption test of the .........Page 137 Fig. 8. Scanning electron microscopy images of two adjacent areas (Bl and .........Page 138 Table 1. Evolution of CT numbers (Hounsfield Units) of some ROI's during the absorption test......Page 139 Fig. 10. Evolution of the mean CT number (in Hounsfield Units) for .........Page 140 Estimation of porosity and hydraulic conductivity from X-ray CT-measured solute breakthrough......Page 142 Fig. 1. Schematic of soil column assembly used to saturate and conduct .........Page 144 Fig. 3. Relative solute concentration (C*) versus cumulative outflow measured using CT .........Page 148 Table 2. Average porosity for undisturbed soil cores determined using CT-measured solute breakthrough methods......Page 149 Fig. 5. Frequency distributions of CT-measured solute velocity for Core #3: (a) velocity .........Page 150 Table 4. Average hydraulic conductivity for undisturbed soil cores determined using CT-measured solute breakthrough methods......Page 152 Table 5. Calculated dispersivities and retardation coefficients as a function of scan .........Page 153 Fig. 8. Relative concentration (C*) of chlorophenol versus cumulative outflow for both .........Page 154 Table 1. Physical properties of undisturbed soil cores determined on a bulk core basis......Page 143 Assessment of solid structure using X-ray computed tomography......Page 158 Fig. 1. Scheme of the computationally inscribed largest possible reference cube in .........Page 162 Fig. 2. Scheme of the measurement of Hounsfield Unit values around an .........Page 163 Table 4. Unsaturated hydraulic conductivity (K) of the soils and horizons investigated, .........Page 165 Fig. 6. Pseudo-3D visualization of macropores (left), dry bulk density and standard .........Page 166 Fig. 7. Pseudo-SD visualization of macropores (left), dry bulk density and standard .........Page 167 Fig. 9. Dry bulk density and standard deviation distribution for horizontal slices .........Page 168 Table 5. Gravimetric water content near earthworm burrow, site F......Page 169 Table 1. Sampling sites......Page 160 Table 2. Properties of soils and horizons investigated......Page 161 Table 3. Circle areas, diameters, mean Hounsfield Unit values and mean dry .........Page 164 3D soil image characterization applied to hydraulic properties computation......Page 174 Fig. 3. Seed map: maximum balls (or seeds) have been set in .........Page 176 Fig. 5. Construction of a link c[sub(1)]c[sub(2)] in the network from two .........Page 177 Fig. 6. (a) 2D original image – black represents solid space and white .........Page 179 Fig. 7. (a) 3D soil image – grey represents the void space; (b) .........Page 180 Evaluation of local porosity changes in limestone samples under triaxial stress field by using X-ray computed tomography......Page 184 Fig. 1. Schematic representation of the X-ray-transparent triaxial cell.......Page 186 Fig. 3. Normalized porosity change as a function of hydrostatic pressure in .........Page 188 Fig. 5. Stress–strain diagram and X-ray radiographs of ductile failure of limestone, .........Page 189 Fig. 6. Porosity evolution as a function of differential stress and images .........Page 191 Fig. 8. Porosity evolution as a function of differential stress in the .........Page 192 Fig. 9. Porosity change as a function of differential stress and CT .........Page 193 Fig. 11. Permeability change during ductile failure.......Page 194 Monitoring void ratio redistribution during continuous undrained triaxial compression by X-ray computed tomography......Page 198 Fig. 1. Triaxial apparatus on CT scanner bed.......Page 200 Fig. 4. Relationship between attenuation and sample diameter.......Page 201 Fig. 5. Variation in slice void ratio with axial strain level.......Page 202 Fig. 6. Void ratio redistribution along the stress path.......Page 203 Fig. 1. Indicative two-dimensional particulate soil model.......Page 206 Fig. 2. Modified Rowe cell (not to scale).......Page 207 Fig. 4. Cross-sectional image of approximately the same section (a) before and .........Page 209 Fig. 5. Longitudinal sectional images reconstructed from axial scans.......Page 210 Industrial X-ray computed tomography studies of lake sediment drill cores......Page 212 Fig. 1. Examples of the use of grey-scale values for qualitative investigations .........Page 213 Fig. 2. Three CT images, up to 5 cm apart, showing angular .........Page 214 Fig. 3. Photograph (left), X-ray radiograph (centre) and representative CT images (right) .........Page 215 Fig. 4. 3D visualization of a 5 cm high section of the .........Page 216 Fig. 5. Density profile of an approximately 9 cm long core section .........Page 218 Analysis of analogue models by helical X-ray computed tomography......Page 220 Fig. 1. Experimental modelling of mountain-building processes by Cadell (1890), who shortened .........Page 221 Fig. 2. (a) Helical X-ray CT scanner and experimental apparatus. During rotation of .........Page 222 Fig. 3. Initial experimental set-up for testing the influence of basal rheological .........Page 224 Fig. 4. Comparison of structural evolution between brittle and brittle-viscous domains for .........Page 225 Fig. 6. Two three-dimensional views of an analogue model at 6 cm shortening. .........Page 226 Fig. 8. Vertical sections through the brittle-viscous multilayer model at 2 cm extension, .........Page 227 Fig. 10. Horizontal section through a 3D view of the analogue model .........Page 228 Table 1. Material parameters and distributors of analogue materials......Page 223 Preliminary microfocus X-ray computed tomography survey of echinoid fossil microstructure......Page 232 Fig. 1. Geometry of the Aristotle's lantern and portions of the test .........Page 233 Fig. 2. Slices of two different fossil spines (a and b); the .........Page 235 Fig. 3. Three slices through a cidaroid spine showing a complex 'tidemark' .........Page 236 Fig. 4. Two Slices through a fossil pyramid, separated by 0.95 mm .........Page 237 Fig. 6. Five slices through the plate fragment. The horizontal field of .........Page 238 Fig. 7. Three-dimensional rendering of the volume of the plate shown in Figure 6.......Page 239 E......Page 244 L......Page 245 O......Page 246 P......Page 247 S......Page 248 X......Page 249

x-ray Computed Tomography (ct) Is A Technique That Allows Non-destructive Imaging And Quantification Of Internal Features Of Objects. It Was Originally Developed As A Medical Imaging Technique, But It Is Now Also Becoming Widely Used For The Study Of Materials In Engineering And The Geosciences. X-ray Ct Reveals Differences In Density And Atomic Composition And Can Therefore Be Used For The Study Of Porosity, The Relative Distribution Of Contrasting Solid Phases And The Penetration Of Injected Solutions. As A Non-destructive Technique, It Is Ideally Suited For Monitoring Of Processes, Such As The Movement Of Solutions And The Behaviour Of Materials Under Compression. Because Large Numbers Of Parallel Two-dimensional Cross-sections Can Be Obtained, Three-dimensional Representations Of Selected Features Can Be Created. In This Book, Various Applications Of X-ray Ct In The Geosciences Are Illustrated By Papers Covering A Wide Range Of Disciplines, Including Petrology, Soil Science, Petroleum Geology, Geomechanics And Sedimentology.