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$Drilling-induced tensile wall-fractures - Stanford University$

List of Illustrations Figure A. Cover photo from AAPG Bulletin (publication of Chapter 6)..........................xii Figure 1.1. Location and general geology of study area...................................................12 Figure 1.2. Generalized stratigraphic column...................................................................14 Figure 1.3. Schematized fault map for Lake Mead region................................................17 Figure 1.4. Photo collage of compaction bands in the Aztec sandstone...........................20 Figure 1.5. Schematic of anticrack conceptual model......................................................23 Figure 1.6. Collection of orientation data in the field.......................................................25 Figure 1.7. Located orientation data from Valley of Fire.................................................26 Figure 1.8. Orientation data for outcrops with multiple compaction band sets................27 Figure 1.9. Stereographs for combined orientation data...................................................29 Figure 1.10. Stereographs for restored orientation data....................................................32 Figure 1.11. Paleostress orientations and interpretation...................................................36 Figure 2.1. Location of the Valley of Fire State Park, Nevada.........................................41 Figure 2.2. Compaction bands (CBs) in outcrop near Silica Dome..................................43 Figure 2.3. Typical CB fin in outcrop...............................................................................48 Figure 2.4. Compaction band thickness profile data.........................................................49 Figure 2.5. Composite photomicrograph of a CB.............................................................51 Figure 2.6. Porosity profiles across a CB..........................................................................52 Figure 2.7. Backscatter electron images of sandstone and a CB......................................53 Figure 2.8. Distribution of porosity inside a CB...............................................................55 Figure 2.9. Backscatter electron images of grain damage in a CB...................................56 Figure 2.10. Backscatter electron image of incipient CB.................................................55 Figure 2.11. Schematic representations of idealized CB model.......................................58 Figure 2.12. Near-tip stress components for the embedded layer model..........................65 Figure 2.13. Stress distributions for the Eshelby inclusion model....................................66 Figure 2.14. Stress comparison of Eshelby and anticrack models....................................69 Figure 2.15. Near-tip stress comparison of Eshelby and anticrack models......................70 Figure 2.16. Mean normal stress distribution around an anticrack tip..............................70 Figure 3.1. Anatomy of a compaction band in the Aztec sandstone.................................76 Figure 3.2. Model of a semi-infinite CB embedded in an infinite layer...........................79 Figure 3.3. Outcrop basis for the embedded layer CB model...........................................79 Figure 3.4. Hypothetical 1-D distribution of stress near a CB tip....................................84 Figure 4.1. Location of the Valley of Fire State Park, Nevada.........................................87 Figure 4.2. Array of subparallel CBs in the Aztec sandstone...........................................87 Figure 4.3. Typical compaction band patterns exposed in outcrop..................................90 Figure 4.4. Mechanical interaction between CBs and æolian bedding.............................91 Figure 4.5. Tip-to-tip thickness profile of a 25-m-long CB..............................................91 Figure 4.6. Various CB propagation behaviors observed in outcrop................................93 Figure 4.7. Examples of tip-to-tip interactions observed in outcrop................................94 Figure 4.8. Composite photomicrograph of CB anatomy.................................................95 Figure 4.9. Schematic representations of the idealized CB model...................................97 Figure 4.10. Schematic of the global and anticrack tip coordinate systems.....................99 Figure 4.11. Contour plots of near tip stress around an anticrack..................................100 Figure 4.12. Polar near-tip stress as a function of θ for a fixed radius...........................102 Figure 4.13. Effect of differential stress on propagation path stability...........................102 x
Figure 4.14. Mechanical interactions between anticrack tips.........................................105 Figure 4.15. Essential schematic of displacement discontinuity BEM...........................105 Figure 4.16. Stiffness dependence of closing-mode displacement discontinuity...........109 Figure 4.17. Near-tip stress comparison of Eshelby and anticrack models....................109 Figure 4.18. Propagation path stability as a function of scale and remote stress............111 Figure 4.19. Scale and remote stress dependence of propagation path stability.............111 Figure 4.20. Element length and stress dependence of propagation path stability.........113 Figure 4.21a. Remote stress and spacing effects on CB tip interactions........................116 Figure 4.21b. Remote stress and spacing effects on CB tip interactions........................117 Figure 4.21c. Remote stress and spacing effects on CB tip interactions........................118 Figure 4.22. Influence of a CB length on approaching tip interactions..........................119 Figure 4.23. Conceptual model of strain and grain damage around a CB......................122 Figure 4.24. Relationship of a CB array to permeability and paleostress.......................124 Figure 5.1. Location of the Valley of Fire State Park, Nevada.......................................126 Figure 5.2. Typical CB in outcrop and its effect on fluid flow.......................................128 Figure 5.3. Representative outcrop array of subparallel, anastomosing CBs.................129 Figure 5.4. Composite photomicrograph of a representative CB...................................132 Figure 5.5. Permeability estimation methodology workflow.........................................133 Figure 5.6. Backscatter electron images of sandstone and CBs......................................135 Figure 5.7. Porosity-permeability estimates versus measured values.............................136 Figure 5.8. Computational estimation of permeability anisotropy.................................138 Figure 6.1. Location of the Valley of Fire State Park, Nevada.......................................144 Figure 6.2. Compactive deformation bands in the Aztec sandstone...............................145 Figure 6.3. Typical outcrop pattern of subparallel compactive DBs..............................149 Figure 6.4. Typical cross-hatch pattern of compactive DBs...........................................149 Figure 6.5. Typical anastomosing pattern of compactive DBs.......................................151 Figure 6.6. Idealized band pattern and model grid representation..................................153 Figure 6.7. Schematic representations of band pattern upscaling...................................153 Figure 6.8. Key parameters for computing effective block permeability.......................156 Figure 6.9. Effective permeability for perfectly parallel band patterns..........................159 Figure 6.10. Effective permeability for orthogonal cross-hatch band patterns...............161 Figure 6.11. Effective permeability for acute cross-hatch band patterns........................162 Figure 6.12. Effective permeability for a real anastomosing band pattern.....................164 Figure 7.1. Location and air photo of the Aztec sandstone, Valley of Fire, NV............170 Figure 7.2. Compaction bands in outcrop and thin section.............................................172 Figure 7.3. Compaction band trace map.........................................................................174 Figure 7.4. Schematic of transmissibility calculation parameters..................................177 Figure 7.5. Triangular discretization of compaction band trace map.............................181 Figure 7.6. Well locations for single-phase flow simulations.........................................183 Figure 7.7. Pressure drop results for single-phase flow simulations..............................184 Figure 7.8. Well configurations for reservoir production simulations............................186 Figure 7.9. Saturation-map snapshots for reservoir production simulations..................188 Figure 7.10. Production efficiency for the two reservoir production scenarios..............189 Figure 7.11. Contaminant leak simulation configurations..............................................191 Figure 7.12. Contaminant plume with bands parallel to regional gradient.....................193 Figure 7.13. Contaminant plume with bands oblique to regional gradient.....................194 Figure 7.14. Contaminant plume with bands normal to regional gradient.....................195 xi
Page 1 and 2: STRUCTURAL GEOLOGY, PROPAGATION MEC
Page 4 and 5: Abstract Low-porosity, low-permeabi
Page 6 and 7: delivered with fortitude, humor, su
Page 8 and 9: Chapter 3—Energy-release model of
Page 12 and 13: Figure A. Cover photo that accompan
Page 14 and 15: likely present in subsurface sandst
Page 16 and 17: hooking-tip interactions—using th
Page 18 and 19: and sandstone, my co-authors—Moha
Page 20 and 21: the hard data from which accurate p
Page 22 and 23: Although the Aztec sandstone experi
Page 24 and 25: Waterpocket Fault 36 o 26‘ N 0 1
Page 26 and 27: Cenozoic Mesozoic Paleozoic Quatern
Page 28 and 29: 3.3. Deformation The Aztec also has
Page 30 and 31: There also are relatively high-angl
Page 32 and 33: (e) (f) (c) 500µm compaction band
Page 34 and 35: dihedral angle of 80° or more, and
Page 36 and 37: 5. Compaction band orientations Ori
Page 38 and 39: n = 20 M n = 20 P n = 22 B n = 20 R
Page 40 and 41: were encountered, giving the dihedr
Page 42 and 43: Eichhubl et al., 2004) did not lend
Page 44 and 45: P (a) (c) S P S Figure 1.10. Stereo
Page 46 and 47: possible, and use these to better c
Page 48 and 49: 1.5(ρgz) (b) WEST Willow Tank Uppe
Page 50 and 51: 9. Acknowledgements My sincere than
Page 52 and 53: The term compaction band (CB) was c
Page 54 and 55: Pollard, 2002). The particular util
Page 56 and 57: Hue-based image analysis using MATL
Page 58 and 59: a direct genetic relationship (Hill
Page 60 and 61:
Compaction band fin Depositional be
Page 62 and 63:
suggests—that to first approximat
Page 64 and 65:
Porosity Porosity 0.3 0.25 0.2 0.15
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pore-clogging clay—due presumably
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500 µm Figure 2.9. Electron backsc
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(a) (b) σ 3 σ 1 x 3 x 1 x 1 (c) u
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6. Elastic properties Despite a lon
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Comparison of the two approaches es
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term in (6a) and (6c) begins to dom
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MPa MPa 80 70 60 50 40 30 20 10 0 0
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2002) and use a BEM approach (Crouc
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MPa 10 4 10 3 10 2 10 1 10 −5 10
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concentration of quartz plasticity
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conducted on well-cemented sandston
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~ 62 m compaction band trend 500µm
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Sternlof et al. (2005) have suggest
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2005). It consists of a long (infin
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⎡ ∆ ⎤ ⎧ p 1 ∆ ⎛ M ⎞
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which point the inelastic strain ha
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they can exert significant effects
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interact is inversely proportional
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(a) (b) (c) (d) Figure 4.3. Typical
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Viewed individually, CB traces tend
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(a) (b) (c) (d) (e) (f) Figure 4.7.
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1973; Mardon, 1988; Peck et al., 19
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undamaged host rock. That CBs canno
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0.5 0.4 0.3 0.2 0.1 0.5 0.4 0.3 0.2
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Normalized stress magnitude 3 2.5 2
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helps to explain why the oblique ap
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and ts = G·ds + H·dn (2) where tn
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plastic compaction, as suggested by
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To determine the sensitivity of pro
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segments will self-correct to provi
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6.3. Approaching tip interactions A
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0.2 0.15 0.1 0.05 0 −0.05 −0.1
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0.2 0.15 0.1 0.05 0 −0.05 −0.1
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the hooking patterns commonly obser
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(a) (b) (c) σ1 compaction band max
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σ 3 σ 2 σ 1 Figure 4.24. Schemat
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NV UT CA AZ Park Road Map Detail Pa
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compaction band Figure 5.2. Typical
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3. Computational method The methodo
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compaction band A 5 mm A‘ compact
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4. Application to the Aztec sandsto
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Permeability (mD) 10 4 10 3 10 2 10
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B‘ A‘ A c f m c m c f c f c f c
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equivalent of the Aztec sandstone,
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effective permeability represents a
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NV UT CA AZ Park Road Map Detail Pa
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Commonly from ~1 mm to ~1.5 cm in t
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Although systematic arrays of DBs p
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to 2 m, with both sets in a cross-h
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y identical blocks all subject to t
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contiguous areas. This type of char
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(0,b) n 3 (0,0) f 2 n 2 n 1 (a,0) (
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6.1. Parallel Effective permeabilit
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By contrast, band-parallel effectiv
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Relative Effective Permeability 1.0
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(a) (b) (c) 0 meters 3 = 10-2 kb /k
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Though grossly systematic, anastomo
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168
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100 meters 5 meters NV UT CA AZ Par
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compaction band trend 500µm Figure
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Cover Outcrop Band N 100 meters 20
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(CBs) and the matrix rock in all si
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The finite volume discretization fo
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isotropic) can lead to numerical di
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5. Simulations Three sets of 2-D si
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Normalized ∆P ∆P ratio (n/p) 4.
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P P P P I I P P Case 1 P P Case 2 I
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Case 1 Case 1 Case 1 (a) (b) (c) In
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5.2.2. Discussion The elliptical pa
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5.3.1. Results With the regional gr
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(a) (b) Leak 200 meters Regional gr
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anticipated sustainable pumping rat
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Finally, there is the issue of fore
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200
Page 214 and 215:
Bakke, S., and Øren, P. E., 1997,
Page 216 and 217:
Carpenter, D. G., and Carpenter, J.
Page 218 and 219:
Eichhubl, P., Taylor, W. L., Pollar
Page 220 and 221:
Karimi-Fard, M., Durlofsky, L. J.,
Page 222 and 223:
-, 1987, Fracture from a straight c
Page 224 and 225:
Shipton, Z. K., and Cowie, P. A., 2
Page 226:
Wong, T. F., David, C., and Zhu, W.
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